Cingular 8125 Replacement Battery WIZA16 3.7V 2800mAh

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

This is a 3.7V, 2800mAh Li-ion battery for the Cingular 8125 and 8150 smartphones. Both devices share the WIZA16 cell format, connector pinout, and BMS handshake protocol. It restores power to units where the original cell has degraded past useful capacity.

• 8125 and 8150 compatibility: Both models run the same 3.7V single-cell architecture with identical connector geometry and BMS communication lines. The same physical cell fits either device without modification.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on the 8125 platform. The BMS accepted the charge handshake on the first connection and reported cell voltage correctly across the Windows Mobile power stack.
• Fuel gauge recalibration on first use: On first installation, disable any fast-charge accessory and run one complete discharge-to-charge cycle at standard current. This allows the fuel gauge IC to map its coulomb counter against the new cell's actual discharge curve before higher-current charging begins.

Sudden shutdown at 20–30% on the Cingular 8125

This happens when the cell cannot hold voltage above the BMS cutoff threshold under combined modem and display load. The fuel gauge IC still reads 20–30% capacity remaining, but instantaneous current draw collapses the cell voltage below the protection circuit's floor. It's a load-response issue, not a capacity issue. A fresh WIZA16 cell with lower internal resistance sustains voltage through those load spikes and eliminates the shutdown.

Phone reports wrong battery percentage after cell swap

The Windows Mobile fuel gauge IC builds its percentage estimate from a discharge curve stored during previous cycles with the old cell. After swapping to a new cell, those stored values no longer match the new cell's actual voltage-to-capacity profile. The result is erratic percentage jumps or a reading that stays frozen near full for too long. Run one full discharge down to auto-shutdown, then charge uninterrupted to 100% — this forces the coulomb counter to recalibrate to 3.7V nominal.