Setting up this automatic self regulating automatic battery charger circuit is very simple and may be done in the following way:
Initially, do not connect the fixed transformer power supply; instead connect a 0-24V, variable supply voltage to the circuit.
Remove the anode of D6 from the relay contact and connect it to the positive of the power supply.
Keep both the presets somewhere at the center position.
Switch ON the power and adjust the voltage to 11.5 volts or lower.
Adjust P2, so that the relay just activates.
Now increase the volts to about 13.5 volts, and adjust P1 so that the relay just deactivates.
The setting procedure of the circuit is now complete.
Check the whole procedure by continuously varying the voltage up and down.
You may now remove the variable power supply and connect the fixed transformer, bridge power supply to it.
DON’T FORGET TO RECONNECT THE ANODE OF D6 BACK TO THE RELAY CONTACT OR THE BATTERY POSITIVE.
The battery connected to this circuit will be charged only as long as its voltage is in between the above "window" level.
If the battery voltage crosses the above "window", the relay will trip and stop the battery from charging.
Parts List for self regulating automatic battery charger circuit.
R1, R2 = 10K,
P1, P2 = 10K PRESET,
T1, T2 = BC 547B,
C1 = 2200uF/25V
C2 = 47uF/25V (Please connect this capacitor across the relay coil)
D1---D4 = 1N5408,
D5, D6 = 1N4007,
RELAY = 12 VOLT, SPDT,
TRANSFORMER = AS PER THE CONNECTED BATTERY AH (DIVIDE BY 5)
The above self-regulating battery charger circuit was successfully built and tested by Mr. Sai Srinivas, who is just a school kid but nevertheless has an immense interest in the field of electronics. The following images were sent by him which displays his talent and intense dedication in the field.