Vivo X7 B-A6 Compatible Battery 3.85V 3000mAh Li-Polymer

Vivo X7 Series — 3.85V Li-Polymer Replacement Battery (B-A6)

The B-A6 is a 3000mAh, 3.85V lithium-polymer cell that replaces the factory battery in the Vivo X7, X7 Dual SIM, and X7 Dual SIM TD-LTE. It slots into the same footprint — 79.40 × 60.30 × 4.00 mm — and connects to the same charge IC and fuel gauge. Capacity matches the original at 11.55Wh.

• X7 Dual SIM and TD-LTE compatibility: All three variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. Vivo did not alter the power rail or cell interface between the standard X7 and either dual-SIM variant, so one part number covers all three.
• Bench tested on actual hardware: We ran the B-A6 through charge and discharge cycles on the X7 platform and confirmed the BMS negotiated correctly with the charge IC, held voltage within spec under display and modem load, and triggered protection cutoffs at the expected thresholds.
• First-cycle fuel gauge reset: After installation, disable fast charging and run one full discharge down to automatic shutoff, then charge uninterrupted to 100%. This gives the coulomb counter one clean reference cycle against the new cell before high-current charging begins.

Why the X7 shows wrong battery percentage after a cell swap

The X7's fuel gauge IC builds its capacity model from hundreds of charge and discharge data points logged against the original cell. When a new cell goes in, those stored curves no longer match the actual discharge profile. The OS reads voltage and current against an outdated map, so reported percentage drifts from real state of charge. One full uninterrupted discharge-to-shutdown followed by a complete charge to 100% resets the coulomb counter and lets the IC rebuild an accurate model against the new cell.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the fuel gauge IC is still calibrated to the old, degraded cell — it reads 25% remaining but the new cell's actual voltage under modem or screen load drops faster than the stored curve predicts. The BMS hits its low-voltage cutoff before the OS registers 0%. It is not a fault with the replacement cell. Run one complete discharge cycle without interruption and the shutdowns stop once the IC recalibrates to the new cell's voltage curve, which sits above 3.4V at true cutoff.