Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x13-inch baking dish.
Blend black beans and water together in a blender until smooth; pour into a bowl. Stir brownie mix into black bean mixture until batter is smooth; fold in 1/2 cup chocolate chips. Pour batter into prepared baking dish. Sprinkle remaining 1/2 cup chocolate chips over batter.
Bake in the preheated oven until a toothpick inserted 2 inches from the side of the pan comes out clean, 25 to 27 minutes. Cool brownies completely on a wire rack before cutting into squares.