About this replacement
Motorola Moto G9 Plus (XT2087) — 3.87V Li-Polymer Replacement Battery (MG50)
This is a 3.87V, 4900mAh Li-Polymer cell built to replace the MG50 battery in the Motorola Moto G9 Plus, including XT2087-1 and XT2087-2 variants. It fits the 2020 model released globally. Capacity is rated at 18.96Wh, matching the original cell specification.
- XT2087-1 and XT2087-2 compatibility: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol — this cell covers both without modification or adapter.
- Bench tested on actual hardware: We cycled this cell on an XT2087-2 unit and confirmed the BMS negotiated charge termination correctly at 4.40V, with no false cutoff on the first charge.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge down to auto-shutdown, then charge to 100% on standard 5W. This gives the fuel gauge IC a complete discharge curve before high-current charging begins on 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 that tracks charge in and out relative to a stored cell discharge curve. When you swap the cell, that stored curve still reflects the old degraded battery. The IC will misreport state-of-charge until it maps the new cell's actual voltage-to-capacity profile. One full slow-charge cycle — without interruption and without fast charge — forces the IC to rewrite that reference curve. After that single cycle, percentage readings stabilise.
Sudden shutdown at 20–30% on the new cell
This happens when the modem radio or display triggers a high-current draw and the cell voltage drops sharply below the BMS cutoff threshold — even though the gauge still shows 20–30% remaining. The fuel gauge IC hasn't yet calibrated the knee of the new cell's discharge curve, so it predicts more capacity than the cell can actually deliver under load. Run two full unconstrained discharge-charge cycles first. After calibration, the gauge will trigger shutdown warnings before the voltage cliff, not during it.