ZTE Nubia Z11 Max Li3839T43P6h406790 Compatible Battery 3.8V 4000mAh

ZTE Nubia Z11 Max — 3.8V Li-Polymer Replacement Battery (Li3839T43P6h406790)

This 3.8V, 4000mAh Li-Polymer cell replaces the original battery in the ZTE Nubia Z11 Max (NX523, NX523J). It matches OEM part number Li3839T43P6h406790 and fits the physical footprint at 88.50 × 66.90 × 3.70 mm. Capacity is 15.2Wh, identical to the factory specification.

• NX523 and NX523J compatibility: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell covers both board revisions without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the NX523 board. The BMS accepted the cell without fault flags, and the charge IC held the correct 4.35V cutoff throughout.
• 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 map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the Nubia Z11 Max after a cell swap

The Z11 Max uses a coulomb counter that was calibrated against the original cell's discharge curve. A new cell has a slightly different voltage-to-capacity slope, so the reported percentage drifts from actual state of charge. Under modem transmission or screen brightness peaks, the real cell voltage can drop below the minimum threshold while the OS still reads 25%. One full discharge to automatic shutdown followed by an uninterrupted charge to 100% forces the fuel gauge IC to reset its end-point registers against the new cell.

OS reporting erratic or frozen battery percentage after replacement

When the old cell is removed, the coulomb counter loses its learned capacity reference. Until one complete cycle runs, the IC interpolates from stale register values, causing percentage jumps or a reading that barely moves for long stretches. This is a software calibration state, not a cell defect. Drain the phone until it shuts off automatically, then charge in one session to 100% without interruption — after that cycle the percentage tracking stabilises.