I am having problems with my spec2 when I added the 4th cell. I am charging it with the apex ac optional charger with the stock charging jack. The problem started 3-4 runs after running with the 4th cell (extremely fast). I then started to see a decrease in speed and later on the car would act as if it had only 3cells to power it. So I was wounder if I could find out what the problem is.