Reddit mentions of 110 PCS Wirefy Solder Seal Wire Connectors - Heat Shrink Butt Connectors - Electrical Wire Terminals - Marine Insulated Butt Splices

Jesus, have you never heard of insulated butt splices? Solder-and-seal connectors are even better.

You can solder or there are a variety of solderless connectors out there. A lot of people take the opportunity while they're replacing the fan to add in some type of connector (JST is popular and fine for something low current like a fan) to make any future swaps easier. If you're a bit timid about soldering you can use something like this - solder shrink connectors. I've never used them but have seen folks on another printing group recommend them. They're pretty much just shrink wrap with a bead of solder in the middle, you just stick the two wires in and heat. It solders and shrink wraps them all in one easy step.

I don't have any experience with any other crimpers than the ones I mentioned above but these are pretty highly rated. You might also consider using heat shrink/solder butt connectors. I've got the kit I linked to here and have been impressed with it. You will need a heat gun though but no crimping involved. Just use enough heat to melt the solder and shrink the heat shrink .

If it doesn't have to be something that can be disconnected easily, then this might work: https://www.amazon.com/dp/B01M0EZBYQ

Practice on some spare wires first. Takes a bit of trial and error, but then works great.

Not being able to disconnect might be against code. But then, it's only low voltage. So, probably not a big deal

1.

Which wires specifically? In general, I was planning on going for heat-shrink solder terminal connectors and crimp connectors.

One of the reasons I posted this is because there are quite a few connectors and I am still not entirely 100% sure what I need. Obviously when screwing something in to a screw terminal block, the ring crimp connectors. But when joining wires, I would prefer to use the heat-shrink-solder type, but there are also butts and blades (heh).

I bought this set of terminals, figured I'd need them anyways: Assorted crimp terminals

I am probably going to buy this set of solder terminals: Fancy solder terminals

I am pretty good at soldering (though usually circuit boards, not automotive wires, hence not entirely knowing what to do.) I have easy access to a heat gun as well.

2.

Well, both - the breaker goes on the battery, and it sets the maximum amperage for the entire new fuse block and everything attached to it. The fuses go for each individual circuit. I want to use just one fuse for each circuit, instead of having several different circuits sitting on the same fuse, largely for my own desire for neatness and debug-ability. I could have one main fuse instead of the main breaker, but I figure that they will serve the same function and I may as well go for the re-usable option.

I was going to go for this breaker: Fat breaker

That said, I bought this fuse kit, which includes up to a 35A fuse, which will be more than enough. I also bought this fuse holder, in case I decide to use one main fuse instead of one main breaker. (I figured I'd need both of these anyways for some project, may as well get them even if I don't use them right now.)

Fuse Kit

In-line Fuse Holder

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In general, I think my system will basically look like this:

Battery 12V + Breaker = safe 12V

Save 12V + ignition 12V (do I need a fuse here?) + Relay = ignition-switched 12V

Ignition-hot 12V + Fuse Block + ATC/ATO Fuses = eight fused circuits

Fused circuits, obviously, feeding from above. I will probably add a 20A switch in line with high-power circuits, just in case, as an emergency switch.

Fused circuits will terminate at something like this Ground Bar.

 

What do you think of this proposed setup?

I do realize that it's kind of overkill for what I want.

But you can probably agree that overkill is better than your car burning down!