Slow Cooker Baked Beans

1½ pounds ground beef
½-1 cup chopped onions
2 28-ounce cans baked beans
15-ounce can of light red kidney beans, drained
½ cup ketchup 
1/3 cup barbecue sauce
¼ cup packed brown sugar
3 tablespoons cider vinegar

Brown the ground beef, and drain the fat. Place in a slow cooker. Add remaining ingredients. Cover and cook on low for 4-6 hours, stirring occasionally.