| Living on an anchored boat, I would like feedback on the following: Most anchor windlasses use a series (starter) motor with negative ground. The motor housing connects to the windlass, the gypsy, the chain and seawater, creating a conductive path between battery negative and the sea. It is widely believed, that this causes the galvanizing (zinc) of the chain to disappear rapidly. Reason I and many others have an extra switch in the negative windlass lead, which lives in the 'OFF' position, except when the windlass is used. On a similar note, some have an extra negative switch for the starter motor of the main engine, keeping negative and ground separated, to prevent the fast eating away of sacrificial zinc anodes etc. Both windlass motor and starter motor are typically automotive of the shelve. I have understood, that professional marine motors have their negative terminal separated from the housing (ground), for that reason. It seems to me, that an ELECTRIC boat forum should have a clear consensus on a simple question as :"Should there be a conductive path between battery negative and the ocean?"
Rob S/V Linda
--- On Wed, 3/2/11, luv2bsailin <luv2bsailin@yahoo.com> wrote:
From: luv2bsailin <luv2bsailin@yahoo.com>
Subject: Re: [Electric Boats] Rewiring DC electric system and Grounding
To: electricboats@yahoogroups.com
Date: Wednesday, March 2, 2011, 12:00 AM
For what it's worth, when I first rigged up an electric drive system in my brother Paul's Santana 30-30 I talked to the diver who was doing his monthly bottom cleaning and asked him to look for any changes down below. Next month he reported increased corrosion on the shaft zinc and prop which I assumed was being caused by leakage currents from the battery chargers. Installing an insulated shaft coupler fixed that problem. On my Albin 25 install, belt reduction and plastic-mounted "food-grade" shaft bearings provide the isolation. On my (other) brother's Electric Yacht drives, the bearings and shaft are similarly isolated from the frame.
Jim McMillan
--- In electricboats@yahoogroups.com, Matthew Geier <matthew@...> wrote:
>
> On 01/03/11 21:56, John Raynes wrote:
> >
> >
> > Brian,
> >
> > Thank you for bringing the "Grounding" question to this forum. I hope
> > there is an expert among us who can really nail down how to create a
> > ground for electric propulsion. I recommend a ground bus bar wired to
> > the underwater metal, ie rudder and steering system and attached a
> > ground wire from the negative side of the battery for my ground.
>
> Be very very careful about this if you ever plug into shore power at a
> marina. 'Bad things' can happen if you set up a current loop with the
> marina earthing system and other boats.
> A friend found this web page
> <http://www.sailmail.com/grounds.htm>. There is also another web page
> out there written by an electrical consultant who was called in to
> survey a marina's electrics after a couple of 'unfortunate' incidents
> with galvanic corrosion. I can't find it just at the moment.
>
> There is no simple answer - every earthing idea has serious drawbacks.
> The main issue is that salt water is very conductive - so when berthed
> at a salt water marina, you effectively have an extra wire joining all
> the external metal parts of all the boats together. And earth fault in
> just one boat can have drastic effects on all those around it.
>
|
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