3.7V Li Battery Fuel Gauge not showing correct charging voltages

It sounds like you're encountering discrepancies in voltage readings from your 3.7V Li battery fuel gauge when charging. Let's address this issue and understand how you can achieve accurate voltage and percentage readings during both charging and discharging scenarios.

### Understanding Li-Ion Battery Charging and Voltage Readings

1. **Voltage Readings During Discharge**:
  - When your battery is discharging (not connected to a power supply), the fuel gauge should ideally provide accurate readings of the battery's voltage and estimate the remaining capacity (percentage).

2. **Voltage Readings During Charging**:
  - During charging, the behavior can vary depending on the type of fuel gauge and how it integrates with the charging circuit:
    - **Voltage During Charging**: The voltage at the battery terminals will be higher than the battery's nominal voltage (3.7V) due to the charging current and the charging algorithm used (constant current, constant voltage, etc.).
    - **Fuel Gauge Behavior**: Some fuel gauges might not accurately reflect the charging voltage in real-time, especially if they are designed to measure the battery voltage primarily during discharging.

### Steps to Ensure Accurate Charging Information

To ensure you get accurate charging voltage readings and percentage estimates:

1. **Check Manufacturer Specifications**: Refer to the datasheet or user manual of your battery fuel gauge. It should provide details on how it handles charging scenarios and whether it accurately reports charging voltage.

2. **Understand Charging Algorithms**: Different charging algorithms (CC/CV, for example) result in different voltage levels at different stages of charging. Ensure your fuel gauge is compatible with the charging algorithm used for your battery.

3. **Monitor Charging Parameters**: Use a multimeter or a dedicated battery charger with monitoring capabilities to cross-check the actual voltage at the battery terminals during charging. Compare this with the readings from your fuel gauge to assess accuracy.

4. **Update Calibration or Parameters**: Some fuel gauges allow calibration or adjustment of parameters to improve accuracy. Check if your fuel gauge supports this and if adjusting parameters can align its readings with actual charging voltages.

5. **Consider Real-time Monitoring**: For critical applications, real-time monitoring systems that directly measure voltage and current at the battery terminals might provide more accurate data than fuel gauges relying on indirect measurements.

### Practical Considerations  https://www.pneda.com/

- **Stabilization Time**: Allow some time after connecting the charger for the fuel gauge to stabilize its readings. Initial fluctuations are common as the charging process begins.

- **Testing Different Charging Conditions**: Test the fuel gauge under various charging conditions (different charge rates, different states of charge) to understand its behavior and accuracy across different scenarios.

### Conclusion

Achieving exact charging voltages and percentage readings requires ensuring compatibility between your fuel gauge and the charging system. Refer to documentation, monitor actual charging parameters, and consider calibration or adjustment options if available. If persistent inaccuracies occur, consulting with the manufacturer or technical support of your fuel gauge may provide specific insights or solutions tailored to your setup.