Xiaomi Redmi Note 12 Pro Replacement Battery BP4K 3.87V 4400mAh

Xiaomi Redmi Note 12 Pro — 3.87V Li-Polymer Replacement Battery (BP4K)

This is a 3.87V, 4400mAh (17.03Wh) lithium-polymer cell for the Xiaomi Redmi Note 12 Pro (model 22101320C). It replaces the original BP4K battery when the existing cell can no longer hold charge through a full day of use. It fits the same physical cavity and connects to the same BMS circuitry as the factory unit.

• Note 12 Pro and 22101320C compatibility: Both model references share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The BP4K part number covers the full production run of this device — no hardware revision changed the battery interface.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Note 12 Pro unit. The BMS accepted the cell without fault codes, and the protection circuit triggered correctly at the low-voltage cutoff threshold during deep discharge testing.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. The fuel gauge IC needs to map the new cell's discharge curve before high-current charging is applied to an uncalibrated cell. This prevents percentage drift in the first week of use.

Sudden shutdown at 20–30% on a replacement cell

A new cell does not automatically inherit the fuel gauge IC's stored calibration data from the old battery. When the phone's coulomb counter is still tuned to the old cell's voltage curve, it misjudges how much capacity remains. Under modem or display load, the actual cell voltage drops below the BMS protection threshold before the OS knows it's low. One full discharge-to-cutoff cycle followed by an uninterrupted full charge resets the coulomb counter against the new cell's actual curve.

USB-PD or Xiaomi fast charge not activating after replacement

On the first charge cycle after a cell swap, the charge IC on the Note 12 Pro may not negotiate fast-charge protocols until the BMS has completed one full handshake sequence at standard 5V input. This is a firmware-level safety behaviour — not a fault with the replacement cell. Charge once at standard rate using the original cable and adaptor, then unplug and reconnect. Fast charge should activate normally from the second cycle onward.