Battery charger circuit diagram

Relay J realizes the self-locking and automatic power-off of switch K. When the battery is connected, press K and the power indicator light L lights up. At the same time, J is powered on and K is self-locked by its contact J& mdash ;0, and charging starts. , at this time, due to the lack of battery power, the emitter voltage of T1 is lower than (7.5V+0.65V), T1 is cut off, T2 is also cut off, and they have no effect on T3. When the battery voltage is charged to 7.5V, the Tl emitter voltage is 7.5V+0.65V, T1 is saturated and turned on, T2 is also turned on, the base voltage of T3 drops and is cut off, J loses power and is released, J-0 is disconnected, charging stop. Indicator light L goes out. Batteries with different voltages can also be charged by adjusting W. Diode D in the circuit is an isolation diode , which can prevent reverse discharge of the battery. R is the charging current limiting resistor, which can be selected between 5 and 10 ohms. There are no special requirements for other components . All components can be overlapped on a plastic box, and the IC does not need a heat sink. Short-circuit K for debugging, and adjust W so that the IC output voltage is 7.5V, the battery's full voltage. Battery charger circuit diagram :