I see adapters for other Panny cameras for using a big battery to power the camera through a 4-pin XLR connector, but not for the HMC. Got any suggestions on where to find such an animal?
I am using the Anton Bauer Elipz battery, that is 10.5k and lasts over 6 hours depending on your use. As well it can power their lights and other accessories. It mounts on the bottom of the camera and has an adapter for the back which also connects to things like their lights.
I have two of these, and have yet to need more than one on any given day. Its adapter to work with their battery is made for the 150.
You can get a pretty good voltage converter for $15 or so off ebay. Mine have short circuit protection and are high efficiency. You set the "dial" with a small screwdriver while measuring the output voltage till you get about 7.4V.
I then installed a more standard size plug onto my existing PS cable (the part that goes from PS to camera) and used those push on clips that allow you to splice power off a line (often used when wiring trailer connections - I forget what the real name is). Of course you could cut the cable and splice that way.
The reason I splice is that I have not been able to find a female mate to the connector on the cable and I still want to be able to plug it into the PS. I would love to be able to find just this cable so I could use it as a dedicated battery cable but I have not been able to find it without buying the whole damn PS as well.
Works great. In a crunch though I found a car adapter with variable voltage selection that had enough amps. Solid state cams need less juice than tape cams like the HVX200 so the 1.2 amp one I found does the job.