Sinon said this is your biggest concern, in part because all the electronics in modern cars can drain down batteries even when they are sitting idle. “Without you driving your car on a daily basis, the battery is going to tend to go dead,” said Sinon. “Some of these cars have upwards of 100 computers. It takes four or five computers just to open the door on a modern-day car.” At a minimum, Sinon advises, start your car once a week and let it run for five to 10 minutes. That will get the car up to good operating temperature and recharge the battery.