J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment basic electrical

Chris provided a great answer with the voltage drop associated with lead acid batteries.

On the wiring topic.... when I rewired Rhapsody I found many old ground connections that were suspect with some having grown green vertigree and wiring that was degraded by moisture that had turned brittle. These boats were not built using tinned marine grade wire now required by ABYC standards. I upsized the wire size one gauge smaller (larger diameter wire) for the ground and ran new marine grade tinned wire from the battery to the electrical panel. I did the same with the wiring from the battery switch to the power panel, and replaced the "hidden" fuse socket by the battery switch to one the was more accessible.

There is an old thread on the DC electrical panel you may be interested in going through which includes a schematic for the primary DC wiring.