About this replacement
Garmin Forerunner 955 Solar — 3.85V Li-Polymer Replacement Battery (361-00146-00)
This is a 3.85V, 220mAh lithium-polymer cell for the Garmin Forerunner 955 Solar GPS sports watch. It replaces OEM part 361-00146-00 and fits the 955 Solar variant specifically. Swap it in when the original cell no longer holds charge through a training session or multi-day tracking period.
- Forerunner 955 Solar fitment: The 955 Solar runs a tighter internal cavity than the standard 955 — the 28.60 × 21.80 × 3.50mm cell dimensions matter here. This cell matches that footprint and the flex-connector tab orientation used on the 955 Solar board.
- Bench tested on actual hardware: We cycled this cell through a full charge and GPS-active discharge on the 955 Solar platform. The BMS handshake completed cleanly, and the fuel gauge IC registered a full 220mAh reference after one complete charge cycle from near-zero.
- Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and run it to 100% before use. The fuel gauge IC on this platform loses its calibration reference when the cell is removed — it cannot recalibrate without a full charge cycle from near-zero. Skip this step and the percentage readout will be inaccurate from day one.
Why solar charging affects cell voltage behaviour on the 955
The 955 Solar feeds harvested solar current through a charge controller that tops up the cell in small, variable increments throughout the day. A new cell with a fresh anode surface accepts this trickle differently than a degraded original — expect the charge percentage to fluctuate slightly during outdoor sessions in the first week. This is the charge controller adjusting to the new cell's impedance, not a fault. After four to five full charge-discharge cycles, the controller stabilises and the readout steadies.
Watch not pairing to phone after battery replacement
Removing the cell cuts power to the BLE radio stack entirely, which clears the active pairing session stored in volatile memory. The Garmin Connect app still shows the watch as paired on the phone side, but the watch itself has lost the bond. Go into the Garmin Connect app, remove the device, then use the watch's Bluetooth settings to initiate a fresh pair. The watch needs to be powered on and sitting at the pairing screen — not just unlocked — before the app will detect it.