This is what I did today, I made a 12volt power distribution center, in the pass side foam (spare). In the pic everything mounts to a stainless steel plate/sheet , I plan to finish the box in the same way and add a hinged cover (spare parts from a scrapped coffee truck). The relay board is from a Suzuki, has 3 fused 12volt, 30amp relay controling 1 fused 12 volt switched and 1 30 amp 12volt switched output (which I split to 3) Just to be clear :
12 volt batt constant = 12volt
12volt when key is in run position only = 12volt switched.
Everything is nicely protected by a maxi 40 amp, which I mite downsize when I figure out what its for....
Big radio, sub
alarms
Engine swaps, ecm controle, fan harness junction, HEATER
Or just use the box to hide your personals....
Fun project easy to do. Hope it gives ideas.
Regards
Joe