AT&T Maven 2 Z831 Replacement Battery 3.8V 2300mAh

AT&T Maven 2 (Z831) — 3.8V Li-ion Replacement Battery

This is a 3.8V, 2300mAh Li-ion replacement battery for the AT&T Maven 2 (model Z831) Android smartphone. It fits the battery bay directly and restores power after the original cell degrades. Capacity figure comes from the product data sheet: 2300mAh / 8.74Wh.

• Maven 2 and Z831 compatibility: Both names refer to the same hardware — AT&T's retail branding versus ZTE's model number for the same board. The battery connector, BMS handshake voltage, and bay dimensions (72.90 × 53.60 × 4.70mm) are identical across both designations.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Z831 board. The BMS accepted the charge IC handshake without fault flags, and the protection circuit tripped correctly at low-voltage cutoff — no runaway, no thermal anomaly.
• Fuel gauge recalibration on first use: After installing a new cell, disable fast charging for the first full discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging pushes current into an uncalibrated measurement baseline.

Sudden shutdown at 20–30% on the Maven 2 after a cell swap

The Maven 2 fuel gauge IC uses a discharge curve stored from the previous cell. A new cell with a slightly different internal resistance profile hits a voltage cliff under modem or display load — the board reads it as a valid 25% state of charge, then collapses when current demand spikes. The fuel gauge IC has not yet seen a full cycle on the new cell, so it cannot predict that cliff accurately. One complete discharge down to auto-shutoff, followed by a full charge to 100%, resets the coulomb counter and eliminates most of these early shutdowns.

USB charging not initialising on the first cycle after battery replacement

When the replacement cell arrives at a low storage voltage — sometimes below 3.4V — the Maven 2 charge controller enters trickle-charge mode and does not negotiate the full USB current profile. The phone may show no charging animation for the first 10–15 minutes. Leave the cable connected without interruption; once the cell climbs above approximately 3.5V, the charge IC re-enters normal CC/CV mode and the charging indicator appears. Do not unplug and replug repeatedly — that resets the trickle-charge timer each time.