Charging 10 x 1.2v AA batterys

[badflyer]

Hi chaps,

I wish to charge 10 x 1.2v AA Ni-MH batterys at the same time. What would be a safe charge current to charge them at? I have a 12v 1A DC mains adapter and used it to start with. I measured a initial charge current of 40mA. Is this to low or high?

cheers

 

[Nigel Goodwin]

I wish to charge 10 x 1.2v AA Ni-MH batterys at the same time. What would be a safe charge current to charge them at? I have a 12v 1A DC mains adapter and used it to start with. I measured a initial charge current of 40mA. Is this to low or high?

You need more than 12V to charge 10 x Ni-Mh, the usual charging current is 1/10th of their rated capacity - so you would charge a 1AH battery at 100mA or so.

To provide proper recharging an intelligent charger is advisable, this will test during charging, and drop to a safe trickle charge once fully charged. The usual method is to check the 'DeltaV' of the batteries (where the voltage across them drops slightly at full charge - or to test their temperature, once fully charged the temperture increases as you overcharge them.

The normal chargers just bang current in for a fixed period, so if the battery is already partially charged it will be overcharged.