O2 WIZA16 XDA Mini s Replacement Battery 3.7V 2800mAh

O2 XDA Mini s / XDA Mini Pro — 3.7V Li-ion Replacement Battery (WIZA16)

This is a 3.7V Li-ion cell rated at 2800mAh (10.36Wh), built to fit the O2 XDA Mini s and XDA Mini Pro. Both handsets use the same battery bay and connector, so one part number covers both. This replaces the original WIZA16 when the existing cell can no longer hold enough charge for daily use on these mid-2000s Windows Mobile devices.

• XDA Mini s and Mini Pro shared battery platform: Both devices run the same voltage rail and use an identical physical connector and bay depth. The BMS on each handset communicates the same charge termination signals, so one cell works across both without modification.
• Bench tested on actual hardware: We ran this cell through a full charge and discharge cycle on an XDA Mini s unit. The BMS accepted the cell cleanly, charge termination triggered correctly at 4.2V, and no false low-battery flags were raised during discharge.
• Fuel gauge recalibration on first use: After fitting this cell, let it discharge fully to automatic shutdown, then charge uninterrupted to 100% before resuming normal use. The XDA Mini s fuel gauge IC was calibrated to the original cell's discharge curve — one complete cycle resets that baseline against the new cell.

Sudden shutdown at 20–30% on the XDA Mini s after a cell swap

The XDA Mini s uses a coulomb-counting fuel gauge IC that references a stored discharge curve from the original factory cell. A new cell with a different internal resistance profile will hit a voltage cliff under screen or radio load before the gauge reads zero. The handset interprets that voltage drop as a hard cutoff and shuts down — even though the gauge still shows charge remaining. One full discharge-to-shutdown and uninterrupted recharge cycle allows the IC to map the new cell's actual voltage curve, and the premature shutdowns typically stop after that.

Phone reports wrong battery percentage after fitting the replacement cell

This happens because the fuel gauge IC on the XDA Mini s retains calibration data from the old, degraded cell. When a new cell is installed, the IC applies the wrong discharge model and reports percentage inaccurately — often reading high early and dropping sharply near the end. This is not a fault with the replacement cell. Discharge the device fully until it shuts itself off, then charge straight to 100% without interruption. After that single cycle the gauge recalibrates to the new cell and percentage readings stabilise.