Put-battery-charger

Description: A short-circuit-proof battery charger provides an average charging current of approximately 8 A to a 12-V lead/acid storage battery. The charger circuit has the additional advantage of being unaffected and undamaged by incorrect battery connections. With an input voltage of 115 V, the circuit activates when the battery is correctly connected. The battery supplies the current necessary to charge the timing capacitor C1, which is used in the PUT ( Programmable Unijunction Transistor) relaxation oscillator. When C1 charges to the peak point voltage of the PUT, the PUT triggers, turning on the SCR (Silicon Controlled Rectifier), which in turn delivers charging current to the battery. As the battery charges, its voltage increases slightly, which raises the peak point voltage of the PUT. Consequently, C1 must charge to a slightly higher voltage to activate the PUT. The voltage across C1 continues to rise until it reaches the zener voltage of D1, which clamps the voltage on C1, preventing the PUT oscillator from oscillating and halting the charging process. The maximum battery voltage is regulated by potentiometer R2, which determines the peak point firing voltage of the PUT. In the depicted circuit, the charging voltage can be adjusted between 10 V and 14 V, with the lower limit set by D1 and the upper limit established by TL.

The circuit design of this short-circuit-proof battery charger integrates several key components to ensure safe and efficient operation. The use of a PUT in the relaxation oscillator configuration allows for precise control of the charging process. The timing capacitor C1 plays a crucial role by storing energy and controlling the oscillation frequency of the PUT. When the battery is connected, it provides the necessary voltage to charge C1, thereby initiating the charging cycle.

The SCR serves as a switch that regulates the flow of current to the battery once the PUT is activated. This switching action is essential for maintaining the charging current at approximately 8 A, which is suitable for a 12-V lead/acid battery. The inclusion of a zener diode (D1) is a critical safety feature; it prevents overcharging by clamping the voltage across C1, effectively stopping the oscillation of the PUT when the battery reaches its maximum voltage.

The potentiometer R2 allows for user-defined adjustments of the maximum charging voltage. This feature is particularly useful for accommodating different battery types or conditions, ensuring that the charger can be tailored to meet specific requirements. The adjustable range of 10 V to 14 V provides flexibility in charging various lead/acid batteries while safeguarding against potential damage due to overvoltage.

Overall, the circuit's design emphasizes safety and reliability, making it an effective solution for charging lead/acid batteries without the risk of short circuits or damage from improper connections. The thoughtful arrangement of components and their interactions ensures optimal performance while maintaining user safety.A short-circuit-proof battery charger will provide an average charging current of about 8 A to a 12-V lead/acid storage battery. The charger circuit has an additional advantage; it will not function nor will it be damaged by improperly connecting the battery to the circuit.

With 115 V at the input, the circuit commences to function when the battery is properly attached. The battery provides the current to charge the timing capacitor Cl used in the PUT relaxation oscillator. When Clcharges to the peak point voltage of the PUT, the PUT fires turning the SCR on, which in tum applies charging current to the battery.

As the battery charges, the battery voltage increases slightly which increases the peak point voltage of the PUT. This means that Cl has to charge to a slightly higher voltage to fire the PUT. The voltage on Cl increases until the zener voltage of Dl is reached, which clamps the voltage on Cl, and thus prevents the PUT oscillator from oscillating and charging ceases.

The maximum battery voltage is set by potentiometer R2 which sets the peak point firing voltage of the PUT. In the circuit shown, the charging voltage can be set from 10 V to 14 V-the lower limit being set by Dl and the upper limit by TL