About this replacement
Bea-fon M7 Premium / M7 Lite Premium — 3.85V Li-Polymer Replacement Battery (CXD475778P)
This 3.85V, 3400mAh Li-Polymer battery replaces part number CXD475778P in the Bea-fon M7 Premium and M7 Lite Premium smartphones. It restores power to devices where the original cell has degraded, swollen, or lost the ability to hold a usable charge. Capacity is 13.09Wh — matching the original cell specification.
- M7 Premium and M7 Lite Premium fitment: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers both. The 79.30 × 56.50 × 4.90mm envelope fits the chassis without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the M7 platform. The BMS accepted the charge handshake on the first cycle and held voltage above the low-battery cutoff threshold through full discharge.
- 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 map the new cell's discharge curve before high-current charging pushes into an uncalibrated state — preventing erratic percentage readings from the start.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff failure. Under peak load — modem transmitting, screen at full brightness — the cell voltage sags faster than the fuel gauge IC expects. The phone's protection circuit reads that sag as a critically low cell voltage and shuts down, even though the reported percentage still looks safe. It happens most often on a fresh cell because the coulomb counter is still calibrated to the old, worn cell's discharge curve. Run one full discharge to below 5% and a full charge to 100% without interruption — this resets the coulomb counter baseline and the shutdowns typically stop.
USB fast charge not working after battery replacement
After a cell swap, the charge IC on some M7 units defaults to a conservative trickle rate on the first cycle — it does not immediately negotiate the higher-current protocol with the new BMS. This is a protection behaviour, not a fault. Plug in via the original cable and charger, let the first charge complete fully without unplugging early, and the charge IC recalibrates its current ceiling. If fast charge still does not engage after two full cycles, check that the USB-C port is clean and the cable supports the required current rating.