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.com
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
On 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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Posted by: James Lambden <james@electroprop.com>
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