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12 Volt Battery Grounding?

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ct95949
Captain

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Aruba
300 Posts

Initially Posted - 03/14/2006 : 13:49:00

I've been reading Don Caseys very good book 'Sailboat Electrics Simplified'.He writes about grounding the batterys to earth(water)by cabling them to the engine block which is connected to the propeller shaft.For those of us with outboards what is the best/usual method?
Brass seacock,keel cable winch,keel bolts?
Thanks,Craig

'90 SR/WK #6017. PO of '79 SR/SK.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 03/14/2006 : 14:15:28

There are two very large schools on sailboat grounding. Grounded and ungrounded. There very smart people on both sides of the fence. I have no desire to provide an electrical path to the water on my boat. I am of the school that the best place to be in a storm is next to a taller mast, which isn't hard with our little rigs.

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DaveC25
Navigator

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USA
152 Posts

Response Posted - 03/14/2006 : 15:06:18

To me it seems that you would not want your boat to be electrically connected to the water ("grounded").

If the mast is up on your boat during a storm, you would expect the fiberglass hull to be a great insulator, causing the mast to look like it's floating (not grounded). Any lightning that was looking to get to the water (or to the cloud, whichever way the charge aligns) would not find the mast as an easy conductor.

Of course, no one really can predict what lightning is going to do anyways since it's such a high voltage.... so who knows what's best. In a way you want the thing to be isolated so you don't get hit, but if you do get randomly hit then you'd like some paths for the lightning to follow to the water rather than through the cabin so it doesn't blast a hole through your hull. But you can't have it both ways... so just drink heavily when a storm appears. :)

-DaveC25

PS: It makes no sense to electrically ground your boat to the water because of the internal electrical system, unless you're trying to use the water as a return path...which you don't do.

Notice the huge lightning rod on top of the launch tower... :)

Edited by - DaveC25 on 03/14/2006 15:11:23

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 03/14/2006 : 15:34:46

Most boats, ours included, do NOT have a chassis ground. Nothing is wired to engine, shaft, keel, etc.

Most larger boats (ours not included) have something called a BONDING SYSTEM. All through hulls, keel, shaft, are wired together and then wired to zincs. The bonding system is NOT connected to the battery. Nor is the AC system.

On the simple C25 (I love simple, thats why I own one) there is really not too much to worry about bonding. There is little or nothing to corrode - store OB up and out of the water, through hulls are minimal, no shaft (except on rare inboards). I usually leave my shore power plugged in but turned off at the dock - this prevents any stray current corrosion. My iron keel is epoxy encapsulated and painted. I've observed no rust or corrosion in the last 3 years.

Bottom line - ground nothing, run + and - 12 vdc wires, and isolate the AC system. Leave it just as Catalina designed.

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ct95949
Captain

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Aruba
300 Posts

Response Posted - 03/14/2006 : 16:09:49

I couldn't figure out how I would ground the batterys in a fiberglass boat,it's nice to know not everyone does this.I also never thought I would need 6 gauge wire in my house system but I was wrong about that so I figured I'd better ask about this.I love simple too-especially when it comes to wiring.
Thanks,Craig

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oldsalt
Admiral

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USA
578 Posts

Response Posted - 03/15/2006 : 16:32:49

Nice picture Dave, but did you know that the one of the guys who designed the lightning arrestor system for the shuttle gantry also owned a Catalina 22 for which he designed and installed a lightning arresting system?

It was struck by lightning and destroyed.

Really.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 03/15/2006 : 17:47:51

Yup, you just tie the negative black (or now yellow) ground wiring back to the battery. It's just like the basic wiring pictures in Casey's book, but with no big lurking engine down below, it just goes back to the battery in a big loop: battery, red to switches, fuses and loads, black back to the battery.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 03/15/2006 : 19:15:12

When this topic comes up, I always defer to others

I have seen one boat hit and have my own opinion - which you can probably find in an old post when I was more adamant about it- however I always like to post this pic.......excerpted from the put-in-bay something or other

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.