This lead-acid battery charger circuit incorporates the LM 317 integrated circuit (IC) to ensure precise charging voltage delivery to the battery. The design of this charging circuit is influenced by the requirement to charge the battery to a level equivalent to 1/10 of its Ampere-hour (Ah) capacity. Q1, R1, R4, and R5 are components that regulate the charging current for the battery, with the option to adjust the charging current using potentiometer R5. As the battery undergoes charging, the current through R1 increases, impacting the conduction of Q1. Due to the connection between Q1’s collector and the adjust pin of the LM 317 IC, this results in an increase in voltage at the LM 317’s output. Once the battery reaches full charge, the charging current is reduced, entering a mode known as trickle charging.
Lead-Acid Battery Charger Schematic Circuit Diagram:
PCB Layout:
3D Diagram:
Components of Lead Acid Battery Charger Circuit
- 7815
- Rectifier Bridge
- 1 (5W), 1K x 2, 1.2K, 1.5K x 2, 10K resistors
- 1N4007, x 3, 1N4732A diodes (Zener)
- NPN Transistor 2SD882
- 4 x LEDs
- 50KΩ Potentiometer
- 12 Volt Relay
Component Description
7815
The 7815 is a linear voltage regulator from the 78XX series. You might have used 7805 and 7812, which provide 5V and 12V regulated voltages, respectively. The 7815 Voltage Regulator, on the other hand, generates a steady regulated voltage of 15V.
Lead Acid Battery
Gaston Plante invented the lead-acid battery in 1859, and it is a rechargeable battery. The key advantages of a lead battery are that it dissipates relatively little energy (if it dissipates less energy, it can run for a long time with great efficiency), it can deliver strong surge currents, and it is inexpensive.
How to Recharge a Lead Acid Battery?
To charge a battery from AC we need a step-down transformer, a rectifier, a filtering circuit, and a regulator to maintain the constant voltage. Then we can give the regulated voltage to the battery to charge it. Think if you have only DC voltage and charge the lead acid battery, we can do it by giving that DC voltage to a DC-DC voltage regulator and some extra circuitry before giving it to the lead acid battery. A car battery is also a lead-acid battery.
