Spray a large slow-cooker crock with nonstick cooking spray. Place the cabbage in the bottom, then add the onion and toss gently. Add the potatoes, caraway seeds, 3/4 teaspoon salt and 1/2 teaspoon pepper. Sprinkle the potatoes with bacon and pour the beer over the potatoes and bacon.
Cook until the potatoes are tender, 3 hours on the high setting or 6 to 7 hours on the low setting. Stir gently before serving.