About this replacement
Magellan RoadMate 1300 / 1340 — 3.7V Li-ion Replacement Battery (338937010172)
This 3.7V 720mAh Li-ion cell replaces the original battery in the Magellan RoadMate 1300 and RoadMate 1340 portable GPS navigators. It restores independent operation and maintains power when the vehicle ignition is off. Dimensions are 50.07 × 36.07 × 6.29mm — confirm fit before ordering if your unit has been serviced previously.
- RoadMate 1300 and 1340 fitment: Both models share the same battery bay dimensions, connector pinout, and 3.7V supply rail — one cell covers both. The BMS communicates charge state to the same firmware on either unit.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the RoadMate platform. The BMS held charge termination correctly at 4.2V and the low-voltage cutoff triggered cleanly without triggering a hard reset loop.
- First outdoor fix after installation: After fitting this cell, power the unit on outdoors and let it acquire a satellite fix before driving. GPS firmware performs a cold start after any full power interruption — first fix takes 5–10 minutes outdoors. Subsequent warm starts are under a minute.
Why the RoadMate 1300 shuts off without a low-battery warning
The RoadMate 1300 reads charge state from a calibration curve stored in firmware. When a new or heavily discharged cell is fitted, that curve is misaligned with the actual cell voltage. The unit can show two or three bars on the battery indicator and then cut off seconds later — the BMS trips at its voltage floor before the display reflects the real state. Run two or three full charge cycles to let the firmware recalibrate the indicator against the new cell's discharge curve.
GPS accuracy dropping as battery charge falls below half
Some RoadMate units reduce RF receiver gain at lower supply voltages to protect core navigation functions. This shows up as wider position error circles or momentary track jumps in areas where signal is already marginal. The supply voltage floor where this kicks in is around 3.5V. Keep the unit connected to vehicle power during long routes — reserve battery power for short stops and parking lot navigation rather than extended highway use.