I have my kids old powerwheels battery in my coop (4x4x4) with 3 individual white led's inside and 3 flashing reds outside. Paid maybe $5 for the lights on ebay, and have a cheap solar panel hooked up to it. I don't know if it's bright enough to promote laying, mine are still little, but it does provide some break from the darkness. The flashing red led's on the outside can be seen from pretty far and still scare me half the time.