ZTE Z981 Li-Polymer Replacement Battery 3.85V 3400mAh

ZTE Z981 / Imperial Max — 3.85V Li-Polymer Replacement Battery (Li3934T44P8h876744)

This is a 3.85V, 3400mAh Li-Polymer battery for the ZTE Z981, Z988, Imperial Max, Z963U, and related variants. It replaces the original cell when capacity has degraded through normal charge cycling. Voltage and form factor match the OEM spec: 86.00 × 66.30 × 4.10 mm.

• Z981 / Z988 / Imperial Max platform fit: These models share the same battery bay dimensions, 3.85V voltage rail, and BMS connector pinout. The fuel gauge IC on each device communicates with the cell over the same interface, so one cell covers the full compatibility group.
• Bench tested on actual hardware: We ran this cell on a Z981 unit through a full charge and load cycle. The BMS accepted the cell without error flags, charge current stepped down correctly at the CV phase, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
• First-cycle fuel gauge recalibration: After installation, disable fast charging and complete one full discharge down to auto-shutoff, then charge uninterrupted to 100%. This gives the coulomb counter a clean reference curve against the new cell before high-current charging sessions begin.

Sudden shutdown at 20–30% on the Z981 after a cell swap

The Z981's fuel gauge IC stores a discharge curve calibrated to the original cell. A new cell with different internal resistance hits a voltage cliff at moderate load — modem transmit bursts or screen-on drain — before the reported percentage reaches zero. The phone interprets the voltage drop as a fault and shuts down even though the gauge still shows charge remaining. One full uncalibrated discharge-to-shutoff cycle lets the IC relearn where the actual cutoff voltage falls on the new cell's curve.

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

A fresh Li-Polymer cell has higher internal impedance than a well-cycled one. During the constant-current phase of charging, the charge IC pushes current into a higher-resistance cell, and the difference dissipates as heat. This is normal for the first three to five cycles and decreases as impedance settles. If the phone stays hot past cycle five or the charge IC throttles to trickle without reaching full capacity, check that the replacement cell contacts are fully seated and that no debris is on the connector — poor contact increases resistance further and compounds the heating.