12v fuse box: why one?


I have been seeing this around the 'net.

questions to the experienced builders or electricians.
why only one? why not two?

is it because of the battery?

and been fishing in the clouds… why I haven’t seen a 12v fuse box that has more than 12 fuses? why max at 12? hence the question above about having more than one 12port 12v fuse boxes.

myself, still haven’t finalized my “wish” list to what elec item to get.

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I’ve completely ditched the idea of built in wiring. Now I just have 8 acc. outlets attached to the side of my battery box. Plenty of power for everything I need, and each individual item has a fuse in their ciggy plug.

I have switched away from anything complicated because it ends up being more trouble than it’s worth. I don’t need my rig to be picture perfect, instead I opt for comfortable, convenient, practical, and portable. While having every convenience I want or need, I am camping, I don’t need to try to duplicate a house or apartment, or the myriad of problems that go along with them.


"Old school, cheap, reliable, and easily replaceable for the win!" ~ Traveler@Heart

i understand your thought process. but that does not answer my questions.

the question is. why do people only limit to one 12 fuse 12v fuse box? why not two?

whats the reasoning for not going with two fuse box (12 fuses)? being limited by the battery?

myself i doubt i will go above 6 fuse 12v box. :slight_smile:


Generally fuses are used for a circuit, not individual items. So all your interior lights might be on a single circuit, so only require a single fuse. Even many full houses have under 12 circuit breakers.

In vehicles, battery capacity is limited to how much power it can put out at once, and is pretty easy to overload it. Dead shorts are another real possibility.


"Proper planning, preparation, and equipment, ensure proper performance." ~ Road Warrior

You can have as many circuits as you want, but why would you want to? I recommend against VD’s “Keep it Simple” method of straight wiring to cigarette lighters unless, like him, they are all right next to the battery. The point of the fuse box is to kill the power near the battery so you don’t have hot wires running all over the place.

Most of the 12v marine switch panels are fused at each switch. On my rig I ran a heavy gauge to the fuse block and each panel became a "circuit " with a 15-20A fuse. Then each switch has a 3-10A fuse depending on the load. In theory, I have 24 fuses running the back of the rig.

Based on your avitar, looks like you’re in Seattle. I’m up in the San Juans. I’d be happy to take a look at your wiring diagram. I’m no electrical engineer, but I have a pretty involved system (490W Solar, Inverter, 3 house batteries + 2 Starters on an isolater. all sorts of fun stuff) and have’t started a fire yet…

Lemme know.

yes, i am from Seattle, but i live in the other washington, (moved here for a job).

i plan to use just one fuse box myself.

was just wondering why do people just use one? why not two? :slight_smile:

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Its a good question and I guess I never really thought about it. I found some Blue Sea blocks with 16, but that is about the max commercially available. I suspect it has to do with the overall load of the box. Just like the 200A breaker box in your house has limited slots because otherwise you would overload the main.
Like I said, I use my fuse box more like a distribution center and the switches are the true fuses.

I assume there’s nothing to stop you from running a second fuse box if you actually need it… just as long as the cable runs and input to each are sufficient for all the loads (consult your electrical expert).

Only a guess, but I assume that’s much the same reason most manufacturers don’t make boxes with more than 12 fuses… because the studs, circuits, etc need to be built to withstand the maximum voltage of all fuses (worst case scenario) within it.
As it stands, a 12 fuse box usually has a 100amp max… with would be HUGE in this type of build. :exploding_head:

There would be no need for 2 fuse boxes. I can’t see how you would have anymore than a maximum of maybe 6 circuits in a 12v system set up? Maybe o have misinterpreted the question.

I read of one build that had two 12 v fuse boxes, one on each side of the van. A good idea to simplify wire runs. I think they were each 6 circuit