How to use the XH-M602 to protect your 12V lead-acid battery from overcharging

Introduction

Overcharging is one of the leading causes of premature battery failure in 12V lead-acid systems. The XH-M602 battery charging control module provides a simple, reliable, and low-cost solution: it monitors battery voltage and automatically disconnects the charger via a relay when the set threshold is reached. This guide covers wiring, calibration, and practical tips for getting the most out of the XH-M602.

Understanding the XH-M602

The XH-M602 operates on DC 12V and uses an onboard potentiometer to set the charge cut-off voltage. When the battery voltage reaches this threshold, the module de-energises its relay, breaking the charger circuit. Three LED indicators provide status feedback: power (red), charging (yellow), and full charge (green).

Wiring the XH-M602

The module has the following key connections:

• VCC / GND: Connect to your 12V power supply (same as the battery or charger supply).
• Battery terminals (BAT+ / BAT-): Connect directly to the battery for voltage sensing.
• Relay COM / NO / NC: Wire your charger through the relay. Connect the charger positive to COM, and the battery positive to NO (Normally Open). When charging, the relay is energised and current flows. When full, the relay opens and disconnects the charger.

Important: Ensure the relay rating matches your charger current. The onboard relay is typically rated for 10A — verify this against your charger specifications.

Calibrating the Cut-off Voltage

For a 12V lead-acid battery, the recommended full-charge voltage is approximately 14.4V to 14.7V (for flooded/AGM types). To calibrate:

1. Connect a fully charged battery or a bench power supply set to your target cut-off voltage.
2. Use a multimeter to monitor the voltage at the BAT terminals.
3. Slowly adjust the potentiometer until the relay clicks off (green LED lights).
4. Verify by reducing the voltage slightly — the relay should re-engage (yellow LED).

Practical Tips

• Use a heatsink or ensure adequate ventilation if operating near the relay’s maximum current rating.
• Add a flyback diode across the relay coil if driving inductive loads.
• For solar charging applications, pair with a solar charge controller for MPPT functionality — the XH-M602 acts as a secondary overcharge guard.
• Re-calibrate periodically as potentiometers can drift over time.

Where to Buy

The XH-M602 is available at Embeded Studio with fast delivery across Pakistan. Need more features? Check out the XH-M603 (with timer) or the XH-M604 (with digital display and dual threshold).