NiMH Charger Voltage

[CoTang]

I'm planning to make a NNiMH 9.6V (170mAH) charger and my question is how much voltage should I apply to the battery when charging? Would 11 Volts @ 17mA be good? or does it have to be 9.6V @17mA the same rating as the battery?

Thanks.

 

[Nigel Goodwin]

I'm planning to make a NNiMH 9.6V (170mAH) charger and my question is how much voltage should I apply to the battery when charging? Would 11 Volts @ 17mA be good? or does it have to be 9.6V @17mA the same rating as the battery?

Thanks.

They should be charged with a constant current, so the voltage doesn't matter (as long as it's a fair bit higher than the battery voltage). I would suggest a source voltage of around 20V, with a constant current source of 17mA feeding the battery.

 

[pike]

whoa 20v. My cordless drill has a 12v battery and uses only a 15v charger

 

[Nigel Goodwin]

whoa 20v. My cordless drill has a 12v battery and uses only a 15v charger

And simply 'bungs' the 15V through a low value resistor to the battery :lol:

This is a really poor method of charging, used simply for it's low cost, with a total disregard for the shortening of battery life it causes.

 

[ante]

Hi

It should be at least 1.8 volts / cell available @ the desired current.
In case of 9.6 Volts pack it is 8 cells * 1.8 = 14.4 Volts.

Ante :roll:

 

[CoTang]

NiMH

Alright, that great thanks guys!