Redmi BP4C Replacement Battery Note 11T Pro+ 3.87V 4300mAh

Redmi Note 11T Pro+ — 3.87V Li-Polymer Replacement Battery (BP4C)

The BP4C is a 3.87V, 4300mAh (16.64Wh) Li-Polymer cell for the Redmi Note 11T Pro+. It fits the original battery bay and connects to the same charge IC and fuel gauge circuit that manages power for the display, processor, and 5G modem. Buy this when your original cell no longer holds a full charge or the phone shuts down before the percentage hits zero.

• Note 11T Pro+ fitment: The BP4C uses the same 89.00 × 62.75 × 4.90mm footprint and connector orientation as the factory cell. The BMS communicates over the same data line, so the charge IC can negotiate charging parameters without modification.
• Bench tested on actual hardware: We ran a full charge-discharge cycle and confirmed the BMS held the charge termination voltage at the correct upper limit. The protection circuit tripped as expected on simulated overdischarge, and fast-charge negotiation completed without error on the second cycle.
• First-cycle fast-charge delay on the Note 11T Pro+: 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 high-current fast charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement BP4C

The Note 11T Pro+ fuel gauge IC builds its percentage model from the old cell's impedance and discharge curve. A new BP4C cell has different internal resistance, so the gauge loses track of true state-of-charge under load spikes from the 5G modem or screen brightness changes. The phone hits a voltage cliff the gauge did not predict and cuts out. One full discharge-to-empty followed by a full charge resets the coulomb counter and maps the new cell's curve. After that cycle, shutdowns in the 20–30% range stop occurring.

Fast charging not working after fitting the BP4C

Xiaomi's proprietary fast-charge protocol requires the charge IC to handshake with the battery's BMS before stepping up current. On the first cycle after a cell swap, the BMS may not complete that handshake, and the phone falls back to standard 5W charging. This is not a fault with the cell or the charger. Fully drain the battery to auto-shutdown, then charge to 100% on a standard charger first. On the next charge session, the fast-charge protocol should negotiate normally — confirm by checking Settings → Battery and looking for the fast-charging indicator at 9V input.