In a large (non-aluminum) kettle, heat oil over low heat; add onion, carrot, garlic, and peppers. Cover and cook until vegetables are very soft, about 10 minutes. Remove lid, add chili powder, pepper and lime juice and cook an additional 2-3 minutes, stirring occasionally. Add beans and tomatoes Heat to a low boil and then simmer on low for about 20 minutes. Serve with diced avocado. Yum!