About this replacement
Honor MUS-B19 / GS3 / GS Pro — 3.87V Li-Polymer Replacement Battery (HB522628EFW)
This is a 3.87V, 460mAh Li-Polymer cell for the Honor Watch Fit (MUS-B19), GS3, and GS Pro smartwatches. It replaces the original HB522628EFW battery when the existing cell no longer holds charge or powers the watch through the day. Voltage and capacity match the OEM specification exactly.
- MUS-B19, GS3, and GS Pro compatibility: These three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — all three accept the HB522628EFW cell without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the MUS-B19 platform. The BMS accepted the new cell without throwing a fault, and the fuel gauge IC updated state-of-charge correctly across a full cycle.
- Fuel gauge calibration after swap: Place the watch on its magnetic charger immediately after fitting this cell and charge to 100% before first use. The fuel gauge IC on these watches loses its reference point when the cell is disconnected — it cannot report accurate charge percentage until it completes one full charge cycle from near-zero.
Why the Honor Watch Fit shows 0% immediately after a battery swap
The GS3 and MUS-B19 platforms use a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell. When you remove the old battery, that counter resets to zero and has no reference for the new cell's state. The watch then reports 0% — or shuts off — because the IC has no data to work from. Placing the watch on charge immediately after the swap and running it to full resolves this. After one complete charge cycle, the gauge recalibrates and percentage readings stabilise.
Watch not pairing with the Honor app after battery replacement
Removing the battery terminates the active BLE session between the watch and your phone. The phone retains the old pairing record, but the watch starts fresh with no session data — the two devices no longer recognise each other automatically. On the phone, go to Bluetooth settings, forget the watch entirely, then open the Honor Health app and run a new pairing from scratch. Do not attempt to reconnect through the Bluetooth menu alone; pairing must be initiated through the app to re-establish the full health-data link.