Motorola GA40 Moto G4 Plus Replacement Battery 3.8V 2700mAh

Motorola Moto G4 Plus — 3.8V Li-Polymer Replacement Battery (GA40 / SNN5966A)

This 3.8V, 2700mAh Li-Polymer cell replaces the original GA40 / SNN5966A battery in the Motorola Moto G4 Plus, Moto G4 Plus TD-LTE, XT1644, and XT1643. It fits the same physical bay and uses the same connector as the factory cell. Capacity is 10.26Wh — identical to the OEM spec.

• XT1643 and XT1644 compatibility: Both variants use the same 3.8V power rail, identical flex connector pinout, and the same BMS handshake protocol — one cell covers the full G4 Plus range without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an XT1644 unit. The BMS accepted the cell without fault flags, and the charge IC stepped through trickle, CC, and CV phases as expected.
• Fuel gauge recalibration on first use: After installing this cell, disable fast charging and run one complete discharge down to automatic shutdown, then charge to 100% on standard 5V/1A. This gives the coulomb counter a clean baseline against the new cell's discharge curve before fast charge current is applied.

Sudden shutdown at 20–30% on the Moto G4 Plus after a cell swap

The G4 Plus fuel gauge IC holds a learned discharge curve from the old, degraded cell. When a new cell is installed, that stored curve no longer matches how the fresh cell drops voltage under load. The modem and display together can pull enough current to cause a brief voltage dip that the old curve misreads as near-empty — triggering an immediate shutdown even though meaningful charge remains. One full discharge-to-shutdown and recharge cycle rewrites the coulomb counter's reference, and the shutdowns stop.

Phone not powering on after the replacement cell sat in storage

Li-Polymer cells shipped in storage mode or left uncharged for weeks can drop below 2.5V per cell — the threshold at which the BMS latches into lockout to prevent damage. The G4 Plus will show no screen, no charge indicator, and no response to the power button. Connect the phone to a 5V/1A charger and leave it for 20–30 minutes without pressing anything; the BMS trickle-charges the cell back above the 2.8V unlock threshold before handing control to the main charge IC. Once the charge indicator appears on screen, the cell has cleared lockout and will charge normally.