Combine beans, sweet potatoes, tomatoes, onion, bell pepper, broth, chili powder, cumin, chipotle and salt in a 6-quart slow cooker.
Cover and cook on low for 5 1/2 to 6 hours until sweet potatoes are nearly tender.
Stir in rinsed quinoa, cover and cook on high for 45 to 60 minutes until grains are tender and their small pale rings have opened.
Turn off the cooker and stir in lime juice. Let stand for 10 minutes to finish thickening.
Stir from the bottom to distribute the quinoa and beans evenly.
Divide among 6 bowls and top each with 1 tablespoon yogurt.