Xiaomi Mi 11 Lite BP42 Compatible Battery 3.87V 4100mAh

Xiaomi Mi 11 Lite — 3.87V Li-Polymer Replacement Battery (BP42)

This is a 3.87V, 4100mAh Li-Polymer replacement battery for the Xiaomi Mi 11 Lite, Mi 11 Lite 4G, Mi 11 Lite 5G, and Mi 11 Youth 5G. It uses OEM part number BP42 and slots into the same battery bay as the original cell. Swap it when your original battery no longer holds charge or causes unexpected shutdowns.

• Mi 11 Lite family compatibility: The Mi 11 Lite, Mi 11 Lite 4G, Mi 11 Lite 5G, and Mi 11 Youth 5G all share the BP42 footprint — same connector pinout, same BMS handshake protocol, same 3.87V nominal rail. One cell covers the full lineup.
• Bench tested on actual hardware: We ran this cell through charge and discharge on the Mi 11 Lite platform. The BMS accepted the cell without faults, balanced current draw correctly under screen-on load, and the charge IC cycled through to full capacity without interruption.
• First-cycle fast charge protocol: On first use after installation, disable fast charging and complete one full discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before Xiaomi's proprietary fast-charge protocol pushes higher current into an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity fault. Under heavy load — active modem, high brightness display, or simultaneous background sync — the cell voltage drops below the BMS cutoff threshold before the fuel gauge reads zero. The fuel gauge IC is still using the old cell's discharge curve, so it misreads the actual state of charge. Complete two full discharge-charge cycles at standard current and the coulomb counter recalibrates against the new cell. After recalibration, the gauge tracks real voltage and the shutdowns stop.

USB-PD fast charge not accepted on the first cycle after swap

After a cell replacement, the charge IC may reject fast-charge handshake on the first cycle because the BMS has not yet confirmed a valid charge history on the new cell. The phone charges at standard 5V current instead of the expected fast-charge rate. Plug in with the stock charger, let it complete a full charge at slow rate, then unplug and reconnect — the fast-charge handshake typically completes on the second connection. If it still doesn't negotiate, clear the battery stats and repeat one full cycle.