Saturday, April 14, 2012

Re: [Electric Boats] Re: DC/DC Converters

 

Hi Eric,
I don't know ABYC's rational behind grounding the negative of the house bank, but experience taught me NOT to do that, because it makes the zinc's in the propeller area and the galvanizing on the anchor chain eat away much faster.
For that reason I have a switch for the negative of the starter motor and a switch for the negative of the anchor winch, that live in the "OFF" position when not in use, isolating the house bank negative from ground.

Rob on Linda

--- On Wed, 4/4/12, Eric <ewdysar@yahoo.com> wrote:

From: Eric <ewdysar@yahoo.com>
Subject: [Electric Boats] Re: DC/DC Converters
To: electricboats@yahoogroups.com
Date: Wednesday, April 4, 2012, 9:24 PM

 

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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