AT&T Z922 Replacement Battery 3.7V 1500mAh Li-ion

AT&T Z922 / Avail 2 Series — 3.7V Li-ion Replacement Battery

This 3.7V, 1500mAh Li-ion cell replaces the original battery in the AT&T Z922, Avail II, Avail II 3G, and Avail 2 smartphones. It fits the same footprint at 49.00 × 47.80 × 5.50mm and connects to the same charge IC without modification. Use this when your original cell no longer holds voltage under screen or modem load.

• Z922 and Avail 2 platform fit: These four models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The BMS handshake on each device accepts this cell without firmware intervention.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Z922 platform. The BMS accepted the cell on first connection, charge termination triggered correctly at full voltage, and the protection circuit tripped as expected under a controlled short condition.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes higher current into an uncalibrated cell.

Sudden shutdown at 20–30% on the Z922 after a cell swap

The Z922 fuel gauge IC stores a charge curve learned from the original cell. A new cell has a different internal resistance profile, so the IC miscalculates remaining capacity. When the modem transmits or the screen brightness spikes, current draw pulls cell voltage below the BMS cutoff threshold — even though the reported percentage looks healthy. The fix is one full discharge-charge cycle with the screen on and mobile data active. After that cycle, the coulomb counter recalibrates to the new cell and shutdown events at false-high percentages stop.

Phone warm near the battery compartment during the first few charges

A new Li-ion cell starts with slightly higher internal impedance than a broken-in cell. The charge IC pushes current into that impedance, and some energy converts to heat rather than stored charge. This is normal for the first two to three cycles as the cell's internal resistance drops. If the device stays warm beyond the third full charge, check that the back cover sits flush — trapped heat with no airpath can keep the charge IC in a sustained high-current phase longer than intended.