Motorola MB50 Replacement Battery 3.87V 4700mAh Li-Polymer

Motorola Moto Edge S30 — 3.87V Li-Polymer Replacement Battery (MB50)

This is a 3.87V, 4700mAh (18.19Wh) Li-Polymer replacement battery for the Motorola Moto Edge S30, Moto Edge S30 5G (2021), XT2175-2, and Moto G200 5G. It uses OEM part references MB50 and SB18D10749. Swap it when your original cell no longer holds adequate charge through a normal day of use.

• Moto Edge S30 / G200 5G platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — which is why a single cell (MB50) covers the full XT2175 line. Voltage rail sits at 3.87V nominal, matching the power management IC on each board.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on an XT2175-2 board. The BMS accepted the cell without error flags, thermal cutoff held within normal thresholds, and the coulomb counter initialised correctly after the first full cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes high current into an uncalibrated cell — preventing false percentage readings from the start.

Sudden shutdown at 20–30% on the Moto Edge S30

This happens when the cell's internal impedance climbs high enough that it cannot sustain voltage under the load spike from the modem or display. The phone's power management IC reads a voltage drop it interprets as empty — even though the coulomb counter still shows capacity remaining. The fix is to complete one full discharge cycle after installation so the fuel gauge IC recalibrates its low-voltage cutoff against the new cell. Target a resting voltage above 3.6V before triggering the first full charge cycle.

USB-PD fast charge not activating on first cycle after replacement

After a cell swap, the charge IC sometimes refuses to negotiate fast-charge protocols until the BMS has completed one standard charge cycle at low current. This is a deliberate safety behaviour — the IC will not push high current into a cell whose impedance profile it has not yet measured. Plug in using the standard charger and allow a full slow charge to complete. On the second cycle, fast charging should activate automatically.