Battery Charger

Battery Charger Circuit Using SCR

In the Battery Charger Circuit, the SCR is activated when a voltage is applied to its Gate terminal via resistor R1 and diode D1. Subsequently, it commences rectifying the AC voltage, albeit for just one half of the cycle. As DC current begins to flow through resistor R2, the battery undergoes a charging process.

This specific Battery Charger Circuit employs an SCR for rectifying the AC mains voltage to charge the battery. When the connected battery is depleted, its voltage drops. To prevent forward biasing voltage from reaching the base of transistor Q1, R4 and D2 are utilized. This action turns off the transistor, allowing the triggering voltage to be applied to the SCR’s gate (H1) through R1 and D3. Consequently, the SCR starts conducting and rectifying the AC input voltage, which is then supplied to the battery through resistor R6 (5W). Consequently, the battery begins to charge.

Upon achieving full charge, the voltage divider circuit consisting of R3, R4, R5, and D2 delivers a forward bias signal to activate transistor Q1. As Q1 switches on, it interrupts the trigger voltage to the SCR’s gate, turning off the SCR. In this scenario, a minimal charge is directed to the battery via R2 and D4 for trickle charging. It’s worth noting that this charger is primarily suitable for slow charging due to its half-wave rectification. Whereas fast charging necessitates full-wave rectification of the charging voltage.

Battery Charger Schematic Circuit diagram with Parts list:


  • Assemble the circuit on a high-quality PCB or a standard circuit board.
  • The T1 step-down transformer can be 230V primary and 18V /3A secondary.
  • The POT R4 can be used to set the voltage of the battery at which the charging should stop.
  • Crocodile clips can be used to connect the battery to the charger circuit.

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