Unfortunately I've not been running them long enough to know. I have started to keep a charge journal to see if for example, the 5100's take more charge than the 5000's. Currently I use the 5000's when I get to the track for practice, then I use the 5100's for Qual 1 and 2 (both are 5 min races) I don't charge in the middle, I get race speed out of them for the full 10 mins combined plus a lap or two of warm up. I'm sure I could get more, while the Qual rounds are being run I charge the 5000's and use them for the main. Works like a champ, one charge cycle at the track and I'm good to go. We have two weeks left on our season, next year we are moving to 6 mins quals and 10 min mains. I think either is capable of a good 13 mins at full race pace and maybe 15 mins if you baby it a bit.