About this replacement
Xiaomi Mi 4c — 3.85V Li-Polymer Replacement Battery (BM35)
This is a 3000mAh (11.55Wh) lithium-polymer cell at 3.85V, replacing the OEM BM35 battery in the Xiaomi Mi 4c and Mi 4c Dual SIM. It fits the same footprint as the original — 68.90 × 59.57 × 4.45 mm — and connects to the same charge IC and fuel gauge circuitry. Install it when the original cell no longer holds voltage under screen or modem load.
- Mi 4c and Mi 4c Dual SIM compatibility: Both variants share the same BM35 connector pinout, voltage rail, and BMS handshake. One cell fits both. No hardware differences between the single and dual SIM models affect battery installation or charge IC communication.
- Bench tested on actual hardware: We cycled this cell through the Mi 4c charge IC and confirmed BMS communication, charge termination at the correct cutoff voltage, and stable discharge under combined screen and LTE modem load without unexpected cutoff events.
- Fuel gauge recalibration on first use: On first installation, disable fast charging and run one full discharge-to-charge cycle at standard current. This gives the fuel gauge IC a clean discharge curve to map against the new cell before high-current charging pushes current into an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the Mi 4c after a cell swap
This is a voltage cliff issue, not a capacity issue. Under combined modem and display load, the new cell's voltage sags below the BMS protection threshold before the reported percentage reaches zero — because the fuel gauge IC is still running the old cell's discharge curve. The phone interprets this as a normal cutoff and shuts down, even though the reported percentage says otherwise. One full discharge cycle without fast charging lets the coulomb counter remap to the new cell and eliminates most of these early shutdowns.
USB fast charge not activating on the first cycle after replacement
After a cell swap, the charge IC on the Mi 4c may not handshake correctly with the fast-charge protocol on the first plug-in. This happens because the BMS on a fresh cell starts in a conservative charge state until it has completed at least one standard charge cycle. Forcing a fast-charge session into an uncalibrated cell can also skew the fuel gauge reading early on. Let the battery complete one full charge at standard USB current — around 5V/1A — then fast charging will activate normally on subsequent cycles.