About this replacement
Eufy T8140R / Cam 2 Pro — 3.7V Li-ion Replacement Battery (1INR19/66-4)
This is a 3.7V Li-ion 18650 cell rated at 10400mAh (38.48Wh), built to replace the original battery in the Eufy T8140R and Cam 2 Pro wireless security cameras. Both cameras run on the same 1INR19/66-4 cell format with identical connector and BMS handshake requirements. Swap this in when the original cell no longer holds a charge or the camera stops staying online.
- T8140R and Cam 2 Pro compatibility: Both models use the same 18650 cell format, 3.7V nominal rail, and the same BMS communication protocol. The physical footprint — 67.00 x 38.80 x 37.00mm — matches the battery compartment on both without modification.
- Bench tested on actual hardware: We ran this cell through motion-trigger cycles, sustained IR LED draw, and WiFi reconnect events. The BMS held voltage above the cutoff threshold across all three load spikes without tripping into protection mode.
- First-install power cycle: After inserting the battery, power cycle the camera once through the Eufy app. The firmware must register the new cell before motion events log correctly to cloud storage — skipping this step causes missed clips even when the camera appears online.
Camera going offline in the app after battery installation
Replacing the battery clears the camera's active session token. The Eufy app loses its authenticated link to the device even though the camera has power. This is not a faulty battery — it is a firmware re-registration event. Open the Eufy app, remove the camera from your device list, and re-add it. The camera will reconnect and resume normal recording.
App reporting 0% or incorrect charge percentage after swap
Eufy cameras use a voltage-threshold indicator, not a fuel gauge IC. After a battery swap, the firmware has no baseline reference and defaults to 0% or an inaccurate reading. Run the camera through one full charge cycle — charge to 100%, allow normal use until the app shows a low-battery alert, then charge fully again. After that cycle, the voltage thresholds recalibrate and the percentage display tracks correctly.