Xiaomi Mi 10 Lite BM4R Replacement Battery 3.85V 3900mAh

Xiaomi Mi 10 Lite Series — 3.85V Li-Polymer Replacement Battery (BM4R)

The BM4R is a 3900mAh Li-Polymer cell at 3.85V nominal, built to replace the original battery in the Xiaomi Mi 10 Lite, Mi 10 Lite 5G, and associated model variants including M2002J9S and M2002J9R. It fits the original battery bay without modification. Capacity is rated at 15.02Wh.

• Mi 10 Lite and 5G variant compatibility: Both the standard Mi 10 Lite and the 5G variant (M2002J9R, M2002J9S) share the BM4R form factor and connector pinout. The BMS handshake on this cell matches the fuel gauge IC communication used across this model family — no software flags during boot.
• Bench tested on actual hardware: We cycled this cell on a Mi 10 Lite unit through charge and discharge under screen-on and modem load. The BMS held within spec across cut-off thresholds. No overcurrent trips or thermal events were recorded during the test run.
• First-cycle fast charge protocol: 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 actual discharge curve before Xiaomi's proprietary high-current protocol begins pushing elevated current into an uncalibrated cell.

Why the Mi 10 Lite reports wrong battery percentage after a cell swap

The fuel gauge IC on the Mi 10 Lite uses a coulomb counter that was calibrated against the original cell's discharge curve over hundreds of cycles. When a new cell goes in, that stored curve no longer matches the actual chemistry of the replacement. The IC keeps reporting against old data until it observes a full discharge-to-charge cycle on the new cell. Run the phone down to automatic shutdown, then charge uninterrupted to 100% — one cycle is usually enough to resync the counter to within a few percentage points of accuracy.

Sudden shutdown at 20–30% charge remaining

This is a voltage cliff issue, not a capacity issue. Under high-draw loads — 5G modem activity, screen at full brightness, or GPS — the cell voltage drops sharply below the threshold the system considers safe, and the phone cuts power to protect the BMS. On a degraded original cell this happens because the cell can no longer sustain voltage under load at lower states of charge. After fitting the BM4R, if shutdowns persist at 20–30%, the fuel gauge IC is still reading the old cell curve. Complete one full discharge-charge cycle without fast charging to recalibrate — shutdowns should stop once the coulomb counter is tracking the new cell's voltage curve accurately.