Slow-Cooker Barbecued Beans

Ingredients

• 1/2 pound bacon, cut into ½-inch pieces
• 1 medium onion, chopped
• 1 cup tomato ketchup
• 1/2 cup brown sugar
• 1/4 cup light molasses
• 1 tablespoon cider vinegar
• 1 teaspoon ground mustard
• 2 15 ounce cans great northern beans, drained and rinsed
• 2 15-ounce cans black beans, drained, ½ cup liquid reserved