Olympia Vox Color Replacement Battery 3.7V 900mAh Li-ion

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

This 3.7V, 900mAh (3.33Wh) lithium-ion cell is a direct replacement for the Olympia Vox Color and Vox Color 2159 handsets. Both models share the same battery bay dimensions (53.00 × 34.00 × 4.80mm) and the same charge management circuit, so one cell covers both. Fit the cell, close the cover, and the phone powers on normally.

• Vox Color and Vox Color 2159 compatibility: Both handsets draw from the same 3.7V nominal rail and use an identical connector pinout and bay geometry. No adapter or modification is needed — the cell seats flush and the contacts align correctly on both variants.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a controlled rig. The BMS held the charge cutoff at 4.2V and triggered low-voltage protection cleanly at the rated floor — no false cutoffs, no thermal events during the charge phase.
• Fuel gauge recalibration on first cycle: On first use after fitting, run the battery from 100% down to automatic shutdown without plugging in mid-way. This lets the fuel gauge IC map the new cell's actual discharge curve before it starts reporting percentage to the OS — skipping this step causes erratic percentage readings for the first several days of use.

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

The fuel gauge IC inside the phone was calibrated against the discharge curve of the original cell. When a new cell goes in, that learned curve no longer matches the actual voltage-to-capacity relationship of the replacement. The IC reads a voltage point and maps it to a percentage based on old data — so it can report 40% when the cell is actually at 25%. One full discharge cycle from 100% to automatic shutdown, followed by a full charge to 4.2V without interruption, forces the coulomb counter to reset its baseline against the new cell.

Sudden shutdown at 20–30% on the Vox Color after battery replacement

This is a voltage-cliff failure, not a capacity problem. When the modem transmits or the screen brightness peaks, instantaneous current draw spikes sharply. If the cell's internal resistance is even slightly elevated — common in a new cell that has not yet been through a full cycle — terminal voltage drops below the BMS cutoff threshold for a fraction of a second, and the phone shuts off despite the gauge showing charge remaining. Run one complete discharge-charge cycle first. If shutdowns continue past three full cycles, check that the cell contacts are fully seated — a partial connection raises effective resistance and worsens the voltage sag under load.