In a large skillet, brown the lean ground beef thoroughly. Once cooked, drain off any excess fat and set the beef aside.
Add the bacon to the same skillet and cook for 5 to 7 minutes, stirring occasionally, until it's crispy.
Stir in the diced onion with the bacon and continue to cook for an additional 4 to 5 minutes, until the onions are soft and translucent.
Transfer the cooked ground beef, bacon, and onion mixture into a large 6-quart slow cooker.
Now, add the undrained pork 'n beans, the rinsed and drained kidney beans, the rinsed and drained white beans, ketchup, brown sugar, and liquid smoke to the slow cooker.
Stir all the ingredients gently until everything is well combined.
Place the lid on your slow cooker and cook on the low setting for 4 to 5 hours, or on the high setting for 2 to 3 hours, stirring occasionally. If the beans seem a little dry, feel free to add a few tablespoons of water.
Serve warm as a delicious and hearty main dish or a satisfying side. Enjoy!