Fry bacon until crisp. Drain bacon, retaining some of the fat. Cook onion slices in the remaining bacon fat, until tender (but not brown). Crumble bacon and put it aside. Stir brown sugar, mustard, garlic powder, salt, pepper, onion powder and vinegar in with the onions. Cover and allow to simmer 15 to 20 minutes.
Drain lima beans, butter beans, and kidney beans. Add these to the baked beans. Put all beans into the crock pot, add onion mixture and crumbled bacon. Cook 3 to 5 hours in covered crock pot on low heat.
