Motorola BN80 Backflip Replacement Battery 3.7V 1100mAh

Motorola Backflip / ME600 / MB300 — 3.7V Li-ion Replacement Battery (BN80 / SNN5851A)

This is a 3.7V, 1100mAh Li-ion cell built to replace the original BN80 battery in the Motorola Backflip and related models including the Motus, ME600, and MB300. The original OEM pack degrades after repeated charge cycles, leaving the phone unable to hold a usable charge. Swapping this cell restores the hardware to its factory power baseline.

• Backflip, Motus, ME600, MB300 platform fit: These models share the same battery bay geometry, connector pinout, and 3.7V power rail. The BMS handshake protocol is consistent across the BN80, SNN5851, SNN5851A, and BN70 part numbers, so the fuel gauge IC on each device accepts this cell without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Backflip hardware. The BMS accepted charge from the first connection, voltage held steady through screen-on and modem-active load, and no thermal events were recorded during the charging phase.
• Fuel gauge recalibration on first use: After fitting this cell, disable any fast-charging accessory and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before it locks in percentage reporting — skipping this step causes erratic percentage jumps in early cycles.

Sudden shutdown at 20–30% on the Backflip after a cell swap

The Backflip's fuel gauge IC was calibrated to the discharge curve of the original aged cell. A new cell has a steeper voltage cliff near the low end of its capacity range — the phone cuts power before the coulomb counter reaches zero because the voltage drops below the CPU's minimum threshold under modem or screen load. This is not a defective cell. Run two full discharge-charge cycles without interruption. After the second cycle, the fuel gauge IC recalibrates against the new curve and shutdown behaviour returns to normal.

Phone reports wrong battery percentage after fitting the BN80 replacement

The Backflip stores the previous cell's capacity data in the fuel gauge IC's non-volatile register. When a new cell goes in, the IC maps charge state against outdated reference data, which throws percentage readings off by 10–20% in either direction. A full drain to automatic shutdown followed by an uninterrupted charge to 100% forces the IC to rewrite its reference points against the new cell. One full cycle is usually enough — two cycles resolves persistent drift. Do not pull the battery mid-cycle during this recalibration window.