> The Sparrow motor is rated at 150V. I have used 14 batteries at one
> point - 168V.
What you are forgetting is that the motor is NOT connected directly to
the battery pack: there is a motor controller in between.
The motor controller _lowers_ the voltage and _raises_ the current, by
an amount set by the present conditions. The motor controller works like
a step-down transformer, except that it works at DC instead of AC.
> what allows an ADC motor to go over [its] voltage rating.
It never does.
> And just how high can it go?
Like the man said: 150 V.
> Or this really all about RPMs?
Yes, RPM does have a role to play in this equation.
Roughly speaking, the voltage across a DC motor is directly proportional
to its RPM. (More precisely, it is somewhat higher than that, in order
to generate torque.)
The motor controller takes the full pack voltage (156 V nominal) and
drops it down to the voltage that the motor needs at that RPM. So, when
you're stopped, the motor voltage will be just a few volts, even though
the pack voltage is about 156 V. When you're going at highway speed, the
motor voltage may by 50 V or so, even though, again, the pack voltage
is about 156 V.
Conversely, the motor controller raises the motor current compared to
the battery pack current. So, when you're stopped but starting to move,
the motor current may be 400 A, even though the pack current may be only
about 50 A. The torque of a DC motor is proportional to its current.
The only time that the motor voltage is the same as the pack voltage
(and the current is the same in the motor as in the pack) may be when
you're "flooring it", and the battery is nearly empty: then the motor
controller gives the motor all the pack can give. That's pretty rare.