MeiZu C9 Replacement Battery BA818 3.85V 3000mAh

MeiZu C9 / M818H Series — 3.85V Li-Polymer Replacement Battery (BA818)

The BA818 is a 3.85V, 3000mAh Li-Polymer cell that fits the MeiZu C9, M818H, C9 Pro, and M819H. It matches the original voltage rail and connector pinout used across this handset line. Capacity figure is 11.55Wh as listed in the product specification.

• C9 / M818H platform fit: The C9, M818H, C9 Pro, and M819H all share the same battery bay geometry, connector orientation, and 3.85V nominal rail. One BA818 cell services the full group without modification.
• Bench tested on actual hardware: We ran the BA818 through charge and discharge cycles on compatible hardware. The BMS accepted the charge IC handshake cleanly, held the 4.35V upper cutoff, and tripped the low-voltage cutoff at the expected floor without false readings mid-cycle.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the BA818 replacement cell

A new Li-Polymer cell has a slightly different discharge curve than the aged cell the fuel gauge IC was originally calibrated to. When the phone's reported percentage still reads 20–30%, the actual cell voltage can drop below the modem's or display's sustain threshold under load. The phone cuts out to protect itself, even though the gauge says charge remains. One complete discharge-charge cycle at standard rate retrains the coulomb counter and aligns the percentage readout with the real voltage curve.

Device won't power on after the BA818 sat in storage

Li-Polymer cells self-discharge at roughly 2–5% per month. If the battery sat discharged for an extended period, the BMS may have tripped its deep-discharge lockout below 2.5V per cell and will refuse to pass current to the phone. Connect the phone to a low-current charger — a standard 5V/1A USB adapter works better here than a fast charger — and leave it for 20–30 minutes before attempting to power on. If the BMS recovers, the charge IC will take over and the boot screen should appear. If the cell remains at or below 2.4V after that window, the cell is outside recovery range and needs replacement.