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Topic: Charging salvaged NiMH batteries (Read 212 times) previous topic - next topic

Lycaon

I salvaged some components out of a cordless phone, including a nimh battery pack with what appears to be two AAA batteries in series...  I'm curious as to whether I can use these in a circuit somehow with the abiility to recharge them while the circuit is powered via USB or perhaps a solar cell.  I do know LiPo and LiIon batteries need special circuitry to manage the charging, but I'm not sure about the NiMH batteries...  Anyone know if this is easily doable?

MarkT

If you have a variable supply try charging (current limited) to 1.35V per cell,
then discharge through a load to 1.2V per cell (monitor both cells) and repeat
if capacity is poor.

Suggest a current limit of about 1/4 nominal capacity (4 hour charging
rate).

Otherwise you'll have to separate them and use a standalone NiMH charger
(these charge two or four AA or AAA cells, typically)

If they've been fully discharged to 0V they won't be too healthy (true of nearly
all rechargables).
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Lycaon

I can get ahold of voltage regulators; so since it's two cells in series, should I apply a ~2.7v to charge them?  How would I know when it's 'done'?

Boardburner2

Best done by current regulation not voltage.this can be just a resistor.
You know when they are done by measuring the terminal voltage

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