About this replacement
Eufy S220 SoloCam — 3.7V Li-ion Replacement Battery (SW18650 34M 2P)
This is a 3.7V, 6800mAh Li-ion battery for the Eufy 2K Solar Security Camera S220 SoloCam series, including T3814 and AKT8223 variants. It replaces the original SW18650 34M 2P cell pack when capacity fade causes the camera to miss motion events or drop offline overnight. Voltage and physical dimensions match the original: 66.50 × 37.40 × 19.50mm.
- S220 SoloCam compatibility: The S220, T3814, and AKT8223 share the same battery bay geometry and 3.7V BMS handshake. All three draw from the same cell configuration, so one battery SKU covers the full model group without modification.
- Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on the S220 platform. The BMS accepted the pack without fault codes, IR night vision activated correctly at low-light threshold, and the motion processor drew current without triggering a protective cutoff.
- Post-install power cycle: After fitting the new battery, power cycle the camera once through the Eufy app. The firmware must re-register the cell before motion event logs write correctly to cloud storage — skipping this step can cause silent recording gaps even though the camera appears online.
Solar panel not recovering a depleted S220 cell in winter
The S220's BMS has a minimum re-entry voltage — if the cell drops below roughly 2.5V, the solar panel's low winter output cannot push enough current to cross that threshold. The panel may show as "connected" in the app while delivering no meaningful charge to a fully depleted pack. At that point the only recovery path is removing the battery and charging it directly via USB until it reaches at least 3.0V, then reinstalling it so the BMS re-enters normal charge acceptance mode.
App showing 0% or stuck percentage after battery swap
The S220 uses a voltage-threshold indicator, not a fuel-gauge IC — it estimates state of charge from resting cell voltage rather than tracking coulombs. Immediately after a swap, the firmware reads an intermediate resting voltage and maps it to the wrong percentage bucket. Run the camera through one full solar or USB charge cycle, then let it sit idle for 30 minutes. The resting voltage will stabilise and the app percentage will reset to an accurate reading.