Between these two, motor appears to be the exact same, just two different voltages, graph nor website state which controller is used for the test.

As an example, ~0 RPM, standing start:

144v, 87ft lbs @ 19 amps

96v, 127ft lbs @ 33 amps

Information came from here:

http://hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-23.htm
Lots of inexperience here, but looks like I'd be sacrificing quite a bit of starting torque by going with the higher battery voltage. Though I'd have considerably more torque at my top end cruise of 4500RPM @ 144v, the 96v is higher from 0 to 3500RPM.

These motors follow a general characteristic of torque climbing linearly with speed to the peak (why not constant torque like other induction motors? who knows...), then dropping off as the supply voltage is unable to drive the required current at higher speeds (and resulting higher back EMF of the stator coils)... so the speed of that peak increases with higher voltage (2400 rpm @ 96V, 4800 @ 144 V).

Onee problem is that there is a lot going on to obscure the motor performance, including:

- supply (battery) voltage is not constant (sags at higher currents)
- current is limited (presumably by the controller) at different levels in different tests

The current limit for the "96 V" test is stated as 650 amps, and reaches 601 amps; the current limit for the "144 V" test is stated as 500 amps, and reaches 486 amps.

Both graphs show data in that linearly climbing torque region around 1500 rpm. At that speed

- in the "96 V" chart, 80 volts drives 400 amps (for 32 kW) and produces 120 lb-ft of torque which is 34.3 HP (25.6 kW) by calculation or 35 HP read from the chart
- in the "144 V" chart, 140 volts drives only 160 amps (for 22.4 kW) and produces 82 lb-ft of torque which is 23.4 HP (17.5 kW) by calculation or 22 HP read from the chart

The combinations of these sets of data points for the same motor at the same speed (in both stall and 1500 rpm cases) are nonsensical if they are for the same motor. In the low-speed region where torque is limited by available current, they should be the same. This leads me to conclude that one of two things is going on:

- either the controller is not working properly and it is not maintaining appropriate slip speed so it is unable to use higher voltage to drive higher current, or
- the dynamometer is not controlled properly and is not providing the highest mechanical load which the motor can drive at each speed.

I wouldn't be surprised if the tests at different voltages used different controllers, or a single controller which was not tuned appropriately for the higher voltage. The dynamometer may be just a flywheel, so there is no control of load or speed, just observation of how rapidly speed changes (which implies torque).

The performance charts from the DC series-wound motor suppliers (such as Netgain) appear to have been generated with a simple friction brake and are worthless. These charts for the AC- series initially look much better because they cover a meaningful range of speeds, but they appear to me to be of little value in actually describing the performance of the motors.

Physical reality is that with more supply (battery) voltage available, a properly working controller will be able to drive more current at a given shaft speed and thus produce more torque, but limited by

- the battery current capacity,
- the controller current limit, and
- heating of the motor

Whatever the current limit of the system, a higher supply voltage will be able to maintain that current (and resulting torque) to a higher shaft speed, unless an electrical power limit is reached (due to some component heating, for instance).