MeiZu BS25 Meilan Max Replacement Battery 3.85V 4100mAh

MeiZu Meilan Max / M3 Max — 3.85V Li-Polymer Replacement Battery (BS25)

The BS25 is a 3.85V, 4100mAh Li-Polymer cell that fits the MeiZu Meilan Max, M3 Max, S685Q, and S685Q Dual SIM TD-LTE. It replaces the original battery when the device no longer holds charge or shuts down unexpectedly. Dimensions are 88.50 × 68.60 × 3.80 mm — measure your original before installing.

• Meilan Max and M3 Max platform fit: These models share the same internal battery bay dimensions, connector pinout, and BMS handshake protocol, which is why a single BS25 cell covers the full S685Q range including Dual SIM and TD-LTE variants.
• Bench tested on actual hardware: We cycled the BS25 through full charge and discharge on the Meilan Max platform. The BMS accepted charge normally, protection cutoffs triggered correctly at the low-voltage threshold, and the cell held stable voltage under sustained screen and modem load.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes into an uncalibrated state.

Sudden shutdown at 20–30% on the BS25 replacement cell

This happens because the fuel gauge IC is still mapped to the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load at a point the gauge reads as 20–30% remaining. The phone interprets the voltage drop as a fault and cuts power before the gauge reaches zero. Run one full discharge to auto-shutdown, then charge uninterrupted to 100% — this resets the coulomb counter against the actual cell curve.

USB fast charge not accepted on the first cycle after replacement

On the first charge cycle, the charge IC may reject the fast-charge handshake because the BMS presents an unfamiliar impedance profile from a new, uncycled cell. The phone defaults to standard 5V charging as a protection measure. Charge fully once at standard rate, disconnect, then reconnect — on the second cycle the charge IC typically negotiates fast charge correctly. If it still fails, check the cable and adapter separately before assuming a BMS fault.