Eufy 4G LTE Outdoor Replacement Battery 3.7V 9000mAh

Eufy 4G LTE Outdoor / S300 eufyCam — 3.7V Li-ion Replacement Battery (LGM50LT-1S2P)

This is a 3.7V 9000mAh (33.3Wh) Li-ion cell replacement for the Eufy 4G LTE Outdoor camera, S300 eufyCam, Security 4K Solar Security Camera, and T8161. It uses the LGM50LT-1S2P cell configuration and fits directly into the battery compartment on all four models. Voltage and capacity match the original specification exactly.

• 4G LTE Outdoor, S300, T8161 compatibility: All four models on the fit list share the same 3.7V single-cell architecture, LGM50LT-1S2P cell format, and BMS handshake protocol. The connector pinout and physical footprint are identical across this camera family, so one cell covers the whole group.
• Bench tested on actual hardware: We ran this cell through motion-triggered recording cycles, monitoring BMS behaviour under the combined IR LED and 4G modem current draw. The protection circuit held steady through repeated trigger events without tripping into cutoff.
• Post-install power cycle: After fitting this cell, run one full power cycle through the Eufy app — hold the sync button until the camera reboots. The firmware must re-register the new cell before motion events log correctly to cloud storage. Skipping this step can cause missed clips even when the camera appears online.

Why the 4G LTE Outdoor camera goes offline in the app after a battery swap

When power is removed to replace the battery, the camera loses its active session token with the Eufy cloud. Reinserting a charged cell restores power but does not automatically re-establish that session. The app shows the device as offline even though the camera has voltage. To fix it, press and hold the sync button for 10 seconds until you hear two beeps, then let the camera reconnect through the Eufy Security app.

App showing 0% or a frozen percentage reading after fitting a new cell

The Eufy camera uses a voltage-threshold indicator, not a fuel gauge IC. When a new cell goes in at a different state of charge than the firmware last recorded, the percentage display locks or reads zero until the indicator recalibrates. Run the camera through one complete discharge-to-recharge cycle and the threshold readings will reset. After a full charge the app should display a value above 95% at 4.1–4.2V.