Dice raw bacon into small pieces and cook in a medium skillet over medium-high heat on the stove-top until crispy. Using a slotted spoon remove cooked bacon from pan and allow to drain on a plate lined with paper towels.
Drain all but 1 tablespoon of the bacon grease off from the pan and place pan bacon on stove and add the diced onion and cook until the onion just starts to turn golden in color.
Add the canned beans, cooked bacon, onion, brown sugar and BBQ sauce all to a 5 to 6 quart or larger slow cooker.
Cover and cook on HIGH for 4 hours. Turn slow cooker off and allow the beans to set for at least 1 hour to allow the sauce to thicken.