Circuit Schematic Diagram of Automatic AA Ni-Cad Battery Charger
The following automatic AA Ni-CAD battery charger circuit will be turned off when the batteries are full. It works on 1 to 8 batteries. To set the charger operation mode, there are switches provided. For 1.2 Ah AA cells batteries, you can use 14 hour rate with 45mA or 5 hour rate with 90mA. 14 hours rate 90mA can also be used by switch and fitter 12R in order to set the high performance of 1.2Ah AA cell battery charges. 16V DC input is used by the circuit or maximum 12V AC input. Charge up to 8 cells in series at a time can also be done, but you need 17V to 18V for the input supply.
To avoid overtax the charger, it is best to keep everything simple by charging one set of cells at a time and using two or more time-cycles to charge the larger cells.