BBK VIVO iQOO 3 B-K7 Replacement Battery 3.85V 4400mAh

BBK VIVO iQOO 3 Series — 3.85V Li-Polymer Replacement Battery (B-K7)

This is a 3.85V, 4400mAh (16.94Wh) Li-Polymer replacement battery for the VIVO iQOO 3, iQOO 3 5G, and V1955 smartphones. It uses OEM part number B-K7 and matches the original cell's dimensions at 78.60 × 63.00 × 5.60mm. It slots into the same position as the factory cell with no modification to the housing.

• iQOO 3 and iQOO 3 5G compatibility: Both variants share the same physical cell bay, voltage rail, and BMS connector pinout. The B-K7 part number covers the full iQOO 3 lineup because the charge IC and fuel gauge reference the same 3.85V nominal chemistry across all V1955 board revisions.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on iQOO 3 hardware and confirmed the BMS accepted the cell without triggering an over-voltage or under-voltage cutoff. The charge IC stepped through trickle, constant-current, and constant-voltage phases without interruption.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. The fuel gauge IC on the iQOO 3 is calibrated to the old cell's discharge curve — letting it map the new cell at low current first prevents the coulomb counter from throwing inaccurate percentage readings from day one.

Sudden shutdown at 20–30% on the iQOO 3 after a cell swap

This happens because the fuel gauge IC is still running the discharge curve from the degraded original cell. When the new cell hits a voltage point the old curve maps to 20–30%, the system incorrectly reads imminent cutoff and shuts down — even though real capacity remains. The fix is one full uninterrupted discharge from 100% to automatic shutdown, followed by a full charge without interruption. After that cycle, the coulomb counter resets its reference and the percentage readings stabilise.

USB-PD or proprietary fast charge not activating on the first cycle after replacement

On the first charge after a cell swap, the iQOO 3's charge IC may stay in standard 5V charging mode and refuse to negotiate a higher voltage with the adapter. This is a BMS handshake behaviour — the charge controller holds back until it confirms the new cell's internal resistance profile falls within expected parameters. Run that first cycle on standard charge through a basic 5V USB source. On the second cycle, fast charging typically resumes without any further steps.