I have been searching the net for a good way to acheive 12v. I talked to 4 wheel auto here in Edm. They're advice is to come up with a calculated load and size a transformer accordingly. Now I know I read some where about putting in a third battery strictly for 12v use in. Charging it off of the alternator after dropping the voltage and installing a fuse box. I plan on a stereo with amp and some good lighting probably exnaying the microwave and foot massager. Any advice or experience.