Split battery power
 

Ok how about this one. Split the battery power so that some essential components (starter, ecm, radiator fan) run off the main battery, but everything else (lights, radio, wipers, blower fan) runs off a separate deep cycle battery in the trunk. This would save the power needed to be generated by the alternator to run these things. You would, of course, need to charge the second battery manually, but you could use solar. You could also incorperate the electric power steering on the second battery.

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.

Also, if you have an automatic, you could use the alternator like someone else on here suggested using the ac. Rig it up somehow to only kick on while coasting. The alternators on most cars are so overpowered it would still charge the battery sufficiently and rob a negligible (OT: Is there a spell checker on this forum?) amount of fuel. If it didn't require so much work, I'd like to move the alternator to the driveshaft and wire to a contactor to start charging when the brake lights turn on. DIY regen braking, but seems like a lot of work to me for what darren observed to be ~10% FE gain.

Download Firefox and there's a spell-checker everywhere :thumbup: