Boat battery connection

[Donald]

So most boat batteries use a threaded stud (5/16 or 3/8) and the battery cable have lugs. Old days they just used a wing-nut. No more.

The battery manufacturers supply a SS plain hex nut. Most no lock washer. A few do.

What's the proper way knowing BITOG members will be anal about exactly how to do this.

Understand the battery cable will come off at least once a year, so not a one time deal.

My thinking is a SS split ring washer under the nut and under that a SS flat washer.

Then there are internal or external split ring washers but they can scrape off plating from the battery cable lugs as their teeth grab.

I have seen some supplied hex nuts with attached star washer supplied by a battery manufacturer.

 

[mk378]

No washer between the battery and the terminal lug. This is where the current flows so that needs to be clean and tight. The battery has a flat lead pad for the terminal to rest on. You can do basically whatever you want with a top washer and nut. Don't make it much tighter than a wing nut would be since it is only soft lead at the base.

For gosh sake quit overthinking this stuff and get out on the water!

 

[AuthorEditor]

YMMV, but I have not used any washers on my sailboat battery cable connections--just the supplied SS nuts for maximum connectivity to the battery. Washers would introduce a bit of resistance. You can use copper washers I suppose, but I have not had any problems. I check the battery water periodically and check to make sure everything is tight.

 

[wings&wheels]

As noted, clean and tight are key, but not too tight. I use a SS nnut, split washer and dielectric paste, and relatively low torque to not damage the terminals as they are a stud molded in relatively soft lead.

 

[AuthorEditor]

This guy recommends using nylock nuts, which is not a bad idea:

 

[andyd]

Wabbout another wingnut?

 

[Donald]

I am not suggesting any washer between the battery and lead pad on the battery. The electrical flow is from the lead pad on the battery around the stud to the battery cable lug. No real electrical flow from the stud or nut.

 

[55hambone]

This guy recommends using nylock nuts, which is not a bad idea:

I've always used a nylock nut with a stainless steel washer on top of the terminals. It won't come loose until I take it apart.

 

[Dave1027]

I like having a wingnut on at least the positive terminal. That way I can more easily take the positive lead off for storage/charging.

 

[tnt_motorsports]

FWIW I use a plain nut and washer on my travel trailer batteries. The cable / terminal goes straight on the post, then the washer, then the nut. I tighten it with a ratchet and socket. Stays that way until fall when I take them out.

Just my $0.02

 

[Donald]

I like having a wingnut on at least the positive terminal. That way I can more easily take the positive lead off for storage/charging.

Its not recommend and may not be USCG approved.

 

[paulo57509]

Last year when I started looking into a starting issue on the Lexus, the first thing I looked at was the battery connections. The negative battery terminal was kind of mangled (no doubt from a history of self-discharging issues before I took ownership).

Because the OEM negative battery terminal is part of the cable and NLA, I started looking into replacing the battery terminals which required making a new negative battery cable that would bolt on to the new OEM Toyota terminals - similar to a marine cables.

I know nothing about termination and crimping large (4 AWG) cables and lugs. I stumbled across this site:

Marine How To - DIY for Boaters - Marine How To

For DIY boaters in an attempt to try and keep the sport as affordable & safe as possible. How To articles for sailboats and powerboats.

marinehowto.com

I'm not a boat guy so I can't vouch for the validity of claims made. But from the articles I've read, the info appears sound to me.

Side note - the starting issue has since been found and repaired; the issue was not due to the battery connections. I have the material and tools to make my own cables now but this has moved down to the bottom of the priority list.

 

[mr_boring]

Wabbout another wingnut?

Word....... I don't even have a boat anymore but I've still got the spare wingnuts floating around somewhere. A big handful of them.....

 

[X15]

Last year when I started looking into a starting issue on the Lexus, the first thing I looked at was the battery connections. The negative battery terminal was kind of mangled (no doubt from a history of self-discharging issues before I took ownership).

Because the OEM negative battery terminal is part of the cable and NLA, I started looking into replacing the battery terminals which required making a new negative battery cable that would bolt on to the new OEM Toyota terminals - similar to a marine cables.

I know nothing about termination and crimping large (4 AWG) cables and lugs. I stumbled across this site:

Marine How To - DIY for Boaters - Marine How To

For DIY boaters in an attempt to try and keep the sport as affordable & safe as possible. How To articles for sailboats and powerboats.

marinehowto.com

I'm not a boat guy so I can't vouch for the validity of claims made. But from the articles I've read, the info appears sound to me.

Side note - the starting issue has since been found and repaired; the issue was not due to the battery connections. I have the material and tools to make my own cables now but this has moved down to the bottom of the priority list.

There's some very good info on that site, this article specifically addresses Donald's question:

Battery Melt Down Narrowly Averted - Marine How To

Note The Melting of The Battery Case (originally published July 2012) The connections to your batteries matter. How you make them, how you torque them and how clean they are all matter. Not following best practices or marine wiring standards can impact your personal

marinehowto.com

I'm not in full agreement with everything they say though, such as the suggestion to use a split ring lock washer. They are useless, they don't do any real locking, and if reused too many times or are over-torqued they can break and weaken the joint.

 

[Dave1027]

Its not recommend and may not be USCG approved.

It's the way the Searay came brand new and does have a USCG certification plate on it. It's an outboard if that matters.