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  Are threaded battery posts a standard diameter?

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Author Topic:   Are threaded battery posts a standard diameter?
sail16 posted 04-15-2007 04:44 PM ET (US)   Profile for sail16   Send Email to sail16  
Are the threaded posts on 12 volt marine batteries a standard diameter or size? If so, what would they be?
JBCornwell posted 04-15-2007 05:22 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
They are either 1/4-20 or 5/16-18.

I prefer the ones where the ground post is 1/4-20 and the +12 post is 5/16-18.

While on the subject I recommend using nylon locking hex nuts rather than the butterflies usually supplied.

Red sky at night. . .

acseatsri posted 04-18-2007 07:23 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
The positive is either 5/16 or 3/8, depending on brand. The negative is 5/16. I've never seen a 1/4-20.

PS- lose the wingnuts and use stainless nuts and lockwashers.

swist posted 04-19-2007 08:40 AM ET (US)     Profile for swist  Send Email to swist     
There was some discussion on wingnuts vs regular nuts in another thread sometime last year. It wasn't a foregone conclusion that you should "lose" the wingnuts. Regular nuts need to be tightened with a wrench and your average battery case can't take too much of that. Why do the manufacturers put wingnuts there in the first place?

And I'm not an expert on this but aren't lockwashers a potential problem with high current connections where you need as much mating contact as possible between the terminal and connector? I suppose if you tighten them enough so that the washer's points aren't holding the surfaces apart it is OK, but then don't you run the overtightening risk? I think you would need a flat washer between the lockwasher and the nut to avoid this.

swist posted 04-19-2007 08:42 AM ET (US)     Profile for swist  Send Email to swist     
Last sentence is wrong. It should be battery terminal, then cable connector, then flat washer, then lockwasher, then nut.

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