About this replacement
TomTom Go 820 / Go Live 825 Series — 3.7V Li-ion Replacement Battery (VF6M)
This 3.7V, 1000mAh Li-ion cell replaces part number VF6M in the TomTom Go 820, Go Live 820, Go 825, and Go Live 825 GPS navigators. It fits the slim internal bay on these portable navigation units and restores power when the original cell no longer holds a usable charge. Dimensions are 43.80 × 35.80 × 6.70mm — verify against your existing cell before fitting.
- Go 820 / Go Live 825 platform fit: These models share the same battery bay dimensions, connector, and 3.7V power rail, which is why one cell covers the full range. The internal BMS on each unit expects the same voltage profile, so no firmware differences affect compatibility across the series.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Go 820 platform. The BMS accepted the cell without error flags, charge termination triggered correctly at 4.2V, and low-voltage cutoff activated at the expected threshold before the unit powered off.
- Cold-start satellite acquisition after fitting: After any full power interruption, the Go 820 loses its satellite almanac cache and performs a cold start. Take the unit outdoors after fitting and leave it powered on — first satellite fix typically takes 5–10 minutes. Subsequent power cycles will lock on much faster once the almanac is rebuilt.
GPS accuracy reduced when battery runs low on the Go 820
The Go 820's receiver draws roughly 150–200mA during active navigation. As the cell voltage drops below around 3.5V, the unit begins reducing receiver sensitivity to protect remaining charge. This shows up as position drift or slower lane-level updates on screen — not a GPS signal problem, but a power management response. Fitting a fresh cell with a full 1000mAh capacity restores full receiver sensitivity immediately.
Go 820 shuts off mid-route with no low-battery warning
This happens when the battery indicator has not been calibrated to the new cell. The Go 820 reads state-of-charge by tracking voltage, and a degraded or brand-new cell can sit outside the curve the device expects. The unit hits its internal voltage-drop cutoff before the on-screen warning reaches zero. Run one full charge-to-discharge cycle on the new cell — charge to 100% via USB, use until the unit powers off naturally — and the indicator will re-calibrate to match actual capacity.