The Offshore Voyaging Reference Site

Cover The Negative Terminal On Batteries

One of the things I love about my job is that, despite having maintained and refitted boats for over 50 years, I’m still learning, often as the result of the discussions we have in the comments.

This has certainly been the case here as I think about reducing short-out risk on batteries, particularly lithium. One realization leads to another.


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Alastair Currie

I find it difficult to source secure terminal covers. Plenty of choices but none appear to snuggly fit. I have been using best fit for years but got caught out a few years ago. I was removing a stainless braided fuel line, and as I slid the line away the bow went under the terminal boots and bridged the two terminals. There was a bright spark, loud crackle and smoke, in the very short time it took to pull the line clear.

A frightening moment for sure. The braid was destroyed in places and the hose punctured at a hot spot (but empty).

I have decided to go for lithium and will plan a complete overhaul of the charging system. However, the batteries will be moved to a dedicated, secure, isolated area as part of the upgrade.

Cover the terminals securely.

Alan Chesney

I used my wedding ring to close the circuit across terminals of a newly charged battery one time. I ended up with a gold-plated terminal, a gold-plated wrench along with one badly burned finger. Lessons painfully learned: Remove ring and cover terminals!

Jesse Falsone

The Blue Sea cablecap works. Just installed them over my MRBF fuseholders.

Jesse Falsone

I’m referring to the product pictured. Works well but only with a single MRBF fuse not the double holder. Also, make sure you buy the one with the correct cable size. I bought three and one was too small for my 1/0.

Matt Marsh

The surveyor who did our boat when we bought it in 2020 explicitly flagged the lack of negative terminal covers as a must-fix ASAP item.
Capping the positives is all well and good, until you need to disconnect a positive cable. At which point you have a 12″ wrench in there, and the rubber cover is removed, and the fuse is on the downstream side of your wrench. That, he said, is when you’ll be damned glad you removed only one rubber cover at a time.

Marc Dacey

Boots are a good idea, but I have shut off switches for both positive and negative sides. Has proven to be a good idea more than once, although putting the bank in a place fully accessible from above, which I realize is a bit of a privilege, has made sudden welding much less likely an issue.

Jim Schulz

Here’s an idea for covering hard-to-cover connections that need protection with clear vinyl tubing. This school has a pretty good
collection of posts in the often garbage-filled Youtube space.

https://youtu.be/DB-ul07hPJE?feature=shared

Bruce Pappas

John, is it necessary to cover the battery terminals, if the battery is enclosed in a battery-dedicated box? I have two boxes – one with 4 6v batteries and a second with 2 6v batteries. Both are enclosed. Thanks.

Rokas Babrauskas

Any suggestions for rubber covers on battery terminals when you have two lugs and two cables as batteries are joined in parallel?