Charging A Lead Acid Battery

James Beck wrote:
In article <Kfktj.9$wK4.1@trndny01>, ehsjr@bellatlantic.net says...

James Beck wrote:

In article <ddac6f54-dd64-45ac-bd54-
3f43655f468d@i7g2000prf.googlegroups.com>, redbelly98@yahoo.com says...


On Feb 14, 10:29 am, James Beck <j...@reallykillersystems.com> wrote:


In article <4b78e703-68e3-4822-b318-a1cd9fb8ff04
@e6g2000prf.googlegroups.com>, redbell...@yahoo.com says...





On Feb 13, 9:09 am, James Beck <j...@reallykillersystems.com> wrote:


In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbell...@yahoo.com says...

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim

What about all the voltage drops between the wall wart and battery:

1 to 1.5V drop-out voltage of regulator
1.2-1.3V between regulator "out" and "adj" pins (across 2.5R resistor)
0.6-0.7V diode drop across 1N400x

Mark

Build it and try.
As the current drops I'll bet you don't get the drops you think,
especially across the resistor used for the current sense. You are also
assuming that the 9V wall wart is regulated. A cheap unregulated wall
wart that is a "nominal" 9V under X% of load will usually be quite a bit
higher than you expect as the load drops. A CV float charger could be
used with any wall wart that is the V drop of the regulator or higher.

You make good points, I had been thinking simplistically about the
voltage drops at 500 mA.

Mark


Mind you, you can have problems with a simple float charger too.
If you rely on the regulator's current and thermal limit to hold the
current under a certain level it will get HOT. I also had a National
part that the info in the datasheet didn't match real life and we blew
out a few wall warts before I caught it.

Jim

I'm amazed at this thread. The "very simple charger"
I diagrammed *stinks* if _used_ as a float charger, which
is what you were de facto discussing when you talked about
forgetting and leaving the batteries on it too long.
If used that way, it *might* prevent damage to the
batteries by the cumulative voltage drop which you and
Mark have discussed, but it is the *wrong* tool for
that job, and the wrong usage of the tool.

I am glad to see that you are taking the discussion to a
float charger. I'm responding below because you mentioned
relying on the chip's thermasl & current limits and that
some wall warts blew.

It would be poor practice to design a float charger that
relied on the regulator's current and thermal limit to
hold the current under a certain level, assuming by
"the regulator's" you mean the IC chip. Those things - the
current and thermal limit - only indirectly hold the
current under a certain level. They are design maximums
for the chip, not for whatever load the chip is feeding.


When the datasheet and app note show the part being used in this very
way, I would assume the manufacturer has rated the part as such.
Wouldn't you?
Click to expand...
That would depend on the datasheet, but in general, yes, I would
probably trust it.

The circuit design needs to keep the current under the
maximum rating of the chip under worst case conditions.
The designer specifies a heat sink and/or a design that
keeps the chip temperature below the maximum spec. He/she
needs to ensure that any other limitations (eg Vin-Vout
rating) for the chip are adhered to.

The IC had a built in current limit and, like I mentioned above,
National had several design examples that used over current protection
as an integral part of the design. The problem was that the limit was
wrong on the datasheet and in the app note. 1 - 1.2A was suppose to be
min to max range, it turned out to be 1.9 - 2.2A or some such.


A float charger may not need current limiting for normal
conditions, but it does for worst case: a shorted battery.
That's where a float charger without current limiting fails.
Under normal conditions, the battery will limit the current
drawn as the battery voltage increases, and additional
limiting may not be required. Still, you need to consider
the whole circuit. You mentioned that you had some blown wall
warts. If the batteries require more than the wall wart can
deliver, that may be a specification rather than circuit
problem. (ie use a bigger wall wart) If they blew because the
circuit relied on the chip to shut down when it got too hot,
that's a design issue. You indicated an error in the National
datasheet was the cause - do you still have the details? It
could be helpful to know which part and what spec was wrong.

