BBK VIVO S3 Replacement Battery 3.7V 1200mAh BK-B-33A

BBK VIVO S3 / V312 Series — 3.7V Li-ion Replacement Battery (BK-B-33A)

This is a 3.7V, 1200mAh Li-ion cell for the BBK VIVO S3, VIVO k302, VIVO k302+, and VIVO V312 smartphones. It replaces OEM parts BK-B-33A and BK-B-46. If your original battery no longer holds a charge or the phone shuts down unexpectedly, this cell restores normal operation.

• VIVO S3 / V312 platform fit: The S3, k302, k302+, and V312 share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell covers all four models without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a VIVO V312 unit. The BMS accepted the cell without fault codes, charge termination triggered correctly at 4.2V, and the fuel gauge IC tracked state-of-charge without erratic jumps after one full cycle.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-charge cycle at standard rate. The fuel gauge IC was calibrated to the old cell's discharge curve — one slow cycle lets it map the new cell before fast-charge current is applied to an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the VIVO S3 after a cell swap

This happens because the fuel gauge IC still holds the discharge curve from the original cell. When the new cell's actual voltage drops below the old curve's predicted floor — typically around 3.6–3.5V under modem or screen load — the system interprets it as a critical low-battery event and shuts down, even though the reported percentage reads higher. It is not a fault with the replacement cell. One full slow-rate discharge-charge cycle forces the coulomb counter to rebuild the curve against the new cell, and the shutdowns stop.

USB charging not recognised on the first cycle after installation

A freshly installed cell at low state-of-charge can cause the charge IC to skip its USB-PD or proprietary handshake on the first plug-in. The charger may show connected but no current flows, or the phone screen stays dark. Plug into a standard 5V/1A wall adapter — not a fast charger — for 10–15 minutes first. Once the cell reaches roughly 3.0V, the charge IC completes the handshake normally and charging proceeds.