hi guys - i just bought a DR-100 for my son to use taping classical and chamber music concerts. he will add external mics when he is able, and will be renting out a pair of km184s in the imterim. he will occasionally need to record for 4-6 hours at a time for rehearsals, etc., and rather than have to worry about running an AC power cord, i was wondering if there was a good sled-type battery choice for him to use with the tascam. what would you recommend to supply a long running time for the DR-100? (btw, what kind of run time are you getting from the internal batteries on the dr-100?) thanks.