3/8” lugs on 5/16” battery posts?

[marchem]

It turns out that the GC2 batteries I bought at Costco have 5/16” posts on both the positive and negative, rather than 3/8” on the positive and 5/16”on the negative. Since I bought FTZ heavy duty lugs assuming 3/8” posts, I've got too many 3/8” lugs and not enough 5/16”lugs, and not enough time to order the right size and get the project done before my wife divorces me (just kidding, I think). How bad would it be to use a 3/8”lug on a 5/16”post? Given that there’s plenty on surface contact between the lead at the base of the post and the lug it doesn’t seem terrible to do. All of there are with 1/0 wire.

 

[Ron20324]

...How bad would it be to use a 3/8”lug on a 5/16”post? ...

Really, it is only a 1/32 gap all the way around.

 

[marchem]

Really, it is only a 1/32 gap all the way around.

I know, but it looks a lot larger than that!

 

[Benny17441]

The gap difference is actually 1/16. If the terminal totally closed does not grab the post it really does not matter how small the gap may be. A solution might be to place a small screw in the gap and screw it down. If that sounds a little crude finding a metal shim might be better.

 

[Ward H]

@marchem
I asked a similar question on my upgrade thread. Here it is and Maine's replay.

"My aux battery has a 5/16” positive stud. I’ll be fusing that battery with a MRBF fuse. The MRBF terminal block is made to mount on a 3/8” stud.
Is it OK to put the MRBF terminal block on the 5/16” stud?"

Maine's Answer
"Yes this can be done so long as you use a thick washer on top of the MRBF mount to disperse the load to the battery."

You could probably do the same thing.

 

[marchem]

@marchem
I asked a similar question on my upgrade thread. Here it is and Maine's replay.

"My aux battery has a 5/16” positive stud. I’ll be fusing that battery with a MRBF fuse. The MRBF terminal block is made to mount on a 3/8” stud.
Is it OK to put the MRBF terminal block on the 5/16” stud?"

Maine's Answer
"Yes this can be done so long as you use a thick washer on top of the MRBF mount to disperse the load to the battery."

You could probably do the same thing.

Thanks for that. I vaguely remember that discussion, but I’ve been thinking about all of this for so long it’s almost overwhelming.