I agree with you that "The best piece of equipment that can be installed in a boat for protection from Galvanic Corrosion and Electric Shock Drowning is an isolation transformer."
An isolation transformer is the greatest safety equipment for near by swimmers, by far. It will however not help much on board your boat. If you have systems of different potential. As an example a isolated EV system. There is a potential for sparks (which could ignite gas fumes) and human or equipment bridging. Unless everything has the same potential IE all grounds are connected.. So do you have a Honda generator aboard or a propane stove? Quit a few boaters do.
But let be realistic here very few of these "floating" EV systems are truly isolated to begin with. Most chargers are not isolated, so most floating systems are not floating to begin with they are earth grounded via an under sized AC ground cable that was never meant to ground a battery bank. My philosophy is that since over the life of the boat the systems will ultimately be bridged via a purchase of a new charger that is not isolated, or some other wiring snafu it is better to just have the proper sized cables to earth ground your bank to begin with.
As to 48 volts being much worse then 12,24, or 36 volt systems, for galvanic corrosion I will respectfully disagree with that. E-11 has been in active use for 5 decades and most boats produced meet E-11 standards. And many many boats have House banks from 12 to 48 volts, the bigger the boat normally the higher to voltage of the House bank. None of these 24/36/48 volt House banks that are earth grounded cause serious corrosion issues, otherwise E-11 would have been rewritten years ago. E-11 is time tested and heavily researched and a highly trusted guideline. Theoretically your insurance company my use an E-11 violation to not cover a claim, though I have never heard of that actually happening.
Now as you stated that would not effect your EV system which is technically covered via TE-30. Not that TE-30 says all that much about lower voltage systems.
So we are where we started, as I already stated, I personally value human safety on board and swimmers nearby above any "real or imaginary" concerns about equipment safety. IE galvanic corrosion. E-11 takes the same stance and therefore has a common ground. TE-30 is also mostly about safety and rightly wants to isolate high voltage systems. High voltage has high bridging potential, because the wire sheathing for most common marine wires are rated and tested to voltages they are likely to see. IE under 220 volts, you don't want to have a voltage potential that exceeds your wire sheathing, wires inside duplex cables would just sort like the sheathing was not there.. I have seen wire sheathing with ratings as high as 700 volts and as low as 300 volts. This and many other reasons is why 300 volts is a magic number for me. And why I choose a low voltage system.
Now we disagree, I don't disagree that you don't have some good reasons for your opinions on 48 volts and below systems. I think I was pretty clear about that on the get go. I also hope you agree that I have good reasons for my opinions on 48 volt systems following E-11. We can agree to disagree. And we both agree that over 48 volts isolation is best, but hard, you have to make sure every device connected to your traction pack is isolated equipment. Chargers, DC bridges everything. You pretty much can't use the pack as a house bank at this point. That is a lack of flexibility I did not want, my traction pack is my house bank, and I like it that way.
Now we could argue about what cause and how serious an issue galvanic corrosion is, but it is one of those classic what is the best anchor arguments. Pretty equal size groups of people have been arguing that fight for longer then I have been alive, and I am fairly old.
My zincs (aluminum's really) are in good shape, and last me years and years.. ;-)
On Mar 1, 2018, at 4:37 PM, James Lambden james@electroprop.com [electricboats] <electricboats@yahoogroups.com> wrote:
TE-30 can be used for any voltage. The standard exceeds any lower standard. But it has to be done completely without missing any of the necessary components.There are many advantages for floating a battery bank. The number one advantage is you can troubleshoot what is going on. A grounded system is completely blind and requires disassembly to troubleshoot. A floating system can be diagnosed on the fly while the boat is in operation.I would not want 48 volts DC to come anywhere near the grounds on a boat. If there was a short to ground and current through the grounding system, the boat would sink in an awful hurry. This isn't 12 volts anymore. 48 volts will eat metal in a hurry.So I guess I respectfully disagree with going with a grounded system. Except in the case of some metal boats.But to float a system does require additional expensive components and you don't want to just float a system and not monitor it. A floating system is said to be a "maintenance system" which means that any faults that occur should be remedied immediately or as quickly as possible.A floating system can remain completely operational with one ground fault, or multiple ground faults on one polarity, but as soon as there are two ground faults on different polarities (positive and negative) then the circuit with the lowest current breaker will trip and become unusable….hence the objective of fixing any ground fault immediately.The issue is usually in the installation, combined with the movements of the boat and the actions of the crew. When installed properly a floating system should work for decades without any changes.James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.comOn Feb 28, 2018, at 1:05 AM, 'james@deny.org' james@deny.org [electricboats] wrote:I was not correcting you. Your statement that the consensus of this mailing list was to leave the EV system floating, is probable true. At least by number of posts. I personally disagree, for low voltage systems, I prefer everything to be earth grounded. Which would follow E-11 recommendations.The issue with giving advise one way or the other is that there is no consensus from the boating world at large. E-11 covers up to 48 volts DC and 220 volts AC and TE-30 really only covers 300 volts and up. Leaving us all with no real "professional" guidelines for DC systems above 60 volts but below where TE-30 would cover.E-11 is a marvel and I think anyone that boats in the US should get a copy from ABYC's web site, and follow it to the letter. Worth the money.. It will in my opinion make your boat safer. On the other hand I was not impressed by TE-30 at all. The list time I bought it. It was just a few pages that basically just said "follow automotive standards", as all production automotive systems are over 300 volts, really that is all it covers.But let's be clear earth grounding low voltage systems protects people.. It's effects on equipment is debatable and in my opinion of secondary importance. But I would defiantly float a 300+ volt EV system, I would not want a 300+ DC volt potential on my common earth ground.But a 120 volt battery bank, that gets tricky, not sure I would earth ground that or not. Again I punted when I built my system I purposely keep my battery bank inside E-11 standards IE 48 volts, so I had some standard to follow. My preference. A lot of people and manufacturers on this list float their EV systems. There preference.But everyone should earth ground the rest of the boat systems to comply with E-11, and that is where a lot of folks on this list may be lacking. Because when you removed your old engine block, that was most likely your system earth ground. Again a 20 dollar marine shaft brush can bring those systems back into E-11 compliance..I stand corrected then, but unrepentant. Thanks for the reference.
---In electricboats@yahoogroups.com, <james@...> wrote :For 48 volts and less, I follow the ABYC E-11 recommendations and have a common ground between all systems. At higher voltages ABYC TE-30 says keep them separate.I personally went with a 48 volt system because I wanted to be able to have a common ground. I don't like having different potentials between different systems that I or a swimmer nearby could be a bridge path between.More important then if you bridge the two DC grounds together, make sure your old AC system still has earth ground. Most marine systems used the engine block via the shaft to ground to earth. If your boat does not have another path, once you removed the old engine your entire ground system may be isolated from earth.If so a cheap 35 dollar shaft brush will re-earth your system. See my earth ground bellow:
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