Ed



The part was a National LM2941CT and the wall warts blew because the
current limit of the IC was wrong on the datasheet. I didn't want to go
to a bigger wall wart, we didn't want to charge at a greater rate
anyway. I'm sure (hope) they have corrected the datasheets by now, but
the funny thing was one of the applications engineers sent me a "fix"
for this problem that entailed a small sense resistor and a transistor
to implement a half assed current regulator and they had that wrong too.
It was set up to pull the feedback pin lower as the current increased,
that would increase the voltage out as the current demand increased
causing the system to slam hard against the + rail. I think they were
relying on the internal current limiting to do its' thing at the level
the datasheet had listed erroneously. I had already fixed the problem
myself. The point was I didn't want to add complexity to the design,
that was why I chose the part in the first place, but I ended up adding
parts anyway.

As a side note, they have changed the datasheet, but there is still one
hold over. In the application notes they still show a "1A Coil Driver"
or some such, that is suppose to limit the current to 1A using the
internal current regulation of the part. Well, it won't do it.

Jim
Click to expand...
Thanks, that's good information to know. Also as a side note,
I've read comments by others who are skeptical, or suspicious
or uncertain (searching for the right term, not sure what
it is) of LDO's in general because they've been burned
by them, too.

Ed


 
In article <Kfktj.9$wK4.1@trndny01>, ehsjr@bellatlantic.net says...
James Beck wrote:
In article <ddac6f54-dd64-45ac-bd54-
3f43655f468d@i7g2000prf.googlegroups.com>, redbelly98@yahoo.com says...

On Feb 14, 10:29 am, James Beck <j...@reallykillersystems.com> wrote:

In article <4b78e703-68e3-4822-b318-a1cd9fb8ff04
@e6g2000prf.googlegroups.com>, redbell...@yahoo.com says...




On Feb 13, 9:09 am, James Beck <j...@reallykillersystems.com> wrote:

In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbell...@yahoo.com says...

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim

What about all the voltage drops between the wall wart and battery:

1 to 1.5V drop-out voltage of regulator
1.2-1.3V between regulator "out" and "adj" pins (across 2.5R resistor)
0.6-0.7V diode drop across 1N400x

Mark

Build it and try.
As the current drops I'll bet you don't get the drops you think,
especially across the resistor used for the current sense. You are also
assuming that the 9V wall wart is regulated. A cheap unregulated wall
wart that is a "nominal" 9V under X% of load will usually be quite a bit
higher than you expect as the load drops. A CV float charger could be
used with any wall wart that is the V drop of the regulator or higher.

You make good points, I had been thinking simplistically about the
voltage drops at 500 mA.

Mark


Mind you, you can have problems with a simple float charger too.
If you rely on the regulator's current and thermal limit to hold the
current under a certain level it will get HOT. I also had a National
part that the info in the datasheet didn't match real life and we blew
out a few wall warts before I caught it.

Jim

I'm amazed at this thread. The "very simple charger"
I diagrammed *stinks* if _used_ as a float charger, which
is what you were de facto discussing when you talked about
forgetting and leaving the batteries on it too long.
If used that way, it *might* prevent damage to the
batteries by the cumulative voltage drop which you and
Mark have discussed, but it is the *wrong* tool for
that job, and the wrong usage of the tool.

I am glad to see that you are taking the discussion to a
float charger. I'm responding below because you mentioned
relying on the chip's thermasl & current limits and that
some wall warts blew.

It would be poor practice to design a float charger that
relied on the regulator's current and thermal limit to
hold the current under a certain level, assuming by
"the regulator's" you mean the IC chip. Those things - the
current and thermal limit - only indirectly hold the
current under a certain level. They are design maximums
for the chip, not for whatever load the chip is feeding.
Click to expand...
When the datasheet and app note show the part being used in this very
way, I would assume the manufacturer has rated the part as such.
Wouldn't you?

The circuit design needs to keep the current under the
maximum rating of the chip under worst case conditions.
The designer specifies a heat sink and/or a design that
keeps the chip temperature below the maximum spec. He/she
needs to ensure that any other limitations (eg Vin-Vout
rating) for the chip are adhered to.
The IC had a built in current limit and, like I mentioned above,
Click to expand...
National had several design examples that used over current protection
as an integral part of the design. The problem was that the limit was
wrong on the datasheet and in the app note. 1 - 1.2A was suppose to be
min to max range, it turned out to be 1.9 - 2.2A or some such.

