Motorola Moto Edge 50 5G QR50 Replacement Battery 3.91V 4850mAh

Motorola Moto Edge 50 5G — 3.91V Li-Polymer Replacement Battery (QR50)

This is a 3.91V, 4850mAh Li-Polymer replacement battery for the Motorola Moto Edge 50 5G. It fits the XT2407, XT2407-1, and XT2407-2 variants. OEM part numbers QR50, SB18E18870, and SB18E18871 all cross to this cell.

• XT2407 variant coverage: The XT2407, XT2407-1, and XT2407-2 share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell fits all three without modification.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on the XT2407 platform. The BMS accepted the charge handshake correctly, and the fuel gauge IC tracked state-of-charge without erratic jumps after the first full cycle.
• First-cycle calibration tip: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes power into an uncalibrated cell.

Sudden shutdown at 20–30% on the Moto Edge 50 5G after a cell swap

This happens because the fuel gauge IC is still using the discharge curve it mapped to the old, degraded cell. When the modem fires a high-draw burst — 5G mmWave polling, screen-on with GPS active — the new cell's voltage drops faster than the old curve predicts. The phone reads 25% remaining, but the hardware voltage hits the low-cutoff threshold and the device shuts off. One full discharge-to-shutdown followed by a full uninterrupted charge resets the coulomb counter and corrects this behaviour.

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

After a cell swap, the charge IC on the Edge 50 5G may not negotiate fast-charge protocols on the first charge cycle. The BMS flags the new cell as uncalibrated and defaults to a conservative trickle rate until it completes one baseline cycle. Plug into the original Motorola charger and let it run a full charge without interruption. Fast charging resumes normally from the second cycle onward once the BMS has logged the cell's impedance baseline.