Using this circuit you can easily charge any Ni-Cad battery from 50 to 400 mA charging current. You can easily charge more than one battery at a time. The charging current can be selected according to the battery you are going to charge. It is absolutely safe for your expensive rechargeable batteries. Supply voltage: 12-24 VAC Charging current: 50-400 mA (selectable) A 2x12V 500 mA transformer is required