A float charger may not need current limiting for normal
conditions, but it does for worst case: a shorted battery.
That's where a float charger without current limiting fails.
Under normal conditions, the battery will limit the current
drawn as the battery voltage increases, and additional
limiting may not be required. Still, you need to consider
the whole circuit. You mentioned that you had some blown wall
warts. If the batteries require more than the wall wart can
deliver, that may be a specification rather than circuit
problem. (ie use a bigger wall wart) If they blew because the
circuit relied on the chip to shut down when it got too hot,
that's a design issue. You indicated an error in the National
datasheet was the cause - do you still have the details? It
could be helpful to know which part and what spec was wrong.

Ed
Click to expand...
The part was a National LM2941CT and the wall warts blew because the
current limit of the IC was wrong on the datasheet. I didn't want to go
to a bigger wall wart, we didn't want to charge at a greater rate
anyway. I'm sure (hope) they have corrected the datasheets by now, but
the funny thing was one of the applications engineers sent me a "fix"
for this problem that entailed a small sense resistor and a transistor
to implement a half assed current regulator and they had that wrong too.
It was set up to pull the feedback pin lower as the current increased,
that would increase the voltage out as the current demand increased
causing the system to slam hard against the + rail. I think they were
relying on the internal current limiting to do its' thing at the level
the datasheet had listed erroneously. I had already fixed the problem
myself. The point was I didn't want to add complexity to the design,
that was why I chose the part in the first place, but I ended up adding
parts anyway.

As a side note, they have changed the datasheet, but there is still one
hold over. In the application notes they still show a "1A Coil Driver"
or some such, that is suppose to limit the current to 1A using the
internal current regulation of the part. Well, it won't do it.

Jim
 
James Beck wrote:
In article <ddac6f54-dd64-45ac-bd54-
3f43655f468d@i7g2000prf.googlegroups.com>, redbelly98@yahoo.com says...

On Feb 14, 10:29 am, James Beck <j...@reallykillersystems.com> wrote:

In article <4b78e703-68e3-4822-b318-a1cd9fb8ff04
@e6g2000prf.googlegroups.com>, redbell...@yahoo.com says...




On Feb 13, 9:09 am, James Beck <j...@reallykillersystems.com> wrote:

In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbell...@yahoo.com says...

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim

What about all the voltage drops between the wall wart and battery:

1 to 1.5V drop-out voltage of regulator
1.2-1.3V between regulator "out" and "adj" pins (across 2.5R resistor)
0.6-0.7V diode drop across 1N400x

Mark

Build it and try.
As the current drops I'll bet you don't get the drops you think,
especially across the resistor used for the current sense. You are also
assuming that the 9V wall wart is regulated. A cheap unregulated wall
wart that is a "nominal" 9V under X% of load will usually be quite a bit
higher than you expect as the load drops. A CV float charger could be
used with any wall wart that is the V drop of the regulator or higher.

You make good points, I had been thinking simplistically about the
voltage drops at 500 mA.

Mark


Mind you, you can have problems with a simple float charger too.
If you rely on the regulator's current and thermal limit to hold the
current under a certain level it will get HOT. I also had a National
part that the info in the datasheet didn't match real life and we blew
out a few wall warts before I caught it.

Jim
Click to expand...
I'm amazed at this thread. The "very simple charger"
I diagrammed *stinks* if _used_ as a float charger, which
is what you were de facto discussing when you talked about
forgetting and leaving the batteries on it too long.
If used that way, it *might* prevent damage to the
batteries by the cumulative voltage drop which you and
Mark have discussed, but it is the *wrong* tool for
that job, and the wrong usage of the tool.

I am glad to see that you are taking the discussion to a
float charger. I'm responding below because you mentioned
relying on the chip's thermasl & current limits and that
some wall warts blew.

It would be poor practice to design a float charger that
relied on the regulator's current and thermal limit to
hold the current under a certain level, assuming by
"the regulator's" you mean the IC chip. Those things - the
current and thermal limit - only indirectly hold the
current under a certain level. They are design maximums
for the chip, not for whatever load the chip is feeding.

The circuit design needs to keep the current under the
maximum rating of the chip under worst case conditions.
The designer specifies a heat sink and/or a design that
keeps the chip temperature below the maximum spec. He/she
needs to ensure that any other limitations (eg Vin-Vout
rating) for the chip are adhered to.

