Redmi BM5G K50i Replacement Battery 3.87V 4950mAh

Redmi K50i / Note 11T Pro — 3.87V Li-Polymer Replacement Battery (BM5G)

The BM5G is a 3.87V, 4950mAh (19.16Wh) lithium-polymer cell that replaces the factory battery in the Redmi K50i and Note 11T Pro smartphones. It fits directly into both models, which share the same chassis dimensions and power architecture. Use the Capacity from the product data — 4950mAh — as the reference spec.

• K50i and Note 11T Pro shared platform: Both devices run on the same Dimensity 8100 power rail with identical BMS connector pinout and voltage thresholds, which is why they use the same BM5G cell. Swapping between these two models carries no compatibility risk at the hardware level.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a K50i unit. The BMS accepted the charge handshake without error flags, and thermal output during CC-CV transition stayed within expected limits for a new high-impedance lithium-polymer cell.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge-charge cycle at standard current. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins pushing current into an uncalibrated cell.

Sudden shutdown at 20–30% on the BM5G replacement cell

This happens because the fuel gauge IC on the K50i was calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load before the gauge reaches 0%, so the phone shuts down while showing charge remaining. The fix is one full discharge to auto-off followed by an uninterrupted charge to 100% with the device off or in airplane mode. After that cycle, the coulomb counter has enough data to track the new cell's actual voltage curve accurately.

USB-PD fast charge not recognised after BM5G installation

On the first charge cycle after a cell swap, the charge IC may fall back to standard 5V input and refuse to negotiate fast charge protocols. This occurs because the BMS on a new cell starts with conservative current limits until it completes one full charge cycle and validates cell impedance. Plug in using the original charger and let the first cycle complete at whatever rate the device accepts. Fast charge negotiation typically restores automatically from the second cycle onward — no settings change needed.