Solar auto battery charger
 

I've got a Chev van that I use now and then to haul big tools 'n stuff but I leave it idle for a week or two at a time. The battery is always dying (surprise, surprise) and I'm not doing my Beemer any favors by jumping that big beast w/ it. (Benz - dry months; Bimmer wet months cuz my Benz trunk leaks. :D )

I've got a step van I'm converting into a mobile shop and camper (long project, slow moving) and I put a solar panel on top, about 18" by 36".

The rig is a Grumman w/ chev 6.2 diesel, and all the starting I was doing to keep the engine alive and oiled was draining the batteries cause I wasn't driving umpteen miles after each start. It's uninsured and under extended planned non-operation status (no yearly reg. fees) so I'd best not take it out on the road til I'm ready.

The solar panel keeps the batteries topped up just fine.

I'd like to do something similar for my smaller van. I've been reading about the new flexible solar cell material and I found a site that has some at good prices:

http://www.siliconsolar.com/solar_panels.htm

My question is, anybody know how many watts worth I should use for optimum battery health? I'd probably go a tad bigger than minimum needed.

If your battery is shot after only a week of sitting, then it's probably bad. Start by replacing that battery. You can get those VW solar panels cheap on Ebay. I have two. They work fine as a battery tender, but will not hold a charge on a bad battery, and will not charge one that is low. IIRC, they are just a few watts at best. This is more than enough to stay ahead of your phantom loads in the car.

Good call. Actually, it takes a couple of weeks for the battery to go dead, but even that sounds like too much.

I'll do some more research.