A float charger may not need current limiting for normal
conditions, but it does for worst case: a shorted battery.
That's where a float charger without current limiting fails.
Under normal conditions, the battery will limit the current
drawn as the battery voltage increases, and additional
limiting may not be required. Still, you need to consider
the whole circuit. You mentioned that you had some blown wall
warts. If the batteries require more than the wall wart can
deliver, that may be a specification rather than circuit
problem. (ie use a bigger wall wart) If they blew because the
circuit relied on the chip to shut down when it got too hot,
that's a design issue. You indicated an error in the National
datasheet was the cause - do you still have the details? It
could be helpful to know which part and what spec was wrong.

Ed
 
In article <ddac6f54-dd64-45ac-bd54-
3f43655f468d@i7g2000prf.googlegroups.com>, redbelly98@yahoo.com says...
On Feb 14, 10:29 am, James Beck <j...@reallykillersystems.com> wrote:
In article <4b78e703-68e3-4822-b318-a1cd9fb8ff04
@e6g2000prf.googlegroups.com>, redbell...@yahoo.com says...



On Feb 13, 9:09 am, James Beck <j...@reallykillersystems.com> wrote:
In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbell...@yahoo.com says...

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim

What about all the voltage drops between the wall wart and battery:

1 to 1.5V drop-out voltage of regulator
1.2-1.3V between regulator "out" and "adj" pins (across 2.5R resistor)
0.6-0.7V diode drop across 1N400x

Mark

Build it and try.
As the current drops I'll bet you don't get the drops you think,
especially across the resistor used for the current sense. You are also
assuming that the 9V wall wart is regulated. A cheap unregulated wall
wart that is a "nominal" 9V under X% of load will usually be quite a bit
higher than you expect as the load drops. A CV float charger could be
used with any wall wart that is the V drop of the regulator or higher.

You make good points, I had been thinking simplistically about the
voltage drops at 500 mA.

Mark

Mind you, you can have problems with a simple float charger too.
Click to expand...
If you rely on the regulator's current and thermal limit to hold the
current under a certain level it will get HOT. I also had a National
part that the info in the datasheet didn't match real life and we blew
out a few wall warts before I caught it.

Jim
 
D

Dave.H

Guest
How would I go about building a charger for a lead acid battery.
Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
flashlight lanterns, but as far as I can tell they don't sell the
charger.

Battery
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
(CAT. NO. SB2498)

Thanks
 
"Dave.H"
How would I go about building a charger for a lead acid battery.
Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
flashlight lanterns, but as far as I can tell they don't sell the
charger.

Battery
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
(CAT. NO. SB2498)
Click to expand...

** N19309




....... Phil
 
In article
<135de534-4250-4e24-a05b-dbe9337f22bb@n20g2000hsh.googlegroups.com>,
"Dave.H" <the1930s@googlemail.com> wrote:

How would I go about building a charger for a lead acid battery.
Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
flashlight lanterns, but as far as I can tell they don't sell the
Click to expand...
They have a truly irritating number of ads
(site-loads-like-sightless-burrowing-rodent-posteriors), but EDN has an
extensive archive of "design ideas" that can be useful to browse through.

Uses a dedicated IC, and is a 4 cell rather than 3 cell charger:

http://www.edn.com/contents/images/121103di.pdf


Here's one from a bicycle enthusiast - not terribly sophisticated, but should
work:

http://www.myra-simon.com/bike/charger.html

Here's a more complex one from a Ham Radio enthusiast:

http://www.geocities.com/vk3em/sla-charger/PDFs/SLA-ChargerMkIIManualV1-3.PDF

--
Cats, coffee, chocolate...vices to live by
 
Dave.H wrote:
How would I go about building a charger for a lead acid battery.
Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
flashlight lanterns, but as far as I can tell they don't sell the
charger.

Battery
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
(CAT. NO. SB2498)

Thanks
Click to expand...

Very simple charger:

-----
+9 ------Vin|LM317|Vout---+
----- |
Adj [2.5R]
| | 1N400x
+----------+---->|---+
| +
[Batt]
|
Gnd --------------------------------+

You need a 9 or 12 volt wall wart capable of
at least 500 mA, an LM317 chip, a heat sink for
the chip, and 2 5 ohm, 1 watt (at least) resistors
in parallel to make the 2.5 ohm resistance, and
a 1N400x diode. Charge for 12-14 hours.

