MyPhone BS-41 3350 Replacement Battery 3.7V 900mAh

MyPhone 3350 / Halo 3 / Holo A — 3.7V Li-ion Replacement Battery (BS-41)

This is a 3.7V, 900mAh (3.33Wh) Li-ion battery for the MyPhone 3350, Halo 3, and Holo A smartphones. It replaces OEM part numbers BS-41, BS-45, and MP-U-2. Fits the original battery bay directly, using the same connector and cell footprint as the factory unit.

• 3350, Halo 3, and Holo A compatibility: All three models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol — which is why one cell covers all three. The charge IC on each device negotiates with the same BMS logic, so no firmware differences affect charging behaviour across this group.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a MyPhone 3350 unit. The BMS accepted charge from the first cycle, held the cutoff voltage correctly at 4.2V, and the protection circuit tripped cleanly at the low-voltage threshold without triggering a lockout.
• 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 any high-current charging pushes current into an uncalibrated state.

Why the MyPhone 3350 reports wrong battery percentage after a cell swap

The fuel gauge IC in these phones stores a learned discharge curve from the original cell. When you install a new cell, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The phone reads voltage correctly but translates it against the old profile, so the percentage shown is off. Run one full discharge to shutdown followed by a full uninterrupted charge to 100% — this forces the coulomb counter to reset and build a new reference curve.

Sudden shutdown at 20–30% on the MyPhone 3350 after replacement

This is a voltage cliff issue, not a capacity fault. When the modem fires or the screen backlight peaks, the cell must deliver a short burst of current — if the fuel gauge IC is still running the old calibration curve, the phone doesn't know the cell voltage is about to sag below the cutoff threshold under that load. The BMS cuts power to protect the cell before the displayed percentage reaches zero. Fix this by completing the full recalibration cycle described above — one full discharge to shutdown, then charge to 100% without interruption at standard charge rate.