Do they expect you to pay for the car's remaining balance with a voluntary repo if you turn it in and do not want it back?

The bank doesn't want the car either. It will probably be sold at auction to a dealer for the WHOLESALE price. You will still owe the difference between what you owed and what they get PLUS their expenses.

Banks are in the MONEY biz not the CAR biz. Yes, they will get $$$$ but not enogh, so naturally they want MO MUNY.