Hey Kabbage. Welcome to ES, well at least to posting on it.
You pretty much nailed it with the question, as that is what most of us were thinking. I think the crappy wording in our laws are probably a throw back from paraphrasing/reinterpreting the EU standard EN15194 (Electrically Power Assisted Cycles), and the standard it refers to for classifying the power capacity for a motor EN60034-1. I think this even more widely accepted standard for ebikes is also poorly worded. Here is the key part of it:
4.2.7 Maximum power measurement
4.2.7.1 Measurement at the engine shaft
The maximum continuous rated power shall be measured according to EN 60034-1 when the motor reaches
its thermal equilibrium as specified by the manufacturer.
NOTE Thermal equilibrium: temperatures of motor parts do not vary more than 2K per hour.
In circumstance where the power is measured directly at the shaft of the electronic motor, the result of the
measurement shall be decreased by 1,10 to consider the measurement uncertainty and then by 1,05 to
include for example the transmission losses, unless the real values of these losses are determined.
4.2.7.2 Alternative method
When the power is measured at the wheel, the result of the measurement is the reading value.
Annex D gives guidance on how to measure the power at the wheel.
The way I read it, it seems to boil down to what the manufacturer claims the motor can thermally withstand (on a 100% duty cycle for an ebike presumably). Which is wide open for reinterpretation, since is wholly depends on the motor speed, and the temp limit you feel like setting. It is more about protecting the purchaser from a motor melting, than limiting the motors power output. Which would allow you to slap on a 250w sticker on anything, by using a stupidly low thermal limit, then allow people to run it hotter.
Weird standard.
Maybe the Oz wording is a poor attempt at correcting this. By assuming a constant voltage power source, wide open throttle, what can the motor put out. Something along those lines.
The way I think it should be interpreted is that the definition of the motor is the motor + controller, and ungoverned means you are running full throttle, not partial throttle. Then it
starts to make sense.
- Adrian
P.S. I was the guy that asked if she had actually argued the point of the law in the court room at all.
I found the response quite interesting. Basically that it didn't matter. You were more likely to "win" if you don't try and prove that your bike is legal, but prove that it is reasonable that you thought it was legal. Also that none of her clients were there just for having an overpowered ebike, they were all doing something else stupid that drew the attention of the police.
Ah well.