Ed
 
On Tue, 12 Feb 2008 01:30:43 GMT, ehsjr <ehsjr@bellatlantic.net> wrote:

:Dave.H wrote:
:> How would I go about building a charger for a lead acid battery.
:> Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:> flashlight lanterns, but as far as I can tell they don't sell the
:> charger.
:>
:> Battery
:> http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:> (CAT. NO. SB2498)
:>
:> Thanks
:
:
:Very simple charger:
:
: -----
: +9 ------Vin|LM317|Vout---+
: ----- |
: Adj [2.5R]
: | | 1N400x
: +----------+---->|---+
: | +
: [Batt]
: |
: Gnd --------------------------------+
:
:You need a 9 or 12 volt wall wart capable of
:at least 500 mA, an LM317 chip, a heat sink for
:the chip, and 2 5 ohm, 1 watt (at least) resistors
:in parallel to make the 2.5 ohm resistance, and
:a 1N400x diode. Charge for 12-14 hours.
:
:Ed


While that might work, it is a constant current source more appropriate to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf
 
On Mon, 11 Feb 2008 01:22:00 -0800 (PST), "Dave.H" <the1930s@googlemail.com>
wrote:

:How would I go about building a charger for a lead acid battery.
:Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:flashlight lanterns, but as far as I can tell they don't sell the
:charger.
:
:Battery
:http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:(CAT. NO. SB2498)
:
:Thanks


There are several suitable Jaycar 6V SLA chargers.
MB3516, MB3525 for example.
 
There are several suitable Jaycar 6V SLA chargers.
MB3516, MB3525 for example.
Click to expand...
I noticed that, right after I sent the original post. I think the
reason I missed it is because I was only looking in the "Battery
Charger" section. I will use the 6V 500 mA (MB3516) one.
 
Ross Herbert wrote:
On Tue, 12 Feb 2008 01:30:43 GMT, ehsjr <ehsjr@bellatlantic.net> wrote:

:Dave.H wrote:
:> How would I go about building a charger for a lead acid battery.
:> Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:> flashlight lanterns, but as far as I can tell they don't sell the
:> charger.
:
:> Battery
:> http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:> (CAT. NO. SB2498)
:
:> Thanks
:
:
:Very simple charger:
:
: -----
: +9 ------Vin|LM317|Vout---+
: ----- |
: Adj [2.5R]
: | | 1N400x
: +----------+---->|---+
: | +
: [Batt]
: |
: Gnd --------------------------------+
:
:You need a 9 or 12 volt wall wart capable of
:at least 500 mA, an LM317 chip, a heat sink for
:the chip, and 2 5 ohm, 1 watt (at least) resistors
:in parallel to make the 2.5 ohm resistance, and
:a 1N400x diode. Charge for 12-14 hours.
:
:Ed


While that might work, it is a constant current source more appropriate to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf
Click to expand...

Read Jaycar's own description for the specific battery.
It states: "Charge current 500mA for 10- 14 hrs"

There is no "might" about it (as in your statement
"While that might work"). CC charging *does* work on SLAs.
Note that this is not comparing CC charging to other
methods. It is correcting the "might" to "does".

If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.

Ed
 
"ehsjr"
Ross Herbert wrote:

While that might work, it is a constant current source more appropriate
to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better
still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf


Read Jaycar's own description for the specific battery.
It states: "Charge current 500mA for 10- 14 hrs"
Click to expand...

** Jaycar are a mob of dumb parts grocers - they are experts on NOTHING
!!


There is no "might" about it (as in your statement
"While that might work").
Click to expand...

** No - it will not work as a good charger should.

It will destroy the battery.


CC charging *does* work on SLAs.
Click to expand...

** It destroys them by overcharging - you ASS.


If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.
Click to expand...

** YOU are a good match for the creeps at Jaycar.

In the KNOW NOTHING stakes.



