The Full Charge Capacity (FCC) of the BQ4050 fuel gauge is updated based on charge-discharge cycles. However, when the actual capacity decreases and the Full Charge Capacity becomes less than the Design Capacity minus 256 mAh, the Full Charge Capacity ceases to update and remains at the value of (Design Capacity - 256 mAh). What is the root cause?
This is not an isolated defect, but a widespread issue across batch-produced products (tens of thousands of units). After more than 100 usage cycles, the actual capacity degradation may exceed 256 mAh or even slightly more. Since the total battery capacity is 10,000 mAh, the percentage of degradation corresponding to 256 mAh is relatively small. The capacity decreases slightly per cycle rather than a sudden drop in a single cycle. Subsequently, the FCC value ceases to update further and remains stuck at (Design Capacity - 256 mAh). This leads to a critical consequence: the state of charge (SOC) percentage at the end of discharge becomes severely inaccurate— the battery suddenly dies even though a certain percentage of SOC is still displayed. Therefore, the factory must resolve this issue urgently. What could be the potential root causes?
The attachment contains the BQ4050 configuration.
