Another Novice Q. - recharging - Volts and Amps

K

Kris Krieger

Guest
Apologies in advance if this is a dopey question, but, when it comes to
recharging batteries, and using a solar cell to do that, what I've been
assuming, based on th info that peopl ehere have kindly provided, and also
that I've foind on-line, is that teh mA output of the solar cells should
not exceed 2/10ths to maybe 3/10ths of the battery's mA rating, and teh
voltage produced by the solar cells should be as close as possible to the
total voltage of the battery or batteries. But I wanted to check whether
that assumption is correct, becasue I think I'm getting closeto getting
some parts and trying a couple of assemblies.

Thanks In Advance!

- Kris
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it comes to
recharging batteries, and using a solar cell to do that, what I've been
assuming, based on th info that peopl ehere have kindly provided, and also
that I've foind on-line, is that teh mA output of the solar cells should
not exceed 2/10ths to maybe 3/10ths of the battery's mA rating, and teh
voltage produced by the solar cells should be as close as possible to the
total voltage of the battery or batteries. But I wanted to check whether
that assumption is correct, becasue I think I'm getting closeto getting
some parts and trying a couple of assemblies.

Thanks In Advance!

- Kris
Click to expand...
Hi Kris,
Different batteries need different charging conditions.
Look at the specs for your batteries.
The charging requirements will be discussed.
Some batteries may say: Charge at .1c for 10 Hrs.
This means to charge them at one tenth the AH rating for 10 Hours.
The VPC (volts per cell ) will also be specified.
For example: NiCads are about 1.2 VPC and can charge at about 1.3-1.5 VPC
(follow manufacturers specs) at .1 -.3 c. (again, follow specs.).
So if you have a 12 volts NiCad pack that would be a 10 cell NiCad battery.
If you are using lead acid cells, the numbers are different.
Keep in mind that photo cell manufactures inflate their specs by using
bright sunlight averages.

Tom
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it comes to
recharging batteries, and using a solar cell to do that, what I've been
assuming, based on th info that peopl ehere have kindly provided, and also
that I've foind on-line, is that teh mA output of the solar cells should
not exceed 2/10ths to maybe 3/10ths of the battery's mA rating, and teh
voltage produced by the solar cells should be as close as possible to the
total voltage of the battery or batteries. But I wanted to check whether
that assumption is correct, becasue I think I'm getting closeto getting
some parts and trying a couple of assemblies.

Thanks In Advance!

- Kris
Click to expand...
There are a few suppliers that sell solar scavenger panels for charging
vehicle batteries while parked outside the workplace, there are certainly
car ones that sit on the dashboard and possibly permanent one's that can be
bonded onto the roof, I believe there are also motorcycle types available.

If you make a home brew panel, don't forget you need a blocking rectifier to
stop the battery discharging into the solar cell when there's no sunlight
and the forward volt drop of the rectifier has to be taken into account when
specifying the solar panel voltage.
 
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:CrydnV3Ospmxm_3VnZ2dnUVZ_vninZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it comes
to recharging batteries, and using a solar cell to do that, what I've
been assuming, based on th info that peopl ehere have kindly
provided, and also that I've foind on-line, is that teh mA output of
the solar cells should not exceed 2/10ths to maybe 3/10ths of the
battery's mA rating, and teh voltage produced by the solar cells
should be as close as possible to the total voltage of the battery or
batteries. But I wanted to check whether that assumption is correct,
becasue I think I'm getting closeto getting some parts and trying a
couple of assemblies.

Thanks In Advance!

- Kris

Hi Kris,
Different batteries need different charging conditions.
Look at the specs for your batteries.
The charging requirements will be discussed.
Some batteries may say: Charge at .1c for 10 Hrs.
This means to charge them at one tenth the AH rating for 10 Hours.
The VPC (volts per cell ) will also be specified.
For example: NiCads are about 1.2 VPC and can charge at about 1.3-1.5
VPC (follow manufacturers specs) at .1 -.3 c. (again, follow specs.).
Click to expand...
Ah, OK, that at least gives me a ballpark figure - thanks :) !

(I do try looking all these things up via Google before posting
questions, but often, I don't know the terms that will get me the correct
*type* of answer - IOW, if I want info about charging, I don't want to
look at endless lists of people selling battery chargers, but the latter
is the sort ofthing I've been having to trudge through...so even just
getting the right terminology has been a huge help).

So if you have a 12 volts NiCad pack that would be a 10 cell NiCad
battery. If you are using lead acid cells, the numbers are different.
Keep in mind that photo cell manufactures inflate their specs by using
bright sunlight averages.

Tom
Click to expand...

THe Max I'll use will be 4 1.2V NiMH batteries, for small lighting
units. What I'm trying to figure out is how to avoid "cooking" the
batteries ;) by putting in *too much* voltage, but I also want to take
into account the very thing that you mentioned, i.e. the "brightest
possible sunlight" rating for the cells.

I had bought some Malibu NiMH batteries at WalMart, but now i'm looking
at ordering something more along the lines of Energizers (for example,
http://www.rei.com/product/719570?cm_mmc=cse_froogle-_-datafeed-_-
product-_-na&mr:trackingCode=B42A264C-BE3F-DD11-98CA-001422107090
&mr:referralID=NA or these
http://www.circuitcity.com/ssm/Duracell-AA-Rechargeable-Batteries-4-Pack-
DC1500B4/sem/rpsm/oid/52666/catOid/0/rpem/ccd/productDetail.do) or one of
the other known/name brands, because just today I read some cautions
regarding "bargain" batteries.

I at least found some interesting LEDs at
http://www.optekinc.com/viewparts.aspx?categoryID=53 , some of them claim
to put out 18,000umc average using 20mA and typical "forward" voltage of
3.4, so that I can run off of a reasonable LED driver (considering some
Maxim items, or the "Micro-Puck").


ANyway, I'll look around and see whether ther eis info about recharging.
THis is good to know because, assuming I can do what i'm intending, and
call sell the units, I can also incoude costomer info as to the best
replacement batteries, should replacements be necessary.

Thanks again :)

- Kris
 
"ian field" <dai.ode@ntlworld.com> wrote in
news:sbU7k.69776$8k.12981@newsfe18.ams2:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it comes
to recharging batteries, and using a solar cell to do that, what I've
been assuming, based on th info that peopl ehere have kindly
provided, and also that I've foind on-line, is that teh mA output of
the solar cells should not exceed 2/10ths to maybe 3/10ths of the
battery's mA rating, and teh voltage produced by the solar cells
should be as close as possible to the total voltage of the battery or
batteries. But I wanted to check whether that assumption is correct,
becasue I think I'm getting closeto getting some parts and trying a
couple of assemblies.

Thanks In Advance!

- Kris

There are a few suppliers that sell solar scavenger panels for
charging vehicle batteries while parked outside the workplace, there
are certainly car ones that sit on the dashboard and possibly
permanent one's that can be bonded onto the roof, I believe there are
also motorcycle types available.
Click to expand...
Not my applications - yet! INteresting to know, tho'. If I can actually
pull off this lighting project, it will be a good springboard, I think,
to learnign moer about otehr Solar options and how to implement them.
((Tho' for a whole-house system, I'd hire a pro <g!>))

If you make a home brew panel, don't forget you need a blocking
rectifier to stop the battery discharging into the solar cell when
there's no sunlight and the forward volt drop of the rectifier has to
be taken into account when specifying the solar panel voltage.
Click to expand...
All the circuit diagrams I've looked at (this is for solar accent
lighting, but much brighter than what is usually available) seem to use a
diode as tha "backflow regulator", which I think <?> might be what you
mean?, unless one is looking at the circuits that have integrated
battery management - tho' I don't yet really understand how one uses
them, i.e. how to go from "sensing a full charge" to actually bleeding
off or shunting away any additional power - tho' I'm still going through
data sheets.

Ideally, I'd like an IC that not only senses whenthe battery is full, but
also switches the input either off, or into a "bleeder" circuit (or just
back inot the Ground).

