Run Time 15 minutes? Batteries or gearing?

[Hatredy]

Outcast 8s Max 5 1100kv combo with 32/47 gearing and 2 HRB 14.8V 4S 9500mAh 120c eBay batteries. It also has a chassis dust cover. I'm only getting about 15 minutes of run time using short throttle bursts. I can only get wide open for 2 to 3 seconds in my backyard. Shouldn't I be getting a lot more run time? Am I geared too high or are my batteries crap? I have a 29 gear I could use but I would rather not if it isn't the issue. I don't have a temp gun but nothing seems super hot when it quits. It just loses driving power all at once.


Thanks

 

[Moirae]

what's the voltage after you're done?