Vivo B-X5 Replacement Battery 7.78V 2345mAh Li-Polymer

Vivo X90 5G / V2241A — 7.78V Li-Polymer Replacement Battery (B-X5)

The B-X5 is a 7.78V, 2345mAh Li-Polymer cell for the Vivo V2241A, X90 5G, V2218, and X90s 5G. It slots into the same battery bay as the original and connects to the same BMS rails. This listing covers the standard-capacity tier at 18.24Wh.

• X90 series compatibility: The V2241A, X90 5G, X90s 5G, and V2218 share the same 7.78V dual-cell Li-Polymer architecture and connector pinout, which is why one part number covers all four models. The BMS handshake protocol is identical across the group.
• Bench tested on actual hardware: We ran the B-X5 through charge and discharge cycles on the X90 platform. The BMS accepted the cell without error flags, and the charge IC ramped to full current within the first cycle after an initial calibration pass.
• First-cycle fast-charge protocol: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before the charge IC pushes high current into an uncalibrated state of charge register.

Why the X90 5G reports wrong battery percentage after a cell swap

The X90 5G uses a coulomb counter that tracks charge in and out relative to a learned discharge curve from the original cell. When you install a new cell, that learned curve no longer matches the new cell's actual voltage-to-capacity relationship. The fuel gauge IC reads voltage correctly but maps it to the wrong state of charge. One full discharge down to auto-shutoff, followed by an uninterrupted charge to 100%, forces the IC to rewrite the curve against the new cell. After that single cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display pulls a current spike the cell cannot sustain at its present state of charge, causing terminal voltage to sag below the BMS undervoltage cutoff — typically around 3.0V per cell on this platform. The phone shuts off even though the fuel gauge still shows charge remaining. The fix is to complete two full calibration cycles so the coulomb counter learns where the real voltage cliff sits on the new cell. If shutdowns persist past three cycles, check that the replacement cell rests at or above 3.6V per cell after a full charge.