Have a 98 volvo S70. Just installed a new battery since finding a dead car, that wouldn't turn over, and no lights would come on. After one week, my daughter says the battery is completely dead again. There were no lights, etc left on, the night before. Something is drawing down the battery over night once she locks up her car. Where is the best place to start and how? What is a common fault on the S70 that might cause this? Bad ignition switch? Thanks for any and all help.