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Trickle Charge Batteries

spike1947

Feb 4, 2016
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Hi

I am wanting to know how I can rig up a simple trickle charge for 4 x AAA Ni-MH Rechargeable Batteries .I need them to run a 5 volt laser for a security set up I am making .

cheers

spike
 

cjdelphi

Oct 26, 2011
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How simple? 4 x 1.2v = 4.8v

Get an adjustable regulator, set 4.8v and stick a resistor on it to trickle charge..

I've never been too sure about charging cells in series, but i think nimh cells don't mind too much
 

Arouse1973

Adam
Dec 18, 2013
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LM317 as a current source, used this for years charging 7.2 volt NIMH, with no probs.
Adam
 

spike1947

Feb 4, 2016
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How simple? 4 x 1.2v = 4.8v

Get an adjustable regulator, set 4.8v and stick a resistor on it to trickle charge..

I've never been too sure about charging cells in series, but i think nimh cells don't mind too much

Hi cjdelphi

I don't want to buy a regulator I want to build my own ! .

cheers

spike
 

BobK

Jan 5, 2010
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You can charge them forever at C/20. Any higher and it gets complicated.

Bob
 

cjdelphi

Oct 26, 2011
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A couple of transistors and a sense resistor for current regulation? Cheaper and quicker if you buy an lm317/resistor

Substitute the 10ohm resistor for a value that trickle charges your battery... i selected 10ohm as it sounded reasonable to charge your batteries, just provide the circuit a higher voltage than your battery total voltage
 

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BobK

Jan 5, 2010
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All that is needed is a voltage source significantly higher than the batteries full charge voltage and a resistor. The resistor should be calculated to drop (Vin - Vbatt) at a current of C / 20.

This will cause a higher charging current when the battery is depleted, which is okay, going down to the C/20 current when the battery is fully charged.


Bob
 

spike1947

Feb 4, 2016
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All that is needed is a voltage source significantly higher than the batteries full charge voltage and a resistor. The resistor should be calculated to drop (Vin - Vbatt) at a current of C / 20.

This will cause a higher charging current when the battery is depleted, which is okay, going down to the C/20 current when the battery is fully charged.


Bob
Thanks guys , very helpful I now have all the info I need to crack on .

cheers

spike
 

Alec_t

Jul 7, 2015
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As explained on the other forum, you need a supply to handle the laser current plus a trickle charge.
 
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