Motorola Moto G9 Plus MG50 Replacement Battery 3.85V 4750mAh

Motorola Moto G9 Plus XT2087 — 3.85V Li-Polymer Replacement Battery (MG50 / SB18C80753)

This is a 3.85V, 4750mAh lithium-polymer battery for the Motorola Moto G9 Plus (XT2087-1 and XT2087-2). It replaces the original MG50 cell when the factory battery degrades, swells, or stops accepting a charge. Dimensions match the original cavity at 83.10 × 64.92 × 5.10mm.

• XT2087-1 and XT2087-2 coverage: Both variants use the same MG50 cell on the same 3.85V power rail with the same flex connector and BMS handshake. One battery fits both board revisions without modification.
• Bench tested on actual hardware: We ran this cell on a G9 Plus board and confirmed the BMS accepted charge current, reported state-of-charge to the OS, and held cutoff voltage at both ends of the discharge curve.
• First-cycle fast-charge protocol: After installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before TurboPower pushes higher current into an uncalibrated cell.

Why the Moto G9 Plus reports wrong battery percentage after a cell swap

The G9 Plus uses a coulomb counter in the fuel gauge IC, calibrated to the charge curve of the original cell. When you install a fresh cell, the IC still references the old degraded curve, so reported percentage drifts from actual charge state. The fix is one full discharge down to automatic shutdown followed by a full uninterrupted charge to 100%. After that single cycle, the coulomb counter resets its reference points against the new cell and percentage accuracy returns to normal.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the modem or display pulls a brief high-current spike and the cell voltage drops below the BMS low-voltage cutoff threshold — even though the fuel gauge still reads 25%. A freshly installed cell that hasn't been calibrated yet makes this worse, because the IC doesn't know where the real voltage cliff sits. Run the first-cycle calibration described above, and the BMS cutoff and the gauge reading will align. If shutdowns persist after calibration, check that the connector is fully seated — a partial connection raises contact resistance and amplifies voltage sag under load, dropping the cell below 3.0V at the terminals.