Last year I arrived at Frankfurt Flughafen, and needed to make a day trip to Essen on DB to attend an event. I check my 21" roller at the 24-hour Left Luggage check room, taking my computer bag with me on the train. On arrival at the Essen Hbf, I "parked" the computer bag in a coin locker while attending my event). Doing the reverse on the return, I claimed the bag in the early morning when returning to FRA - the charge was €7,50.