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I don't remember what the datatag says on it. I have a feeling that it does't mention a voltage or I would have remembered the voltage rating. Unfortunately I cannot see the tag because of the batteries on top of it. I may be able to see it from underneath, but that will have to wait for another day.
I think it could handle more than 72V. When I was running lower field current than I am now, even at 20A field and full 72V to the armature at high revs the brushes were not arcing, at least that I could hear. The higher you go with field current the less chance of arcing there will be.
I just went out and measured the motor case: 7-3/8"X18". The case is quite long because it houses the brushes/commutator at the drive end, where most motor cases end before the brushes on the non-drive end.
For a 72V conversion I would advise you to stay away from this motor. It is simply too small and in my ~3200 lb car it gets quite warm after a 20 minute drive. (That being said, my brushes and commutar look perfectly fine after 1000 miles). If you plan to run higher voltage it may not be too bad (less amps and less heat), but good luck finding a sepex controller higher than 72V anyway. I suppose you could always buy a higher voltage series wound/PM controller to power the armature and a separate small controller for the field like I am doing.
Also, running a higher voltage with this motor will require you to run it at very high speeds (5000 rpm+) unless you really crank the field current up, and I do not know how much current the field is actually capable of handling. I give my field 50A peak which makes the power peak at 3800 rpm. That's when my controller is in full bypass (I can feel the bypass kick in just below 50 km/h (31 mph) in second gear), when the motor is getting the full 72V. With the same field current (50A), this would not happen with a 120V pack until 6300 rpm, and I do not know if the field can handle much more than 50A to lower this rpm.
If you are thinking of going 72V, I suggest you get a larger motor. It's backwards thinking to my logic when I was motor shopping, but 72V will generally require more amps to achieve acceptable acceleration. And this heats up small motors quickly.
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