Evergreen Solar EC115 for sailboat

On most boats, the negative ground 12V system and the bonding system (designed to prevent electrolysis) meet at the engine block. If I was attempting to tie a positive ground system in, I would want a disconnect in the negative from the battery to the engine. I would not want the  positive potential on the bonding system.

The wiring problems would also be exacerbated by the presence of a shore power charger (hard wired) or an onboard generator.

I haven't thought all the potential problems and interfaces though. It could be done, particularly for a boat with a simple system. But I think I would just ask James to recommend a negative gound controller, and eliminate the headaches.

Ken

Robert:
Here is a link that will explain panel shading.
http://howto.altenergystore.com/The-Basics/Solar-Electric-Panels-Overview/a36/p2/

I do not generally worry about one panel being more shade tolerant than another. I take the attitude that shading is bad for all panels and think you should do everything possible to avoid it. As an example, if shading one cell results in a 50% drop in production with one panel, and another panel has a 45% reduction, do you worry about the 5% difference? Or do you say that I am going to avoid the drop, period, whether it is 45% or 50%. I treat periods of partial shade as zero panel output, and then am pleasantly surprised if I actually got something.

I tend to take the same approach to panel aiming. The variance between panels is usually less important than your location (Lattitude/hours full sun). At 38 degrees North (San Francisco Bay), laying a panel flat would cost you about 15% of the panels production on an annual basis. So, having a fixed tilt would save that loss. Being off 45 degrees from true south would result in about a 10% loss, annually. (Note, these figures would vary for a person that would only use their boat for the summer months.)

If the panel mounting is adjustable for both tilt and azimuth, you can actually pickup similar percentages. AS an example, aiming a panel with a fixed tilt, SE in the morning, S midday, and SW in the afternoon, might pickup about 10% over a fixed south panel. And, if you are laying around the boat in an anchorage, it is not that hard to adjust a couple of times of day. Similarly, being able to adjust tilt late in the afternoon can capture a few more watts, if you pull into an anchorage later in the day.

Ken

Also should be noted, In the US, ABYC standards mandate NEGATIVE GROUND systems only.

James

The ABYC is the American Boat & Yacht Council

Among other things, They develope consensus safety standards for the design, construction, equipage, maintenance, and repair of small craft.

Their standards are really good ideas, but the statement that they "mandate negative ground systems" is an over statement. They have no legal position to mandate anything.

The real mandates are

The United States Coast Guard. Title 33, CFR 183 which contains mandatory requirements for electrical systems on boats.

NFPA 302, Fire Protection Standard for Pleasure and Commercial Motor Craft. This standard is approved by the American National Standards Institute and is applicable to motorboat installations.

That being said, I think that there are some real safety issues with mixing the two different polarity systems on a boat, or in an RV. Sooner or later someone, somewhere, will inadvertantly cross the systems.

Ken