Use a 4-quart slow cooker. In a large skillet over medium heat, cook the bacon, onion, and garlic, stirring, until the bacon is cooked. Drain off any accumulated fat and transfer the bacon mixture into the slow cooker insert. Add the beans and root beer. In a small bowl, combine the vinegar, molasses, tomato paste, mustard, chilipowder, salt, and pepper. Stir this sauce into the beans. Cover and cook on low for 8 hours.