MyPhone BM-01 Fun 2 Replacement Battery 3.7V 1800mAh

MyPhone Fun 2 / Next-S — 3.7V Li-ion Replacement Battery (BM-01)

This is a 3.7V, 1800mAh Li-ion replacement cell for the MyPhone Fun 2 and Next-S smartphones. Part number BM-01 matches the original factory specification. It restores calling, messaging, and app performance when the stock battery has degraded or stopped holding charge.

• Fun 2 and Next-S compatibility: Both models share the BM-01 cell format — same voltage rail, same connector orientation, and the same charge IC on the motherboard. One replacement covers both devices without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Fun 2 platform. The BMS accepted charge handshake normally, and the protection circuit tripped correctly at low-voltage cutoff — no anomalous behaviour at full load.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging starts — skipping this step causes percentage drift and early shutdowns.

Sudden shutdown at 20–30% on a replacement BM-01 cell

This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff — where terminal voltage drops sharply under modem or screen load — at a different state-of-charge than the IC expects. The phone reads 25% but the actual cell voltage has already fallen below the modem's operating floor. One full discharge to automatic cutoff followed by an uninterrupted charge to 100% forces the coulomb counter to reset against the new cell's actual curve.

Phone warm near the battery during the first few charging sessions

A new BM-01 cell typically has higher internal impedance than a broken-in cell. The charge IC compensates by pushing slightly more voltage, which dissipates as heat until impedance drops after a few cycles. This is normal for the first two to three charges and not a fault in the replacement cell. If warmth persists beyond the third full charge cycle, check that the charge port is clean and that no debris is trapping heat against the back cover.