Rinse the beans under cold water, sorting out any rocks/particles. Set aside.
In a heavy pot (cast iron), saute the bacon pieces until halfway cooked and the fat is rendered. Add the green peppers and onions to the pot and cook until starting to get brown, about 3 minutes. Add the beans and cover with water by 1 inch. Bring to a boil, and then add the brown sugar, ketchup, mustard, chili powder, salt, pepper and garlic. Reduce the heat to a simmer, place on the lid and cook until the beans are tender and the liquid is thick 3 to 4 hours.