Great to hear that you got a new Tinybox. NiMH batteries usually have a long lasting life. Will you be able to get access to some electricity at "Sweden Rock Festival"?
Can you possibly recharge them there?
Will you bring your old batterybox too? As a back-up?
Taping at festivals can be really good and also tricky. First day goes well then the second day arrives and feets, backs, necks and arms starts to tell you to not stand any longer.
Also, how much memory do you have on the digital recorder?
Always good to bring two recorders if possible, just in case.
Good luck and I´m sure you´ll record some really great bands and will end up with superb recordings as always!