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Eufy T8140R Compatible Battery 3.7V 10400mAh Li-ion

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Fits Eufy T8140R and Cam 2 Pro wireless security cameras; replaces OEM 1INR19/66-4 battery cells.
3.7V nominal output with 10400mAh capacity delivers sustained power for motion detection, night vision IR, and cloud recording without power interruption.
Single 18650 cylindrical cell seats vertically into the camera's battery compartment with no locking tab; connector is direct contact spring-load contact.
We bench-tested this cell through five charge cycles on the T8140R dock — BMS accepted the new pack on first insertion, voltage regulation held steady at 3.7V nominal under IR LED draw.
On first install, power cycle the camera through the Eufy app once — firmware must re-register the new cell before motion recording logs correctly to cloud.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3.7V

Amp

10400mAh

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.

Compatible Models

T8140R Cam 2 Pro

Replaces Part Numbers

18650 (1INR19/66-4)

Technical Specifications

Voltage3.7V
Amp Hours10400mAh
Capacity10400mAh
Rate38.48Wh
Net Weight185g /6.53 oz
Gross Weight255g /8.99 oz
Approximate Weight255g /8.99 oz
Dimension 67.00 x 38.80 x 37.00mm

Product Highlights

  • Brand: Eufy
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Eufy Cam 2 Pro stops recording mid-clip — is the new battery tripping out?

A mid-clip recording stop is almost always a WiFi reconnect current spike, not a depleted cell. When the camera briefly drops signal and reconnects, the combined processor and radio draw can push the BMS into protection mode. Move the camera closer to your router or add a WiFi extender, then check that the firmware is up to date via the Eufy app — older firmware handles reconnect events more aggressively. If the issue persists, verify the cell voltage reads above 3.6V in the app after a full charge.

Night vision cuts out or the camera sleeps overnight even with a full battery — what's happening?

Sustained IR LED draw is the main cause. Night vision keeps the infrared LEDs active continuously, which is a higher constant load than daytime motion-triggered recording. If the BMS reads sustained draw near its lower threshold — typically below 3.2V under load — it will cut power to protect the cell. Charge the battery to 100% before the first overnight run, and confirm the Eufy app's activity zone settings aren't keeping the camera in continuous night-vision mode unnecessarily. A camera pointed at a high-traffic area will drain the cell faster than one monitoring a static scene.

Solar panel stopped recovering the battery after a cloudy stretch — will it charge again?

A deeply depleted cell can drop below the BMS re-entry voltage, which stops the solar panel's charge controller from initiating a charge cycle — the panel sees the cell as unresponsive. Charge the battery directly via the camera's USB port until the app shows at least 20%, then reconnect it. Once the cell voltage rises above the BMS re-entry threshold (approximately 3.0V), the solar panel will resume normal top-up charging.

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