About this replacement
Huawei Mate 8 / Ascend Mate 8 — 3.8V Li-Polymer Replacement Battery (HB396693ECW)
This is a 3.8V, 4000mAh Li-Polymer replacement battery for the Huawei Mate 8 and Ascend Mate 8 series, including the Ascend Mate 8 Dual SIM and M200-UL00 variants. It replaces the original HB396693ECW cell when the factory battery degrades and can no longer hold a usable charge. Dimensions are 91.38 × 66.08 × 3.85 mm — confirm your original cell matches before installation.
- Mate 8 series compatibility: The Mate 8, Ascend Mate 8, Dual SIM, and M200-UL00 all share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell fits the full line without modification.
- Bench tested on actual hardware: We ran this cell on a Mate 8 unit and confirmed the BMS negotiated correctly with the charge IC — no charge rejection, no fault flags in the battery status register.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the Mate 8 after a cell swap
This happens because the fuel gauge IC is still using the old cell's voltage-to-capacity curve. When the new cell's voltage drops faster than the IC expects under modem or screen load, the phone hits the hardware cutoff before the percentage display reaches zero. The IC reports 25% remaining, but the actual cell voltage has already fallen below the safe floor. One full discharge cycle — draining to automatic shutdown, then charging uninterrupted to 100% — rewrites the IC's learned curve against the new cell and clears this behaviour.
Huawei fast charging not working on the first cycle after replacement
Huawei's proprietary charge protocol requires a handshake between the charger and the battery BMS before high-current charging is permitted. On a freshly installed cell, the BMS may not complete this handshake on the first cycle and defaults to standard 5V/1A input instead. This is not a fault — it is a one-cycle initialisation behaviour. Charge fully once using the original Huawei wall adapter, unplug, then reconnect; fast charge typically resumes on the second cycle.