Are 750 watt ebikes actually legal?

[Ken M]

I live in Ohio and the law states ebikes must have a motor LESS than 750 watts. This is also the same as the federal law, and the same wording for ebikes when it comes to that new tax refund for ebikes.


So does that mean, an ebike with a motor rated exactly 750 watts is technically illegal? Also not eligible for that tax refund if the bill passes?

You are technically correct but few people understand "less than." In reality the ebikes rated at 750W could be reported to the CPSC as non-compliant. Someone wanting to cause some problems for these companies will eventually do that so they should just change their rating to 749.99W to be technically compliant.

In reality a motor rating as stated in in the federal and 3-class system is nebulous but no one takes the time to understand this. Here's the best explanation I have found (there are reasons why the PhD electrical Engineer that wrote the federal specification intended it to be a motor rating - mainly because the NHTSA was more focused on motor alone speed to 20mph).

Futility of Motor Power Ratings

"There's no such thing as a rated watt!" Read here for why we don't advertise a simple power rating for the motors we sell. Also, have a look at our Youtube video where Justin talks about the power to propel bicycles in <a href="https://www.youtube.com/watch?v=ALde6zhLPs0">"School of Watts"</a>.

ebikes.ca

 

[Ken M]

I’m way late to this party, but I agree that the language in Ohio law is murky. I’ve seen interpretations by personal injury lawyers that refer to “750 watts or less,” but who knows?

As a practical matter, I very much doubt that police are checking motor wattage, whether you have 500 watts, 750 watts or 1,500 watts. The only time a real legal issue might arise would be if you caused a serious crash in which someone was injured or killed. In civil court proceedings there could be hell to pay. In the event of a serious injury or death, you could potentially be a test case for a murky law in criminal court. That seems pretty unlikely, but there are some pretty ambitious prosecutors out there so it’s not impossible. Even if you won, the cost of legal defense could really sting.

In any case, ride safely.

Lawyers have no clue about anything technical like this but you are correct that this could be an issue in an injury trial which is why riders should understand what a motor rating is vs a drive system peak power.

 

[Stefan Mikes]

IMO, there aren't any 750w motors, just motors people claim are 750w. I wouldn't sweat it. This is worth a watch on how muddy the waters are.

There is one thing that has been slightly overlooked in the video, which is the electrical vs. mechanical power. The 250 W continuous power is not the electrical power (V*A) but mechanical power, that is, (V*A) * mechanical efficiency. Contrary to what was said in this video, the mechanical efficiency would rather be up to 80% (not 90% as it was explained there). Let us take one of the few big brand motors with actually low power, which is Specialized SL 1.1 motor by Mahle, with torque of 35 Nm. The continuous power of that specific motor is equal to the peak power, and it is 240 W mechanical power. It is possible to digitally measure the electrical peak power of that motor, which is 303 W. Meaning, the mechanical efficiency of that motor is 240/303 W = 0.792 (79.2%). Now, if a cheap motor manufacturer claims 750 W of continuous power, they probably mean the electrical power. Hence, those cheap motors probably deliver far less of mechanical power than advertised.

 

[Robspace1]

There is one thing that has been slightly overlooked in the video, which is the electrical vs. mechanical power. The 250 W continuous power is not the electrical power (V*A) but mechanical power, that is, (V*A) * mechanical efficiency. Contrary to what was said in this video, the mechanical efficiency would rather be up to 80% (not 90% as it was explained there). Let us take one of the few big brand motors with actually low power, which is Specialized SL 1.1 motor by Mahle, with torque of 35 Nm. The continuous power of that specific motor is equal to the peak power, and it is 240 W mechanical power. It is possible to digitally measure the electrical peak power of that motor, which is 303 W. Meaning, the mechanical efficiency of that motor is 240/303 W = 0.792 (79.2%). Now, if a cheap motor manufacturer claims 750 W of continuous power, they probably mean the electrical power. Hence, those cheap motors probably deliver far less of mechanical power than advertised.

Best way is just try before you buy. If you plan on tackling big hills alot and don't feel like getting soaked in sweat and take forever getting to the top, then buy a bike with enough power to overcome that dreaded gravity. I have 1000w. Just right for my weight on my very steep hills.

 

[PedalUma]

Generally there is a 5% rule. If you are riding a bike within 5% of the nominal rated limit, you are fine. Peak is something different.

 

[Stefan Mikes]

Generally there is a 5% rule. If you are riding a bike within 5% of the nominal rated limit, you are fine. Peak is something different.

Not necessarily. You can ride for at least 30 minutes close to the peak power of the "full power" mid-drive motor (peak 520 W mechanical, 666 W electrical) I am familiar with without actually overheating it (that is, going beyond the thermal protection limit).

As the video correctly explains, the "continuous rated power" is the motor power that could be pedalled continuously without ever overheating it. However, as the video also correctly explains, the peak power of different "250 W" motors will be totally different, as some of them deliver (say) 50 Nm, and other 90 Nm max.

 

[Gumboocho]

Confusion above: Some apparently don't understand the phrases "below 750 Watts" vs "no more than 750 Watts." The manufacturers seem: not to understand it as they sell "750 Watt" e-bikes, but not 749 Watt e-bikes (could be 749.9999 & be legal!) But in my state the law does not say what kind of watts -- or is that relevevant RMS Volts is quite different from Peak-to-Peak Volts. Big difference. I don't know if the RMS vs Peak-to-Peak applies to Watts though. Also my state law says that an e-bike must have a motor less than 750 watts, but does not forbid having multiple motors! An e-bike with two 500W motors has "a motor less than 750W", just as a hat with 2 white feathers is a hat having "a white feather"! If you have 2 pimples, you also have a pimple. If your car must have a window, but you have a car with 5 windows, you do have a car with a window!
There must be some electrical way to limit the power to a motor to 749 Watts. I think that many motors will increase or decrease the watts based on the voltage supplied. So I suppose that a voltage regulator could lower the voltage. I don't understand MobilityScootrike which advertises 500 W 3-trike at 500 W, yet you can add a "power-booster" (only at manufacture) to give it 1500W, which they claim does not increase the speed. & they tell me that both the 500W & the "powerbooster" 1500 W models have a 500W label. I have been thus far unable to get from them an explanation of what their power booster is, & whether or not one could disconnect it & reconnect it at will. Of course the watts measurement has some degree of inaccuracy +/-. So one would think that some manufacturers might solve the 750 vs 749 Watts issue just by labeling it 749. I am thinking that one should consider the NM more than Watts in selecting an e-bike.