WIZA16 Cingular 8125 Replacement Battery 3.7V 2350mAh

Cingular 8125 / 8150 — 3.7V Li-ion Replacement Battery (WIZA16)

This is a 3.7V, 2350mAh Li-ion replacement battery for the Cingular 8125 and 8150 Windows Mobile smartphones. It replaces OEM part number WIZA16. If your original battery swells, won't hold a charge, or the phone dies unexpectedly, this is the direct cell swap.

• 8125 and 8150 compatibility: Both devices run on the same voltage rail, use the same physical battery bay, and share the WIZA16 OEM part number. One cell covers both handsets without any adapter or connector modification.
• Bench tested on actual hardware: We ran this cell on the 8125 platform and confirmed the BMS communicates correctly with the charge IC, accepts a full charge cycle without thermal event, and releases voltage cleanly under combined modem and display load.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The 8125 fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve during that first full cycle — skipping it causes erratic percentage readings for days.

Sudden shutdown at 20–30% on the Cingular 8125

This is a voltage cliff, not a capacity problem. Aged Li-ion cells develop high internal resistance and can no longer sustain voltage under the combined load of the modem radio and backlit display. The BMS reads the voltage drop as a hard cutoff and shuts the device down even though the fuel gauge still shows charge remaining. A new cell with lower internal resistance holds voltage through those load spikes. After fitting this replacement, the shutdown-at-30% pattern stops within one full recalibration cycle.

Phone warm near the battery door during the first charge

A fresh Li-ion cell has slightly higher impedance than a broken-in one. On the first charge, the 8125 charge IC pushes current into that higher-impedance cell and generates more heat than normal. This is expected and settles after one or two full cycles as impedance drops. If the device is still noticeably warm after the third charge, check that the battery door is fully seated — a loose contact forces the charge IC to retry, extending charge time and heat. Skin temperature at the battery door should drop to ambient within a few seconds of removing it from the charger.