Running Slow With New Batteries

[dgcars]

I have a '02 48V DS. The cart runs slow. Put a new set of batteries in it, and still running slow. Changed the mcor and still the same. The voltage between the m- and b+ on the controller while runnig is 41 to 42 volts. If you put cart on stands and take the A2 wire off motor,the voltage is battery voltage. Put a rebuilt controller on it and it did the same thing. Is new controller bad or something else? All cables are cleaned, and after running it, for 10 min.,? I feel no hot cables.