About this replacement
Motorola Moto G5 Plus — 3.8V Li-Polymer Replacement Battery (HG40)
This is a 3.8V, 2800mAh Li-Polymer battery for the Motorola Moto G5 Plus and its variants, including the Dual SIM, Dual SIM TD-LTE, and XT1677 models. It carries OEM part numbers HG40 and SNN5984A. When the original cell degrades and can no longer hold a charge through a normal day, this replaces it.
- Moto G5 Plus variant coverage: All listed variants — standard, Dual SIM, TD-LTE, and XT1677 — share the same battery bay dimensions, connector pinout, and BMS communication protocol. One cell fits across the entire G5 Plus line.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a G5 Plus unit and confirmed the BMS handshake completed correctly, charge IC accepted the cell without flagging errors, and the fuel gauge IC initialised at full capacity.
- First-cycle fuel gauge reset: After installation, disable fast charging and run one complete discharge down to automatic shutdown, then charge fully to 100%. This gives the coulomb counter a clean reference cycle against the new cell's discharge curve before fast-charge current is applied.
Sudden shutdown at 20–30% on the Moto G5 Plus after a cell swap
A new cell has a slightly different voltage-vs-capacity curve than the original. The fuel gauge IC on the G5 Plus was calibrated to the old cell, so it misjudges where the voltage cliff sits. When the modem or display pulls a high-current burst, the cell voltage drops below the BMS cutoff threshold before the OS expects it — triggering an abrupt shutdown. One full discharge-charge cycle forces the coulomb counter to relearn the new cell's actual cutoff voltage, which sits around 3.2–3.3V under load.
USB fast charge not activating after battery replacement on the G5 Plus
On the first cycle after installation, the charge IC may refuse to enter fast-charge mode because the BMS has not yet completed its initial authentication exchange with the phone's power management IC. This is normal behaviour — it is not a defective cell. Charge once at standard rate to full capacity, then disconnect and reconnect the charger. Fast charging should negotiate correctly from the second cycle onward once the BMS has a completed charge cycle on record.