Definatly want to run a relay. Both those above will work but you can make a custom one for a bit less $$$. You can pickup a fuse block for about $10 and a relay with socket for about $4. Just make sure you dont go over a 30amp draw and you will be fine. Run the coil power for the relay from your cig lighter and the main power from the battery. I ran a diode between the coil just in case. The diode was about $1 for 2 at radio shack. Then you have a decent supply. You want to make sure you run the proper gauge wire also, but it really is simple.