How To: Secondary Stand Alone Fuse Block Install

No one else notice that bad ass cover for the fuse box? I want one! How do I get one coup?

 

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Just doing some wiring set up and research now.
If my understanding is right, if you use an add a fuse to power the whole fuse block, you're potentially drawing the fuse block's Max Amperage rating through that little in line fuse? Wouldn't that negate the fuse blocks ~125 amp rating?

 

I think you may be confused or I'm confused about what you're trying to say. The Add-a-fuse will hold the relay closed off of accessory power so its relatively low amps. The higher power would be flowing through the switched part of the relay directly from the battery to the panel. You can choose to use an accessory power tap that will automatically turn on your aux power panel every time you turn on your vehicle or you can choose an always on power source to power your relay so that your aux panel is always on. Alternatively, you can configure a switched source to choose when you want your aux panel to be powered. Bottom line, if you want a switched source of power to power your aux panel, you'll use a relay or if you want it to be powered all the time, you'll want to use an appropriately rated circuit breaker. I hope that makes sense.

You have other options as well, if you don't know about this mega thread over in the technical forum.

-J

 

Following

 

I think so...
My brain works better with diagrams though. Basically though I catch your last part, a relay before the panel, is the way to go to supply the Blue Sea panel (or Bussman).

I edited your post above ^^ because I think you meant using breaker? Check it out.

 

Sorry, I'm not really in a position to make a diagram for you so you'll have to take this piss poor description:

Fuse tap from ignition accessory (or switched source if you want to be able to toggle panel) -> pin 86 of relay -> pin 85 to ground. This is your power holding relay, when active, you have power.

From battery -> appropriately rated Circuit Breaker (for circuit protection) -> pin 30 of your relay -> out pin 87 to power panel. This is your source of power from your battery. Make sure you use the appropriately rated relay for your panel IE 150A or 200A.

Circuit breaker.
Relay. Overkill, but you get my point. You'll want a relay if you're using switched power. I would suggest getting a relay that's rated at or above your circuit breaker. You'll want your CB to pop before your relay.

Now, if you don't care if your power panel has power with the vehicle turned off, say for example, to run a fridge or your onboard air compressor, you can forego the relay and fuse tap. It would be as follows:

Battery -> Circuit breaker -> Power panel.

*Yes, I did forget to include the circuit breaker in my initial reply to your post - sorry.

-J

Edit to add: typically, from what I've seen, people will forego the relay all together and leave the panel hot (CB protected). They will typically switch each item wired into that panel via a much cheaper relay rated for that individual circuit. I hope this makes more sense?

 

Ok that was an awesome write up. So I understand now you just need a high current relay basically right? Similarly rated to the max amperage of the panel? Probably overkill to have it but I guess thats the right way.
The typical relays used on these set ups are 30/40 amps relays

 

It just depends on what you want to do really. I would personally run the more simple setup which I am planning on building myself, eventually. I'm leaning towards the Bussman RTMR relay panel though instead of this Blue Seas panel. The busman holds both relays and fuses in a more compact footprint and I'll treat it as follows; Battery -> Circuit Breaker -> aux fuse panel. I'll switch each individual circuit on my new power panel depending on what I want to do. As of now, I just need to run aux lights so I need to make sure that I account for expandability. To make it expressly clear, circuit breaker is not synonymous with relay. A circuit breaker is to be treated as a resettable circuit disconnect (think resettable fuse), whereas a relay is used in place where electrical switching safety is concerned. Like instances where you wouldn't want to run a high voltage power line through your firewall, instead you can run a much lower amperage wire connected via a switch to toggle the on/off state of the relay from a second location (say, an overhead switch panel). That way, your higher power stays closer to the source in more relative safety.

If you wanted to be able to switch your auxiliary power panel on/off from within the cab of the truck, you'll absolutely want to use a relay (in addition to a separate circuit breaker) in this instance as you don't want to run large power cables multiple times through the firewall. So in that case, you'll want to set it up like what I mentioned earlier (battery -> circuit breaker -> relay -> aux power panel). When I say switch the power panel, I am talking about the entire panel as one complete unit, like turning the entire auxiliary power bus on/off instead of each individual powered circuit (think going outside your house and throwing the main breaker to your internal breaker box). You'll rate your circuit breaker at the max amperage of your panel so if it's a 200A panel, you'll want a 200A breaker. This breaker will trip when the panel electrical draw exceeds 200A, otherwise sustained draws of over 200A could start melting your panel possibly starting a fire under your hood. If you choose a lesser rated relay than 200A in this example, your relay will fail due to exceeded power draw through the switch of the relay. I haven't looked too deep into these solid state relays, but I still wouldn't roll the dice on that, just get the right size relay for panel at a minimum (200A in this example). Large relays in this case are very expensive at ~100$ or more. With 100$ you can purchase 14 40A SPST relays and switch each circuit off of your power panel. So in this instance, running the more basic setup will be cheaper in the long run. Your auxiliary power panel will be treated as always hot and circuit you run off of that panel would be switched through a smaller individual relay for that circuit.

Below are some options you have if you were looking at building your own aux power panel.

https://ceautoelectricsupply.com/waterproof-power-distribution-centers/
https://www.waytekwire.com/item/46345/EATON-s-Bussmann-Series-15305-5-2-4-RTMR-Mini-Fuse/

-J

 

search function for the win!!!

 

Could you give an example of say, how you'd wire up a light bar to this? I'm finally starting to understand this, but basically all of my stuff (Sound system, light bars, horns etc etc) All have inline fuse's and relay type stuff. Soooo? I'm just confusing myself to be honest, but I'd love to build something like this since I currently have about 8 things clinging on to the positive terminal of my battery.

 

Okay, I think I just answered my own question, basically instead of running your accessory to the battery you run it to the fuse box with the needed amp fuse, and you wire everything else the same. This is just a neater, and safer option since its protected by a circuit breaker.

 

Bingo! You just attach things to the fuse panel instead of straight to the battery and then the panel serves the same purpose as your in-line fuse holder (it holds the fuse)

otherwise everything is exactly the same

 

Fuck yaaaa. Damn okay it's going to be a huge pain in my ass to rewire everything. But could be worth it.

 

So, I originally (back in 2016) did a aux panel in a Husky clear plastic box. It has done really well, but I'm worried more and more that one day I'm going to have to take my truck in to get serviced or fixed and they'll need that fuse panel behind the battery and won't be able to get into it because of my box. So I've been looking at what everyone else has, and none of them really have a good solution for relays. Yeah, one or two screwed to the plate, but not if you need multiple.

Additionally, my parts wouldn't fit on the driver's side, so I decided to use the empty space on the passenger side as I'll not be getting a dual-battery setup.

So to that end I decided to go for a cleaner look, without using the bussman solution. Here's what I've got so far (still in progress).
Also, this took 5+ hours to learn fusion360, and a week wait for OSHcut to cut, bend and ship.

 

I forgot to show the placement photo.