Warm the oil in a large soup pan over medium heat. Add the onion and carrot and saute until the onion is translucent. About 5 minutes.
Now add the bell pepper and sauté for another 2 minutes, then add the garlic, chili powder and cumin and cook for a further minute.
Pour in the tomatoes, kidney beans, thyme/oregano, salt and pepper, and 4 to 5 cups of water. As much as you need to get the consistency you like. Let it come to a gentle simmer, then partially cover with a lid and cook for around 20 minutes or until the vegetables are tender. After this time, if you aren't quite ready to serve, turn it to low and let it simmer gently until you are.
Taste to check seasonings and adjust as necessary. Depending on the brand of canned tomatoes you use, you might need to balance the acidity with a little sugar. It makes a huge difference especially with cheaper canned tomatoes. Add it now to taste. Stir then serve.
In a slow cooker
Sauté the onion and carrot in 1 tablespoon of olive oil over medium heat until the onion is translucent.
Add them along with all of the other ingredients to a slow cooker and cook on high for around 4 hours or on low for 7 - 8 hours.
NOTES
If you are in the UK/Europe, DO NOT use 3 tablespoons of chili powder. Yours is very different. Instead, use 1 to 2 teaspoons, depending on how hot you like your food and add a little (1 to 2 teaspoons) smoked paprika too for some smokiness.