Best bet if you are looking at this for long term use is to follow the above advice and add an inverter. I wired one under one of my seats so I have enough to run small chargers, not so much for use of electronic devices in motion but I often need to charge cordless drill batteries, laptop, portable printer, rechargeable test equipment etc when traveling from one customers site to the next.
Laptop and driving?

“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein