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Thanks!
I did it, a Mega Fuse is added to the unused spot.
I have the Victron Buck Boost 50 Amp to charge lithiums from the starter battery.
The Buck boost is adjustable current and voltage-wise for safe charging of lithium batteries.
There is no cable on the current fuse screw, but will be added soon.
No code needed to restart anything, all radio settings remain, only the time and date needed to be reset.
I have a 2018 159" high roof with UC5.
I was going to disconnect the battery to find access for doing this, but I realised that maybe I should double check if this would erase/jeopardize anything. So I searched and searched and found this thread.
OReilly's has the square headed screws (Not stainless) #01336 "SUPER START" is the brand. In the battery section where the other battery connectors and lugs are.
I will replace these with stainless if available.
So again, thank you to all who posted about adding the fuse.
 

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Where in these pictures would I add a positive power lead for my powered subwoofer? Can they go on any one of the locations? I'm thinking to put it on top of the upfitters connection since I'm not using that power?
 

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Help understand these slow blow fuses. 100a doesn’t mean it blows at 100a. How do you size fuses taking this into account?

In my case I am using a victron cyrix and 2awg wire to send the power to the house batteries. It seems a 80a fuse is appropriate?

https://m.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/bolt-down-fuses/littelfuse_mega_datasheet.pdf
The general idea of fusing is protect "everything else" by "failing first".

A fuse (or breaker) doesn't limit or regulate the current under normal conditions, it is more like a disaster protection method.

In addition to slow, medium, and fast tripping protection methods, it is useful to also realize that most of these methods (other than specialized magnetic based breakers) trip on "temperature", not actually on "current". This means that they will trip faster on a hot day in a circuit that uses smaller awg wire than on a cold day with heavy awg wire carrying away the heat.

A slow blow fuse is often used to help a load "ride through" a heavy inductive load start up, example induction stove, motors, etc. Our home air conditioner is fused like this for the same reason. It is still fairly fast, just not a hyperactive trigger switch.

Going through the list of items for a reality check:

- The cyrix is essentially an intelligent on / off relay, it also does not regulate, just switches. It's current carrying capacity is on the label of the particular unit. This is one source of info on max fuse sizing.

- 2 awg wire - so in theory about 100 amps continuous capable (but it will warm a bit) Could use this as an "indication" of a 100 amp fuse max fairly safely.

- House bank bulk charging capability. Some batteries, such as Lifeline AGMs can bulk charge at very high rates. (2C easily). Others struggle with 0.3C. You don't have to fuse to this level, but it is a possible indicator of what "normal operation" could look like.

Probably you have seen from my other posts that I am a big believer in actively controlled battery to battery charging methods, vs just a random result from a connection. One of the reasons is exactly related to your question. If you have a B to B charger with a defined 60 amp design, that is the max it will draw, so it is easier to estimate this protection sizing.

I am not criticizing, just pointing out that one approach vs the other makes it easier to estimate what is going on in the wires.

Summarizing my far too long of post, from what you have posted, it seems like the main point of the fuse in that application is to protect the wire from an accidental dead short to ground. If that is really what the fuse is for, then 80 is not any benefit vs 100 amps on your installation. (MHO)
 

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... would depend what draw you are connecting... keeping in mind this location is unfused...
 

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I figured it out.
It's M6-1.0 for all 3 studs (some older/aftermarket replacements are two M6 and one M8).
I used matching flange nut I've found at the ACE hardware.
Promaster-Aux-Battery-Coonectors.jpg
Does anyone know which thread is used on the studs of the negative post clamp bracket?
Thanks.
 

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Does anybody see a reason that this would be a good or bad spot to connect?

View attachment 58692
This is exactly where I am planning to connect my house battery charger.
To fuse it I am thinking to sequence:
  • short (2in) AWG 2/0 with copper lugs; one end attached to the spot marked with green arrow on that picture
  • 100A ANL fuse
  • 10ft AWG6 to the charger
Is it a bad idea?
The only difficulty I see is to fit everything in this tight spot without modifying the fuse box cover.
 

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I hit the same problem, after briefly contemplating $60 for a new old stock fuse interface just for the bolts (I need a cover anyways), I went for the diy. I just hammered the bolt through the top of my vice to bend the washer for engagement and then ground off the sides.


63067
63068
 

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I have a 20A charger that I need to fuse to the main battery. I am running a 30A breaker back by the charger, but want to have a 30A Mega fuse in the free space on the main battery positive bus, but it doesn't seem like they make one. Your link shows a 40A option. Do you think that would be acceptable? For my application, the online calculators are saying the derated ampacity for my wire is 48A. Not a lot of headroom, but I have a 30A breaker on the other end of the wire and the charger should only pull 20A. What do you think?
 

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I have a 20A charger that I need to fuse to the main battery. I am running a 30A breaker back by the charger, but want to have a 30A Mega fuse in the free space on the main battery positive bus, but it doesn't seem like they make one. Your link shows a 40A option. Do you think that would be acceptable? For my application, the online calculators are saying the derated ampacity for my wire is 48A. Not a lot of headroom, but I have a 30A breaker on the other end of the wire and the charger should only pull 20A. What do you think?
Try this one
 

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Try this one
I saw those, but they're the shorter MIDI size, whereas the free space in the fuse block is for the larger MEGA fuse size. I found this 40A size that shows the correct dimensions, but would still like to go smaller for smaller wire if possible...
 

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So I have the third connection with a 70A fuse that per everything I see here wouldgo to the factory upfitter connection, BUT I do NOT actually have the upfitter connection in my 2018 2500 rig. Most of the ones I've see on here without the upfitter seem to have a blank spot there. Anybody have an idea what this might be in this case?
 
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