This lack of charging issue is new to me. I have a 2000 Corvette in which I finally replaced the original battery this year (2007). I alway have the intention of charging it's battery every month during the winter when it is in storage, but it never happens. I just charge it in the spring and it works perfectly all summer. We also have 4 vehicles and only two drivers in our household. My wife only drives her XC90 and I drive the other three. So some of my cars sit for a long time without being driven. I never have any problems with any of the batteries. Also my boat sits from Oct to May every year and starts without issue.