- Kris
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:X9udnZAE58lEr_3VnZ2dnUVZ_jmdnZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:CrydnV3Ospmxm_3VnZ2dnUVZ_vninZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it comes
to recharging batteries, and using a solar cell to do that, what I've
been assuming, based on th info that peopl ehere have kindly
provided, and also that I've foind on-line, is that teh mA output of
the solar cells should not exceed 2/10ths to maybe 3/10ths of the
battery's mA rating, and teh voltage produced by the solar cells
should be as close as possible to the total voltage of the battery or
batteries. But I wanted to check whether that assumption is correct,
becasue I think I'm getting closeto getting some parts and trying a
couple of assemblies.

Thanks In Advance!

- Kris

Hi Kris,
Different batteries need different charging conditions.
Look at the specs for your batteries.
The charging requirements will be discussed.
Some batteries may say: Charge at .1c for 10 Hrs.
This means to charge them at one tenth the AH rating for 10 Hours.
The VPC (volts per cell ) will also be specified.
For example: NiCads are about 1.2 VPC and can charge at about 1.3-1.5
VPC (follow manufacturers specs) at .1 -.3 c. (again, follow specs.).

Ah, OK, that at least gives me a ballpark figure - thanks :) !

(I do try looking all these things up via Google before posting
questions, but often, I don't know the terms that will get me the correct
*type* of answer - IOW, if I want info about charging, I don't want to
look at endless lists of people selling battery chargers, but the latter
is the sort ofthing I've been having to trudge through...so even just
getting the right terminology has been a huge help).

So if you have a 12 volts NiCad pack that would be a 10 cell NiCad
battery. If you are using lead acid cells, the numbers are different.
Keep in mind that photo cell manufactures inflate their specs by using
bright sunlight averages.

Tom



THe Max I'll use will be 4 1.2V NiMH batteries, for small lighting
units. What I'm trying to figure out is how to avoid "cooking" the
batteries ;) by putting in *too much* voltage, but I also want to take
into account the very thing that you mentioned, i.e. the "brightest
possible sunlight" rating for the cells.

I had bought some Malibu NiMH batteries at WalMart, but now i'm looking
at ordering something more along the lines of Energizers (for example,
http://www.rei.com/product/719570?cm_mmc=cse_froogle-_-datafeed-_-
product-_-na&mr:trackingCode=B42A264C-BE3F-DD11-98CA-001422107090
&mr:referralID=NA or these
http://www.circuitcity.com/ssm/Duracell-AA-Rechargeable-Batteries-4-Pack-
DC1500B4/sem/rpsm/oid/52666/catOid/0/rpem/ccd/productDetail.do) or one of
the other known/name brands, because just today I read some cautions
regarding "bargain" batteries.

I at least found some interesting LEDs at
http://www.optekinc.com/viewparts.aspx?categoryID=53 , some of them claim
to put out 18,000umc average using 20mA and typical "forward" voltage of
3.4, so that I can run off of a reasonable LED driver (considering some
Maxim items, or the "Micro-Puck").


ANyway, I'll look around and see whether ther eis info about recharging.
THis is good to know because, assuming I can do what i'm intending, and
call sell the units, I can also incoude costomer info as to the best
replacement batteries, should replacements be necessary.

Thanks again :)

- Kris
Click to expand...
When you search you may try something like "solar battery charging tutorial"
When you add 'tutorial' you will get better hits on your search.
BTW: NiMH have very fussy charging characteristics.

May I suggest deep cycle sealed lead acid.

Tom
 
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:X9udnZAE58lEr_3VnZ2dnUVZ_jmdnZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:CrydnV3Ospmxm_3VnZ2dnUVZ_vninZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:HN6dnUa5Bpt2esLVnZ2dnUVZ_h3inZ2d@earthlink.com...
Apologies in advance if this is a dopey question, but, when it
comes to recharging batteries, and using a solar cell to do that,
what I've been assuming, based on th info that peopl ehere have
kindly provided, and also that I've foind on-line, is that teh mA
output of the solar cells should not exceed 2/10ths to maybe
3/10ths of the battery's mA rating, and teh voltage produced by the
solar cells should be as close as possible to the total voltage of
the battery or batteries. But I wanted to check whether that
assumption is correct, becasue I think I'm getting closeto getting
some parts and trying a couple of assemblies.

Thanks In Advance!

- Kris

Hi Kris,
Different batteries need different charging conditions.
Look at the specs for your batteries.
The charging requirements will be discussed.
Some batteries may say: Charge at .1c for 10 Hrs.
This means to charge them at one tenth the AH rating for 10 Hours.
The VPC (volts per cell ) will also be specified.
For example: NiCads are about 1.2 VPC and can charge at about
1.3-1.5 VPC (follow manufacturers specs) at .1 -.3 c. (again, follow
specs.).

Ah, OK, that at least gives me a ballpark figure - thanks :) !

(I do try looking all these things up via Google before posting
questions, but often, I don't know the terms that will get me the
correct *type* of answer - IOW, if I want info about charging, I
don't want to look at endless lists of people selling battery
chargers, but the latter is the sort ofthing I've been having to
trudge through...so even just getting the right terminology has been
a huge help).

So if you have a 12 volts NiCad pack that would be a 10 cell NiCad
battery. If you are using lead acid cells, the numbers are
different. Keep in mind that photo cell manufactures inflate their
specs by using bright sunlight averages.

Tom



THe Max I'll use will be 4 1.2V NiMH batteries, for small lighting
units. What I'm trying to figure out is how to avoid "cooking" the
batteries ;) by putting in *too much* voltage, but I also want to
take into account the very thing that you mentioned, i.e. the
"brightest possible sunlight" rating for the cells.

I had bought some Malibu NiMH batteries at WalMart, but now i'm
looking at ordering something more along the lines of Energizers (for
example,
http://www.rei.com/product/719570?cm_mmc=cse_froogle-_-datafeed-_-
product-_-na&mr:trackingCode=B42A264C-BE3F-DD11-98CA-001422107090
&mr:referralID=NA or these
http://www.circuitcity.com/ssm/Duracell-AA-Rechargeable-Batteries-4-Pa
ck- DC1500B4/sem/rpsm/oid/52666/catOid/0/rpem/ccd/productDetail.do)
or one of the other known/name brands, because just today I read some
cautions regarding "bargain" batteries.

I at least found some interesting LEDs at
http://www.optekinc.com/viewparts.aspx?categoryID=53 , some of them
claim to put out 18,000umc average using 20mA and typical "forward"
voltage of 3.4, so that I can run off of a reasonable LED driver
(considering some Maxim items, or the "Micro-Puck").


ANyway, I'll look around and see whether ther eis info about
recharging. THis is good to know because, assuming I can do what i'm
intending, and call sell the units, I can also incoude costomer info
as to the best replacement batteries, should replacements be
necessary.

Thanks again :)

- Kris



When you search you may try something like "solar battery charging
tutorial" When you add 'tutorial' you will get better hits on your
search. BTW: NiMH have very fussy charging characteristics.
Click to expand...
Thanks!, I'll try that.

May I suggest deep cycle sealed lead acid.

Tom
Click to expand...
My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible, and
I know that people can buy the NiMH batteries pretty easily. That's the
only reason I've sort-of "fixated" on them. THat, and it's easy to get the
mA ratings that will drive the LEDs I want to use (found one that uses 20
mA, and 3.4V average, but gives out an amazing (to me) average of
18,000micro-candela, which is 226 lumens, which is a bit more than is given
off by a 20-watt incandescent bulb (220 lumens). With the LED driver (I
think it was you who'd recommended those), that should work out well and I
could, I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running off
of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough voltage,
and generate enough current, to run the drivers. I've also used store-
bought solar lights, which had either NiCad or NiMH (depending upon th
etype), so I know those will work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris
 
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:

On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible,
and I know that people can buy the NiMH batteries pretty easily.
That's the only reason I've sort-of "fixated" on them. THat, and it's
easy to get the mA ratings that will drive the LEDs I want to use
(found one that uses 20 mA, and 3.4V average, but gives out an amazing
(to me) average of 18,000micro-candela, which is 226 lumens, which is
a bit more than is given off by a 20-watt incandescent bulb (220
lumens). With the LED driver (I think it was you who'd recommended
those), that should work out well and I could, I think, use two such
LEDs, which should be about the lumens produced bya 40 watt
incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running
off of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough
voltage, and generate enough current, to run the drivers. I've also
used store- bought solar lights, which had either NiCad or NiMH
(depending upon th etype), so I know those will work when left
outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery is
lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid batteries
are almost certainly not a consideration. I'm not aware of any
lead-acid batteries in a "dry cell" format.
Click to expand...
AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries will be
just the normal NiMH things that pop into regular ol' solar
garden/accent lights. Since the betteries will eventually need to
be replaced, I'd like them to be things that people can find very
easily and that don't cost an arm and a leg. Someone (Tom B.?) had
recommended an LED driver, and I've been looking around at otehrs as
well (mainly to read teh application notes and datasheets and
whatnot so as to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier plus
an LED driver (in case it'd be helpful to anyone else, the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form a
combination battery+solar-cell charging+battery management circuit.

