If you float a power portm meaning it is not grounded, and connect the center pin to ground and a power wire to ground it will work but in my experience not as well as 12 volt. I have run a GPS off the 6 volts but when I got a new one a few years ago it would not work on the 6 volt. I bought an inverter and now have a 12 volt power port on my 6 volt car. That works great.
https://www.amazon.com/DIGITEN-Conve.../dp/B019GY2FLW