ZTE Nubia Z11 Li3829T44P6h806435 Replacement Battery 3.85V 3000mAh

ZTE Nubia Z11 — 3.85V Li-Polymer Replacement Battery (Li3829T44P6h806435)

This is a 3.85V, 3000mAh (11.55Wh) Li-Polymer cell for the ZTE Nubia Z11 and Nubia Z11 Dual SIM TD-LTE (NX531J / NX531). It fits the same battery bay as the original and uses the same OEM part number Li3829T44P6h806435. Swap it in when the original cell no longer holds charge through a normal day of use.

• NX531J and Dual SIM TD-LTE compatibility: Both variants share the same physical bay dimensions (79.50 × 63.10 × 3.40mm), the same 3.85V rail, and the same BMS connector pinout — so one cell covers both board revisions without any wiring changes.
• Bench tested on actual hardware: We ran the cell through a full charge and discharge cycle on the NX531J board. The BMS handshake completed on first contact, charge IC accepted the cell without error flags, and the coulomb counter tracked state-of-charge correctly across the full curve.
• First-cycle fuel gauge recalibration: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle at standard rate. The Z11's fuel gauge IC is calibrated against the old cell's discharge curve — one unconstrained cycle lets it map the new cell before high-current charging pushes into an uncalibrated state-of-charge estimate.

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

The Z11's fuel gauge IC holds a discharge curve learned from the original cell. When a new cell goes in, that stored curve no longer matches actual cell voltage under load. The modem and display together can pull enough current to cause a sharp voltage drop — the BMS sees the cell voltage fall below the protection threshold and cuts output before the displayed percentage reaches zero. This is not a faulty battery. Run one full discharge cycle without fast charging and let the coulomb counter re-learn the new cell's voltage-capacity relationship. After recalibration, the gauge will track real state-of-charge accurately and the early shutdowns will stop.

Phone warm near the battery during the first few charges after replacement

A fresh Li-Polymer cell has slightly higher internal impedance than a cell that has been cycled. The Z11's charge IC pushes the same current profile it used with the broken-in original cell, so more energy is lost as heat across that higher resistance on the first few cycles. This is normal and resolves within three to five charge cycles as the cell's impedance settles. If the phone feels hot — not just warm — after the fifth cycle, check that the battery flex connector is fully seated, as a partial connection increases contact resistance and amplifies heating.