I know that I can build a super-simple unit that will drive one
normal-brightness LED; I found a few different schematics for simple
low-brightness units, and the simplest are little more tahn a solar
cell, diode, battery, resistor, and LED, with no sort of overcharge
protection or any other accomidation for any special needs that one
or another sort of battery might have. THey're robust, but they
won't work for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much light
as does a smooth clear enclosure (I think the commercial ones are
acrylic). Also, the potential customers and sales venues I've
polled all have the same complaint: commercial solar lights are too
dim. Ultra-cheap is not part of my equation here - I am most
definitely not going seeking to try to compete with the "$5-$9
light" market; Wal-Mart has that very well-covered. Rather, the
units, being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the time
and skill it takes to construct a particular design. I do want to
squeeze as many Lumens as possible out of a *maximum* of 4 NiMH
batteries, to be charged during the daytime by solar cells, plus I
want to charge the batteries in about 5-6 hours in good sunlight -
and that last part is why I'm looking into overcharge protection,
since it's likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to the
relationship between the solar cell(s) V/mA rating, and the battery V/mA
rating - I don't want to "cook" the batteries.

TIA!

- Kris
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:Q-SdnWZbG9nt4f_VnZ2dnUVZ_r3inZ2d@earthlink.com...
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:

On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible,
and I know that people can buy the NiMH batteries pretty easily.
That's the only reason I've sort-of "fixated" on them. THat, and it's
easy to get the mA ratings that will drive the LEDs I want to use
(found one that uses 20 mA, and 3.4V average, but gives out an amazing
(to me) average of 18,000micro-candela, which is 226 lumens, which is
a bit more than is given off by a 20-watt incandescent bulb (220
lumens). With the LED driver (I think it was you who'd recommended
those), that should work out well and I could, I think, use two such
LEDs, which should be about the lumens produced bya 40 watt
incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running
off of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough
voltage, and generate enough current, to run the drivers. I've also
used store- bought solar lights, which had either NiCad or NiMH
(depending upon th etype), so I know those will work when left
outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery is
lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid batteries
are almost certainly not a consideration. I'm not aware of any
lead-acid batteries in a "dry cell" format.


AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries will be
just the normal NiMH things that pop into regular ol' solar
garden/accent lights. Since the betteries will eventually need to
be replaced, I'd like them to be things that people can find very
easily and that don't cost an arm and a leg. Someone (Tom B.?) had
recommended an LED driver, and I've been looking around at otehrs as
well (mainly to read teh application notes and datasheets and
whatnot so as to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier plus
an LED driver (in case it'd be helpful to anyone else, the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form a
combination battery+solar-cell charging+battery management circuit.

I know that I can build a super-simple unit that will drive one
normal-brightness LED; I found a few different schematics for simple
low-brightness units, and the simplest are little more tahn a solar
cell, diode, battery, resistor, and LED, with no sort of overcharge
protection or any other accomidation for any special needs that one
or another sort of battery might have. THey're robust, but they
won't work for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much light
as does a smooth clear enclosure (I think the commercial ones are
acrylic). Also, the potential customers and sales venues I've
polled all have the same complaint: commercial solar lights are too
dim. Ultra-cheap is not part of my equation here - I am most
definitely not going seeking to try to compete with the "$5-$9
light" market; Wal-Mart has that very well-covered. Rather, the
units, being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the time
and skill it takes to construct a particular design. I do want to
squeeze as many Lumens as possible out of a *maximum* of 4 NiMH
batteries, to be charged during the daytime by solar cells, plus I
want to charge the batteries in about 5-6 hours in good sunlight -
and that last part is why I'm looking into overcharge protection,
since it's likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to the
relationship between the solar cell(s) V/mA rating, and the battery V/mA
rating - I don't want to "cook" the batteries.

TIA!

- Kris




After you explained that you would be using small batteries the lead acid
Click to expand...
suggestion would not apply.
Yes there is a relationship between the charger and the batteries, a rather
important one.
Since you indicated that you may use NiMH the relationship is even more
serious.
You will not get reliable charging without some type of charge regulator.
I think when you first posted a while back someone mentioned that they are
available as commercial units for less than you can make one.

Tom
 
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:K7qdnTlMrY6hN__VnZ2dnUVZ_qPinZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:Q-SdnWZbG9nt4f_VnZ2dnUVZ_r3inZ2d@earthlink.com...
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:

On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to
be easier to deal with, but these units are going into things that
I'll (hopefully!) be selling, so I need to make it all as easy as
possible, and I know that people can buy the NiMH batteries pretty
easily. That's the only reason I've sort-of "fixated" on them.
THat, and it's easy to get the mA ratings that will drive the LEDs I
want to use (found one that uses 20 mA, and 3.4V average, but gives
out an amazing (to me) average of 18,000micro-candela, which is 226
lumens, which is a bit more than is given off by a 20-watt
incandescent bulb (220 lumens). With the LED driver (I think it was
you who'd recommended those), that should work out well and I could,
I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference
running off of anything other than NiCad, NiMH, or Lithium-Ion
batteries,so my impression was that those are the only two that have
both enough voltage, and generate enough current, to run the
drivers. I've also used store- bought solar lights, which had
either NiCad or NiMH (depending upon th etype), so I know those will
work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about
them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery
is lead-acid, for example (although there are smaller sizes, and
some variations that don't have a liquid electrolyte, available).
If you are considering AA, C or D cells for your project, lead-acid
batteries are almost certainly not a consideration. I'm not aware of
any lead-acid batteries in a "dry cell" format.


AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries will be
just the normal NiMH things that pop into regular ol' solar
garden/accent lights. Since the betteries will eventually need to
be replaced, I'd like them to be things that people can find very
easily and that don't cost an arm and a leg. Someone (Tom B.?) had
recommended an LED driver, and I've been looking around at otehrs as
well (mainly to read teh application notes and datasheets and
whatnot so as to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier plus
an LED driver (in case it'd be helpful to anyone else, the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form a
combination battery+solar-cell charging+battery management circuit.

I know that I can build a super-simple unit that will drive one
normal-brightness LED; I found a few different schematics for simple
low-brightness units, and the simplest are little more tahn a solar
cell, diode, battery, resistor, and LED, with no sort of overcharge
protection or any other accomidation for any special needs that one
or another sort of battery might have. THey're robust, but they
won't work for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much light
as does a smooth clear enclosure (I think the commercial ones are
acrylic). Also, the potential customers and sales venues I've
polled all have the same complaint: commercial solar lights are too
dim. Ultra-cheap is not part of my equation here - I am most
definitely not going seeking to try to compete with the "$5-$9
light" market; Wal-Mart has that very well-covered. Rather, the
units, being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the time
and skill it takes to construct a particular design. I do want to
squeeze as many Lumens as possible out of a *maximum* of 4 NiMH
batteries, to be charged during the daytime by solar cells, plus I
want to charge the batteries in about 5-6 hours in good sunlight -
and that last part is why I'm looking into overcharge protection,
since it's likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to
the relationship between the solar cell(s) V/mA rating, and the
battery V/mA rating - I don't want to "cook" the batteries.

