BBK VIVO Y93 Replacement Battery B-F3 3.85V 3900mAh

BBK VIVO Y93 Series — 3.85V Li-Polymer Replacement Battery (B-F3)

The B-F3 is a 3.85V, 3900mAh (15.02Wh) lithium-polymer cell that replaces the original battery in the VIVO Y93, Y93s, Y93st, and V1818CA. It fits the mid-range VIVO Android lineup where the original cell has degraded, failed to hold charge, or stopped functioning entirely. Voltage and capacity match OEM spec exactly.

• VIVO Y93 series compatibility: The Y93, Y93s, Y93st, and V1818CA share the same battery bay dimensions, connector pinout, and BMS handshake protocol — all confirmed against the B-F3 footprint of 88.50 × 62.50 × 4.16mm. One cell covers the full variant spread without modification.
• Bench tested on actual hardware: We cycled the B-F3 through full charge and discharge on a VIVO Y93 unit, monitoring BMS communication, charge acceptance, and cutoff behaviour. The protection circuit engaged correctly at both low-voltage and over-current thresholds with no fault codes logged.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge down to auto-shutdown, then charge to 100% on standard current. This gives the fuel gauge IC a clean reference cycle against the new cell's discharge curve before fast charging pushes high current into an uncalibrated cell.

Why the VIVO Y93 reports wrong battery percentage after a cell swap

The VIVO Y93 uses a coulomb counter IC that builds its reference map from the previous cell's charge and discharge history. When you swap to a new B-F3 cell, that map is stale — the IC is still predicting voltage curves for the old, degraded cell. The result is percentage readings that lag, jump, or plateau mid-charge. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter against the new cell's actual curve.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity defect. At 20–30% state of charge, the modem radio and display backlight together can pull enough current to cause the cell voltage to sag below the BMS cutoff threshold — typically around 3.0V — triggering an immediate shutdown even though the OS still shows charge remaining. An uncalibrated fuel gauge makes this worse because the OS doesn't know the real state of charge. Run the recalibration cycle described above and confirm the cell reads above 3.85V on a full charge before use.