Vivo Z5x Replacement Battery B-G7 3.85V 4900mAh

Vivo Z5x — 3.85V Li-Polymer Replacement Battery (B-G7)

The B-G7 is a 3.85V, 4900mAh Li-Polymer cell that replaces the original battery in the Vivo Z5x and Z5x Premium Edition. It restores full capacity when the original cell has degraded through charge cycles. This battery fits all Z5x variants listed, including Dual SIM and TD-LTE models.

• Z5x variant compatibility: All Z5x models in this listing share the same battery bay dimensions, connector pinout, and BMS communication protocol. The 90.10 × 65.10 × 4.70mm cell seats correctly across standard, Premium Edition, and Dual SIM TD-LTE builds without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on Z5x hardware, confirming the BMS handshake completes normally and the charge IC accepts current without fault flags. Voltage at full charge held at 4.35V as expected for this chemistry.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging is introduced into an uncalibrated state.

Why the Z5x reports wrong battery percentage after a cell swap

The Z5x uses a coulomb counter that tracks charge relative to a stored discharge curve from the old cell. When a new cell goes in, the IC still references the old curve, so the percentage shown does not match actual charge state. This mismatch causes the OS to display inflated or deflated readings until the gauge relearns. One full discharge to automatic shutdown followed by a complete uninterrupted charge resets the reference points. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–25% on the replacement cell

This happens when the fuel gauge IC has not yet calibrated the new cell's voltage cliff. Under high load — modem switching, screen at full brightness — cell voltage drops sharply below the BMS cutoff threshold before the reported percentage reaches zero. The phone interprets this as a fault and shuts down to protect the cell. Run one full cycle with mobile data active and screen brightness high to force the gauge IC through a realistic load profile. After calibration, shutdown should not occur above 5–8%.