TIA!

- Kris




After you explained that you would be using small batteries the lead
acid suggestion would not apply.
Yes there is a relationship between the charger and the batteries, a
rather important one.
Since you indicated that you may use NiMH the relationship is even
more serious.
You will not get reliable charging without some type of charge
regulator. I think when you first posted a while back someone
mentioned that they are available as commercial units for less than
you can make one.

Tom
Click to expand...
I didn't know what they were at that point, but I've learned a little more
since then ;) I've been concentrating on Maxim, mostly because they have a
lot of really good Application Notes, also because I think I can get all
the major items from there. "Charge regulator" is a new/different phrase
for me, tho', so I'm searching on it, and checking into that the Maxim site
lists under that term.

What gets confusing is that there often seem to be several possible units,
or combinations of units, that perform similar functions, so I've been
trying to differentiate them and find which would be best. I did find a
couple of Charge Regulators, too.

What surprises me is that the ICs seem to be quite inexpensive - most of
the units I'm looking at are under $2 each. I still would have to add up
the associated resistors, inductors, and whatnot, but I *think* I can keep
it under $20...

I guess the next step is for me to collect the datasheet titles/locations,
find one or two solar cells (and configurations thereof) that seem like
they'd do the job, and then write to Maxim and ask how it all should go
together - although the schematics for the individual applications actually
make some sense to me, the problem is that I don't know whether I can just,
so to speak, "paste the two diagrams together" and then stick in teh solar
cell(s) and diode, or whetehr there is somethign special that needs to be
done so as to make something that both works, and is safe ;) They were
good about answering the first question I sent them, so I'm hoping they can
give me a clue about meshing the various application notes. If there will
be a charge control IC, I'm assuming that I don't have to worry too much
about an "overpowered" solar-cell input...

ANyway, thanks for all the info (and patience ;) ) over the past couple of
weeks; I've learned a lot and think I might actually be able to get this
project going!

- Kris
 
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:

Kris Krieger wrote:
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:


On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:


"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to
be easier to deal with, but these units are going into things that
I'll (hopefully!) be selling, so I need to make it all as easy as
possible, and I know that people can buy the NiMH batteries pretty
easily. That's the only reason I've sort-of "fixated" on them.
THat, and it's easy to get the mA ratings that will drive the LEDs I
want to use (found one that uses 20 mA, and 3.4V average, but gives
out an amazing (to me) average of 18,000micro-candela, which is 226
lumens, which is a bit more than is given off by a 20-watt
incandescent bulb (220 lumens). With the LED driver (I think it was
you who'd recommended those), that should work out well and I could,
I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference
running off of anything other than NiCad, NiMH, or Lithium-Ion
batteries,so my impression was that those are the only two that have
both enough voltage, and generate enough current, to run the
drivers. I've also used store- bought solar lights, which had
either NiCad or NiMH (depending upon th etype), so I know those will
work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about
them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery
is lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid
batteries are almost certainly not a consideration. I'm not aware of
any lead-acid batteries in a "dry cell" format.



AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside
of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries
will be just the normal NiMH things that pop into regular
ol' solar garden/accent lights. Since the betteries will
eventually need to be replaced, I'd like them to be things
that people can find very easily and that don't cost an arm
and a leg. Someone (Tom B.?) had recommended an LED driver,
and I've been looking around at otehrs as well (mainly to
read teh application notes and datasheets and whatnot so as
to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier
plus an LED driver (in case it'd be helpful to anyone else,
the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form
a
combination battery+solar-cell charging+battery management
circuit.

I know that I can build a super-simple unit that will drive
one
normal-brightness LED; I found a few different schematics for
simple low-brightness units, and the simplest are little
more tahn a solar cell, diode, battery, resistor, and LED,
with no sort of overcharge protection or any other
accomidation for any special needs that one or another sort
of battery might have. THey're robust, but they won't work
for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much
light as does a smooth clear enclosure (I think the
commercial ones are acrylic). Also, the potential customers
and sales venues I've polled all have the same complaint:
commercial solar lights are too dim. Ultra-cheap is not
part of my equation here - I am most definitely not going
seeking to try to compete with the "$5-$9 light" market;
Wal-Mart has that very well-covered. Rather, the units,
being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the
time and skill it takes to construct a particular design. I
do want to squeeze as many Lumens as possible out of a
*maximum* of 4 NiMH batteries, to be charged during the
daytime by solar cells, plus I want to charge the batteries
in about 5-6 hours in good sunlight - and that last part is
why I'm looking into overcharge protection, since it's
likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to
the relationship between the solar cell(s) V/mA rating, and the
battery V/mA rating - I don't want to "cook" the batteries.

TIA!

- Kris





I think you've gone down a path that may be counter productive.
First: The amount of power you will get from the solar panel
will depend predominantly on how much surface area you can get
exposed to the sun. You can include instructions to the
consumer concerning installation for maximum exposure, but
the only factor _you_ can control is the surface area.

What does that mean at this point? You know the size of what
you are building, so _you_ need to find solar cells that
will fit that area. *That* selection will dictate how much
power the design will have available, and it will be a range
from minimum (0 on a cloudy day) to maximum. The amount of
power available from the panel will vary throughout the day.

Only when you know how much power will be available in a
typical *week* can you properly design the electronics.

So, post again once you have found a solar panel (or
combination of panels) that will fit the device you are
making. How much power will be available to work with
under the "typical" conditions of your intended market?

You want something simple and better than a typical solar
powered garden light. So do I - and I also want cheap
oil. Neither is generally available these days. You
can maximize what a typical solar powered garden light
(like cat# SPL-09 at http://www.allelectronics.com/ see
also cat# SPL-05) produces with increased complexity and
construction cost. If you can live with the performance
level of either of those, you job is done - just incorporate
their panels & circuitry in your prroduct. Oterwise, you
have to put in the work to search for the best panels
you can get to fit your product, and obtain the best
performance possible from that power source.

Without knowing how much power is available, it is impossible
to say how long it will take to charge a cell, nor can the
charging circuit be designed for best performance.

IIRC, no one has told you to do that work - identifying
the panels - in the various threads, posts and replies since
you started looking for an answer. Of course, I may have
missed it, so if you have identified the panels, how much
charging power is available to work with?

Ed
Click to expand...
Actually, the initial consideration was finding how much brightness would
be enough, and which LEDs (and/or combination thereof) will provide it.
From there, it goes backwards to find out how to run them off of a
*maximum* of four 1.2V NiMH batteries. From there, working backwards
again, is the charge controller IC - finding the one that will charge,
and keep from overcharging, 3 to 4 of the batteries. THe solar cells
(not panels, just cells) is actually the last thing. WHat I'm trying to
figure out is whether I should have the solar cells producing the same
total voltage as that which the batteries will have (3.6V for three of
them, 4.8V for 4); since I've learned that NiMH are supposed to be fast-
charged rather than trickle-charged, I'm tryign to figure whether solar
cell amperage is more important for doing that, with voltage being
insignificant, or what.

Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:kOGdnVPS95_Nuf7VnZ2dnUVZ_hSdnZ2d@earthlink.com...
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:

Kris Krieger wrote:
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:


On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:


"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to
be easier to deal with, but these units are going into things that
I'll (hopefully!) be selling, so I need to make it all as easy as
possible, and I know that people can buy the NiMH batteries pretty
easily. That's the only reason I've sort-of "fixated" on them.
THat, and it's easy to get the mA ratings that will drive the LEDs I
want to use (found one that uses 20 mA, and 3.4V average, but gives
out an amazing (to me) average of 18,000micro-candela, which is 226
lumens, which is a bit more than is given off by a 20-watt
incandescent bulb (220 lumens). With the LED driver (I think it was
you who'd recommended those), that should work out well and I could,
I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference
running off of anything other than NiCad, NiMH, or Lithium-Ion
batteries,so my impression was that those are the only two that have
both enough voltage, and generate enough current, to run the
drivers. I've also used store- bought solar lights, which had
either NiCad or NiMH (depending upon th etype), so I know those will
work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about
them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery
is lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid
batteries are almost certainly not a consideration. I'm not aware of
any lead-acid batteries in a "dry cell" format.



AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside
of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries
will be just the normal NiMH things that pop into regular
ol' solar garden/accent lights. Since the betteries will
eventually need to be replaced, I'd like them to be things
that people can find very easily and that don't cost an arm
and a leg. Someone (Tom B.?) had recommended an LED driver,
and I've been looking around at otehrs as well (mainly to
read teh application notes and datasheets and whatnot so as
to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier
plus an LED driver (in case it'd be helpful to anyone else,
the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form
a
combination battery+solar-cell charging+battery management
circuit.

I know that I can build a super-simple unit that will drive
one
normal-brightness LED; I found a few different schematics for
simple low-brightness units, and the simplest are little
more tahn a solar cell, diode, battery, resistor, and LED,
with no sort of overcharge protection or any other
accomidation for any special needs that one or another sort
of battery might have. THey're robust, but they won't work
for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much
light as does a smooth clear enclosure (I think the
commercial ones are acrylic). Also, the potential customers
and sales venues I've polled all have the same complaint:
commercial solar lights are too dim. Ultra-cheap is not
part of my equation here - I am most definitely not going
seeking to try to compete with the "$5-$9 light" market;
Wal-Mart has that very well-covered. Rather, the units,
being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the
time and skill it takes to construct a particular design. I
do want to squeeze as many Lumens as possible out of a
*maximum* of 4 NiMH batteries, to be charged during the
daytime by solar cells, plus I want to charge the batteries
in about 5-6 hours in good sunlight - and that last part is
why I'm looking into overcharge protection, since it's
likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to
the relationship between the solar cell(s) V/mA rating, and the
battery V/mA rating - I don't want to "cook" the batteries.

TIA!

- Kris





I think you've gone down a path that may be counter productive.
First: The amount of power you will get from the solar panel
will depend predominantly on how much surface area you can get
exposed to the sun. You can include instructions to the
consumer concerning installation for maximum exposure, but
the only factor _you_ can control is the surface area.

What does that mean at this point? You know the size of what
you are building, so _you_ need to find solar cells that
will fit that area. *That* selection will dictate how much
power the design will have available, and it will be a range
from minimum (0 on a cloudy day) to maximum. The amount of
power available from the panel will vary throughout the day.

Only when you know how much power will be available in a
typical *week* can you properly design the electronics.

So, post again once you have found a solar panel (or
combination of panels) that will fit the device you are
making. How much power will be available to work with
under the "typical" conditions of your intended market?

You want something simple and better than a typical solar
powered garden light. So do I - and I also want cheap
oil. Neither is generally available these days. You
can maximize what a typical solar powered garden light
(like cat# SPL-09 at http://www.allelectronics.com/ see
also cat# SPL-05) produces with increased complexity and
construction cost. If you can live with the performance
level of either of those, you job is done - just incorporate
their panels & circuitry in your prroduct. Oterwise, you
have to put in the work to search for the best panels
you can get to fit your product, and obtain the best
performance possible from that power source.

Without knowing how much power is available, it is impossible
to say how long it will take to charge a cell, nor can the
charging circuit be designed for best performance.

IIRC, no one has told you to do that work - identifying
the panels - in the various threads, posts and replies since
you started looking for an answer. Of course, I may have
missed it, so if you have identified the panels, how much
charging power is available to work with?

Ed


Actually, the initial consideration was finding how much brightness would
be enough, and which LEDs (and/or combination thereof) will provide it.
From there, it goes backwards to find out how to run them off of a
*maximum* of four 1.2V NiMH batteries. From there, working backwards
again, is the charge controller IC - finding the one that will charge,
and keep from overcharging, 3 to 4 of the batteries. THe solar cells
(not panels, just cells) is actually the last thing. WHat I'm trying to
figure out is whether I should have the solar cells producing the same
total voltage as that which the batteries will have (3.6V for three of
them, 4.8V for 4); since I've learned that NiMH are supposed to be fast-
charged rather than trickle-charged, I'm tryign to figure whether solar
cell amperage is more important for doing that, with voltage being
insignificant, or what.

Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris
Click to expand...
Kris,

It would be wise to consider solar panel size at this point rather than
last, if only for reality check.

Solar lights usually are very dim. That is primarily because the size of
the solar panels and the amount of power they can produce during sunshine.
The batteries only have to be as "large" as the power produced. The best
solar lights I have seen have 8" x 12" panels which are not mounted to the
light itself (this also helps in that the lights themselves can be placed in
shady areas).

Scott
 
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:rfd9k.9$dz.4@trndny01:

Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:8vU8k.58$BR.4@trnddc06:


Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:


[edited]


Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris

As you said, you are working backwards. You don't yet understand
that doing it that way can result in a specification for cells
that are "unobtanium".

Ed



"Unobtanium"??, it's a modest LED night-lamp, not an airport beacon
:p

I *already* know the batteries and their output, and the input needed
by the LED driver and what it will output to run the LEDs (which will
run off the batteries at night) - those are not the problem.

To charge my 4 little 1.2V AA NiMH batteries, I have seen the
following solar cells (and more, this isn't an all-inclusive list):
0.5V, 200mA
0.5V, 450mA
0.5V, 800mA
0.5V, 2000mA
1V, 200mA
2V, 200mA
3V, 400mA
4V, 25mA
etc.

I also know that, depending upon how I connect cells, I can up the
Volts or up the Amps, or both if it's a series-parellel combination.
The biggest Q. is the volts. I read that, using a 5V solar cell,
charging time would be the battery mA divided by the cell mA, but
what if it was a 2V cell, or a .5V cell?

Well, I'll write to Maxim, since it's their components I'm interested
in. They can prob. best tell me the input I need for the
battery-management IC.

- Kris


Sorry, Kris, but in terms of the necessary specifications,
you have posted nothing useful to make an informed design
decision. That is not an attack on you, it is just that
you are working in an area that is new to you.
Click to expand...
I found teh answer to my question here:
http://www.solar-world.com/SolarMini-Panels&Motors.htm

Specifically:
"...the solar operating voltage must be higher than the battery voltage..."

That was all I was asking.

Netting your problem out, you want to drive an unknown
(in terms of voltage and current) load
Click to expand...
The Q was not about the "load", it was *simply* and *specifically*, I'll
repeat, this:
Given NiMH batteries, size AA, rated at 1.2V and 1500mA, what would I need
in terms of soalr cell output to charge tem using a battery
charge/control/protection IC (the Maxim DS2715).

I don't understand what in that is "unknown" or otherwise unspecific.


for an unknown amount
of time with an unknown number (but less than 5)
Click to expand...
I'd repeatedly specified "between 3 and 4"...

NiMh AA
cells of unknown capacity, said NiMh's to be charged with an
unknown number of solar cells of unknown capacity in an
unknown environment.
Click to expand...
*Of course* the number of solar cells was unknown - anyway, the "number" is
not relevant, what is relevant is the *output*, and my Q. was specifically
about *needed output*, so that I could go back to the catalogues, look at
the sizes/ratings, and determine what I'd need in terms of numbers, and
arrangements.

As for environment, not relevant to teh question - the question dealt with
ratings. I'm not so stupid that I think SOLAR cells will "work" at night
or in deep shade, or that they generate the same power on cloudy days as on
bright, sunny days. But I did not ask about differnces in output on cloudy
versus sunny days, I asked, based purely upon ratings, about charging a
specifically-described battery.


The key design question is: how much input power will be
available?
Click to expand...
No, the key design question was, as Tom Biasi had notd when I first began
asking my Solar Light questions, was:
"One place to start would be to determine how much illumination you need.
Find LEDs that can give you that. What voltage and current do you need to
power the LEDs for the period of time that you would like? What battery
will provide that?"

The question I asked in this thread was the final question of Tom's initial
input:
"What solar arrangement can charge the battery in the time that you want?"

I didn't know how to do the math. Now I think I might know it.

