MS50 Motorola Moto G50 5G Compatible Battery 3.85V 4500mAh

Motorola Moto G50 5G — 3.85V Li-Polymer Replacement Battery (MS50)

This 3.85V, 4500mAh Li-Polymer cell replaces the original MS50 battery in the Motorola Moto G50 5G (XT2149, XT2149-1). It fits the 2021 model and carries the same OEM part reference SB18D09927. Dimensions are 87.00 × 65.24 × 4.70mm — matching the stock cell footprint in the rear housing.

• XT2149 and XT2149-1 compatibility: Both variants use the same battery connector, voltage rail, and BMS handshake. The MS50 part number covers the full G50 5G lineup without modification.
• Bench tested on actual hardware: We cycled this cell on an XT2149 unit and confirmed the BMS accepted the charge handshake on the first connection. The protection circuit engaged correctly at both high and low voltage thresholds.
• First-cycle fast charge discipline: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

New Li-Polymer cells have a steeper voltage cliff than a worn cell the fuel gauge IC was originally calibrated against. When the modem fires a 5G uplink burst or the display hits full brightness, current draw spikes and the cell voltage briefly drops below the BMS cutoff threshold — even if the reported percentage looks safe. The phone reads the old cell's discharge curve and misjudges the remaining capacity. One full discharge-to-shutdown followed by a complete charge at standard rate forces the coulomb counter to remap to the new cell. After that cycle, percentage readings stabilise and the early shutdowns stop.

USB-PD fast charge not accepted on first cycle after swap

After a cell replacement, the charge IC on the G50 5G sometimes withholds fast-charge negotiation on the first charge cycle. This is a deliberate safety hold — the IC runs a pre-charge trickle assessment before it allows the higher current USB-PD profile to activate. Forcing a fast-charge connection on the very first cycle can cause the phone to sit at a slow 5W rate and appear stuck. Plug in using the stock charger, let the first cycle complete at whatever rate the IC selects, then reconnect — full fast-charge negotiation should resume at 18W on the second cycle.