It is not a battery problem. You say that you tried 3 batteries !
The ESC cutoff voltage should be about 10.2 volts ( running down to 9.9 gives you a
short lipo life expectancy). The head speed will drop off at 10.5 volts.

Your ESC is cutting out when the lipo is still holding a solid charge, or your
lipo/motor connectors may be intermittant. Check all the basic stuff before you
start buying more lipo's