Nickel cadmium battery charging circuit diagram

In this circuit, choose 10Ω for R1 and 200Ω for R2. When the switch is closed upward, the charging current is 60mA (constant current); when the switch is closed downward, the charging current is 3mA (constant current). The total voltage drop of silicon diodes CR1 and CR2 is 1.2V, while the emitter junction voltage drop of Q1 is 0.6V, so the net voltage drop on R1 or R2 is 0.6V. Divide 0.6V by the required charging current in amps to get the resistance of R1 or R2. The LED indicates the working status of the charging circuit .