Bea-fon M5 Replacement Battery 3.8V 1900mAh Li-ion

Bea-fon M5 Series — 3.8V Li-ion Replacement Battery (M5)

This 3.8V, 1900mAh Li-ion cell replaces the original battery in the Bea-fon M5, M5_EU001B, and M5 Premium. It fits directly into the same battery bay with the same connector orientation. When the original cell loses capacity through repeated charge cycles, this replacement restores normal operation without replacing the handset.

• M5, M5_EU001B, and M5 Premium compatibility: All three variants run the same 3.8V power rail and use the same physical connector and BMS handshake protocol. One cell fits all three without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on M5 hardware. The BMS accepted charge handshake on the first cycle, voltage held steady under call and screen load, and the protection circuit tripped correctly at the low-voltage threshold.
• Fuel gauge recalibration on first install: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before using the phone normally. The M5's fuel gauge IC is calibrated to the original cell's discharge curve — one full cycle resets it to the new cell so percentage readings stay accurate.

Sudden shutdown at 20–30% on the Bea-fon M5

This is the most common complaint after fitting any replacement cell in the M5. The fuel gauge IC still references the old cell's discharge curve, so it misreads the new cell's actual state of charge. When the modem fires during a call or the screen brightness spikes, the cell voltage drops sharply under load — faster than the gauge predicted. The BMS reads that as a low-voltage fault and cuts power. One full discharge-to-shutdown and uninterrupted recharge cycle forces the coulomb counter to rebuild its map against the new cell. After that cycle, shutdowns at 20–30% stop.

M5 not powering on after the replacement battery sat in storage

Li-ion cells self-discharge during storage. If this cell dropped below roughly 2.5V before installation, the BMS enters lockout mode and the phone shows no sign of life — no boot screen, no charging indicator. Connect the M5 to a wall charger, not a PC USB port, and leave it untouched for 20–30 minutes. A wall charger delivers enough current to push the cell past the BMS recovery threshold. Once the cell climbs back above 3.0V, the BMS releases lockout and the phone will power on and begin a normal charge cycle.