ZTE Nubia V18 Li3940T44P6h876442 Compatible Battery 3.85V 4000mAh

ZTE Nubia V18 / NX612 — 3.85V Li-Polymer Replacement Battery (Li3940T44P6h876442)

This is a 3.85V 4000mAh Li-Polymer replacement battery for the ZTE Nubia V18, NX612, and NX612j smartphones. It carries OEM part number Li3940T44P6h876442 and matches the original cell's physical footprint at 85.85 × 63.00 × 4.30mm. Capacity figure comes from the product data — 15.4Wh.

• Nubia V18 / NX612 / NX612j compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The Li3940T44P6h876442 part number covers the full NX612 variant range, including the NX612j regional variant sold in some Asian markets.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the NX612 platform. The BMS accepted the cell without rejecting the handshake, voltage held steady under screen-on and modem load, and the charge IC stepped through its CC/CV stages without fault flags.
• 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 recalibrate against the new cell's discharge curve before high-current charging pushes load into an uncalibrated cell — preventing early percentage drift or false-low readings.

Why the Nubia V18 reports wrong battery percentage after a cell swap

The Nubia V18 uses a coulomb-counting fuel gauge IC that builds its capacity model against the cell it was last calibrated on. When you swap in a new cell, the IC still references the old discharge curve. This mismatch causes the percentage readout to lag, jump, or settle inaccurately — especially between 30% and 70% where the original cell had a well-mapped voltage slope. One full slow-charge discharge cycle rewrites the reference model. After that cycle, percentage accuracy returns to within a few percent of actual state of charge.

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

This is a voltage-cliff failure, not a capacity problem. Under heavy load — modem searching for signal, display at full brightness, background sync — the cell voltage can sag below the BMS cutoff threshold before the fuel gauge registers a low percentage. A fresh Li-Polymer cell with an uncalibrated fuel gauge IC is most vulnerable during the first few cycles. The fix is to run two full discharge-charge cycles without fast charging so the gauge IC maps the actual low-voltage knee of the new cell. If shutdowns persist past three cycles, check that resting voltage at "30%" reads above 3.6V — anything below that points to a BMS calibration fault, not cell failure.