About this replacement
MyPhone L-Line — 3.7V Li-ion Replacement Battery (BM-10)
The BM-10 is a 3.7V Li-ion cell rated at 3000mAh (11.1Wh), built to replace the original battery in MyPhone L-Line smartphones. It fits the L-Line form factor at 75.75 × 54.50 × 5.30mm and connects directly to the stock charge circuit. Swap it in when the original cell no longer holds a charge or shuts down unexpectedly under load.
- L-Line platform fit: MyPhone's L-Line shares a unified battery bay and connector pinout across the series. The BM-10 matches this footprint — voltage rail, physical dimensions, and connector orientation all correspond to the original spec.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the L-Line platform. The BMS accepted the charge handshake without error, and the protection circuit tripped correctly at both the over-voltage and under-voltage thresholds.
- 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 its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated reference.
Why the L-Line reports wrong battery percentage after a cell swap
The L-Line stores the previous cell's discharge curve in its fuel gauge IC. When a new cell goes in, the IC still references the old calibration data, so the percentage reading drifts from the real charge state. This is not a fault with the replacement cell — it is the IC recalibrating to a new internal resistance baseline. Run one full discharge to 3–5% followed by a full uninterrupted charge. After one complete cycle, the fuel gauge re-anchors its coulomb counter and percentage readings stabilise.
Sudden shutdown at 20–30% on the replacement cell
A new cell at standard impedance can experience a sharper voltage drop than the worn cell the phone was calibrated against — especially when the modem transmits or the screen peaks at full brightness. The L-Line's low-voltage protection threshold triggers when the instantaneous voltage sags below the cutoff, even if the displayed percentage looks safe. The fuel gauge IC has not yet learned the new cell's voltage-versus-capacity curve, so it does not predict the sag correctly. Complete two full charge-discharge cycles and the IC will adjust its cutoff prediction — shutdowns at 20–30% should stop after the second cycle.