My son's minivan (work) has had a recent issue of battery drain. Figured the battery was bad so it's owner replaced the aging battery.

Fast forward to the next weekend and it's dead. Jumped it and OK, I disconnected the battery, but when I did, it sparked quite heavily, It is a service van, with equipment. Everyone was turned off but yet a healthy spark. Could the alternator cause a parasitic draw? I know they have an internal regulator.