Garmin Forerunner 910XT Compatible Battery 3.7V 500mAh

Garmin Forerunner 910XT — 3.7V Li-ion Replacement Battery (361-00057-01)

This is a 3.7V, 500mAh Li-ion cell for the Garmin Forerunner 910XT multisport GPS watch. It replaces OEM part numbers 361-00057-01 and 361-00057-00. If your 910XT no longer holds a charge or shuts off mid-session, this is the cell to swap.

• Forerunner 910XT fit: The 910XT uses a single flat Li-ion cell on a 3.7V rail with a proprietary connector and an onboard BMS that monitors charge state and temperature. This cell matches the original footprint at 39.40 × 31.71 × 5.40mm, so it seats without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a 910XT unit. The BMS accepted the cell without fault flags, charged to full at the standard rate, and cut off cleanly at the low-voltage threshold with no erratic shutdowns.
• Cold-start satellite acquisition after swap: After fitting this cell, power the watch on outdoors before your first session. The 910XT performs a GPS cold start after any full power interruption. First satellite fix takes 5–10 minutes outdoors. Subsequent starts lock in under a minute once almanac data is cached.

Why the 910XT shuts off without a low-battery warning

The 910XT reads remaining charge from a voltage curve stored in firmware. When the original cell ages, its voltage curve flattens and then drops sharply — the watch never sees the gradual decline the firmware expects. A fresh cell restores the expected voltage profile. After fitting this battery, run two full charge-discharge cycles outdoors so the firmware can re-calibrate the indicator against the new cell's actual curve. Until then, the low-battery icon may appear late or not at all before cutoff.

GPS accuracy drops in the final stretch of a long session

When cell voltage falls below approximately 3.5V under load, the 910XT reduces power to the GPS receiver to extend operation. Lower receiver power means weaker signal processing and wider position error — you may see track points drift or distance read short on long courses. This is not a firmware bug; it is a hardware power-management response to low voltage. Keeping the cell in good condition and starting sessions with a full charge keeps the receiver running at full sensitivity throughout.