Each Sony NPF style camcorder battery runs at 7.4V. By running them in series, it works at 14.8V which is the minimum power required for the 600 and 900 LED light panels at full brightness. I took two basic Sony NPF battery chargers, gutted them, and then wired them in Series to provide 14.8V DC.
Remove two screws under the rear sticker and then pry apart case
To wire up the cases for Series, basically you take the Negative wire from one and the Positive wire from the other and connect them to the barrel plug. The other two wires (negative and positive) from each charger would be connected together.
Sorry for poor diagram
Next I added a bit of extended wire and used my Barrel Plug (shown here) to connect directly to the LED light. The Barrel Connector is super easy to work with (no soldering), and is clearly marked with + and - for positive / negative placement. It's a very simple and cheap DIY to provide portable power for these large LED panels. If you want use heavier batteries, just make the wiring longer and mount to your light stand.
[Disclaimer] Attempt this DIY at your own risk. Using your batteries in other ways than intended may cause premature failure of your batteries, or damage.
Here's a few parts links related to this DIY:
Sony NPF Style Battery Charger