Soak beans overnight in a large bowl (if desired). Drain, rinse, and add to large Dutch oven. Cover beans with water and bring to a simmer. Lower heat and cook for 45 minutes, or until tender. Drain and cool.
While beans are cooking, heat cooking spray in a small skillet over medium heat. Add chopped onion and saute until golden, stirring often, about 7 minutes.
Combine onions and beans in slow cooker. Add mango puree, barbecue sauce, water, balsamic vinegar, honey, bourbon, chipotle powder, salt, and pepper and stir until well-combined. Cover and cook on low for 6–8 hours, until sauce has thickened.
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