Effective charging control is essential to improve battery efficiency, extend service life, and prevent overcharge or undercharge. A typical battery charging process includes three stages: bulk charge, equalizing charge, and float charge, with automatic transition and proper charge termination control.

1. Automatic Transition Between Charging Stages

Most industrial battery chargers adopt a three-stage charging method (bulk–equalize–float). Common transition control methods include:

• Time-Based Control

Preset charging durations for each stage. The system switches automatically via timer or CPU control.

Advantage: Simple implementation.

Limitation: Lacks real-time battery feedback, resulting in less precise control.

• Voltage or Current Threshold Control

Charging stage changes when the battery voltage or current reaches preset values.

Advantage: More adaptive than time-based control.

• Capacity Monitoring (Integral Method)

The charger continuously monitors battery capacity and adjusts current when a defined capacity level is reached.

Advantage: Higher accuracy.

Limitation: More complex circuitry.

2. State of Charge (SOC) Determination

Accurate judgment of battery charge level ensures proper current regulation. Common methods include:

Terminal Voltage Change Rate:

The voltage rise rate varies during different charging stages. Monitoring voltage variation over time helps identify the charging phase.

Capacity Comparison:

Comparing measured capacity with rated capacity determines charge level.

Terminal Voltage Difference:

A large deviation from rated voltage indicates early-stage charging; a small deviation indicates near full charge.

3. Charge Termination Control

Proper charge termination prevents overcharging, which may cause gas generation, water loss, temperature rise, and reduced battery life.

Main Termination Methods:

Timer Control:

Stops charging after preset time (simple but may cause over/undercharge).

Temperature Monitoring:

Rapid temperature rise indicates full charge. Limited by sensor response speed.

Negative Voltage Slope Detection (ΔV):

Charging stops when a slight voltage drop appears after full charge. Fast response but sensitive to ambient temperature.

Polarization Voltage Control:

Measures polarization voltage (typically 50–100 mV per cell) to determine full charge at cell level.

Advantages:

No temperature compensation required

Reduces corrosion

Allows mixed battery configurations

Supports capacity expansion

Extends overall service life

4. Best Practices for Battery Charging

To ensure optimal performance:

Avoid Overcharge and Undercharge

Overcharge accelerates plate damage and gas emission; undercharge leads to sulfation and capacity loss.

Control Discharge Current

Excessive discharge current increases internal heat and shortens lifespan.

Avoid Deep Discharge

Deep discharge reduces acceptable charging current and slows recharge speed.

Consider Ambient Temperature

Battery capacity decreases at low temperatures; charging and discharging parameters should be adjusted accordingly.

Conclusion

Advanced charging technologies—such as pulse charging and high-frequency switching power supplies—can significantly reduce charging time, improve efficiency, and extend battery life.

Proper charging control involves three key aspects:

Stage transition

Charge level determination

Charge termination

Optimized charging management delivers better energy efficiency, lower operating cost, and longer battery service life.