recently i hav buyed a Ni-Mh battery instead of a lead acid battery bcoz lead acid battery is very heavy for my robo
but when i try to charge my ni mh battery (which is in the form of a pack of pencil cells) using a diode and transformer i failed to keep it charged up to rated voltage
it is a 12v battery i missed the Ah rating of battery
I agree with the point that NiMH batteries are difficult to charge as they differ from standard Lead Acid batteries. I recently used NiMH batteries in one of my project and even I need to design a charger to charge them. there are some useful links where u can find info about it