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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.
Hi Alastair,
A frightening story indeed. And good plan on really thinking about the location and containment when you change to lithium.
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!
Hi Alan,
That’s indeed a frightening story. I agree on removing rings: https://www.morganscloud.com/2022/07/10/5-safety-tips-for-working-on-boat-dc-electrical-systems/
The Blue Sea cablecap works. Just installed them over my MRBF fuseholders.
Hi Jesse,
Good to hear.
Are you referring to the little cap that comes with the MRBF or some other product. O>r are you referring to the product from Ancor.
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.
Hi Jesse,
I don’t agree that the supplied cover is adequate. It leaves the large tab that bolts to the battery and uninsulated, which renders the supplied cover pretty useless. That was my point. See the photo on this tip: https://www.morganscloud.com/jhhtips/another-danger-with-mrbf-fuses/
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.
Hi Matt,
I agree.
Sounds like you had a rare good surveyor. That said, while insulating both makes total sense, it’s far from standard. If my aging memory serves I have never seen it done on car or boat. It’s also telling that Anchor only make a red boot in the line that works best where there is no MRBF. https://www.ancorproducts.com/en/products/Terminals-and-Lugs/Battery-Terminals/Covers
Hi John, unfortunately that link is dead!
Hi Brann,
Yes, thanks to the idiot marketing department at Navico/Brunswick who took down a really good web site and substituted a stupid flip catalog: https://www.navico.com/ancor/products.
I’m guessing they have broken at least 100 links on our site with no way to fix them except to point to said stupid catalog.
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.
Hi Marc,
A battery switch is required anyway, but has nothing to do with short circuit risk across the terminals that I can see, so fusing and covering terminals is really a different issue than battery switches. I also can’t see any benefit in a switch in the negative cable. Once a circuit is interrupted on the positive side no current can flow. Point being that electricity returns to the source (battery), not ground, as many people think.
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
Hi Jim,
Good tip. One thing I’m not sure about is how combustable that stuff is and how it compares to whatever they use to make purpose made boots. That said, not sure this is a problem, just don’t know.
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.
Hi Bruce,
If memory serves, from a compliance point of view it depends on how you read the code. But even if we read it to say you would be compliant, which I think you could, I still think it’s worth covering at least the positive. That way there will be no debate if anything goes wrong and covering both as recommended in the tip is reasonably easy and dramatically reduces the chances of a short, from a dropped tool, so probably worth it.
Any suggestions for rubber covers on battery terminals when you have two lugs and two cables as batteries are joined in parallel?
Hi Rokas,
Jim shared an idea above: https://www.morganscloud.com/jhhtips/cover-the-negative-terminal-on-batteries/#comment-310274
One of my pet peeves when inspecting new vessels (I’m just finishing up 10 days of inspections in Taiwan on new build projects; I’m now headed to the Netherlands for one more, on an aluminum vessel, where there are no shortage of opportunities for…short circuits;-)) is the approach many builders take to insulating DC positive terminals and fuse/switch busses. The “boots” they often use do not fully cover the energized component. It’s as if they are installing the boot for the sake of having a boot, without fully understanding why it is being installed. My rule is, if I can see any part of the terminal, then it’s not fully insulated.
Hi Steve,
I totally agree. For example, while I’m generally a fan of Blue Sea kit the boots on their MRBF fuses are just a fig leaf at best.
Same for the little black boots supplied with the BS surface mount breakers.