Battery Chargers

Any commercially available battery charger will have (should have) a built in diode to allow current flow in only one direction so back charging won't be a problem. If you have more than one battery you may want an isolator to prevent draining of the engine starting battery. This will allow both batteries to charge but only one will be used for running onboard electronics. You can build one yourself but commercially available ones are cheap enough.

                                    Cheers
                                         John

The DC system should be an isolated system on a boat, any stray voltages will rapidly increase corrosion of metalic parts. What you're describing is the grounding of the rigging & mast in case of a lightning strike. I should also add that its a good idea to isolate the shore power ground either with a ground isolator or better yet, an isolation transformer of suitable size for your system (voltage and wattage). Make sure you don't remove the ground (bad things can happen) but just isolateit. This might sound complicated or unnecessary but what you're trying to do is eliminate any electrical paths between your boat and any neighbours or piers. Marinas with supplied shore power are usually full of small underwater electrical currents, most of which can be rendered ineffective through proper grounding and the use of zinc anodes on exposed metalic surfaces.

                                               Cheers
                                                     John

Just for information, the picture below is 'the old man in the sea' and not a self portrait as has been suggested by someone I know.

I have a 1.5 ft x 2 ft copper plate glued to the outside of the hull at the top of the keel and a 1" dia copper bolt goes through it and the hull. Inside the hull, copper wires (1/4"dia) run from the bolt/nut to each chain plate. If the boat stayed in Ontario, I would not bother. My research indicates that it increases your chance of getting hit but reduces the chance of the strike blowing a hole (or many) through the hull. I have heard of very few boats hit around here. The insurance company does not even ask about it. If this was Florida then that may be another matter.

The copper plate was ruffed up with very course sand paper. I used WEST epoxy after grinding the hull down to bare gel coat or glass (forgot which). The copper bolt in the center and many pieces of wood jammed between the plate and the ground held it until until hard. After about 4 years and 11,000 nm one of the corners started to peel so a little more glue and all is ok again. Maybe an adhesive that does not harden would stand up to winter temp changes better. I have seen the temporary cables used. Cheap, easy, deploy as needed.