1996 passat. Please help, my mechanic can't figure it out!

I'm looking for a little help, ok a lot at this point. I have a 96 passat VR6. The battery keeps going dead once and a while. I can drive it for a mile shut it off for 5 minutes and it doesn't have enough juice to turn over. It will then need a quick jump start and might be fine for a day or two. My mechanic thought it was the alternator so we tried that and we still have the same problem. I keep thinking maybe the started is draining it but I'm probably wrong. Does anyone have any ideas? My mechanic want to put the battery on a toggle switch because he can't figure it out.

it most likely is your battery....specially if iether of two things are going on either yo have the original battery or you just bought one...new batteries are coming out with default problems alot of them even when they check them they show they are okay but they are not so i would try that

I should also add this is my 2nd battery in the car.

Had a 2000 Passat with dead battery issues right from day one from dealer to home. Went on for some time before finding a bad cable from altenator to battery.