I was previously using a 1200 maH, 4.8 v NimH pack and used a 0.5 maH load to check the battery before each flight. Before the 1st flight the pack would display 5.2 v on load and after two flights it would run down to 4.8 v which I think is the minimum recomended voltage. Later I ran a test the with engine running and I got a 800 mA current flow at full throttle. So to be on the safe side I began using a 2200 maH Lipo with the regulator set at 5 v. I did test the NimH pack on B6 multipurpose charger/disharger it displayed a 1100 maH discharge which I guess is ok, however after 15 min of discharge at 800 mA the voltage dropped to 4.8 v. I figure the weight penalty wasnt that much. The test was run last year in summer, temperatures are normally 110 F it might have something to do with the higher current drain. As far as the engines are concerned all DL 50s are running strong at our club.