Cingular TRAX Replacement Battery 3.7V 980mAh Li-ion

Cingular TRAX — 3.7V Li-ion Replacement Battery

This 3.7V Li-ion cell replaces the original battery in the Cingular TRAX mobile phone. Capacity is 980mAh (3.63Wh). It restores power to calls, messaging, and core phone functions when the original cell has degraded past usable capacity.

• TRAX platform fit: The TRAX uses a single-cell 3.7V Li-ion pack with a compact form factor — 70.40 × 46.80 × 5.40mm. This cell matches that envelope and connects to the device's charge management IC without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS held cutoff correctly at both ends — no premature shutoff during load, and the charge IC accepted the cell without error flags on the first cycle.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge-charge cycle before relying on the percentage indicator. The TRAX's fuel gauge IC was calibrated to the old cell's discharge curve — one full cycle lets it re-map against the new cell and report accurately.

Why the TRAX reports wrong battery percentage after a cell swap

The TRAX tracks charge state using a fuel gauge IC that builds a model of the cell's voltage-to-capacity curve over time. When you swap in a new cell, that model is still tuned to the old battery. The IC reads voltage accurately but maps it to the wrong capacity percentage. After one full discharge down to cutoff and a full charge back to 4.2V, the gauge re-learns the new cell's curve and percentage readings stabilise.

Sudden shutdown at 20–30% remaining on the TRAX

This usually means the cell is hitting a voltage cliff under load — the modem or display draws a surge of current and the cell voltage drops below the BMS cutoff threshold even though the gauge still shows charge remaining. It is most common when the fuel gauge IC has not yet completed a recalibration cycle after the replacement. Run a full discharge-to-cutoff cycle, then charge fully to 4.2V. If shutdowns continue after two full cycles, check that the battery contacts are clean and seating firmly.