Trickle Charge Batteries

[spike1947]

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]

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]

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

 

[Colin Mitchell]

But you haven't told him what input voltage he needs.

 

[spike1947]

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]

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

Bob

 

[cjdelphi]

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

 

[BobK]

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]

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]

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