How-to Size Fuses in a DIY Camper Van Electrical System

Hi Nate, I posted this a couple of times on another part of your site last year, but it sits as "pending", but then came across this section so thought I would try again as maybe I've posted int he wrong place. I've had the conversation with many people who have the same question as me, so would be great to get your understanding on this, thanks. ... Hello from the UK. Great resource both here and YouTube, thanks so much for for your efforts, your videos etc. are a superb resource and clearly a lot of effort goes into them. I have to ask, and apologies if I look stupid, but the one bit I struggle with is your fuse sizing at your +ve busbar (or Lynx Distributor often in your case). For example, feeding your 12V distribution panel is a 6AWG cable (roughly 60AMP cable capacity I believe, we don't use AWG in the UK), but the fuse is a 100AMP Mega Fuse (which if a Victron one would not actually blow until about 250AMP), so how does that protect the cable? Would the cable not just set on fire before the fuse had a chance to blow, so theoretically once the current exceeds the 60AMP cable capacity? I feel I’ve missed something obvious here, but happy to take the embarrassment to understand this better. Thanks again

All your diagrams recommend ANL on the battery bank, but numerous internet people recommend Class T on the battery because of the short circuit rating. Any comments on ANL vs Class T and why you recommend ANL? Thanks

Hey Nate!

I came to this page from the Battle Born Batteries website:

https://battlebornbatteries.com/why-should-you-invest-in-fuses-for-your-system/

And there is a picture with table with recommended and maximum fuse sizes for different gauges. And that picture has a water mark from your website.

However recommendations here have different values. So I'm wondering if you know where the picture on their website comes from. And why values there are different there. I'm asking because I would like to understand better why there are different approaches out there. Which ones I should discard as non relative. And where those different values on those pictures come from.

Thanks in advance!

Dear Sir, We've supplied complete systems for a number of clients including schematics, BOM, and tech support. We've just done a unique little job with 12KW of LiFePO4 storage in 180Ah batteries. We have a 3kw pure sine wave inverter/charger. We have fusing, disconnect and power meters. What we also have is a 300A ANL fuse in the factory housing that has MELTED! We can say definitively that we have never drawn more than 2.2Kw continuous with only 600W motor loads started sequentially. My point, of course being, the fuse block should NOT be "melting". Additionally, as the 300A fuse has remained intact, it seems clear that the current is not at issue. We feed ALL components with 4/0 wire and heavy guage copper lugs which are crimped in our hydraulic crimper. Our wiring is overkill as the total wire run is under 10 feet round trip. We have no issues elsewhere with hot wires or poor connections. Just the fuse block. Is it possible that the run of the mill Amazon units are not built properly? Is there a trustworthy CSA, ETL, UL certified ANL that we can trust to handle the current? We done 3kw systems before and never have we had this issue. It is, of course, not beyond reason that we have apoor crimp hat is generating resistance and thus heat, and of course I will check this when I visit the site. However, all our fittings are built slowly and carefully and we've never had an issue. If our fittings check out, then I'm hoping you may have some ideas or suggestions for us.

Sincerely, David

Hi Nate, Nevermind my last question, I now see that the 1/0 wire isn't rated for 60C, its 105C giving it a massively higher amp carrying capacity.