Huawei Band 2 Pro C5900 HB5B2 Replacement Battery 3.7V 1100mAh

Huawei C5900 / C5990 / C6000 Series — 3.7V Li-ion Replacement Battery (HB5B2)

This is a 3.7V, 1100mAh Li-ion cell (OEM part HB5B2 / HB5B2H) for the Huawei Band 2 Pro fitness tracker and closely related models including the C5990, C6000, and C7600. The original cell degrades with shallow charge cycles typical of wearable use, dropping usable capacity well before the device reports a low battery. This replacement restores full sensor and display operation.

• C5900 / C5990 / C6000 / C7600 platform fit: These models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol — one cell SKU covers the full group without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Band 2 Pro platform. The BMS accepted the cell on first connection, balancing terminated cleanly at 4.2V, and the protection circuit tripped correctly at the low-voltage cutoff threshold under load.
• Fuel gauge recalibration after install: After fitting this cell, run one full discharge to automatic shutoff followed by a complete uninterrupted charge before resuming normal use. The Band 2 Pro's coulomb counter is calibrated to the old cell's discharge curve — skipping this step causes the percentage readout to jump erratically for several days.

Why the Band 2 Pro reports wrong battery percentage after a cell swap

The Band 2 Pro uses a coulomb counter IC that tracks accumulated charge and discharge current to estimate state of charge. When a new cell with a different internal resistance is installed, the counter's reference curve no longer matches the actual cell voltage behaviour. This causes the displayed percentage to read high, low, or jump in large steps. One full discharge-to-shutoff and charge-to-100% cycle forces the IC to reset its endpoints against the new cell's actual voltage floor and ceiling.

Sudden shutoff with percentage still showing 20–30% remaining

This is a voltage cliff failure — the cell's internal resistance has risen to the point where it cannot hold voltage above the BMS cutoff threshold under the combined load of the heart rate sensor, display, and wireless sync. The percentage shown is based on the coulomb counter, not real-time voltage, so the device cuts out before the counter reaches zero. After fitting the replacement, confirm the first charge reaches a steady 4.2V at the cell terminals. If shutoffs persist after one full recalibration cycle, check that the connector is fully seated.