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Insulating boot from batt positive to master contactor

Desert Rat

Well Known Member
On the RV7, the battery positive cable to master contactor has a 90* bend in the terminal lug to make it fit the contactor post. Standard terminal boots are designed for a straight terminal i.e. they are an "L" shape, and what you really need is an "S" shape.

Maybe I've just never run across it, but in all my various searches for stuff on VAF or google, the only two solutions I recall seeing were to skip it entirely, or just shove it on there and hope for the best.

Anyway, don't know if this will help anybody out or not, but if you use two boots and cut them up, there's a really simple solution. It's hard to see in the picture, but the upper boot 1/2 is held in place by a wire tie.
 

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I used a fair number of these boots in my build, but I don't honestly think they add much safety aside from use on alway-hot exposed conductors such as you have here. They're pretty but not cheap.

In awkward-fit situations like this one, self-fusing silicone tape would probably serve just as well, although a little harder to inspect under in the future since you'd have to cut it off and replace.
 
This is a perplexing situation for me as well. You’ve done an elegant job of concealing that hot connection, but what about the other exposed hot connections? Using self fusing silicone tape will probably work, but difficult to make it look good. I’ve used liquid electrical tape, and it looks good - until you need to remove something on those connections. Liquid pvc isn’t easy to remove. Next question - why would you need to do anything anyway? Is there some concern that something will fall across those exposed connections to short circuit something? I know the answer is yes, so maybe you can build a sort of box around both contactors with all their connections inside of an enclosure, as in any of the LRU’s you have behind the panel. These aren’t internally contact protected, and we aren’t concerned about it because we can ground the box (or it is internally grounded - LIKELY), and therefore protected. Having exposed, potentially high amperage short circuit exposure, even though the area is minimal is a concern.

I haven’t ever had a problem with this, and I have never heard of someone experiencing a short circuit across an exposed master contactor, but that doesn’t mean it hasn’t happened. It probably has. Pretty much, any bazaar thing that can happen, already has…….. so, CYA, which it sounds like you’re doing.
 
I haven’t ever had a problem with this, and I have never heard of someone experiencing a short circuit across an exposed master contactor, but that doesn’t mean it hasn’t happened. It probably has. Pretty much, any bazaar thing that can happen, already has…….. so, CYA, which it sounds like you’re doing.

A Lexan guard attached to the bottom of the battery box with Aluminum angle and nut plates can provide protection, form the guard to cover both contractors and exposed connections.
 
What Terry did looks very slick.

If you google "battery contactor rubber boot" and click on images, you get a lot of interesting boots. Some might work, but I didn't find one that matches what Terry did for his install.

I also agree with Don's suggestion of protecting the exposed bolts slightly differently. This does sound like an opportunity for our 3-d printing guys to make something specific for these old-style contactors. Perhaps a complete snap-on cover, easily removed for inspection. Not sure they can 3-d print clear yet.
 
....This is a perplexing situation for me as well. You’ve done an elegant job of concealing that hot connection, but what about the other exposed hot connections?....

I don't really care much about the other exposed studs because they aren't hot with the master off. Both ends of this cable are always ready to bite as long as they are hooked up, and it's the only thing not fused in some way on the whole airplane.

When I was young and dumb, probably around 17ish. I was working on my first beater car and managed to touch something that was hot. The current path was through the wrench, then through my h.s. class ring, back to ground. sparks flew and I got a nice permanent divot in a ring that's still in my sock drawer as a reminder to be cautious around that kind of thing, and a lesson that whatever you can do to protect/insulate always hot stuff is probably time well spent.

Yes, I know that good shop practice would be to disconnect the neg terminal when you're under the hood, but really, how many of us do that? Not me, certainly not every time.

I've never had a problem since that first experience, but I could easily be that dumb kid again if I didn't watch it, so this is cheap insurance.
 
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I don't really care much about the other exposed studs because they aren't hot with the master off. Both ends of this cable are always ready to bite as long as they are hooked up, and it's the only thing not fused in some way on the whole airplane.

When I was young and dumb, probably around 17ish. I was working on my first beater car and managed to touch something that was hot. The current path was through the wrench, then through my h.s. class ring, back to ground. sparks flew and I got a nice permanent divot in a ring that's still in my sock drawer as a reminder to be cautious around that kind of thing, and a lesson that whatever you can do to protect/insulate always hot stuff is probably time well spent.

Yes, I know that good shop practice would be to disconnect the neg terminal when you're under the hood, but really, how many of us do that? Not me, certainly not every time.

I've never had a problem since that first experience, but I could easily be that dumb kid again if I didn't watch it, so this is cheap insurance.

Yep, after thinking about it, I finally came to the same conclusion - protect the always hot spots - two in my case. I have one boot, looking for another one locally before I make my next ACS or Stein order.
 
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