ZTE Nubia Z7 Max Replacement Battery Li3830T43P3hB34243i 3.8V 3100mAh

ZTE Nubia Z7 Max NX505J — 3.8V Li-Polymer Replacement Battery (Li3830T43P3hB34243i)

This 3.8V, 3100mAh (11.78Wh) lithium-polymer cell is a direct replacement for the ZTE Nubia Z7 Max, Nubia Z7 Max Dual SIM, and NX505J. It slots into the original battery bay and connects to the same flex connector used across these variants. Capacity figures come from product data, not estimates.

• NX505J and Dual SIM compatibility: Both the standard and Dual SIM variants of the Nubia Z7 Max share the same battery bay dimensions (113.10 × 41.24 × 4.00mm), the same 3.8V nominal rail, and the same flex connector pinout — which is why one cell covers both SKUs without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on an NX505J. The BMS accepted charge current normally, protection circuitry tripped correctly at the low-voltage cutoff, and the cell held stable voltage across a screen-on load test.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. This gives the fuel gauge IC a clean reference curve for the new cell before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the Nubia Z7 Max after a cell swap

This happens because the fuel gauge IC is still reading the discharge curve of the old, degraded cell. The new cell has a steeper voltage-to-capacity slope, and when load from the modem or display spikes, voltage drops faster than the gauge predicts. The phone interprets that as a critical low-voltage event and shuts down — even though charge remains in the cell. One full discharge cycle down to automatic cutoff, followed by a full charge with fast charging off, resets the coulomb counter reference and clears the problem.

Phone not powering on after the replacement battery sat in storage

Lithium-polymer cells that sit uncharged for extended periods can drop below 2.5V per cell, triggering a BMS deep-discharge lockout — the protection circuit opens and the phone sees no battery at all. Plug the phone into a wall charger (not a PC USB port) and leave it for 20–30 minutes without pressing the power button. Most BMS circuits on this platform initiate a trickle pre-charge recovery when external voltage is detected, bringing the cell back above the lockout threshold. If the charge LED does not activate within 30 minutes, the cell voltage has dropped past recovery and a new cell is needed.