Heat a large heavy-bottomed soup pot at medium-high heat. Add the olive oil and poblano peppers. Sauté for 2 minutes until the peppers soften. Add the onions and sauté for 7 to 8 minutes, until golden-brown. Add the garlic, chili powder, chipotle and carrots. Sauté for 1 minute. Add the black beans, reserved cooking liquid and salt.