Hereâs a detailed product breakdown for the Tether Tools Relay Camera Coupler for Canon Cameras with BPâ511 Battery (model CRC400):
What It Is
The CRC400 Relay Camera Coupler is a dummy battery insert designed specifically for Canon cameras that use the BPâ511 / BPâ511A battery. It is part of the Tether Tools Case Relay Camera Power System (CPS). When installed in the cameraâs battery compartment, it allows the camera to be powered continuously by external 5 V sources (USB battery pack, wall adapter, etc.) instead of relying on the internal battery. The coupler itself does not store power â it merely passes power from the external source into the camera.
Key Features
Replaces the BPâ511 / BPâ511A battery in Canon cameras. Tether Tools+2B&H Photo Video+2
Works only with the Case Relay Camera Power System (CPS) â you need the Relay power unit or compatible external power source to use this coupler. Tether Tools+1
Includes a builtâin cable (â 10âł / 25.4âŻcm) from the coupler to the Relay power cable. Studio Depot+1
Allows the cameraâs battery door to completely close; the outgoing cable runs through a rubber âtrap doorâ or grommet. This helps keep the connection safe and avoids strain on connection points. Tether Tools+1
Compatible Cameras
Cameras that accept the BPâ511 / BPâ511A battery can use this coupler. Some of these include:
Canon EOS 5D B&H Photo Video+1
Canon EOS 50D B&H Photo Video+1
Canon EOS 40D B&H Photo Video+1
Canon EOS 30D B&H Photo Video+1
Canon EOS 20D, 10D, and earlier models like D30, D60 Tether Tools+1
(Always check for your exact modelâs battery compatibility before purchase.)
Technical Details & Limitations
| Spec | Details / Notes |
|---|---|
| Coupler cable length | Approx. 10âł (25.4âŻcm) from cameraâbattery slot to the Relay cable. Studio Depot+1 |
| No battery in coupler | The coupler draws all its power from the external Case Relay system; it does not provide backup battery power on its own. Tether Tools+1 |
| Battery door must close fully | For proper operation and safety, the cameraâs battery door should completely close, and the cable exit should be routed via the designated cord trap/door if available. Tether Tools |
Benefits
Allows long continuous use (video, timeâlapse, studio shoots) without constantly swapping out Canon BPâ511 batteries.
Uses nonâproprietary external power supplies (USB power banks, AC adapters) which are often more convenient & portable.
Costâeffective over time if you shoot long sessions, since you donât need a stock of BPâ511 batteries.
The Relay system supports âhotâswapâ of external power bank sources without losing power to the camera (thanks to the Relay systemâs internal buffer). Tether Tools

Things to Keep in Mind / Limitations
Since the coupler doesnât hold charge, if the external power source dies or gets disconnected, the camera will lose power unless the Relay systemâs internal buffer (UPS) is in use.
Cable routing is important: avoid sharp bends, tension, or tension at the battery compartment door, which could damage the cable or compromise the doorâs closure.
Heat or load: powering camera in Live View or video mode adds power consumption; external supply/wiring must be adequate.
Compatibility: BPâ511 battery dummy doesnât fit all Canon models â check compatibility; older or newer models may use different battery types.
If you like, I can prepare a clean, readyâtoâuse web/catalog product description for CRC400, or compare it sideâbyâside with some competing solutions to see how it stacks up.





