About this replacement
Garmin Forerunner 110 / 210 / S1 Series — 3.7V Li-ion Replacement Battery (361-00047-00)
This 3.7V, 200mAh lithium-ion cell replaces the original battery in the Garmin Forerunner S1, S1W, 110, and 210 GPS running watches. It matches the OEM dimensions of 33.20 × 30.10 × 4.80mm and connects to the same BMS circuit these watches use to report charge state. Use the capacity figure from this listing — 200mAh — not third-party estimates.
- Forerunner 110 / 210 / S1 platform compatibility: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. A single cell revision — OEM part 361-00047-00 / 361-00064-00 — covers all four variants without modification.
- Bench tested on actual hardware: We ran this cell on a Forerunner 110 test unit. The BMS accepted the new cell immediately, reported charging current correctly through the magnetic contacts, and transitioned to trickle charge without triggering a low-voltage fault.
- Post-swap charge cycle on GPS watches: After fitting this cell, place the watch on its charger before powering it on. The fuel gauge IC on this platform loses its reference point when the cell is disconnected. Without a full charge cycle from near-zero, the watch will display an inaccurate state-of-charge — often 0% or a frozen reading.
GPS and continuous HR monitoring pulling this cell harder than expected
The Forerunner 110 and 210 run GPS acquisition and optical or ANT+ heart rate simultaneously during a tracked run. That combined draw hits a fresh cell differently than a degraded original — internal impedance on the new cell is lower, so instantaneous current spikes during GPS lock are slightly higher until the cell's impedance rises after a few charge cycles. Expect the first week to feel inconsistent. By cycle three or four, draw stabilises and the fuel gauge reads more accurately.
Magnetic charge contacts not registering after reassembly
If the watch shows no charging animation after the swap, the magnetic pogo-pin contacts on the rear of the case have likely shifted during reassembly. This happens when the back cover is reseated under slight lateral pressure. Remove the cover, check that the contact pads are flush and centred, then reseat the cover squarely. Confirm charging has started by checking for the charging indicator — the watch should show activity within 30 seconds of correct contact alignment.