....... Phil
 
On Feb 12, 6:50 pm, ehsjr <eh...@bellatlantic.net> wrote:
Ross Herbert wrote:
On Tue, 12 Feb 2008 01:30:43 GMT, ehsjr <eh...@bellatlantic.net> wrote:

:Dave.H wrote:
:> How would I go about building a charger for a lead acid battery.
:> Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:> flashlight lanterns, but as far as I can tell they don't sell the
:> charger.
:
:> Battery
:>http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:> (CAT. NO. SB2498)
:
:> Thanks
:
:
:Very simple charger:
:
:               -----
:  +9 ------Vin|LM317|Vout---+
:               -----        |
:                Adj      [2.5R]
:                 |          |   1N400x
:                 +----------+---->|---+
:                                      | +
:                                    [Batt]
:                                      |
:  Gnd --------------------------------+
:
:You need a 9 or 12 volt wall wart capable of
:at least 500 mA, an LM317 chip, a heat sink for
:the chip, and 2 5 ohm, 1 watt (at least) resistors
:in parallel to make the 2.5 ohm resistance, and
:a 1N400x diode.  Charge for 12-14 hours.
:
:Ed

While that might work, it is a constant current source more appropriate to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf

Read Jaycar's own description for the specific battery.
It states:  "Charge current 500mA for 10- 14 hrs"

There is no "might" about it (as in your statement
"While that might work").  CC charging *does* work on SLAs.
Note that this is not comparing CC charging to other
methods. It is correcting the "might" to "does".

If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.

Ed- Hide quoted text -

- Show quoted text -
Click to expand...
Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill
 
On Feb 12, 11:14 pm, Bill Bowden <wrongaddr...@att.net> wrote:
On Feb 12, 6:50 pm, ehsjr <eh...@bellatlantic.net> wrote:



Ross Herbert wrote:
On Tue, 12 Feb 2008 01:30:43 GMT, ehsjr <eh...@bellatlantic.net> wrote:

:Dave.H wrote:
:> How would I go about building a charger for a lead acid battery.
:> Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:> flashlight lanterns, but as far as I can tell they don't sell the
:> charger.
:
:> Battery
:>http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:> (CAT. NO. SB2498)
:
:> Thanks
:
:
:Very simple charger:
:
: -----
: +9 ------Vin|LM317|Vout---+
: ----- |
: Adj [2.5R]
: | | 1N400x
: +----------+---->|---+
: | +
: [Batt]
: |
: Gnd --------------------------------+
:
:You need a 9 or 12 volt wall wart capable of
:at least 500 mA, an LM317 chip, a heat sink for
:the chip, and 2 5 ohm, 1 watt (at least) resistors
:in parallel to make the 2.5 ohm resistance, and
:a 1N400x diode. Charge for 12-14 hours.
:
:Ed

While that might work, it is a constant current source more appropriate to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf

Read Jaycar's own description for the specific battery.
It states: "Charge current 500mA for 10- 14 hrs"

There is no "might" about it (as in your statement
"While that might work"). CC charging *does* work on SLAs.
Note that this is not comparing CC charging to other
methods. It is correcting the "might" to "does".

If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.

Ed- Hide quoted text -

- Show quoted text -

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill
Click to expand...
If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that.

Mark
 
In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbelly98@yahoo.com says...
Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
Click to expand...
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim
 
On Feb 13, 9:09 am, James Beck <j...@reallykillersystems.com> wrote:
In article <6194982a-5fc6-406e-b08d-dd15013ba985
@y5g2000hsf.googlegroups.com>, redbell...@yahoo.com says...

Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill

If you forget to turn off a charger like that, it will seriously
overcharge a 6V battery! On the other hand Ed's charger will not do
that

It won't?
It should continue to charge the battery up to the wall wart voltage,
which is still too high if you leave it plugged in too long.
I would, and do, just use a CV source that is set to the float voltage
of the battery. Pick a regulator that has over temp and current
limiting and let it float.

Jim
Click to expand...
What about all the voltage drops between the wall wart and battery:

1 to 1.5V drop-out voltage of regulator
1.2-1.3V between regulator "out" and "adj" pins (across 2.5R resistor)
0.6-0.7V diode drop across 1N400x

Mark
 
"Dave.H" <the1930s@googlemail.com> wrote in message
news:135de534-4250-4e24-a05b-dbe9337f22bb@n20g2000hsh.googlegroups.com...
How would I go about building a charger for a lead acid battery.
Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
flashlight lanterns, but as far as I can tell they don't sell the
charger.

Battery
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
(CAT. NO. SB2498)

Thanks
Click to expand...
If you use a constant current source, make sure it can only rise to the
trickle voltage.

