Magellan RoadMate N393M GPS Replacement Battery 3.7V 1050mAh

Magellan RoadMate N393M Series — 3.7V Li-ion Replacement Battery (BP-TATA3-11/720 B)

This 3.7V 1050mAh Li-ion cell replaces the OEM battery in the Magellan RoadMate N393M-4300 and RoadMate N393M-5000 portable GPS navigators. Both units use the same battery bay, connector, and BMS handshake, so one part number covers the pair. Capacity is 1050mAh (3.89Wh) — matched to what Magellan fitted at the factory.

• RoadMate N393M-4300 and N393M-5000 fit: Both models share the same 50 × 35 × 5mm cell format, 3.7V nominal rail, and battery management circuit. The BMS on each unit checks cell voltage at startup — this replacement passes that check without any workaround.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the N393M platform. The BMS accepted the cell immediately, charge termination triggered cleanly at full voltage, and the protection circuit held cutoff voltage within spec under active navigation load.
• Cold-start satellite lock after fitting: After any full power removal, the GPS receiver loses its almanac cache and must run a cold start. Power the unit on outdoors and leave it stationary — first satellite fix typically takes 5 to 10 minutes. Subsequent warm starts lock in under a minute once the almanac is rebuilt.

Why the RoadMate N393M shuts off without a low-battery warning

The N393M's fuel gauge reads percentage from a calibration curve built on the original cell. When a new cell goes in, that curve no longer matches actual cell chemistry, so the device can show 20% and cut off seconds later. The BMS trips at its hard undervoltage threshold — around 3.0V — before the display ever counts down to zero. Running two or three full charge and discharge cycles recalibrates the gauge. After that, warnings appear at the correct charge level.

Saved routes and POIs missing after battery swap

Some RoadMate firmware stores recent route history and certain POI lists in battery-backed volatile RAM rather than flash. A full power removal — like a battery swap — flushes that RAM completely. Favourites saved to internal flash storage survive the swap; anything only held in RAM does not. After fitting this cell, re-enter any lost routes and save them explicitly to the device's internal memory to protect them from future power interruptions.