sorta2

I don't think this has a lot to do with the car itself but the car is an 05 VW Jetta GLI. When the car sits for a while, about a week, the battery completely dies. Now this is my gf's car and she told me that's its done this before and she's replaced the battery a couple times. I told her that its probably a short or something, but she said when she talked to the dealer they told her that it was normal for it to die like that, which I can't believe. Anyway I took the battery out and threw it on my charger, I popped the cells open and noticed it was a little low on water, all the plates were submerged but just barely so I topped them off. I've charged it for a few hours now so I checked it with my multimeter and the volts just keep dropping on it at a steady pace. Is there anything I can do to this to save it or is it just dead for good. And any ideas on the car?