Here is a charger that should work for you:
(view courier)

12V ----o---------------o------.
| | |
.-. | |
| |1k | |
| | | |
'-' 2N2222 | |
| |c |
o------o-----b| |
| | |e |
| | | |c
| | '---b| 2N3055 (may need heat sink)
| | |e
| | |
| | |
| | 2N2222 |
| c| |
z |b-----. --- Your battery
A e| | -
8.1V Zener | | |
| | | |
| | ___ | |
GND------o------o--|___|-o------'
1R 5W
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

This will supply a constant current of 700mA or so until the battery gets up
to about 6.8V, at which time it'll keep the voltage about constant to
trickle charge the battery.

You can affect the current by choosing a different sense resistor. The 1R
resistor is convienient to obtain, but may not be what you want. Typically,
you charge one of these SLA batteries with 500mA, so a 1.2R resistor might
be better. Also, the zener diode is only required if your power supply isn't
regulated. If it is regulated, you can use a pot and adjust the voltage to
about 8V at the wiper instead.

Hang around while you are charging the battery for the first time. If it is
getting hot, use a smaller current. You don't want those SLA batteries to
start outgassing.

Regards,
Bob Monsen
 
Bill Bowden wrote:
On Feb 12, 6:50 pm, ehsjr <eh...@bellatlantic.net> wrote:

Ross Herbert wrote:

On Tue, 12 Feb 2008 01:30:43 GMT, ehsjr <eh...@bellatlantic.net> wrote:

:Dave.H wrote:
:> How would I go about building a charger for a lead acid battery.
:> Jaycar Electronics sells a 5 amp hour 6 volt SLA battery for use in
:> flashlight lanterns, but as far as I can tell they don't sell the
:> charger.
:
:> Battery
:>http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
:> (CAT. NO. SB2498)
:
:> Thanks
:
:
:Very simple charger:
:
: -----
: +9 ------Vin|LM317|Vout---+
: ----- |
: Adj [2.5R]
: | | 1N400x
: +----------+---->|---+
: | +
: [Batt]
: |
: Gnd --------------------------------+
:
:You need a 9 or 12 volt wall wart capable of
:at least 500 mA, an LM317 chip, a heat sink for
:the chip, and 2 5 ohm, 1 watt (at least) resistors
:in parallel to make the 2.5 ohm resistance, and
:a 1N400x diode. Charge for 12-14 hours.
:
:Ed

While that might work, it is a constant current source more appropriate to
charging Ni-Cd or Ni-Mh cells, not a lead acid battery.

LA battery is best charged with a constant voltage source or better still, a
regulated 2 or 3 stage charger.

Read Jaycar's own reference sheet on SLA batteries.
http://www.jaycar.com.au/images_uploaded/slabatts.pdf

Read Jaycar's own description for the specific battery.
It states: "Charge current 500mA for 10- 14 hrs"

There is no "might" about it (as in your statement
"While that might work"). CC charging *does* work on SLAs.
Note that this is not comparing CC charging to other
methods. It is correcting the "might" to "does".

If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.

Ed- Hide quoted text -

- Show quoted text -


Why is your simple charger so complicated? Why not use a 12 volt DC
wall transformer and 13 ohm resistor (5 watt)? You get 540mA when the
battery is low at 5 volts, and about 400mA as the battery voltage
rises to 7 volts.

-Bill
Click to expand...

The circuit you describe would require *regulated* 12 volts,
making it _more_ complicated than the "very simple" circuit.
The very simple circuit is designed to match the charging
requirements in Jaycar's description. Can't do that with the
12 volt DC wall wart and 13 ohm resistor.

Ed
 
"ehsjr"

The very simple circuit is designed to match the charging
requirements in Jaycar's description.
Click to expand...

** Jaycar are a mob of dumb parts grocers -

they are experts on NOTHING !!


CC charging *does* work on SLAs.
Click to expand...

** It destroys them by overcharging - you ASS.


If you want to talk about "best" chargers, don't snipe
at my post which addressed a "Very simple charger"
It's simple, it works, and it matches Jaycar's description.
Click to expand...

** YOU are a good match for the creeps at Jaycar.

In the KNOW NOTHING stakes.



....... Phil





Can't do that with the
12 volt DC wall wart and 13 ohm resistor.

Ed
Click to expand...
 
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