About this replacement
Huawei Band 3 Pro — 3.82V Li-Polymer Replacement Battery (HB351329ECW)
This is a 3.82V, 100mAh Li-Polymer cell replacing part number HB351329ECW in the Huawei Band 3 Pro fitness tracker. The Band 3 Pro is a slim wrist-worn device with continuous heart rate monitoring, GPS, and sleep tracking. Dimensions are 27.40 × 12.00 × 3.20mm — a tight fit, so exact sizing matters.
- Band 3 Pro platform fit: The Band 3 Pro runs a single-cell Li-Polymer architecture at 3.82V nominal. The BMS on this platform reads cell impedance at startup, so the replacement cell must match the original voltage rating exactly — any deviation triggers a low-battery fault before the fuel gauge can calibrate.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Band 3 Pro platform. The BMS accepted the cell without fault flags, and the fuel gauge stepped through charge states normally from near-zero to full.
- Post-swap charging on the Band 3 Pro: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before use. The Band 3 Pro fuel gauge IC loses its reference point when the original cell is removed. Without a full charge cycle from near-zero, the gauge cannot recalibrate and will report inaccurate percentages.
Why the Band 3 Pro fuel gauge reads incorrectly after a cell swap
The Band 3 Pro uses a coulomb-counting fuel gauge IC that tracks charge by measuring current flow over time. When the original cell is disconnected, the IC loses its accumulated reference data — it has no baseline to work from. The new cell arrives at a partial state of charge, which the gauge cannot interpret without a calibration cycle. One full charge from near-zero resets the counter and restores accurate percentage readings.
Watch not pairing with the Huawei Health app after battery replacement
Removing power during a battery swap terminates any active BLE session between the Band 3 Pro and the paired phone. The watch generates a new session token on next boot, which the phone's Bluetooth stack does not recognise automatically. Open the Huawei Health app, go to device settings, remove the Band 3 Pro from paired devices, then re-pair from scratch. The watch must show a stable charge above 10% before pairing will complete reliably.