Motorola Moto E 2nd Replacement Battery FT40 3.8V 2200mAh

Motorola Moto E 2nd Generation — 3.8V Li-Polymer Replacement Battery (FT40 / SNN5955A)

This is a 3.8V, 2200mAh lithium-polymer replacement battery for the Motorola Moto E 2nd generation smartphone. It fits models XT1526, XT1528, and XT1077, among others. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.

• XT1526, XT1528, XT1077 compatibility: These variants share the same battery bay dimensions, voltage rail, and FT40 connector pinout. The BMS handshake is identical across the series, so one cell covers all listed models without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on an XT1528 unit. The BMS accepted the new cell on first connect, charge termination triggered correctly at 4.35V, and protection cutoff fired as expected under load. No anomalies on first cycle.
• First-cycle fuel gauge calibration: After installing this cell, disable fast charging for the first complete discharge-charge cycle. The fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve. Running fast charge before that calibration completes can push current into an uncalibrated cell and skew percentage readings for weeks.

Sudden shutdown at 20–30% on the Moto E 2nd after a cell swap

A new cell with a fuel gauge IC still calibrated to the old degraded cell will report voltage incorrectly under load. When the modem transmits or the screen peaks brightness, current draw spikes and the actual cell voltage drops below the BMS cutoff threshold — even though the OS shows 20–30% remaining. The phone shuts off because the cell cannot sustain voltage under that instantaneous load, not because the replacement is faulty. Run one complete discharge to the automatic power-off point, then charge uninterrupted to 100% to let the coulomb counter reset against the actual cell capacity.

Battery percentage jumping erratically after installation

The Moto E 2nd's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, the stored curve no longer matches actual cell behaviour, so percentage readings jump as the IC tries to reconcile measured voltage against an outdated model. This is not a hardware fault in the replacement — it is a calibration gap. Drain the phone to zero until it powers off on its own, then charge to 100% without interruption. After that single full cycle, the IC rewrites its reference curve and percentage tracking stabilises.