Why not just switch out the existing battery with a deep cycle, or better yet, a large AH lion batt and save weight at the same time? Splitting the wiring would be a giant mess. You'd really have to redo the entire wire loom of the vehicle. There's literally MILES(or kilometers for those metric folks) in there! I think I remember seeing something on Metro's website about doing an alternator delete where he measured the stock wattage drawn of his metro to be somewhere around 120 watts without lights and he surmised he could get that under 100 watts by replacing key lights with LEDs. You could easily recoup this power with only a few square feet of solar if you drive short distances. I'm considering somthing like this myself this summer. My driving habits are drive 5 miles, park in sun for 8-10 hours, drive 5 miles, park inside.
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