Lead-acid battery charger circuit schematic diagram

Lead-acid battery charger circuit schematic diagram

Charging principle analysis:

1. Maintenance charging:

When the battery voltage is low (can be set, this circuit is preset to be below 9V), the charger works in a low current maintenance charging state. The working principle is that the potential of U1C pin 9 (non-inverting end) is lower than pin 8 (inverting end) , U1C outputs low level, and T4 is cut off. The potential of U1D 11 pin is about 0.18V. At this time, the charging current is about 250mA (the constant current circuit is composed of R14, U1D, and T1B peripheral circuits. Readers of the constant current principle should analyze it by themselves).

2. Fast charging:

As maintenance charging continues, the battery voltage gradually increases. When the battery voltage exceeds 9V, the charger enters the high-current fast charge mode. The potential of U1C pin 9 (non-inverting end) is higher than that of pin 8 (inverting end), and U1C outputs high potential, T4 is turned on, the potential of U1D 11 pin is about 0.48V, and the charger outputs a constant current of about 1A to charge the battery.

3. Pressure-limited float charging:

When the battery is nearly fully charged, the charger automatically switches to a limited-voltage float charge state (the limited-voltage float charge voltage is set to 13.8V, if it is a 6V battery, the float charge voltage should be set to 6.9V). At this time, The charging current will gradually decrease from the fast charging state. When the battery is fully charged, the charging current will be only 10~30mA to supplement the battery's power loss due to self-discharge.

4. Protection and charging indication circuit:

This circuit is equipped with a reverse polarity protection circuit, which is composed of D4, U1C, U1D, T1 and peripheral components. When the battery is reversely connected, the charger limits the output current to prevent an accident. The charging indication is composed of U1A, D7 and peripheral components. When charging, D7 lights up. After the charger enters the float charge state, D7 goes out, indicating the end of charging.

5. This circuit can adjust the charging current and float voltage to meet the needs of batteries of different specifications by slightly modifying the circuit parameters.