Quick questions about rechargable batteries

[MoldnMaker]

If a device uses 2 - 1.2V Ni-cad rechargable cells connected together can these be replaced with 2 - 1.2V Ni-MH cells? Would the built in charger work properly? Is there a difference in the way they charge? This may be a stupid question, but I just wanted to make sure before I replaced a couple dead
Ni-cad cells with the Ni-MH ones.

Thanks in advance.

[LCHIEN]

If a device uses 2 - 1.2V Ni-cad rechargable cells connected together can these be replaced with 2 - 1.2V Ni-MH cells? Would the built in charger work properly? Is there a difference in the way they charge? This may be a stupid question, but I just wanted to make sure before I replaced a couple dead
Ni-cad cells with the Ni-MH ones.

Thanks in advance.

The charging charateristics are somehwat different. Don't remember the exact difference but I do know that my dual-type "fast" chargers have switches for niCad or NiMH use. It might work but may not be optimal,
and that might mean not being fully charged or possibly shortened battery life.

[sacherjj]

I've forgotten much of what I read about these two types of batteries when I was messing with electric powered R/C planes. Basically, the charger has to be designed for the battery chemistry. A NiCad charger will kill a NiMH battery. There are few places where a NiMH can't be substituted for a NiCad, mostly ultra high discharge. Although NiMH may have caught up in the past few years.

Most electronic charging looks at delta V detection. When the cells are "full", the voltage across the pack actually drops just slightly. This is fairly large with NiCad (0.1 V or so), but much smaller with NiMH. A NiCad charger won't detect this smaller change and cook the pack. It might switch off with a timer backup or temperature detection, depending on the advanced'ness of the charger.