About this replacement
Garmin Fenix 5S / 5S Plus — 3.7V Li-Polymer Replacement Battery (361-00096-00)
This is a 3.7V, 150mAh lithium-polymer cell for the Garmin Fenix 5S and Fenix 5S Plus GPS smartwatch. It replaces OEM part number 361-00096-00, the original flat-pack cell fitted behind the watch module. Dimensions are 26.00 x 20.10 x 4.10mm — verify your existing cell matches before ordering.
- Fenix 5S and 5S Plus shared platform: Both models run the same compact case chassis with identical cell footprint, connector pinout, and BMS handshake. One cell covers both variants without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Fenix 5S platform. The BMS accepted the cell without fault flags, and the fuel gauge IC registered correctly after a full charge cycle post-swap.
- Fuel gauge calibration after swap: Place the watch on its magnetic charger immediately after fitting this cell and charge to 100% before first use. The fuel gauge IC on this platform loses its reference point when power is removed. Without a full charge cycle from near-zero, the percentage display will read incorrectly for days.
Why the Fenix 5S draws more current than the cell capacity suggests
At 150mAh, this is a small cell carrying a demanding load profile. The Fenix 5S runs GPS, optical heart rate, barometric altimeter, and BLE simultaneously during activity tracking. Each sensor stack draws its own current independently, and the GPS chipset alone pulls a disproportionate share relative to the cell size. This is not a defect — it reflects the power budget Garmin set for the 5S chassis. Managing which sensors are active in your activity profiles directly affects how long a single charge lasts.
Charge contacts not making connection on the magnetic charger after reassembly
If the charger cable seats but the watch does not register charging, the rear charge contact plate has shifted during reassembly. This happens when the rear cover is not fully reseated flush to the case after a cell swap. Remove the rear cover, confirm the cell connector is fully pressed in, and refit the cover evenly around the perimeter. Once the cover sits flush, the magnetic charger should register contact and begin charging — confirm the battery icon appears within 30 seconds.