Drain and rinse 2 cans of the beans. Combine beans with chicken broth in a blender container. Blend on high for about 30 seconds or until smooth. Add to the onion mixture in the slow cooker.
Drain and rinse remaining 4 cans of beans, Add beans, tomatoes, green chilis and chicken to slow cooker and stir to combine. Cover and cook on low for 6-8 hours.