if you want to wire up multiple accessories off switched power here is what you should do.
Get a bosh style relay you can get them from shucks or napa or any automotive store. next you will want to find the switched power in the vehicle in the 07 ranger the ignition wire at the ignition harness is a white wire with an orange stripe or you can go the the radio its ignition wire is a white wire with a blue stripe. from there you will want to tap the wire and fuse the connection with about a 15A fuse. if you don't want to use the relay you can be done from there all you have to do is hook it up. The proper thing to do is use the relay. You will want to run a constant power either from the battery, or from the ignition harness. The 12v+ is a red wire there are 3 of them. on the relay you will hook 86 to ignition 12v+, 85 to ground, 30 to constant 12v+, and 87 to what ever you want to run. Leave 87a unpopulated. If you do this you will have plenty of power to run your accessory, and you don't have to worry about overloading a cigerate lighter or the radio power.
I do stuff like this everyday at work. Its kinda scary at first, but it is the right way to wire accessories, and it looks better when your done. Once you do one relay you will find reasons to use more. They are fun.
Just remember to fuse your power connections to be safe, and use a test light or multi-meeter when tagging wires. Good luck