Thanks for this advise As you can imagine I'd have done this if I'd have known before! Is there any way to find out which type of ICE they'll use under a specific train-number? Just checked their website but could find anything about this. Are the guys from DB ticketing able to see what type of ICE it will be?

BTW the problem is not really solved with a charged battery. If you run programs like lets say Photoshop one battery probably won't be enough on a 4+ hour ride. I still have to batteries for my Mac but even this can be way to short if I really work.