Xiaomi Mi 10 Pro Replacement Battery BM4M 3.85V 4200mAh

Xiaomi Mi 10 Pro — 3.85V Li-Polymer Replacement Battery (BM4M)

This is a 3.85V, 4200mAh Li-Polymer cell for the Xiaomi Mi 10 Pro (M2001J1G). It replaces the original BM4M battery when capacity has dropped through normal charge cycling. Rated at 16.17Wh, it restores power to the display, Snapdragon 865 processor, and 5G modem stack.

• Mi 10 Pro and M2001J1G fitment: Both model designations are the same hardware — M2001J1G is the internal hardware ID, Mi 10 Pro is the retail name. The BM4M connector, physical dimensions (118.80 × 41.10 × 5.30mm), and BMS handshake are identical across both.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on the Mi 10 Pro and confirmed the BMS accepted the charge without fault flags. The protection circuit responded correctly to charge cutoff at 4.35V and triggered low-voltage protection below 3.0V.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve for the new cell before Xiaomi's 50W fast charge pushes high current into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the Mi 10 Pro after a cell swap

The fuel gauge IC on the Mi 10 Pro retains the discharge curve of the old cell in memory. When a new cell is installed, the IC maps its percentage readings against that stale curve. At around 20–30%, the new cell's actual voltage drops below what the old curve predicts, causing the phone to cut power before the display reaches 0%. One full manual discharge-charge cycle forces the coulomb counter to recalibrate against the replacement cell's actual voltage behaviour.

USB-PD or 50W fast charge not triggering on the first cycle after replacement

Xiaomi's charge IC negotiates fast charge rates only after it reads BMS status from the installed cell. On a cold or freshly installed BM4M cell, the BMS may not respond to the handshake on the first plug-in, so the charger falls back to standard 5V/2A. This is not a fault — it clears after one standard charge cycle completes and the BMS registers a full state-of-charge event. If fast charge still does not trigger after two full cycles, confirm the charger is outputting at least 9V and that the USB-C cable supports USB 2.0 or higher current ratings.