About this replacement
Xiaomi Civi 5G / CC11 — 3.87V Li-Polymer Replacement Battery (BP44)
The BP44 is a 3.87V, 4400mAh Li-Polymer cell for the Xiaomi Civi 5G and CC11 smartphones. It connects directly to the existing BMS connector and charge IC on both models. Capacity is 17.03Wh — matching the original cell specification.
- Civi 5G and CC11 compatibility: Both devices share the same mainboard power rail voltage, connector pinout, and BMS handshake protocol, which is why a single BP44 cell covers both. Swapping a CC11 battery into a Civi 5G unit will not trigger a hardware rejection from the charge IC.
- Bench tested on actual hardware: We ran the BP44 through charge and discharge cycles on a Civi 5G unit. The BMS accepted the cell without fault codes, fast charge negotiation completed normally after the first full cycle, and the fuel gauge IC tracked state of charge without erratic jumps once calibration settled.
- First-cycle calibration tip: On first use after installation, disable fast charging and let the phone complete one full discharge-to-charge cycle at standard current. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated state.
Sudden shutdown at 20–30% on a replacement BP44 cell
This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The reported percentage doesn't match the actual cell voltage, so the phone shuts off the moment the cell voltage drops below the modem and display load threshold — even though the OS thinks charge remains. The fix is one full discharge cycle with fast charging off. After that cycle, the coulomb counter resets its reference point against the new cell, and the percentage reading aligns with real voltage.
USB-PD fast charge not negotiating on the first charge after installation
After a cell swap, the charge IC on the Civi 5G can start the first session in trickle mode while it verifies the new cell's impedance profile. This looks like slow charging or a missing fast charge indicator on that first session. It is not a fault — the IC is protecting an uncalibrated cell. Plug in with the original charger, let the first cycle complete fully, and fast charge negotiation will resume at full rate from the second session onward.