About this replacement
Xiaomi Black Shark 3 Pro — 3.85V Li-Polymer Replacement Battery (BS05FA)
The BS05FA is a 3.85V, 2500mAh Li-Polymer cell that fits the Black Shark 3 Pro, Black Shark 3 Pro 5G, and MBU-H0. It replaces the original battery when capacity has degraded or the cell is physically damaged. Capacity and voltage match OEM spec: 9.63Wh at 3.85V nominal.
- Black Shark 3 Pro and MBU-H0 fitment: All three listed models share the same battery bay geometry, connector pinout, and BMS handshake protocol. The BS05FA part number covers this group — one cell, same voltage rail and NTC thermistor configuration across the variant lineup.
- Bench tested on actual hardware: We ran the BS05FA through full charge and discharge cycles on Black Shark 3 Pro hardware. The BMS accepted the cell without error flags, and the charge IC completed a standard CC-CV sequence without thermal cutoff or charge termination faults.
- First-cycle fast charge protocol: After installation, disable fast charging and run one complete discharge-charge cycle on standard 5V charging. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current fast charging applies elevated current to an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the replacement cell
The Black Shark 3 Pro's fuel gauge IC retains the discharge curve from the old cell. When a new cell is installed, the IC predicts remaining capacity against that old curve. Under GPU or modem load, the actual cell voltage drops faster than the IC expects, and the BMS trips the low-voltage cutoff — the phone shuts off even though the reported percentage still reads 20% or higher. Run one full discharge to auto-off followed by a full charge with fast charging disabled. After that cycle the coulomb counter recalibrates against the new cell curve and the shutdowns stop.
USB-PD fast charge not activating on the first cycle after replacement
On the first charge after a cell swap, the charge IC may not negotiate the fast charge protocol — the phone charges slowly even on a fast charger. This happens because the new cell's internal impedance reads higher than the old cell at rest, and the charge IC defaults to a conservative 5V/1A profile until it completes one full cycle and confirms the cell can handle elevated current. Plug into the OEM charger or a USB-PD charger, let the first cycle complete fully without interruption, and fast charging will activate normally from the second cycle onward.