About this replacement
TomTom GO 400 Series — 3.7V Li-ion Replacement Battery (6027A0090721)
This 3.7V 800mAh Li-ion cell replaces the original battery in the TomTom GO 400 series and related One XL portable GPS navigators. It fits devices including the 4EG0.001.08, 340S LIVE XL, and One XL 340, among others. Physical dimensions are 45.00 × 34.00 × 5.50mm — measure your original before fitting if you are unsure of your exact variant.
- GO 400 and One XL platform fit: These models share a common 3.7V single-cell Li-ion architecture, the same connector pinout, and a BMS handshake that accepts cells within a narrow voltage window at startup. A cell outside that window will be rejected at power-on.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a GO 400 unit and monitored BMS cutoff behaviour at the low-voltage threshold. The protection circuit tripped correctly at the expected floor and accepted a full charge without fault codes.
- First satellite fix after fitting: After any full power interruption, the GPS module loses its ephemeris data and performs a cold start. Power the device on outdoors and leave it stationary — first fix takes 5–10 minutes. Subsequent warm starts drop back under a minute once ephemeris is cached.
GPS accuracy reduced at low battery on the GO 400
When cell voltage drops toward the BMS cutoff floor, some TomTom GO units reduce power to the GPS receiver to extend operation. This lowers receiver sensitivity, which degrades position accuracy — particularly in urban canyons or under tree cover where signal is already marginal. The effect is subtle but real: position dots start drifting or snapping between streets. Keeping the cell above 3.5V during active navigation prevents the receiver from entering that reduced-power state.
Device shuts off without warning before the battery indicator hits empty
The GO 400's fuel gauge is calibrated to the original cell's discharge curve. A new replacement cell — or a degraded one — can have a slightly different curve, so the voltage drops faster than the indicator predicts. The unit hits the hardware cutoff threshold while the on-screen indicator still shows one bar. Run two or three full charge-discharge cycles after fitting to let the gauge recalibrate, and watch for consistent shutoffs above 3.4V as a sign the calibration has settled.