[ablatner]

Let's think about this. Your goal is to make sure your laptop and peripherals have enough power and won't go out during a match (happened to us a couple times the past few years...). First off, get a new laptop battery, or maybe even a cheap new laptop with good battery life. Second, you can get a DC-AC power inverter. It converts a robot battery's 12VDC to 120VAC like a wall outlet. The battery plugs into one end, and the laptop charger the other. Cheaper, simpler, more reliable.

Of course, if want to do your powered cart because it's a fun project, then by all means go for it. Just keep this in mind too.