Transient current

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Jun 27, 2004
122
Hunter 25.5 Cocoa Beach, FL
While going ashore a shoal island to tie my boat, another was already there settled in for the night with generator running. I felt a tingling in my hands while handling wet lines (salt water) and at first thought I had handled jellyfish, but upon releasing the line the sensation stopped so I knew I was picking up electrical current from the other boat. His was a stink-boat manufacturer installed generator and air conditioning system with GFCI protection (which protects him on his boat just fine, of course). I only received shocks when touching my boat or wet lines (whether on shore or standing in water it was the same). I did not measure the potential but the sensation was bearable so the current was very low as well. My sailboat has an iron keel grounded to the mast and the only conductive path from there to my anchor line would have been salt over the hull and deck. I am a bit ashamed to ask about this for I am an electrician and understand the theory (albeit studied long ago) but am wondering if this is a common occurrence with marine electrical systems, and how do these potential differences occur like this in a common brine soup? One more question: would this energy have contributed to the exceptionally brilliant phosphorescence in the water that night?
 
Oct 22, 2008
3,502
- Telstar 28 Buzzards Bay
I doubt the electrical leakage in to the water had anything to do with the bioluminescence, since they aren't really related in any way AFAIK. How close to other boat were you? IIRC, in salt water, the voltages usually die out fairly quickly, since salt water is a fairly good conductor. Is there any chance that the issue was one limited to your boat alone??
 
Dec 25, 2008
1,580
catalina 310 Elk River
Low voltage, high resistance=low current flow. Not likely you were experiencing any current flow from DC on your boat. Were you running a inverter, say to power a TV or such? How far away was the other boat? What line were you handling, anchor? Had his boat drifted on top of your anchor, or was touching your anchor line under water, or possibly both your anchor line had contact under water? Even these possibilities seem improbable, but if he were generating AC and it somehow became in contact with the water you may feel the effect within close proximity to his boat, but I would think you would need to be close to his boat and swimming in the water to feel it's effects, cause his stray current is looking for the least path of resistance to ground and you need to get in-between that path to feel the effect.
 
Jun 27, 2004
122
Hunter 25.5 Cocoa Beach, FL
I was within 15 feet of him with one anchor offshore aft, my keel resting on the bottom, standing in water with running lights on... Come to think of it now this could have been 12vdc from my boat. I recently re-wired my mast lights with a two wire conductor, using the mast for my return on the anchor and steaming lights using a single pole double throw and a two conductor thru-hull (switched positives on each) on the connector. My bow light is mounted to the pulpit rail to which the forward anchor line was probably touching and may have been a factor. Duh. Ok, I've been planning to scrape the paint off my keel anyway, so now it should be easier. Thanks for the input; this proves my father's saying "Two heads are better than one, even if one is a head of cabbage."

Cap'n Cole-slaw, on my way to the marine store for a three conductor thru-hull.
 
Dec 25, 2008
1,580
catalina 310 Elk River
Again, you can not feel 12v DC through your hands. You can take your fingers lick them both and touch each terminal of a car battry and still feel nothing. Even at 30v DC you probably can not detect it. If you use your tong you would feel it, but at these voltages your body simply has too much resistance to draw any current through your hands. You were feeling AC or the Aliens were about to beam you up.
 
Oct 2, 2006
1,517
Jboat J24 commack
Well

Its not that rare for BAD AC work to kill swimers on land ,sea and water parks and with only 100 Ma killing people its not like it takes that bad a mistake
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Again, you can not feel 12v DC through your hands. You can take your fingers lick them both and touch each terminal of a car battry and still feel nothing. Even at 30v DC you probably can not detect it. If you use your tong you would feel it, but at these voltages your body simply has too much resistance to draw any current through your hands. You were feeling AC or the Aliens were about to beam you up.
32 volt DC was a common farm electric supply and it killed more than a few men. If you get the contact resistance low enough to push 15 milliamps across you heart you may die, you can feel less than 5 mA.
 
Jan 1, 2009
371
Atlantic 42 Honolulu
Again, you can not feel 12v DC through your hands. You can take your fingers lick them both and touch each terminal of a car battry and still feel nothing. Even at 30v DC you probably can not detect it. If you use your tong you would feel it, but at these voltages your body simply has too much resistance to draw any current through your hands. You were feeling AC or the Aliens were about to beam you up.
Are you sure? Moist fingers are not salt water covered hands and may well have a lot more resistance. When I dove in salt water to recover an 18 volt lantern I got a very noticeable shock along my arm.

--Tom.
 
Oct 2, 2006
1,517
Jboat J24 commack
Well

24 Volt AC/DC is considerd the SAFE threshold which is why most machine controls and things like door bells work at this level
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Soak your hands in salt water brine for ten minutes and then, while they are still wet. check the resistance between them with a meter.
 
