XH-M604 complete guide — voltage display, dual threshold setup and wiring

Introduction

The XH-M604 is the most capable module in the XH-M60x battery charging control series. It combines voltage-based relay cut-off with a digital LED voltage display and dual threshold control — both an upper (charge cut-off) and lower (discharge reconnect) voltage limit. This makes it suitable not just for overcharge protection, but for complete battery charge/discharge cycle management. This guide covers everything you need to know to wire, configure, and deploy the XH-M604.

Key Components and Terminals

The XH-M604 has the following connections:

• VCC / GND: Module power supply (DC 12V).
• BAT+ / BAT-: Battery voltage sensing terminals. Connect directly to the battery.
• Relay COM / NO / NC: Charger switching output. Wire the charger through the relay contacts.
• P1 potentiometer: Sets the upper voltage threshold (charge cut-off).
• P2 potentiometer: Sets the lower voltage threshold (discharge reconnect).

Understanding Dual Threshold Control

The XH-M604 operates with two voltage thresholds:

• Upper threshold (P1): When the battery voltage rises to this level, the relay opens and disconnects the charger. This prevents overcharging.
• Lower threshold (P2): When the battery voltage drops to this level (e.g., due to load discharge), the relay closes and reconnects the charger. This prevents over-discharge and maintains the battery within a safe voltage window.

This hysteresis-based control loop keeps the battery continuously maintained between the two thresholds — ideal for float charging and standby power applications.

Wiring Diagram

A typical XH-M604 installation for a 12V lead-acid battery:

1. Connect the charger positive to relay COM.
2. Connect relay NO to battery positive (BAT+).
3. Connect charger negative and battery negative to a common ground.
4. Connect BAT+ and BAT- sensing terminals directly to the battery terminals.
5. Power the module VCC/GND from the same 12V supply.

Calibrating the Thresholds

For a 12V AGM lead-acid battery:

• Upper threshold (P1): Set to 14.4V – 14.7V (full charge voltage).
• Lower threshold (P2): Set to 12.0V – 12.2V (reconnect voltage to avoid deep discharge).

Use a bench power supply or a fully charged battery and a multimeter to verify. Adjust P1 until the relay opens at your target upper voltage, then reduce voltage and adjust P2 until the relay closes at your target lower voltage.

Reading the Digital Display

The onboard LED display shows the real-time battery voltage in volts (e.g., 12.6V). This eliminates the need for a separate voltmeter during installation and monitoring. The display accuracy is typically ±0.1V — sufficient for battery management but not a substitute for a calibrated multimeter in precision applications.

Practical Applications

• Solar energy storage: Maintain a 12V battery bank between safe charge/discharge limits automatically.
• UPS and backup power: Keep a standby battery topped up and protected from deep discharge.
• Off-grid systems: Automate battery management without a microcontroller.
• Battery test rigs: Use the display and dual thresholds to cycle batteries for capacity testing.

Where to Buy

The XH-M604 is available at Embeded Studio with fast delivery across Pakistan. Also check out the XH-M602 and XH-M603 for simpler charging control applications.