I found this unit works very well in several cars. The built in cooling fan is a little noisy with no engine running in the car, but once you are moving it is less noticable. I was able to power a laptop for a long period with this unit.I used it on a long flight on an American Airlines Boeing 767. The adapter was capable of charging a laptop but would shutdown if the laptop was powered up. I suspect that the power plug on the aircraft was putting out a low voltage causing the unit to shutdown automatically, but since I'm not sure I'll knock one star off.