ZTE Vital Li3825T43P3h775549 Replacement Battery 3.8V 2500mAh

ZTE Vital / V987 Series — 3.8V Li-ion Replacement Battery (Li3825T43P3h775549)

This 3.8V, 2500mAh (9.5Wh) Li-ion cell replaces the OEM battery in the ZTE Vital, UX990, Smile Q, V987, and compatible models. It matches the original voltage rail and connector footprint. Dimensions are 76.95 × 55.10 × 4.84 mm — verify against your existing cell before installation.

• V987 platform compatibility: The Vital, UX990, Smile Q, and V987 variants share the same 3.8V power architecture, connector pinout, and BMS handshake protocol — which is why one cell part number covers all of them. Swapping between any of these models does not require firmware changes or connector adapters.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the V987 platform. The BMS accepted the charge handshake on the first connection, held voltage above 3.6V through mid-discharge, and triggered cutoff correctly at the low-voltage threshold without erratic behavior.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-charge cycle at standard current. The fuel gauge IC in these ZTE models was calibrated to the old cell's discharge curve — giving it one clean cycle at low current lets it recalibrate before high-current charging pushes into an uncalibrated coulomb counter.

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

This is a voltage cliff issue, not a capacity defect. The ZTE Vital's modem and display together draw enough current that a new, uncalibrated cell can sag below the BMS cutoff threshold — even when the fuel gauge still reads 20–30%. The fuel gauge IC hasn't mapped the new cell's internal resistance, so it predicts remaining capacity incorrectly. One full discharge-charge cycle at standard current gives the coulomb counter enough data to update its model and stop triggering premature cutoffs.

ZTE Vital not powering on after the replacement battery sat in storage

Li-ion cells self-discharge during storage, and if this cell dropped below 2.5V per cell before installation, the BMS will lock out to prevent damage — leaving the phone completely unresponsive. Connect the phone to a wall charger, not a USB port, and leave it for 15–20 minutes without pressing anything. Wall chargers deliver enough trickle voltage to nudge the BMS out of lockout. If the charge indicator does not appear within 30 minutes, confirm the charger output is at least 5V 1A.