Automotive Circuit DiagramsBattery ChargerLCD-LED Display

Automatic Car Battery Charger Schematic Circuit Diagram

The Challenge of Summer Circuits and Indoor Batteries

In the realm of ‘all things outdoors,’ a Summer Circuits edition thrives. But amidst the sunny adventures, a pressing concern lingers indoors: the battery-powered circuits left neglected. As the warmth envelops the days, the family car often finds itself nestled in the garage, a beneficial respite for the owner, their bank account, and the air we all breathe. This hiatus aids in curbing CO2 emissions. Yet, when the time comes to revive the trusty vehicle, a troubling scenario unfolds. The battery, neglected during this reprieve, frequently exhibits alarming signs of depletion, sometimes rendering the engine utterly immobile.

The Modern Dilemma: Battery Maintenance in Contemporary Cars

In the contemporary automotive landscape, the traditional practice of pushstarting has become obsolete and infeasible. The crux of the matter lies in ensuring a well-charged battery, a gesture highly valued in this scenario. The prevalent solution of perpetually connecting an off-the-shelf charger, while seemingly practical, often falls short, unless one possesses a rare ‘electronic’ variant. The majority of economical chargers lack crucial regulation circuitry. Consequently, they pose a significant risk: overcharging the vehicle battery if left perpetually attached. This quandary necessitates an innovative approach. Thus, our proposed project emerges: constructing a charger designed to function as both a standard charger and a float charger. This dual-purpose device allows seamless permanent connection without jeopardizing the battery or inducing fears of overcharging. Remarkably, it achieves this feat without relying on costly or obscure components, making it an incredibly budget-friendly solution.

Automatic Car Battery Charger Schematic Circuit Diagram

Understanding the Circuit Diagram

In this section, we delve into the circuit diagram of the charger. The voltage from the charger’s transformer is rectified by diodes D1 and D2 without smoothing, forming sinewave half-cycles that fall to zero 100 times per second. Thyristor THY2, triggered via resistor R4, charges the battery, with charging current limited by resistor R6, calculated as explained below.

Thyristor Operation and Battery Charging Process

This section explores how THY1 and THY2 function in tandem. THY2 charges the battery during half-cycles of the mains, except when THY1 is triggered. When the battery voltage reaches a certain threshold, THY1 triggers, gradually reducing charging current until it stops completely at full charge. LED1 indicates charging, while LED2 signifies full charge when THY1 is frequently triggered.

Component Selection and Adjustments

This section focuses on component selection and adjustments. R6, THY2, and TR1 must be chosen based on desired charger characteristics. R6 is calculated for maximum charging current but should not exceed 5 A due to circuit limitations. THY2 should be a 100-V type, 1½ to 2 times the desired charging current. The transformer’s power (P) in VA is given by P = 18 × 1.2 × I, where I is the maximum charging current in amps. Potentiometer P1 is adjusted to achieve a charging current close to the set maximum, balancing between float charging and the maximum current, ensuring optimal battery treatment.


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