Sweet Potato Turkey Chili


1-1/2 lbs ground turkey
2 large sweet potatoes, peeled and cut into 1/2 in cubes
2 large sweet peppers, cored and diced
1 large onion, finely diced
4 garlic cloves, minced
2 tablespoons olive oil
1 can (30 oz) black beans, drained and rinsed
1 can (30 oz) diced tomatoes
2 cups tomato sauce
1 teaspoon ground cumin
1 teaspoon chili powder
Salt and pepper to taste