E-Maxx battery ?

My set up was 12020/7xl with 54 tooth ofna spur on 14 cells in an old E-Maxx. I have been having run issues, the motor is very jumpy, not smooth at all. I am pretty certian it is the batteries. The controller has been checked by BK and the motor is new. Connections look good. I have noticed the cells have been dying. I have IB 3800 and 4200. The 4200 are particullarly getting fried/over heated. I have geared down the pinion to 14 tooth. I have put the Titans back on with stock spur, and some of the batteries are still dying. Is it common for the brushless to draw to many amps and kill the NiHi? Is Lipo the only answer?