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Trickle Charge Batteries

spike1947

Feb 4, 2016
56
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
1,166
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
5,178
LM317 as a current source, used this for years charging 7.2 volt NIMH, with no probs.
Adam

Colin Mitchell

Aug 31, 2014
1,416
But you haven't told him what input voltage he needs.

spike1947

Feb 4, 2016
56
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
7,682
You can charge them forever at C/20. Any higher and it gets complicated.

Bob

cjdelphi

Oct 26, 2011
1,166
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
7,682
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
56
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
3,481
As explained on the other forum, you need a supply to handle the laser current plus a trickle charge.

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