[Sparky3D]

It depends on what you are trying to do with it. If it falls into the "custom circuit" category (i.e. lights, camera, on-board vision processing board); then yes, you can have a 6V circuit, as long as it is powered from the PDB or it is a COTS computing device/camera with a built-in battery. There is also a 6V supply available on the digital sidecar to drive servos. We're going to need a little more information to determine if your particular application is legal, though.