Xiaomi Redmi K50 Pro BM5E Replacement Battery 3.87V 4850mAh

Xiaomi Redmi K50 Pro — 3.87V Li-Polymer Replacement Battery (BM5E)

This is a 3.87V, 4850mAh (18.77Wh) Li-Polymer replacement battery for the Xiaomi Redmi K50 Pro (model numbers 22021211RC and 22011211C). It replaces the original BM5E cell that powers the display, processor, modem, and all connectivity functions. Fit this battery when the original shows capacity fade, unexpected shutdowns, or swollen cell symptoms.

• Redmi K50 Pro platform compatibility: The 22021211RC and 22011211C variants share the same BM5E connector pinout, BMS handshake protocol, and voltage rail. One replacement cell covers both regional variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the K50 Pro board. The BMS accepted the cell, reported state-of-charge correctly after one full cycle, and the Xiaomi charge IC engaged without error codes.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter locks in its reference point. Skip this step and the percentage readout will drift for several days.

Why the K50 Pro reports wrong battery percentage after a cell swap

The K50 Pro uses a coulomb counter that calibrates against the discharge curve of the original cell. When a new BM5E goes in, the fuel gauge IC still holds the old cell's reference data. Until it completes one full discharge and charge cycle at a consistent rate, the percentage readout can read 10–15% high or low. One uninterrupted cycle from 100% down to auto-shutdown and back to full — at standard charge speed — resets the reference and brings the readout back in line.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under heavy modem or display load, a fresh cell that hasn't been calibrated can sag below the BMS cutoff threshold while the fuel gauge still reads 25%. The BMS reads real-time cell voltage — not percentage — and trips the cutoff to protect the cell. Run that first full calibration cycle, then check the shutdown threshold: if it persists below 3.4V under load, the cell voltage under peak draw is dropping faster than the fuel gauge tracks. Reduce screen brightness or background sync load during the next calibration cycle.