Redmi Note 11 Pro BM5A Replacement Battery 3.87V 4900mAh

Redmi Note 11 Pro / Note 11i 5G — 3.87V Li-Polymer Replacement Battery (BM5A)

This is a 3.87V, 4900mAh Li-Polymer replacement battery for the Redmi Note 11 Pro (21091116C) and Note 11i 5G (21091116I) smartphones. It replaces part number BM5A and fits the rear-access battery bay on both models. Use this when your original cell no longer holds a useful charge or fails to power on.

• Note 11 Pro and Note 11i 5G compatibility: Both models share the BM5A cell format — same footprint at 92.30 × 65.65 × 4.65mm, same connector pinout, and same BMS handshake protocol with the PMIC on the main board. A single replacement cell covers both variants.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Note 11 Pro board. The BMS accepted the cell without fault flags, the PMIC completed CC/CV charging correctly, and the fuel gauge IC began tracking coulombs from the first cycle.
• Fuel gauge recalibration on first use: On the first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This gives the fuel gauge IC accurate reference points against the new cell's discharge curve before high-current fast charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the BM5A replacement cell

This is a fuel gauge IC calibration gap, not a faulty cell. The fuel gauge was calibrated to your old, degraded cell's discharge curve — it mapped 20% to a voltage that the new, higher-capacity cell hits much later under load. When the modem fires a high-draw burst or the screen peaks, the reported percentage looks fine but the actual cell voltage collapses below the PMIC cutoff threshold. Run one full discharge to automatic shutdown followed by a full charge at standard rate. After that cycle, the coulomb counter resets its reference and the percentage readings align to the new cell.

USB-PD or proprietary fast charge not activating after replacement

On the first cycle after a cell swap, the charge IC on the Note 11 Pro sometimes stays in trickle mode and will not negotiate fast-charge protocols with the adapter. This happens because the BMS presents high cell impedance on a fresh, unformed cell, and the charge IC interprets that as an abnormal battery state. Plug into the original Redmi adapter and leave the phone on a standard charge overnight without interrupting it. Once the cell completes one full CC/CV cycle, impedance drops into the expected range and fast charging activates normally on subsequent connections.