Olympia Vox Color Compatible Battery 3.7V 750mAh Li-ion

Olympia Vox Color / Vox Color 2159 — 3.7V Li-ion Replacement Battery

This is a 3.7V 750mAh Li-ion cell for the Olympia Vox Color and Vox Color 2159 compact smartphones. It fits the original battery bay directly, using the same footprint at 53.00 × 34.00 × 4.80mm. Swap it in when the original cell can no longer hold a usable charge.

• Vox Color and Vox Color 2159 fit: Both models share the same battery bay dimensions and 3.7V single-cell architecture, so one cell covers the full pair. The connector and PCB protection circuit are matched to the charge IC on both boards.
• Bench tested on actual hardware: We cycled the cell through charge and discharge on a calibrated rig, confirmed BMS cutoff triggers correctly at the low-voltage threshold, and verified no thermal event during the first charge cycle on a high-impedance new cell.
• Fuel gauge recalibration on first use: After installing this cell, disable fast charging if your charger supports it, then run one full discharge down to automatic power-off before recharging to 100%. This gives the phone's fuel gauge IC a clean discharge curve to reference, so percentage readings stay accurate from the second cycle onward.

Why the Vox Color reports the wrong battery percentage after a cell swap

The fuel gauge IC in the Vox Color stores a discharge curve learned from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The phone reads voltage, maps it to the old curve, and outputs a percentage that can be off by 15–25 points. One full discharge-charge cycle rewrites the reference curve to match the new cell's actual behaviour, after which the gauge settles to accurate readings.

Sudden shutdown at 20–30% on the new cell

A fresh Li-ion cell has slightly higher internal impedance than a broken-in one. When the modem fires a data burst or the screen peaks brightness, the load pulls enough current to cause a momentary voltage sag below the BMS cutoff threshold — even though the displayed percentage looks safe. The phone interprets this voltage dip as a dead cell and shuts down. After three to five full charge cycles the cell's impedance drops, the sag narrows, and cutoffs at 20–30% stop occurring. If shutdowns continue past five cycles, check that the cell rests at 3.7V open-circuit after a full charge.