Bea-fon M6 Premium Li-Polymer Replacement Battery 3.85V 3600mAh

Bea-fon M6 Premium — 3.85V Li-Polymer Replacement Battery (M6)

This 3.85V, 3600mAh Li-Polymer cell replaces the original battery in the Bea-fon M6 Premium mobile phone. It restores power for calls, messaging, and standard phone functions when the original cell has degraded or failed to hold a charge. Dimensions are 87.40 × 64.40 × 4.10mm — measure your original before fitting.

• M6 Premium platform fit: The M6 Premium uses a 3.85V nominal Li-Polymer cell with a specific connector and BMS handshake tied to this voltage rail. This replacement matches that spec so the charge IC accepts the cell and the fuel gauge IC can track state of charge correctly.
• Bench tested on actual hardware: We cycled this cell through charge, standby, and active modem load states. The BMS held cutoff correctly at both ends — no false low-voltage disconnect and no overcharge past 4.35V.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the M6 Premium after a cell swap

This happens because the fuel gauge IC is still running the discharge curve it learned from the old, degraded cell. The new cell has a steeper voltage drop under modem and screen load than the IC expects, so it reads 25% available but the actual cell voltage collapses below the BMS cutoff threshold. The phone interprets this as a hard fault and shuts down immediately. One full discharge to 3.0V and a complete recharge lets the coulomb counter reset its end-point calibration and eliminates the premature cutoff.

USB fast charge not accepted on the first cycle after replacement

The M6 Premium's charge IC negotiates fast-charge protocol only after it confirms the new cell's internal resistance is within an expected range. A fresh Li-Polymer cell starts with slightly higher impedance than a broken-in cell, so the IC defaults to standard 5V/1A on the first session. This is normal BMS behaviour, not a fault with the replacement cell. Complete one full charge at standard rate — fast charge typically activates from the second cycle onward once the IC has logged acceptable impedance values.