I was thinking of upgrading battery packs, too. My thoughts were to go Nimh, 1500-2000mah, and charge with my wall wart charger. It would take a long time for a full charge, but I imagine I could fly a good day on my batteries, charge overnight, and still be able to fly the next day, then really charge up in on the days off. Then when W sends me my economic stimulus, I can buy a nice charger.