Heat olive oil in a large pot over med-low heat. Saute carrots,onion, and celery till tender but not browned, about 10 min. When there is less than one minute left to cook vegetables, add garlic, and stir.
Stir in lentils,tomatoes, dried thyme, and chicken stock. Raise the heat, and bring to a boil. Then lower heat and simmer for 30 minutes. Add the potatoes, stir, and cook another 10 minutes. Add the kielbasi and water, stir, and cook another 5 minutes, until potatoes are tender, and sausage is heated through. Stir in balsamic vinegar, salt and pepper. A delicious soup in just a little over an hour.