Re: 24V+ Isolated Ground Leak

Bill Hall <billhall95688@...>

How old is the battery disconnect switch or is it corroded internally?

On Mon, Sep 6, 2021 at 11:40 AM Paul Stascavage via <> wrote:
Almost since purchasing our boat, we had a small negative leak that was indicated by the Masse Light.  The electrician in Martinique could not locate the source easily, but said that it was very small and to just keep an eye on the zincs.

Although I tried located the source of this myself many times by disconnecting individual bonding wires, I was never able to locate it.  However, our zincs would get us through 2 years of service with what I considered normal loss (about 30 - 40%) so it didn’t worry me much.

A few months ago, the Masse Light stopped illuminating and I thought maybe something may have fixed itself (wouldn’t that be great?).  But a few weeks ago, when I dove on the zincs, I noticed they had excessive loss and they are slightly less than a year old.

This morning I got out my volt meter, and we do still have a slight negative leak of about 0.009 volts when connecting the voltmeter to the negative post on the battery bank and the bonding wire on the rudder post, but when I checked the positive side, there was a full 25 volts leak indicated!

We recently had our alternator rebuilt so I disconcerted that and found no difference.  I also recently changed the switches on the windless, so I am going to disconnect those and check there as well.  We also had a new VHF radio installed and I will check that, but as that is 12 volts I don’t think that will be it.

I am definitely not electrically proficient, but what boggles me is that when I turn off the battery bank switches, I still show the leakage when testing from the bank.  How is it that with the battery bank isolated, I could still have current going to the bonding system?  What am I missing here?

Any insight and suggestions regarding where I should logically begin my search would be greatly appreciated. I am currently most uncomfortable with that kind of voltage in the bonding system.

Thank you in advance for any and all replies.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Currently Exploring City Island, NY

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