Help with PA20 iPod player, please

I have a 2008 Prius (with the Nav system) and I had an iPod cable installed when I purchased the vehicle. I think it's a PA20, but I didn't get an instruction booklet with the car. It worked fine for a few months, but recently, my audio system not only has stopped recognizing the iPod, but it crashes it. I've got three iPods -- one had to be completely restored (and that wasn't easy since it didn't even register on my Mac), and two have had to have resets. The iPod batteries come up dead each time I plug them into the car adapter -- within seconds. This isn't the aux input and the cigarette lighter, but the special iPod cable that plugs right into the bottom of the iPod. I'm going to take it in this week but expect an argument and would like to have some ammunition. Has anyone had this experience and, if so, can you give me some advice? Is it possible that the Prius battery is sucking the life out of the iPod? And, if that's the case, why now?