To date, all I've ran on my 500 are 2x2200mah, 25c. I've since sold then and got some Nano-Tech 2650mah 25c with 50 burst from HobbyCity. (will be here this week) But when I was running the 2200's I would get 4 1/2 minutes and the power was never a problem. I mean I couldn't do rolls and flips one after another but I mainly sport fly anyway. These new 2650's should be 10 times better than the 2200's. Should be able to pull off 6 1/2 minute flights no problem. One of the biggest things I llike about running 2 lipos vs one 6S is, in a crash, if a lipos get hammered chances are it'll only be one of two and you wont find yourself buying another 6S, just a 3S.