The surface area of your device that will
be exposed to direct sunlight and that you are willing to
dedicate to solar cells will determine that, in terms of
the maximum that can be achieved.
Click to expand...
THat wasn't what I was asking. I was asking what output (from the cells)
I'd need to charge the specified batteries. I didn't ask about sruface
area - I alreasy knew that, which is why I listed several of the available
solar cell outputs, which I'd selected becasue their footprint fell within
the size limits I wanted. So the surface area was not the concern and was
not at all related to the simple question I was asking.

Obviously, the power
will be less if the device is in the shade or the cells
receive less than full sunlight for some other reason.
Click to expand...
Not to be rude, but, duuuuuuuuh... Again, tho', not what I was asking.

You are here asking for help - but _ONLY_ you can answer
that question.
Click to expand...
Well, between all the different solar-cell-related websites, electronics-
related websites, the Tech Support folk at Maxim, and so on, yeah, you're
right, I finally *am* answering the question I'd asked in this thread about
what Solar Cell output is required to charge the specified batteries.

If we don't know how much power is available, it is not
possible to say definitively if your idea is even feasible,
let alone specify how to do it.
Click to expand...
You can't figure out whether it's feasible to run 4 regular (i.e. discrete
5mm dome) LEDs off of a solar-charged battery pack of 3 NiMH AA 1500mA
batteries?, or up to 6 (same type) LEDs off a solar-charged battery pack of
3 or 4 NiMH AA 1500mA batteries?, or what output V and mA you'd need from
solar cells (obviously placed in the sun :p ) to charge even one
1.2V/1500mA NiMH battery? You can't even determine whether that is
*possible*?

OK, whatever...


Thankfully, there were a couple of folks who were very helpful and got me
going in the right direction, whom I'm thanking in a separate post.

- Kris
 
On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in>
wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible, and
I know that people can buy the NiMH batteries pretty easily. That's the
only reason I've sort-of "fixated" on them. THat, and it's easy to get the
mA ratings that will drive the LEDs I want to use (found one that uses 20
mA, and 3.4V average, but gives out an amazing (to me) average of
18,000micro-candela, which is 226 lumens, which is a bit more than is given
off by a 20-watt incandescent bulb (220 lumens). With the LED driver (I
think it was you who'd recommended those), that should work out well and I
could, I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running off
of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough voltage,
and generate enough current, to run the drivers. I've also used store-
bought solar lights, which had either NiCad or NiMH (depending upon th
etype), so I know those will work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris
Click to expand...
Lead-acid batteries are normally large and heavy. Your car battery is
lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid batteries
are almost certainly not a consideration. I'm not aware of any
lead-acid batteries in a "dry cell" format.

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
 
Kris Krieger wrote:
Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:


On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:


"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible,
and I know that people can buy the NiMH batteries pretty easily.
That's the only reason I've sort-of "fixated" on them. THat, and it's
easy to get the mA ratings that will drive the LEDs I want to use
(found one that uses 20 mA, and 3.4V average, but gives out an amazing
(to me) average of 18,000micro-candela, which is 226 lumens, which is
a bit more than is given off by a 20-watt incandescent bulb (220
lumens). With the LED driver (I think it was you who'd recommended
those), that should work out well and I could, I think, use two such
LEDs, which should be about the lumens produced bya 40 watt
incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running
off of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough
voltage, and generate enough current, to run the drivers. I've also
used store- bought solar lights, which had either NiCad or NiMH
(depending upon th etype), so I know those will work when left
outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery is
lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid batteries
are almost certainly not a consideration. I'm not aware of any
lead-acid batteries in a "dry cell" format.



AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries will be
just the normal NiMH things that pop into regular ol' solar
garden/accent lights. Since the betteries will eventually need to
be replaced, I'd like them to be things that people can find very
easily and that don't cost an arm and a leg. Someone (Tom B.?) had
recommended an LED driver, and I've been looking around at otehrs as
well (mainly to read teh application notes and datasheets and
whatnot so as to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier plus
an LED driver (in case it'd be helpful to anyone else, the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form a
combination battery+solar-cell charging+battery management circuit.

I know that I can build a super-simple unit that will drive one
normal-brightness LED; I found a few different schematics for simple
low-brightness units, and the simplest are little more tahn a solar
cell, diode, battery, resistor, and LED, with no sort of overcharge
protection or any other accomidation for any special needs that one
or another sort of battery might have. THey're robust, but they
won't work for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much light
as does a smooth clear enclosure (I think the commercial ones are
acrylic). Also, the potential customers and sales venues I've
polled all have the same complaint: commercial solar lights are too
dim. Ultra-cheap is not part of my equation here - I am most
definitely not going seeking to try to compete with the "$5-$9
light" market; Wal-Mart has that very well-covered. Rather, the
units, being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the time
and skill it takes to construct a particular design. I do want to
squeeze as many Lumens as possible out of a *maximum* of 4 NiMH
batteries, to be charged during the daytime by solar cells, plus I
want to charge the batteries in about 5-6 hours in good sunlight -
and that last part is why I'm looking into overcharge protection,
since it's likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to the
relationship between the solar cell(s) V/mA rating, and the battery V/mA
rating - I don't want to "cook" the batteries.

TIA!

- Kris
Click to expand...
I think you've gone down a path that may be counter productive.
First: The amount of power you will get from the solar panel
will depend predominantly on how much surface area you can get
exposed to the sun. You can include instructions to the
consumer concerning installation for maximum exposure, but
the only factor _you_ can control is the surface area.

What does that mean at this point? You know the size of what
you are building, so _you_ need to find solar cells that
will fit that area. *That* selection will dictate how much
power the design will have available, and it will be a range
from minimum (0 on a cloudy day) to maximum. The amount of
power available from the panel will vary throughout the day.

Only when you know how much power will be available in a
typical *week* can you properly design the electronics.

So, post again once you have found a solar panel (or
combination of panels) that will fit the device you are
making. How much power will be available to work with
under the "typical" conditions of your intended market?

You want something simple and better than a typical solar
powered garden light. So do I - and I also want cheap
oil. Neither is generally available these days. You
can maximize what a typical solar powered garden light
(like cat# SPL-09 at http://www.allelectronics.com/ see
also cat# SPL-05) produces with increased complexity and
construction cost. If you can live with the performance
level of either of those, you job is done - just incorporate
their panels & circuitry in your prroduct. Oterwise, you
have to put in the work to search for the best panels
you can get to fit your product, and obtain the best
performance possible from that power source.

Without knowing how much power is available, it is impossible
to say how long it will take to charge a cell, nor can the
charging circuit be designed for best performance.

IIRC, no one has told you to do that work - identifying
the panels - in the various threads, posts and replies since
you started looking for an answer. Of course, I may have
missed it, so if you have identified the panels, how much
charging power is available to work with?

Ed
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:kOGdnVPS95_Nuf7VnZ2dnUVZ_hSdnZ2d@earthlink.com...
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:

I think you've gone down a path that may be counter productive.
First: The amount of power you will get from the solar panel
will depend predominantly on how much surface area you can get
exposed to the sun. You can include instructions to the
consumer concerning installation for maximum exposure, but
the only factor _you_ can control is the surface area.

What does that mean at this point? You know the size of what
you are building, so _you_ need to find solar cells that
will fit that area. *That* selection will dictate how much
power the design will have available, and it will be a range
from minimum (0 on a cloudy day) to maximum. The amount of
power available from the panel will vary throughout the day.

Only when you know how much power will be available in a
typical *week* can you properly design the electronics.

So, post again once you have found a solar panel (or
combination of panels) that will fit the device you are
making. How much power will be available to work with
under the "typical" conditions of your intended market?

You want something simple and better than a typical solar
powered garden light. So do I - and I also want cheap
oil. Neither is generally available these days. You
can maximize what a typical solar powered garden light
(like cat# SPL-09 at http://www.allelectronics.com/ see
also cat# SPL-05) produces with increased complexity and
construction cost. If you can live with the performance
level of either of those, you job is done - just incorporate
their panels & circuitry in your prroduct. Oterwise, you
have to put in the work to search for the best panels
you can get to fit your product, and obtain the best
performance possible from that power source.

Without knowing how much power is available, it is impossible
to say how long it will take to charge a cell, nor can the
charging circuit be designed for best performance.

