This message was posted on behalf of Intel Corporation
I would love to help you with this.
I think that you shouldn't have problems using the power socket, because the Edison is never going to need more than 15 A, so answering your question, yes it is a safe source.
Having said that, the only recommendation that I can give you is to make sure that the Car Adapter Plug provides enough current to power the Edison, the Edison is not going to draw more than 500 mA.
I hope you find this helpful, and don't doubt to contact us when you have questions.
Have a nice day.