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Old 03-04-2016, 17:23   #1
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Question MRBF confustion

I have been thinking about using a couple of MRBF fuses, but I'm not so sure now. It seems that the MRBF from Blue Sea (and their supplier) only come with a M10 - 3/8" battery connection and a 5/16" stud:

https://www.bluesea.com/products/519...k_-_30_to_300A

All of my batteries have 5/16" Studs (Engine,House,Thruster) which seems the most common.. so why on earth would they have a 3/8" battery connection?

Also why would they have different battery and stud connection sizes?

(yes the 5/16" battery stud would work on the 3/8", but it seems odd).
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Old 03-04-2016, 21:24   #2
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Re: MRBF confustion

I put 100's in and don't have a problem on 5/16" studs. some batteries are 3/8. and also the battery switches and big bus bars are 3/8. I use them a lot on bus bus and switches as well not just batteries.


also it's not 5/16 stud it's actually metric.... so don't lose the nut.


yes it would be better if they came in both sizes. but then I'd have twice as many parts lying around...
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Old 03-04-2016, 21:43   #3
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Re: MRBF confustion

My boat has this sort of fuse on the positive terminals of the batteries. They were installed before we bought the boat and seem to fit up quite well.

I'm sure there are lots of sizes out there.

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Old 11-06-2016, 17:54   #4
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Re: MRBF confustion

I e-mailed Blue Sea and here was their reply for others finding this thread:

I have asked several engineers this question. The most common consciences is as long as there is good surface contact like on the top battery there will be no problem. The stud itself does not conduct much through the threads to the fuse plate. It the surface that most on the currents flows, the studs merely holds it together. The lower battery has the hybrid style and I would avoid this type with the 5191, there is much less contact here.
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Old 11-06-2016, 18:15   #5
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Re: MRBF confustion

Quote:
Originally Posted by geoffr View Post

All of my batteries have 5/16" Studs (Engine,House,Thruster) which seems the most common.. so why on earth would they have a 3/8" battery connection?
Interesting. All of my batteries have 3/8 on the + and 5/16 on the -.
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Old 12-06-2016, 05:31   #6
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Re: MRBF confustion

Quote:
Originally Posted by Stu Jackson View Post
Interesting. All of my batteries have 3/8 on the + and 5/16 on the -.
I think the stud size depends on what the manufacturer offers. All my Deka GC15's have 5/16" studs. Deka offers 3 varieties of terminals on their golf cart batteries but the ones with studs are only available in 5/16".
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Old 12-06-2016, 05:45   #7
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Re: MRBF confustion

Mine are 8mm
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Old 12-06-2016, 06:30   #8
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Re: MRBF confustion

Might be cheaper to purchase here
https://www.waytekwire.com/products/...Fuse-Type=MRBF
rather than theBlue Sea branded holders and fuses.
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Old 13-06-2016, 08:53   #9
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Re: MRBF confustion

nigel1 - that is exactly what I did.. saved a ton of $$

regarding 5/16 vs 3/8 on batteries - from talking to the chandlery here it sounds like historically car batteries (and marine?) all had 3/8 studs, but now more are moving to 5/16 (such as my Trojan T-105s).
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