Sort the beans and remove any debris or stones, and remove the Seasoning Packet and set that aside for use later, then rinse the beans.
Place the beans, onion, sausage, garlic, and chili powder in the slow cooker. (I went overboard with the meat addition, I added smoked sausage, Andouille sausage, and smoked ham, about 1 kilo / 2 lbs.)
Add the water or broth, stir to mix, cover, and set the slow cooker to High setting and cook for at least 5 hours, without lifting the cover.
At the 5 hour mark, check the beans for tenderness. If the beans are not tender, continue cooking, checking again each hour until tender. (Mine were done, and perfect right at the 5 hour mark.)
When the beans are tender, stir in the tomatoes and lemon juice. Turn the slow cooker to Low setting and cook for another 30 minutes.
You can leave on Keep Warm for several more hours if needed, and this blends the flavors as well.
Just before serving, open and stir in the seasoning packet that came with the beans.
Serve with bread, biscuits, or even over rice. Enjoy.