I do mobile blood, urine, sampling as an independent contractor and need to use Andriod Auto navigation, a power hungry app. I was wondering if the USB port behind my shifter is 5V? And if so, would I be better off using the 12V cigarette charger with an adapter? This second option would prevent me from using navigation on the touchscreen, but I still have my hug buddy phone holder to clip on to the vent, if I have to. Anyone out there with some experience on this?