[brucepick]

I left my alt belt connected, so I can run longer distances than what my two batteries can handle on a single charge. Generally the alt's output cable is NOT connected but I can switch it back in if needed for a long trip.

I can clearly feel the increased available power due to reduced load on the engine because it's not trying to charge a battery. MPG results definitely show the gains.

Like MetroMPG, I think the aero inefficiencies of the large panel have offset the gains from not running the alternator.

As for battery weight - that depends, in my ever-so-humble opinion. I don't consider weight to be a great evil. It requires more energy to accelerate the car to a given speed, but the car will coast longer on that kinetic energy. If you have to brake of course, you lose more energy than a lightweight car. And if you don't coast efficiently, you don't get the full benefit of that stored kinetic energy either.

I believe California98Civic's battery charging data are from the Odyssey battery people. I researched that brand too, in planning my project. Their batteries seem to run about .5V above the usual lead acid and so require a bit higher charge voltage. Maybe they also need higher charging amperage. Odyssey claims 99.99% pure lead, if I remember correctly, and a higher purity (or concentration??) of acid, which presumably are behind their higher voltage and overall upgraded performance. My own chargers are 10A units that run about 3.5-4.5 hours most nights. So far, so good. First battery was installed March 2012, 2nd battery in early Aug. 2012.