1. Spray a 4-quart slow cooker with the cooking spray.
2. Stir the flour, baking powder, baking soda, cinnamon, ginger, salt and allspice in a medium bowl.
3. Place the butter and brown sugar into a large bowl. Beat with an electric mixer on medium speed until the mixture is creamy. Beat in the eggs and molasses.
4. Reduce the speed to low. Alternately beat in the flour mixture and the vegetable juice. Stir in the cherries. Pour the batter into the cooker.
5. Cover and cook on HIGH for 2 to 3 hours or until a toothpick inserted in the center comes out with moist crumbs. Spoon the gingerbread into bowls. Top with the whipped cream, if desired.