Place sweet potatoes, stewed tomatoes, tomato sauce, onion, celery, water, chili powder, cumin, cinnamon, salt, black pepper, cayenne pepper, garlic powder, and onion powder in a slow cooker. Cook on high, stirring occasionally, for 5 hours.
Heat a large skillet over medium-high heat and stir in ground turkey and ground beef. Cook and stir until meat is crumbly, evenly browned, and no longer pink, 10 to 15 minutes. Drain and discard any excess grease. Add cooked ground turkey, cooked ground beef, black beans, and corn to sweet potato mixture in the slow cooker; cook until flavors have blended, 1 to 2 more hours. Serve warm.