About this replacement
Garmin ZUMO 350LM / 390LM Series — 3.7V Li-Polymer Replacement Battery (361-00059-00)
This 3.7V 1800mAh Li-Polymer cell replaces the original battery in the Garmin ZUMO 350LM, 390LM, 340LM, and zumo 396 motorcycle GPS navigators. It matches the OEM spec at 6.66Wh and uses the same physical footprint at 50.10 × 34.00 × 9.90mm. Swap it when the original no longer holds charge or causes unexpected shutdowns mid-ride.
- ZUMO 340LM, 350LM, 390LM, zumo 396 compatibility: These models share the same battery bay dimensions, connector pinout, and BMS communication protocol — all drawing from the same 3.7V Li-Polymer cell architecture Garmin standardised across this navigator family.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on a ZUMO 350LM, confirming BMS handshake, charge acceptance, and correct voltage reporting on the device's battery indicator. No false-full readings or cutoff anomalies were observed.
- Cold-start satellite acquisition after swap: After fitting this cell, power the unit on outdoors in open sky and let it run until it acquires a full satellite fix before mounting on the bike. The navigator performs a cold start after any complete power interruption — first fix typically takes 5–10 minutes, while subsequent warm starts run under a minute.
Saved routes and POIs disappearing after a battery swap
The ZUMO series stores some navigation data — including recent destinations and active route state — in battery-backed RAM. When power is completely removed during a swap, that volatile memory clears. Saved favourites and imported GPX routes stored in flash memory are unaffected, but any unsaved recent activity will be lost. Before removing the old battery, sync routes to Garmin BaseCamp or export them via USB to avoid losing any data you cannot recover.
ZUMO shutting off without a low-battery warning
After a battery replacement, the on-screen charge indicator is uncalibrated — it has not yet learned the new cell's discharge curve. The device can hit its hardware voltage cutoff threshold before the visual warning has time to display. This is normal for the first one to two full charge-discharge cycles. Run the unit through at least two full cycles on charge to let the fuel gauge recalibrate, and watch for the indicator stabilising around 3.5V before shutoff on the second cycle.