About this replacement
Eufy 4G LTE Outdoor / S300 eufyCam — 3.7V Li-ion Replacement Battery (LGM50LT-1S2P)
This is a 3.7V, 10000mAh (37Wh) Li-ion replacement battery for the Eufy 4G LTE Outdoor, S300 eufyCam, Security 4K Solar Security Camera, and T8161. It slots directly into the camera housing and reconnects to the existing BMS handshake rail. Capacity figure is sourced from product data — 10000mAh at 3.7V nominal.
- S300 eufyCam and T8161 compatibility: These models share the same cell format, connector pinout, and BMS communication protocol — that is why one part number covers the full group. The camera firmware reads cell voltage over the same data line across all four variants.
- Bench tested on actual hardware: We cycled this cell through the camera's BMS, confirmed charge acceptance at the 4.2V cutoff, and verified the protection circuit trips correctly on over-discharge at 2.5V. Motion-trigger current spikes during the test did not cause false BMS lockouts.
- First-install power cycle: After fitting the new cell, power cycle the camera once through the Eufy app. The firmware must register the new cell before motion recording logs correctly to cloud storage — skipping this step can result in missed clips even when the battery reads charged.
Camera going offline in the Eufy app after battery installation
Swapping the battery clears the camera's active session token stored in volatile memory. The Eufy app loses the authenticated link and marks the device offline, even though the camera is powered and functional. This is not a battery fault — it is a firmware handshake reset. Open the Eufy Security app, go to Device Settings, and run the re-registration prompt to restore the connection.
App showing 0% or stuck percentage after fitting the new cell
Eufy cameras use a voltage-threshold indicator, not a fuel gauge IC. The percentage reading is mapped against a fixed voltage table, and a new cell at partial state of charge may land outside the expected threshold range on first boot. The display will show 0% or freeze until one full charge-to-discharge cycle re-aligns the voltage reading with the correct percentage band. Charge the camera fully to 4.2V, then let it discharge through normal operation before trusting the percentage figure in the app.