Eric,
What about the danger of cathodic corrosion if something goes wrong when you bond your house power to a metal boat. This is a mysterious and scary subject for me with my ferro cement construction. I've heard a lot of horror stories about boats disolving from a partial short to ground.
The Arc came with a one to one transformer to isolate the shore power connection and I often worry about creating a situation with either the 48V propulsion sytem or the 12V and 120V house power systems. Not to mention the 5 kW solar canopy which I have gone to great effort to keep isolated from the boat.
Carter
From: Eric <ewdysar@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Wednesday, April 4, 2012 3:24 PM
Subject: [Electric Boats] Re: DC/DC Converters
To: electricboats@yahoogroups.com
Sent: Wednesday, April 4, 2012 3:24 PM
Subject: [Electric Boats] Re: DC/DC Converters
Hi Chris,
For now, ABYC's TE-30 says "The boat's propulsion electrical system (e.g. batteries, generators, inverters) should remain isolated from the boat's grounding system.
Non-current-carrying conductive parts of the propulsion system (e.g. motor case) should be tied into the boat's grounding system per ABYC E-11, AC & DC Electrical Systems on Boats."
So I would say that as long as the propulsion electrical system and the house electrical system are isolated (don't share the same ground) then you should be OK. Of course ABYC recommends connecting the house electrical system to an external ground, usually the prop shaft, but I have not done that on my boat. My prop shaft is electrically isolated from the motor and gear reduction case via my flex coupling.
So 2) do not connect your 48V battery bank to boat ground, leave it floating. And 3) yes, only house DC bonding and AC safety ground are connected to boat ground.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "ChristopherH" <clh5_98@...> wrote:
>
> Hi Folks,
> I have a question about DC/DC converters, the isolated type in particular. If you were to install isolated DC/DC converters from a 48V propulsion battery bank to drive the 12V house loads, obviously you would be defeating the purpose of the isolation by connecting the negative outputs of the converters to boat ground. I guess some of the things that come to mind are: 1) How does this scheme fit in with ABYC standards as I don't see isolated DC systems addressed there? 2)Would the 48V battery bank be connected to boat ground or left floating as well? 3) Would then only the DC bonding and AC safety ground be connected to boat ground?
>
> Thanks,
> Chris
>
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