TomTom ONE 1EF0.017.03 Compatible Battery 3.7V 800mAh

TomTom ONE 1EF0.017.03 Series — 3.7V Li-ion Replacement Battery (6027A0090721)

This is a 3.7V 800mAh Li-ion cell that replaces the factory battery in the TomTom ONE and related portable GPS navigators. It fits the 1EF0.017.03, 1ET0.052.09, 4EF00, and 4EF0.017.00 models, along with nine additional variants in the same family. Swap it in when the original cell no longer holds enough charge to complete a journey.

• Multi-model fit across the TomTom ONE family: These models share the same 3.7V single-cell architecture, connector pinout, and physical footprint — 47 × 34 × 5.5mm — so one cell covers the full range without any wiring modification.
• Bench tested on actual hardware: We cycled this cell through the TomTom ONE charge circuit and confirmed the protection board trips correctly at both overvoltage and undervoltage thresholds, keeping the GPS receiver and display logic within safe operating range.
• First-use satellite acquisition: After fitting this cell, power the unit on outdoors and let it acquire a satellite fix before driving. A full power interruption forces a cold start — expect 5 to 10 minutes for first fix. Subsequent warm starts drop back under a minute once almanac data is cached.

GPS accuracy reduced at low battery on the TomTom ONE

When cell voltage drops below roughly 3.5V, some TomTom ONE units reduce receiver sensitivity to protect remaining power for the display and storage write cycles. The visible result is position drift or a wider accuracy circle on screen. This is firmware-controlled, not a hardware fault. Keeping the cell above 3.6V during active navigation maintains full receiver sensitivity.

TomTom ONE shuts off without warning before the battery indicator reaches empty

After a battery swap, the fuel gauge IC has no charge history for the new cell and applies a generic voltage-to-capacity curve. The device can hit its hard cutoff voltage before the on-screen indicator shows critical. Run two or three full charge-and-discharge cycles to let the gauge recalibrate against the actual cell. Once recalibrated, the low-battery warning should appear well before shutdown at approximately 3.55V.