I use my laptop in my car on a daily bases. It only has 1 usb port and I use about 5 usb devices. I bought a powered usb hub. It works ok without power if you only use one or two usb devices. However, when I use more devices, they don't operate correctly. And it doesn't have enough power to operate my external dvd rom. Unfortunately, the power adapter is for ac current.
I have searched for a 5v dc power supply that carries enough current to power this hub but with no luck. There are lots of 5v dc power plugs but many only hold about 500mA.
I have one of these that I was hoping I could somehow increase the mA to supply my hub: