Voltage Indicator circuit for gel cell charging

O

ocular

Guest
Have all these 6 volt gel cell torches/lamps , the quality of the
charging circuit is crude as that the end point voltage seems to creep
up to around 7.4 volts - not ideal for float charging.

I need a simple voltage indicator circuit involving an LED (possibly
flashing) that would come on say at 7.0 volts. I could then add this
across the gel cell terminals and leave the existing charging circuit in
place. Then when the end point voltage is reached, the charger could be
removed manually
 
G'day,
Take a look at
http://www1.jaycar.com.au/productView.asp?ID=KA1778&CATID=&keywords=voltage+indicator&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=xxxxxxxxxx&Keyword2=xxxxxxxxxx&pageNumber=&priceMin=&priceMax=&SUBCATID=
and see if that's what you have in mind.

Bob



ocular <ocular@at_powerup.com.au> wrote:

Have all these 6 volt gel cell torches/lamps , the quality of the
charging circuit is crude as that the end point voltage seems to creep
up to around 7.4 volts - not ideal for float charging.

I need a simple voltage indicator circuit involving an LED (possibly
flashing) that would come on say at 7.0 volts. I could then add this
across the gel cell terminals and leave the existing charging circuit in
place. Then when the end point voltage is reached, the charger could be
removed manually
Click to expand...
 
In article <um0hovs86pk12pa9ruvade5vfn7rvc0q3p@4ax.com>,
bobp@bluebottle.com says...
http://www1.jaycar.com.au/productView.asp?ID=KA1778&CATID=&keywords=voltage+indicator&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=xxxxxxxxxx&Keyword2=xxxxxxxxxx&pageNumber=&priceMin=&priceMax=&SUBCATID=

Sounds great - off to jaycar
Click to expand...
 
ocular <ocular@at_powerup.com.au> wrote:
Sounds great - off to jaycar
Click to expand...
Excellent! You can see the schematic at
http://members.ozemail.com.au/~bobpar/lv-schem.gif

Bob
 
Bob's been busy!

How about a list of your kits Bob? I for one would enjoy seeing that!

John :-#)#

On Mon, 13 Oct 2003 01:17:35 +1000, Bob Parker <bobp@bluebottle.com>
wrote:

ocular <ocular@at_powerup.com.au> wrote:
Sounds great - off to jaycar

Excellent! You can see the schematic at
http://members.ozemail.com.au/~bobpar/lv-schem.gif

Bob
Click to expand...
(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
Oh, right...it's there on your home page...back under my rock...

http://members.ozemail.com.au/~bobpar

John :-#(#

On Mon, 13 Oct 2003 01:17:35 +1000, Bob Parker <bobp@bluebottle.com>
wrote:

ocular <ocular@at_powerup.com.au> wrote:
Sounds great - off to jaycar

Excellent! You can see the schematic at
http://members.ozemail.com.au/~bobpar/lv-schem.gif

Bob
Click to expand...
(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
John Robertson <jrr@flippers.com> wrote:
Oh, right...it's there on your home page...back under my rock...

http://members.ozemail.com.au/~bobpar

John :-#(#
Click to expand...

Thanks anyway.
For some reason I was expecting you to suggest how to redesign
that little circuit....
 
In article <j1siov0hgpscl7oegqtffvlglmpca99040@4ax.com>,
bobp@bluebottle.com says...
ocular <ocular@at_powerup.com.au> wrote:
Sounds great - off to jaycar

Excellent! You can see the schematic at
http://members.ozemail.com.au/~bobpar/lv-schem.gif

Bob

I am privileged to talk to the designer of the circuit.
Click to expand...

Can I ask a few questions?

How precise is the voltage switch over. Should I put in a multiturn pot?

I was going to use this LED voltage indicator to identify when the float
voltage of 6.9- 7.0 volts was reached when charging a 6 volt gel cell.

I was thinking of putting a diode between the gel cell battery and the
charging circuit and have the LED voltage indicator on the charging
circuit side. I would then have to allow the voltage drop across the
diode and make the terminal voltage 7.5 volts instead of 7.0 volts.

The LED voltage indicator would then not be powered when the charging
circuit was removed. The green LED would indicate that the charging
circuit is attached and charging and then the Red LED would indicate
that the terminal voltage had been reached.

Would this work?

Would would be the best diode for this?
 
Now that you mention it...maybe add a valve? (tube to those of us in
North America)...I see a lovely green indicator tube - the old one
form the 30's that had a glowing circle, not unlike the Pacman
character facing down, that would close as the signal (voltage) got
stronger...wouldn't that be nice?

(digging deeper under my rock)

John :-#)#

On Mon, 13 Oct 2003 08:16:51 +1000, Bob Parker <bobp@bluebottle.com>
wrote:

John Robertson <jrr@flippers.com> wrote:

Oh, right...it's there on your home page...back under my rock...

http://members.ozemail.com.au/~bobpar

John :-#(#


Thanks anyway.
For some reason I was expecting you to suggest how to redesign
that little circuit....
Click to expand...
(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
G'day,
The switchover point should be accurate within a couple of dozen
millivolts once you've set it. A multi-turn pot would definitely help
you to adjust it more accurately.
I suppose your diode idea would work well enough. The only problem
is that the forward voltage drop of diodes depends to some extent on
how much current is going through them, as well as the temperature.
Try setting the voltage indicator to switch over on a fully-charged
battery at a typical room temperature and see how it goes.
If your charging current is under 1A, a 1N4004 or similar diode
should be OK. More than that but under 3A, use a 1N5404.
Just remember to instal the two-colour LED reversed relative to how
it's shown in the kit, so it shows green until the battery voltage
gets high enough and then goes red.
Good luck with this idea. :)

Regards,
Bob



ocular <ocular@at_powerup.com.au> wrote:
I am privileged to talk to the designer of the circuit.