Oct 2, 2006
1,517
Jboat J24 commack
Better yet make shampoo that is salt based and then handle the power cords you will find the bads ones REAL fast :)
 
Jul 20, 2005
2,422
Whitby 55 Kemah, Tx
The thing that strikes me is you saying "using the mast for my return". You do not wire a boat like a car or home. No part of the boat is to be used for ground! All grounds must be returned to a ground bus bar that is connected to the ground terminal of the battery. That bus bar is also supposed to seperate the mounting of the bar and the bar with some kind of non-conductive material, so not all bus bars work as car bus bars are usually solid metal.
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Any bus bar can be used if it is isolated, fiberglass bulkheads are as good as it gets for mounting electrics. That's what they use to make circuit boards. A heavy bronze bar drilled and tapped for binding screws and mounted on a fiberglass panel is perfect.
 
Jun 27, 2004
122
Hunter 25.5 Cocoa Beach, FL
The thing that strikes me is you saying "using the mast for my return". You do not wire a boat like a car or home. No part of the boat is to be used for ground! All grounds must be returned to a ground bus bar that is connected to the ground terminal of the battery. That bus bar is also supposed to seperate the mounting of the bar and the bar with some kind of non-conductive material, so not all bus bars work as car bus bars are usually solid metal.
Thank you Franklin- though I realize this now your advice reaffirms what I discovered.
 
Jun 27, 2004
122
Hunter 25.5 Cocoa Beach, FL
Again, you can not feel 12v DC through your hands. You can take your fingers lick them both and touch each terminal of a car battry and still feel nothing. Even at 30v DC you probably can not detect it. If you use your tong you would feel it, but at these voltages your body simply has too much resistance to draw any current through your hands. You were feeling AC or the Aliens were about to beam you up.
These are two 6v deep cycle golf cart batteries I believe are rated at 250ah (100 hour discharge rate). Though there isn't a conversion of ah to cca I have seen load tests done on these brand batteries individually at 1000cca for 15 seconds. Franklin pointed out my mistake in grounding my system and I will repair that, of course, though am tempted to see if I can duplicate the situation to test my conclusion that the potential I felt was originating from my boat. I just can't see how a 120vac system on another boat could provide potential to mine through me and to my boat when we were both in the same water. If anyone has an explanation for how this could be I welcome it.

As far as aliens go, I sorely doubt that. Though I was anchored less than a mile south of Cape Canaveral the shuttle launch that morning was scrubbed, so it was still on the pad, keeping the USCG and all other NASA security resources on alert. No alien in his right mind would risk a stunt like that under those conditions much less even be anywhere north of Sebastian Inlet.
 
Nov 21, 2007
673
Beneteau Oceanis 34 Kingston, WA
I'm shocked!

Again, you can not feel 12v DC through your hands. You can take your fingers lick them both and touch each terminal of a car battry and still feel nothing.
But would you not feel sufficient current flowing through another conductor? As a kid I spent a bit of time on a dairy farm with an occasional electric fence powered by a small 6V (?) battery, I know that if you grabbed the fence wire you got quite a shot! I've also had occasions with cars when I was inadvertently grounded and felt current from a small 12V battery. I had always heard that it's not the voltage that matters, it's the current (amps)... I wouldn't be too casual when working with electricity even if it's "only" 12V DC.

Dave
 
Jul 20, 2005
2,422
Whitby 55 Kemah, Tx
Any bus bar can be used if it is isolated, fiberglass bulkheads are as good as it gets for mounting electrics. That's what they use to make circuit boards. A heavy bronze bar drilled and tapped for binding screws and mounted on a fiberglass panel is perfect.
Problem is, the fiberglass on boats is covered with something like paint and that something can carry current. A good boat bus bar is connected to it's mount via rubber. Don't believe me, go look.
 
Jan 3, 2009
821
Marine Trader 34 Where Ever I am
Problem is, the fiberglass on boats is covered with something like paint and that something can carry current. A good boat bus bar is connected to it's mount via rubber. Don't believe me, go look.
Huh? The entire interior of my engine compartment and the electrical locker is painted and in doing service for over 35 years I have never encountered fiberglass, gelcoat or paint, unless some kind of metallic, carrying current. I also have never seen a bus bar, even on multi-million dollar yachts, which we sold, have rubber or any other kind of isolators except the plastic they are mounted on. Perhaps I am misunderstanding you. Chuck
 
Feb 26, 2004
23,353
Catalina 34 224 Maple Bay, BC, Canada
Bus bar mounting

Our main terminal strips for A.C. and D.C. power are mounted right on the hull. My negative bus bar in the engine compartment is through bolted to a wood bulkhead. My regulator is screwed into the fiberglass under the head sink. The boat is 22 years old. It works.

I'm afraid that the contention that mounting bus bars and terminal strips on fiberglass is wrong is incorrect, because the way the bars are made the metal strips that are used to connect the wires are ISOLATED by the phenolic material of the base of the equipment. However, you could still bolt metal connections to fiberglass and there would be no current carried through the 'glass. Same thing with wood.

No rubber feet on any of 'em.
 
Oct 22, 2008
3,502
- Telstar 28 Buzzards Bay
The only type of laminate that I can think of that might carry current is carbon fiber, and even then the resistance would be fairly high.
 
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