A simple automatic Pb-acid charging circuit.

[bobkrech]

I came across an extremely simple, low cost single transistor automatic Pb-acid battery charger circuit. Just what you need to recharge launcher batteries and you can use a simple automotive relay as the on-off control. It's almost a junk box circuit.

https://electronicdesign.com/Articles/Print.cfm?ArticleID=1823

Bob

 

[Pem Tech]

Very cool, thanks Bob.

 

[Race58]

Bob,,
Did I read that circuit right? Do you have to plug it into a 220V outlet?

 

[Reinhard]

This diagram shows a 220V version, but you only need to substitute the 220V/15V transformer with a 120V/15V transformer and you're ready to go.

Reinhard

 

[Race58]

Great, Thanks.

This diagram shows a 220V version, but you only need to substitute the 220V/15V transformer with a 120V/15V transformer and you're ready to go.

Reinhard

 

[bobkrech]

Bob,,
Did I read that circuit right? Do you have to plug it into a 220V outlet?

This diagram shows a 220V version, but you only need to substitute the 220V/15V transformer with a 120V/15V transformer and you're ready to go.

Reinhard

Reinhard is correct. All you need is a transformer or wall wart that put out about 15 volts AC or DC. What's elegant about this circuit is that it starts charging when the battery drops below a set voltage and cuts off when it reaches the fully charged voltage. The battery is not continously trickle charged so you won't shorten it's life by constantly trickle chaging it at 13.8 volts.

Bob

 

[RimfireJim]

Thanks for posting the link, Bob - that looks like a pretty useful circuit. One question (even though I know you didn't design the circuit, but you or someone else might be able to answer it): Are the "V" units designators on VR1, R2 and R3 suppose to be Ohms, not volts? 290 Ohms is not a standard resistor value.

 

[bobkrech]

Thanks for posting the link, Bob - that looks like a pretty useful circuit. One question (even though I know you didn't design the circuit, but you or someone else might be able to answer it): Are the "V" units designators on VR1, R2 and R3 suppose to be Ohms, not volts? 290 Ohms is not a standard resistor value.

Jim

You are correct. They are not standard resistor values. https://www.logwell.com/tech/components/resistor_values.html

The drawing probably got screwed up in translation. The resistors on the lefthandside set the fully charged voltage, the maximum voltage before recharging and a minimum bias voltage for the base of the transistor.

Bob

 

[UhClem]

I always liked the very simple LM317 based float charger from page 20 of the data sheet:

https://www.national.com/ds/LM/LM117.pdf

 

[brockrwood]

I always liked the very simple LM317 based float charger from page 20 of the data sheet:

https://www.national.com/ds/LM/LM117.pdf

This is not necro-posting. It is necro-LIKING. ;-)

 

[Alan15578]

This is not necro-posting. It is necro-LIKING. ;-)

Hmm. We’re having trouble finding that site.

 

[brockrwood]

Hmm. We’re having trouble finding that site.

National Semiconductor. Now part of Texas Instruments. If you want to see the datasheet for the LM317.

 

[MarsLander]

Hmm. We’re having trouble finding that site.

https://www.ti.com/lit/ds/symlink/l...duct%2FLM317-N%2Fpart-details%2FLM317S%2FNOPB

 

[brockrwood]

Here is the old National Semiconductor datasheet at Jameco. This old version shows the world’s simplest, current limited battery charger on page 20.

https://www.jameco.com/Jameco/Products/ProdDS/898800.pdf
@Alan15578

 

[brockrwood]

Here is the datasheet for the LM350. The LM350 is an improved version of the LM317. It can handle 3 amps of current instead of 1.5 amps. It is pin-compatible with the LM317.

https://www.ti.com/lit/ds/snvs772b/...29321&ref_url=https%3A%2F%2Fwww.google.com%2F

 

[OzHybrid]

There are so many good modules readily available today that it's not worth going old school.
There is a 3A(Really only about 1 Amp) up down converter available for about $5
Takes ANY voltage in the input range and converts to ANY voltage in the output range.
Constant voltage, constant current and battery charging modes.

https://www.ebay.com.au/itm/191736124198? I use these a lot just because of the any in, any out(up to 26v) properties.

 

[brockrwood]

There are so many good modules readily available today that it's not worth going old school.
There is a 3A(Really only about 1 Amp) up down converter available for about $5
Takes ANY voltage in the input range and converts to ANY voltage in the output range.
Constant voltage, constant current and battery charging modes.

https://www.ebay.com.au/itm/191736124198? I use these a lot just because of the any in, any out(up to 26v) properties.

So, one trim pot adjusts the voltage and the second one adjusts the current?

What does the third trim pot do?

 

[OzHybrid]

charge cut off point. Led indication when current level indicating end of charge is reached. Diwnload a manual.