NiMh_NiCad Charging Differences?

My Dad made a charger a few years ago that charges 6 AA batteries at a time. (I might post a pic of it later on.) He made it for NICad batteries, but now that NiMh batteries exist I would rather use those. I recently found the charger in the basement so I wanted to ask, what modifications do you think it would need to charge NiMh batteries?

I would guess that they charge differently since chargers have a switch to choose betweem NiMh and NiCad. He doesn't know either so...

I'd appreciate any help. Thanks! /ubbthreads/images/graemlins/grin.gif

The difference is that Nimh have a smaller voltage dropoff as they reach full capacity. If it is a "delta peak" charger, which terminates charging when it detects the battery voltage fall, it may not be sensitive enough to detect the smaller V drop on the Nimh and subsequently overcharge them. If it is a simple timer charger you may be able to use it, but these chargers can be bad for your batteries if not monitored.

NiCD cells are more resistant to overcharging than NiMH cells are, especially when trickle charged.

You can get away with charging NiCD cells with a simple dumb charger (unregulated DC power brick + resistor + diode) as long as you don't leave it plugged in all the time. Not so much with NiMH cells - you really need a smart charger to get the best charge for the batteries, and the longest life out of them.

I don't think I'd ever use a charger made for NiCD batteries to charge NiMH cells.

If it is a slow charger that require 12h to charge a 500mAh NiCd, it will take you TWO DAYS to charge a 2000mAh NiH now---not worth it, buy a smart charger instead /ubbthreads/images/graemlins/icon15.gif