IIRC, no one has told you to do that work - identifying
the panels - in the various threads, posts and replies since
you started looking for an answer. Of course, I may have
missed it, so if you have identified the panels, how much
charging power is available to work with?

Ed


Actually, the initial consideration was finding how much brightness would
be enough, and which LEDs (and/or combination thereof) will provide it.
From there, it goes backwards to find out how to run them off of a
*maximum* of four 1.2V NiMH batteries. From there, working backwards
again, is the charge controller IC - finding the one that will charge,
and keep from overcharging, 3 to 4 of the batteries. THe solar cells
(not panels, just cells) is actually the last thing. WHat I'm trying to
figure out is whether I should have the solar cells producing the same
total voltage as that which the batteries will have (3.6V for three of
them, 4.8V for 4); since I've learned that NiMH are supposed to be fast-
charged rather than trickle-charged, I'm tryign to figure whether solar
cell amperage is more important for doing that, with voltage being
insignificant, or what.

Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris
Click to expand...

The problem is total energy input vs. requirements. You can't get more
joules out of the system than you put in, so you need to figure out how many
joules you'll use. How long will the lights be expected to stay on? How much
power will the lights consume while they are on? The product of those gives
the energy required.

Current solar technology gives you between 3% and 17% efficiency. According
to Wikipedia, the irradiance of the earth averages out to 342W/m/m over a 24
hour period. So, you can get an average of 5MJ/Day from the most efficient 1
m^2 panel you can get. Not bad. However, the panel would need to track the
sun to get maximal efficiency. Without that, you get 1/5 of the energy out.
Hmm. So, 1MJ/Day. Still not bad. Sadly, your panel probably isn't a square
meter. Lets say 1/10 of a meter on a side, right? Then that is 1/100 of a
square meter, so you now have 1e4J/Day. Still OK. However, suppose you have
a bit of shade? My solar panels for my garden lights only get direct
sunlight about 30% of the day. So, lets say 1/2, so now 5e3J/Day. What about
dirt? Another 50%, so now 2.5e3J/Day. This is with the best solar panels
that are available. You'll probably get the 3% variety, unfortunately. So,
adjust down to 18% of the prior, to 441J/Day. That seems closer to what I
expected, unless I got the math wrong.

Ok, now, how much energy do you want to expend? 5W for 4 hours? Hmm, that is
5 * 3600 * 4 = 72kJ per day. Yikes! That is more than 100 times what you'll
get with the little 4x4 solar panel above.

These are ballpark figures. However, they suggest that you are probably only
going to be able to get, at most 1kJ/Day out of the panel, so your lamp will
need to be much lower power. Lets go with something more realistic, like two
20mA white LEDs. Each LED requires about 3.5V forward voltage, so the power
requirement of the duo is 0.1W. So, given you have 1kJ/Day coming in, you
can run them for 10,000 seconds, which is 2.8 hours. Not too bad. That seems
closer to the garden lights I have in my yard.

Regards,
Bob Monsen
 
Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:


Kris Krieger wrote:

Peter Bennett <peterbb@somewhere.invalid> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@news.supernews.com:



On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@dowmuff.in
wrote:



"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@giganews.com:



May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to
be easier to deal with, but these units are going into things that
I'll (hopefully!) be selling, so I need to make it all as easy as
possible, and I know that people can buy the NiMH batteries pretty
easily. That's the only reason I've sort-of "fixated" on them.
THat, and it's easy to get the mA ratings that will drive the LEDs I
want to use (found one that uses 20 mA, and 3.4V average, but gives
out an amazing (to me) average of 18,000micro-candela, which is 226
lumens, which is a bit more than is given off by a 20-watt
incandescent bulb (220 lumens). With the LED driver (I think it was
you who'd recommended those), that should work out well and I could,
I think, use two such LEDs, which should be about the lumens
produced bya 40 watt incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference
running off of anything other than NiCad, NiMH, or Lithium-Ion
batteries,so my impression was that those are the only two that have
both enough voltage, and generate enough current, to run the
drivers. I've also used store- bought solar lights, which had
either NiCad or NiMH (depending upon th etype), so I know those will
work when left outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about
them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery
is lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid
batteries are almost certainly not a consideration. I'm not aware of
any lead-acid batteries in a "dry cell" format.



AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside
of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries
will be just the normal NiMH things that pop into regular
ol' solar garden/accent lights. Since the betteries will
eventually need to be replaced, I'd like them to be things
that people can find very easily and that don't cost an arm
and a leg. Someone (Tom B.?) had recommended an LED driver,
and I've been looking around at otehrs as well (mainly to
read teh application notes and datasheets and whatnot so as
to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier
plus an LED driver (in case it'd be helpful to anyone else,
the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form
a
combination battery+solar-cell charging+battery management
circuit.

I know that I can build a super-simple unit that will drive
one
normal-brightness LED; I found a few different schematics for
simple low-brightness units, and the simplest are little
more tahn a solar cell, diode, battery, resistor, and LED,
with no sort of overcharge protection or any other
accomidation for any special needs that one or another sort
of battery might have. THey're robust, but they won't work
for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much
light as does a smooth clear enclosure (I think the
commercial ones are acrylic). Also, the potential customers
and sales venues I've polled all have the same complaint:
commercial solar lights are too dim. Ultra-cheap is not
part of my equation here - I am most definitely not going
seeking to try to compete with the "$5-$9 light" market;
Wal-Mart has that very well-covered. Rather, the units,
being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the
time and skill it takes to construct a particular design. I
do want to squeeze as many Lumens as possible out of a
*maximum* of 4 NiMH batteries, to be charged during the
daytime by solar cells, plus I want to charge the batteries
in about 5-6 hours in good sunlight - and that last part is
why I'm looking into overcharge protection, since it's
likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to
the relationship between the solar cell(s) V/mA rating, and the
battery V/mA rating - I don't want to "cook" the batteries.

TIA!

- Kris





I think you've gone down a path that may be counter productive.
First: The amount of power you will get from the solar panel
will depend predominantly on how much surface area you can get
exposed to the sun. You can include instructions to the
consumer concerning installation for maximum exposure, but
the only factor _you_ can control is the surface area.

What does that mean at this point? You know the size of what
you are building, so _you_ need to find solar cells that
will fit that area. *That* selection will dictate how much
power the design will have available, and it will be a range
from minimum (0 on a cloudy day) to maximum. The amount of
power available from the panel will vary throughout the day.

Only when you know how much power will be available in a
typical *week* can you properly design the electronics.

So, post again once you have found a solar panel (or
combination of panels) that will fit the device you are
making. How much power will be available to work with
under the "typical" conditions of your intended market?

You want something simple and better than a typical solar
powered garden light. So do I - and I also want cheap
oil. Neither is generally available these days. You
can maximize what a typical solar powered garden light
(like cat# SPL-09 at http://www.allelectronics.com/ see
also cat# SPL-05) produces with increased complexity and
construction cost. If you can live with the performance
level of either of those, you job is done - just incorporate
their panels & circuitry in your prroduct. Oterwise, you
have to put in the work to search for the best panels
you can get to fit your product, and obtain the best
performance possible from that power source.

Without knowing how much power is available, it is impossible
to say how long it will take to charge a cell, nor can the
charging circuit be designed for best performance.

IIRC, no one has told you to do that work - identifying
the panels - in the various threads, posts and replies since
you started looking for an answer. Of course, I may have
missed it, so if you have identified the panels, how much
charging power is available to work with?

Ed



Actually, the initial consideration was finding how much brightness would
be enough, and which LEDs (and/or combination thereof) will provide it.
From there, it goes backwards to find out how to run them off of a
*maximum* of four 1.2V NiMH batteries. From there, working backwards
again, is the charge controller IC - finding the one that will charge,
and keep from overcharging, 3 to 4 of the batteries. THe solar cells
(not panels, just cells) is actually the last thing. WHat I'm trying to
figure out is whether I should have the solar cells producing the same
total voltage as that which the batteries will have (3.6V for three of
them, 4.8V for 4); since I've learned that NiMH are supposed to be fast-
charged rather than trickle-charged, I'm tryign to figure whether solar
cell amperage is more important for doing that, with voltage being
insignificant, or what.

Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris
Click to expand...
As you said, you are working backwards. You don't yet understand
that doing it that way can result in a specification for cells
that are "unobtanium".

Ed
 
Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:8vU8k.58$BR.4@trnddc06:


Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:


[edited]


Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris

As you said, you are working backwards. You don't yet understand
that doing it that way can result in a specification for cells
that are "unobtanium".

Ed



"Unobtanium"??, it's a modest LED night-lamp, not an airport beacon :p

I *already* know the batteries and their output, and the input needed by
the LED driver and what it will output to run the LEDs (which will run off
the batteries at night) - those are not the problem.

To charge my 4 little 1.2V AA NiMH batteries, I have seen the following
solar cells (and more, this isn't an all-inclusive list):
0.5V, 200mA
0.5V, 450mA
0.5V, 800mA
0.5V, 2000mA
1V, 200mA
2V, 200mA
3V, 400mA
4V, 25mA
etc.

I also know that, depending upon how I connect cells, I can up the Volts or
up the Amps, or both if it's a series-parellel combination. The biggest Q.
is the volts. I read that, using a 5V solar cell, charging time would be
the battery mA divided by the cell mA, but what if it was a 2V cell, or a
.5V cell?

Well, I'll write to Maxim, since it's their components I'm interested in.
They can prob. best tell me the input I need for the battery-management IC.

- Kris
Click to expand...
Sorry, Kris, but in terms of the necessary specifications,
you have posted nothing useful to make an informed design
decision. That is not an attack on you, it is just that
you are working in an area that is new to you.

Netting your problem out, you want to drive an unknown
(in terms of voltage and current) load for an unknown amount
of time with an unknown number (but less than 5) NiMh AA
cells of unknown capacity, said NiMh's to be charged with an
unknown number of solar cells of unknown capacity in an
unknown environment.

The key design question is: how much input power will be
available? The surface area of your device that will
be exposed to direct sunlight and that you are willing to
dedicate to solar cells will determine that, in terms of
the maximum that can be achieved. Obviously, the power
will be less if the device is in the shade or the cells
receive less than full sunlight for some other reason.

You are here asking for help - but _ONLY_ you can answer
that question.

If we don't know how much power is available, it is not
possible to say definitively if your idea is even feasible,
let alone specify how to do it.

Ed
 
Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:rfd9k.9$dz.4@trndny01:


Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:8vU8k.58$BR.4@trnddc06:



Kris Krieger wrote:


ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:u3E8k.54$WJ.12@trnddc04:


[edited]



Only *after* I know all that, can I select the specific cells, and
configuration therof...

- Kris

As you said, you are working backwards. You don't yet understand
that doing it that way can result in a specification for cells
that are "unobtanium".

Ed



"Unobtanium"??, it's a modest LED night-lamp, not an airport beacon
:p

I *already* know the batteries and their output, and the input needed
by the LED driver and what it will output to run the LEDs (which will
run off the batteries at night) - those are not the problem.

To charge my 4 little 1.2V AA NiMH batteries, I have seen the
following solar cells (and more, this isn't an all-inclusive list):
0.5V, 200mA
0.5V, 450mA
0.5V, 800mA
0.5V, 2000mA
1V, 200mA
2V, 200mA
3V, 400mA
4V, 25mA
etc.

I also know that, depending upon how I connect cells, I can up the
Volts or up the Amps, or both if it's a series-parellel combination.
The biggest Q. is the volts. I read that, using a 5V solar cell,
charging time would be the battery mA divided by the cell mA, but
what if it was a 2V cell, or a .5V cell?

Well, I'll write to Maxim, since it's their components I'm interested
in. They can prob. best tell me the input I need for the
battery-management IC.

- Kris


Sorry, Kris, but in terms of the necessary specifications,
you have posted nothing useful to make an informed design
decision. That is not an attack on you, it is just that
you are working in an area that is new to you.


I found teh answer to my question here:
http://www.solar-world.com/SolarMini-Panels&Motors.htm

Specifically:
"...the solar operating voltage must be higher than the battery voltage..."

That was all I was asking.


Netting your problem out, you want to drive an unknown
(in terms of voltage and current) load


The Q was not about the "load", it was *simply* and *specifically*, I'll
repeat, this:
Given NiMH batteries, size AA, rated at 1.2V and 1500mA, what would I need
in terms of soalr cell output to charge tem using a battery
charge/control/protection IC (the Maxim DS2715).

I don't understand what in that is "unknown" or otherwise unspecific.



for an unknown amount
of time with an unknown number (but less than 5)


I'd repeatedly specified "between 3 and 4"...


NiMh AA
cells of unknown capacity, said NiMh's to be charged with an
unknown number of solar cells of unknown capacity in an
unknown environment.


*Of course* the number of solar cells was unknown - anyway, the "number" is
not relevant, what is relevant is the *output*, and my Q. was specifically
about *needed output*, so that I could go back to the catalogues, look at
the sizes/ratings, and determine what I'd need in terms of numbers, and
arrangements.

As for environment, not relevant to teh question - the question dealt with
ratings. I'm not so stupid that I think SOLAR cells will "work" at night
or in deep shade, or that they generate the same power on cloudy days as on
bright, sunny days. But I did not ask about differnces in output on cloudy
versus sunny days, I asked, based purely upon ratings, about charging a
specifically-described battery.



The key design question is: how much input power will be
available?


No, the key design question was, as Tom Biasi had notd when I first began
asking my Solar Light questions, was:
"One place to start would be to determine how much illumination you need.
Find LEDs that can give you that. What voltage and current do you need to
power the LEDs for the period of time that you would like? What battery
will provide that?"

The question I asked in this thread was the final question of Tom's initial
input:
"What solar arrangement can charge the battery in the time that you want?"

I didn't know how to do the math. Now I think I might know it.


The surface area of your device that will
be exposed to direct sunlight and that you are willing to
dedicate to solar cells will determine that, in terms of
the maximum that can be achieved.


THat wasn't what I was asking. I was asking what output (from the cells)
I'd need to charge the specified batteries. I didn't ask about sruface
area - I alreasy knew that, which is why I listed several of the available
solar cell outputs, which I'd selected becasue their footprint fell within
the size limits I wanted. So the surface area was not the concern and was
not at all related to the simple question I was asking.


Obviously, the power
will be less if the device is in the shade or the cells
receive less than full sunlight for some other reason.


Not to be rude, but, duuuuuuuuh... Again, tho', not what I was asking.


You are here asking for help - but _ONLY_ you can answer
that question.


Well, between all the different solar-cell-related websites, electronics-
related websites, the Tech Support folk at Maxim, and so on, yeah, you're
right, I finally *am* answering the question I'd asked in this thread about
what Solar Cell output is required to charge the specified batteries.


If we don't know how much power is available, it is not
possible to say definitively if your idea is even feasible,
let alone specify how to do it.



You can't figure out whether it's feasible to run 4 regular (i.e. discrete
5mm dome) LEDs off of a solar-charged battery pack of 3 NiMH AA 1500mA
batteries?, or up to 6 (same type) LEDs off a solar-charged battery pack of
3 or 4 NiMH AA 1500mA batteries?, or what output V and mA you'd need from
solar cells (obviously placed in the sun :p ) to charge even one
1.2V/1500mA NiMH battery? You can't even determine whether that is
*possible*?

OK, whatever...


Thankfully, there were a couple of folks who were very helpful and got me
going in the right direction, whom I'm thanking in a separate post.

- Kris
Click to expand...

Sigh. Here's an analogy that may make it clear to you.
Designing a solar system is like planning a budget.
You cannot say how much money you will have to spend
if you don't know what your income will be. You can't
even tell if a particular purchase is feasable if you
don't know how much will be available.

The energy you can get from the solar cells over a period
of time is your "energy income". You store that "income"
in your batteries, and spend it later on. If you don't
know how much energy is available, you can't tell if a
particular expenditure of energy is feasible. You can't
even tell how much energy you will have to put into the
batteries, so you can't tell what battery capacity
will best fit your design.

Ed
 
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