MeiZu 15 Plus Replacement Battery BA891 3.85V 3400mAh

MeiZu 15 Plus / M891Q — 3.85V Li-Polymer Replacement Battery (BA891)

The BA891 is a 3.85V, 3400mAh (13.09Wh) Li-Polymer cell for the MeiZu 15 Plus, 15 Plus Dual SIM, 15 Plus Dual SIM TD-LTE, and M891Q. It replaces the original battery when capacity has dropped through normal charge cycling. Dimensions are 78.46 × 66.66 × 3.40mm — verify your existing cell before installing.

• 15 Plus and M891Q variant coverage: The Dual SIM TD-LTE and standard 15 Plus share the same battery bay geometry, connector pinout, and BMS handshake protocol — all four model variants accept the BA891 without modification.
• Bench tested on actual hardware: We ran the BA891 through full charge and discharge cycles on the 15 Plus platform. The BMS negotiated correctly with the charge IC, and cell voltage held steady under simultaneous screen and modem load without tripping low-voltage cutoff.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge down to automatic shutdown, then charge to 100% on standard current. This gives the coulomb counter a clean reference curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the BA891 after installation

A new Li-Polymer cell has a slightly different discharge curve than the worn cell the fuel gauge IC was calibrated against. At around 20–30% reported charge, the phone's voltage rail can dip below the modem's minimum threshold during a call or data burst, triggering an emergency shutdown before the gauge reaches zero. This is a calibration mismatch, not a faulty cell. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter reference, and the shutdowns stop.

MeiZu fast charge not recognised on the first cycle after a cell swap

MeiZu's proprietary fast charge protocol includes a BMS handshake between the charge IC and the cell. On the first cycle with a new cell, the charge IC may fall back to standard 5V input while it verifies cell impedance and temperature within the expected range. This is normal behaviour — not a wiring fault or incompatible charger. Charge fully once at standard rate, and the fast charge handshake will re-engage from the second cycle onward. Confirm fast charge is active by checking the charging indicator in the notification bar, which will show the boosted rate once negotiation succeeds.