Originally Posted by
dan_vector
Ummm a 5 cell pack has the cells in series so the packs ability to deliver current remains the same between a 4 or 5 cell pack. I think you meant to say the servo performed better because you went from 4 AA nicds at 4.8v to 6v 5 cell nicd thus increasing the voltage and lowering the servos requirement for current. Higher supplied voltage less demand for current (ohms law)
I highly doubt the current is reduced when the voltage is increased. Servo torque and speed ratings generally improve significantly at higher voltage, suggesting the power level has increased, not stayed the same.
In the general case the higher voltage/less current deal only happens if the power is maintained at the same level. Which usually requires a change in the load. With the same load, higher voltage drives higher current.