Place the dried beans in a large bowl. Cover with 2-3 inches of water, and let soak for 8 hours or overnight at room temperature.
When the beans are finished soaking, drain and place the beans in a slow cooker (minimum 3 1/2-quarts). Place the diced onion and bacon on top.
In a bowl, whisk together the remaining ingredients and pour over the beans. Cover and cook on high for 12 hours. 1-2 hours before the beans are done, you may want to check the sauce for consistency. If it seems too thin, prop the lid open slightly with a wooden spoon to allow the sauce to reduce and thicken slightly while the beans finish cooking.
If cooking overnight, allow the beans to cool to room temperature before placing in the fridge. Reheat before serving.