About this replacement
Vivo IQOO Z1x 5G — 3.85V Li-Polymer Replacement Battery (B-N6)
This is a 3.85V, 4850mAh (18.67Wh) lithium-polymer replacement cell for the Vivo IQOO Z1x 5G smartphone, covering model numbers V2012A and V2012. It uses OEM part number B-N6 and matches the original cell's dimensions at 87.70 × 63.70 × 5.00mm. Swap this in when the original cell no longer holds charge through a normal day.
- IQOO Z1x 5G platform fit: The V2012 and V2012A share the same battery bay dimensions, connector pinout, and BMS communication protocol — one cell covers both variants without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the IQOO Z1x 5G platform. The BMS handshake completed correctly, charge current stepped down as expected at the CV phase, and no thermal flags were triggered at the charge IC.
- First-cycle fuel gauge calibration: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the system pushes high-current fast charge into an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
This happens because the fuel gauge IC was calibrated against the old cell's discharge curve. The new cell hits its voltage cliff at a different state of charge, and the system cuts out before the reported percentage reaches zero. The processor and 5G modem together pull enough current during peak load to cause a voltage sag the gauge did not anticipate. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% — the coulomb counter resets and the shutdowns stop.
USB-PD fast charge not accepted on the first cycle after swap
On the first charge after installation, the phone may negotiate only standard 5V charging rather than the higher-voltage fast charge profile. The charge IC defaults to a conservative current limit when it cannot verify the new cell's impedance profile. This is normal BMS behaviour on a fresh cell — it is not a fault with the battery or charger. Complete one full charge at standard current, disconnect, and reconnect the fast charger; the protocol handshake will complete correctly at 3.85V nominal cell voltage.