Add the diced onion, minced garlic, and diced red bell pepper to the slow cooker.
Stir in the cubed sweet potatoes, drained kidney beans, black beans, and pinto beans.
Pour the fire-roasted tomatoes and vegetable broth over the mixture.
Sprinkle in the chili powder, smoked paprika, cumin, salt, and black pepper. Stir everything until evenly combined.
Cover and cook on low for 6 to 7 hours, until the sweet potatoes are tender.
Taste and adjust salt or pepper if needed. Serve hot with fresh cilantro and lime wedges on the side.