Refried Beans, Crockpot

1 Onion, peeled & halved
3 Cups dry pinto beans, rinsed
1/2 Jalapeno pepper, seeded & chopped
2 Tablespoons minced garlic
5 Teaspoons salt
1 3/4 Teaspoons fresh ground black pepper
1/8 Teaspoon ground cumin, optional
9 Cups water

Place the onion, rinsed beans, jalapeno, garlic, salt, pepper, and cumin into a crockpot. Pour in the water and stir to combine. Cook on HIGH for 8 hours, adding more water as needed. Note: if more than 1 cup of water has evaporated during cooking, then the temperature is too high.
Once the beans have cooked, strain them, and reserve the liquid. Mash the beans with a potato masher, adding the reserved water as needed to attain desired consistency.