About this replacement
Xiaomi Black Shark 2 — 3.85V Li-Polymer Replacement Battery (BS03FA)
This 3.85V, 3800mAh Li-Polymer battery replaces the original BS03FA cell in the Xiaomi Black Shark 2 gaming smartphone. It fits the standard Black Shark 2, Black Shark 2 Dual SIM, Black Shark 2 Dual SIM TD-LTE, and AWM-A0 variants. Capacity is 3800mAh — 14.63Wh — matching the original cell specification.
- Black Shark 2 platform compatibility: All listed variants — including the Dual SIM TD-LTE and AWM-A0 — share the same battery bay geometry, connector pinout, and BMS handshake protocol. The BS03FA part number covers all four configurations without modification.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Black Shark 2 board. The BMS accepted the cell without fault flags, fast charge handshake initiated correctly after the first full cycle, and voltage held steady under sustained GPU load.
- First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell.
Sudden shutdown at 20–30% on the Black Shark 2 after a cell swap
This happens when the fuel gauge IC is still mapped to the old cell's discharge curve. The new cell's voltage drops faster under GPU or modem load than the IC expects, so the OS reads 25% while the cell is already near cutoff voltage. The phone shuts down to protect the cell before the percentage hits zero. One full discharge-charge cycle with fast charging disabled forces the coulomb counter to relearn the new cell's actual capacity endpoints.
Black Shark 2 not powering on after the replacement cell sat in storage
Li-Polymer cells self-discharge in storage, and if the BS03FA cell dropped below approximately 2.5V per cell, the BMS enters lockout mode and refuses to pass current to the board. The phone shows no response — no charging indicator, no boot. Connect the phone to a slow 5V charger and leave it for 15–30 minutes; the charge IC trickle-charges the cell above the BMS recovery threshold before switching to normal charge rate. If the cell recovers, voltage at the connector should read above 3.0V before the phone will power on.