Swisscom Comfort VS3 Compatible Battery 3.7V 500mAh

Swisscom Comfort VS3 — 3.7V Li-Polymer Replacement Battery

This 3.7V, 500mAh lithium-polymer cell replaces the original battery in the Swisscom Comfort VS3 mobile phone. It restores the ability to make calls, send messages, and run basic mobile functions when the original cell has degraded beyond useful capacity. Dimensions are 48.00 × 34.15 × 4.70mm — measure your existing cell before fitting if you are unsure.

• Comfort VS3 fit: The VS3 runs a single-cell Li-Po configuration at 3.7V nominal. This cell matches that voltage rail and the physical envelope of the original, so the connector seats without forcing and the cell lies flat in the chassis cavity.
• Bench tested on actual hardware: We cycled this cell through charge, standby draw, and active call load. The BMS held voltage above the low-battery cutoff threshold through the discharge curve without tripping early or triggering false low-battery alerts at mid-charge states.
• First-cycle fuel gauge recalibration: After fitting this cell, disable any fast-charge mode and run one full discharge-to-charge cycle before normal use. The VS3's fuel gauge IC was calibrated to your old cell's discharge curve — one complete cycle lets it re-anchor to the new cell's actual capacity before reporting accurate percentages.

Why the VS3 reports wrong battery percentage after a cell swap

The VS3 uses a fuel gauge IC that tracks charge state by modelling how voltage drops across a learned discharge curve. When you swap the cell, that learned curve no longer matches the new cell's actual chemistry and impedance profile. The IC keeps using the old model, so it can read 30% when the cell is at 15%, or jump from 60% to 20% without warning. One complete discharge and full charge resets the coulomb counter and forces the IC to build a new model against the replacement cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage collapses under the load spike from the modem or screen backlight — the cell cannot sustain the voltage rail even though the fuel gauge still shows charge remaining. It is a voltage-sag failure, not a capacity failure. A fresh Li-Po cell with higher internal impedance than expected will hit the BMS undervoltage cutoff at around 3.0V under load while the open-circuit voltage still reads higher. If shutdowns persist after two full calibration cycles, check that the connector is fully seated — a partial connection raises contact resistance and worsens sag.