Since lots of people on our team had laptops at the Palmetto Regional, we brought an inverter and a bunch of the robot's batteries. We were able to be charging several laptops at a time for the ten hour bus ride each way. This shows the mass of wires near the inverter and a power strip for plugging in multiple items.
We did this on the way to Phoenix with one laptop playing music at the loudest volume setting for about 5 hours. It totally drained 1 robot size battery. Going from 12VDC to ~115VAC back to 12VDC is kind of inefficient.