By request I'm working on a write up that I will be putting in the Battery mods area, that would be perfect for this use, or as an emergency backup for power failure. You could use it for a Pass Through or use it for USB based chargers. I'm making a simple low cost and easy to get DC/DC converter that is capable of 3 amps of current so it will be more then enough to power the Pass throughs that don't have the inline battery and give full performance of it. You will be able to either hook it up strait to a 12 volt battery of your choice or use a ciggarette lighter plug. Look for it soon as the parts are on the way.
R.F.
R.F.