Are you running your battery connection to the main posts or screw on posts? Don at European Marine did a long post about battery problems with the screw on posts. The synopsis was that internal to the battery, the screw on posts are not connected the same way as the main posts. There are converters (I got a set at OReilly) to run the connections off the main terminals and not the smaller screw terminals. When I read what you described, my first thought was electrical then I remembered Don's post about this.