Navman Mio Spirit 300 Replacement Battery 3.7V 720mAh

Navman Mio Spirit 300 Series — 3.7V Li-ion Replacement Battery (07917TSIP)

This is a 3.7V 720mAh Li-ion cell built to fit the Navman Mio Spirit 300, Spirit 300 Traffic, Spirit 555, Spirit 555 Traffic, and several additional Spirit series GPS navigators. It replaces OEM part 07917TSIP. Fit the cell when the original can no longer hold charge across a navigation session.

• Spirit 300 and 555 platform: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. Swapping between them uses the same cell — 49.95 × 36.05 × 5.59mm with a matched discharge curve the device firmware expects.
• Bench tested on actual hardware: We ran this cell on the Spirit 300 chassis, confirmed BMS initialisation, verified the charge IC accepted the pack without error flags, and checked that the battery indicator tracked correctly across a full discharge cycle.
• Cold-start acquisition after power interruption: After fitting this cell, power the unit fully on outdoors before driving. The GPS performs a cold start after any full power removal — first satellite fix takes 5–10 minutes. Subsequent warm starts drop back under a minute once almanac data is rebuilt.

GPS accuracy reducing as battery charge drops on the Spirit 300

The Spirit 300 reduces receiver sensitivity at low state of charge to protect the remaining voltage headroom for the display and processor. When the cell voltage sags below roughly 3.5V under load, the GPS chipset pulls back its acquisition gain. Position error increases and the blue dot drifts. Replacing a degraded cell that sags quickly under combined GPS-plus-display load restores full receiver gain across the navigation session.

Spirit 300 shutting off without a low-battery warning

The on-screen battery indicator on the Spirit 300 reads state of charge from a voltage lookup table calibrated against a new cell. An aged cell that loses capacity but still reads normal voltage will show two or three bars right up until the firmware hits its hard cutoff voltage and shuts the unit down without warning. This is a calibration drift problem, not a fault in the new cell. After fitting the replacement, run one full charge-to-discharge cycle so the firmware resets its reference point to the new cell's actual voltage curve.