Can I ask a few questions?

How precise is the voltage switch over. Should I put in a multiturn pot?

I was going to use this LED voltage indicator to identify when the float
voltage of 6.9- 7.0 volts was reached when charging a 6 volt gel cell.

I was thinking of putting a diode between the gel cell battery and the
charging circuit and have the LED voltage indicator on the charging
circuit side. I would then have to allow the voltage drop across the
diode and make the terminal voltage 7.5 volts instead of 7.0 volts.

The LED voltage indicator would then not be powered when the charging
circuit was removed. The green LED would indicate that the charging
circuit is attached and charging and then the Red LED would indicate
that the terminal voltage had been reached.

Would this work?

Would would be the best diode for this?
Click to expand...
 
It was one of those "magic eye" tubes which got me into this whole
electronics business. As a kid, I wanted to know how they work.
OK, we'll add a 6U5G to that circuit, complete with a little 6V -->
250V converter. Go to
http://w1.871.telia.com/~u87149908/eyes/6u5g_em35.htm if you don't
know what a 6U5G looks like. I've still got one in storage here.
Now get back under your rock. :)

Bob


John Robertson <jrr@flippers.com> wrote:

Now that you mention it...maybe add a valve? (tube to those of us in
North America)...I see a lovely green indicator tube - the old one
form the 30's that had a glowing circle, not unlike the Pacman
character facing down, that would close as the signal (voltage) got
stronger...wouldn't that be nice?

(digging deeper under my rock)

John :-#)#
Click to expand...
 
In article <c8aoov09t53u5pag55adm2k5nk7c31ukrq@4ax.com>,
bobp@bluebottle.com says...
G'day,
The switchover point should be accurate within a couple of dozen
millivolts once you've set it. A multi-turn pot would definitely help
you to adjust it more accurately.
I suppose your diode idea would work well enough. The only problem
is that the forward voltage drop of diodes depends to some extent on
how much current is going through them, as well as the temperature.
Try setting the voltage indicator to switch over on a fully-charged
battery at a typical room temperature and see how it goes.
If your charging current is under 1A, a 1N4004 or similar diode
should be OK. More than that but under 3A, use a 1N5404.
Just remember to instal the two-colour LED reversed relative to how
it's shown in the kit, so it shows green until the battery voltage
gets high enough and then goes red.
Good luck with this idea. :)

Regards,
Bob



ocular <ocular@at_powerup.com.au> wrote:

I am privileged to talk to the designer of the circuit.

Can I ask a few questions?

How precise is the voltage switch over. Should I put in a multiturn pot?

I was going to use this LED voltage indicator to identify when the float
voltage of 6.9- 7.0 volts was reached when charging a 6 volt gel cell.

I was thinking of putting a diode between the gel cell battery and the
charging circuit and have the LED voltage indicator on the charging
circuit side. I would then have to allow the voltage drop across the
diode and make the terminal voltage 7.5 volts instead of 7.0 volts.

The LED voltage indicator would then not be powered when the charging
circuit was removed. The green LED would indicate that the charging
circuit is attached and charging and then the Red LED would indicate
that the terminal voltage had been reached.

Would this work?

Would would be the best diode for this?
Click to expand...

Thanks for those comments.

The charger is limited to 500ma so I will use the IN4004

I am a little concerned about about the variability of the forward
voltage drop across the diode and setting it up on a fully charged
battery. For a 6 volt 4 A/H Gel cell at 7.0 volts fully charged the
current is about 10ma and hopefully the forward voltage drop across the
diode will be constant at this point. The concern is as the battery gets
older the current to maintain it at 7.0 volts will increase and the
diode forward voltage drop will increase ( will need to look at IN4004
spec sheet to see how much)i.e is there a significant change in forward
voltage drop going from 10 to 20ma?
 
G'day again,
As far as I know, when a battery gets old, it just has less
discharge capacity. I'm not aware of internal losses/self-discharge
increasing above what it had when it was new. Maybe Rod or someone can
correct me on that.
I wouldn't expect that the forward voltage drop of a 1N4004 would
change much between 10 and 20mA. If I didn't have this internet thing
demanding most of my time, I'd go and do a couple of measurements.
If you've got a pair of 1.2K resistors and the time, how about you
connect one resistor in series with a 1N4004 and a 12V supply and
measure the diode's voltage drop. Then put the second resistor in
parallel with the first and see how much the voltage increases? Then
we will all know. :)

Cheers,
Bob


ocular <ocular@at_powerup.com.au> wrote:
Thanks for those comments.

The charger is limited to 500ma so I will use the IN4004

I am a little concerned about about the variability of the forward
voltage drop across the diode and setting it up on a fully charged
battery. For a 6 volt 4 A/H Gel cell at 7.0 volts fully charged the
current is about 10ma and hopefully the forward voltage drop across the
diode will be constant at this point. The concern is as the battery gets
older the current to maintain it at 7.0 volts will increase and the
diode forward voltage drop will increase ( will need to look at IN4004
spec sheet to see how much)i.e is there a significant change in forward
voltage drop going from 10 to 20ma?
Click to expand...
 
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