Here is Universal nicd and nimh battery charger circuit. It use IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V. Low cost circuit
See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431. Easy to build.
This is how to modify old Lead-acid battery charger or convert power supply to battery charger in automatic. To protect over charging by CA723 and power SCR
Power up smart. Increase your time easily!
The Battery full charge alarm circuit for a general battery charger. It is simplified circuit and cheap, use one transistor BC557 and display with 2 LED.