Brown the sausage and onion in a large skillet over medium-high heat for 9 to 10 minutes, crumbling the meat until it reaches 160°F.
Drain the fat, add half the bell peppers, the garlic, chili powder and fennel, and cook for 2 minutes.
Transfer the mixture to a 7-quart crockpot and stir in the tomatoes, tomato sauce, kidney beans, broth and salt.
Cover and cook on low for 4 hours, stir in the remaining peppers, and cook for 2 more hours until those pieces are just tender.
Rest uncovered for 15 minutes and skim any orange fat from the surface before serving.