GNS nüvi 5840 GPS Replacement Battery 3.7V 1800mAh

GNS Garmin nüvi 5840/5843 — 3.7V Li-ion Replacement Battery (NTA2236)

This 3.7V, 1800mAh Li-ion cell replaces the original NTA2236 battery in the Garmin nüvi 5840 and 5843 portable GPS navigators. It fits the standard battery bay with the same footprint at 52.98 × 35.39 × 11.61mm. When the original cell can no longer hold a usable charge, this unit restores the device to full operation.

• nüvi 5840 and 5843 compatibility: Both models share the same battery bay geometry, connector pinout, and charge-management circuit. The NTA2236 part number covers both units — no adapter or wiring change needed.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the nüvi platform. The BMS accepted the charge handshake without fault flags, and the protection circuit responded correctly to overcurrent and over-discharge thresholds.
• Cold-start behaviour after fitting: After a full power interruption from a battery swap, the GPS loses its ephemeris data. Power the unit on outdoors with a clear sky view and let it acquire a satellite fix before driving. First fix after a cold start takes 5–10 minutes — subsequent warm starts run under a minute.

GPS accuracy dropping at low battery on the nüvi 5840

The nüvi's power management reduces RF receiver sensitivity when cell voltage falls below a certain threshold — typically around 3.5V under load. At that point, the GPS chip draws less current, and satellite signal acquisition weakens. You may notice position drift or longer recalculation times before the low-battery warning appears on screen. Keeping the cell above 3.6V under load maintains full receiver performance.

nüvi shuts off mid-route without a low-battery warning

This happens when the battery indicator hasn't been calibrated to the new cell's discharge curve. The device reads the voltage against a stored profile from the aged original battery, so the shutdown threshold arrives before the on-screen warning has a chance to display. Run two full charge-to-cutoff cycles after fitting the new cell. This lets the firmware re-map the discharge curve and restore accurate warning timing.