Comment by marme | Hacker News Reader

Comment by marme | Hacker News Reader

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it should be noted that the motor installed in that first video is 1000 watts which makes the bike legally a moped by federal law in the US which means you must register it with the dmv and get a plate for it, some states outlaw mopeds completely. It must be 750 watts or lower and max speed under 20 mph to be still be considered a bicycle which does require registration or drivers license. Lots of people put the 1000 watt motors because they have little to no markings saying they are 1000 watts so as long as you are not caught going above 20 mpg you will never get in trouble for it.

But they sell 3000 watt motors that can easily reach 50 mph. If you get clocked by a radar gun going 50 mph on a bike there is no amount of reasoning that will not get your bike impounded as an illegal/unregistered moped. To understand the equivalence 750 watts is approximately 1 horsepower so a 3000 watt motor is 4 hp. The average 49cc moped/scooter outputs 2-5 hp so it makes sense they would make you register an ebike with that much power as a moped

You can exceed 20 mp/h with a 250W motor: namely, your legs. :)

While true, not many casual cyclists can maintain 250W for more than 10-15 minutes. And 750W is an all-out sprint for many casual cyclists. 1000W-1500W is a sprint for trained cyclists.

So, that 1000W motor is, in theory, as fast as my sprint, but for a much longer time period. And also in excess of the speed limit on a residential street.

The law in my state defines a bicycle as a "device having two or three wheels with fully operable pedals and an electric motor of less than 750 watts (one horsepower), whose maximum speed on a paved level surface, when powered solely by such a motor while ridden, is less than 20 miles per hour". So you are allowed to go faster than 20 if you're pedaling.

Bonus fun fact: in my state, you can't get a DUI on an e-bike because it is not a "motor vehicle".

The power output (watts) is a function of (volts * amps) so if you have a 48v battery, you can output ~15 amps and get 750 watts. The amperage output is controlled by software, and these mid-drives are programmable. When you buy the kit, you can have it programmed for 750 watts or 1600 watts for off-road use only.

FWIW, on the bottom is a sticker that says "750W".

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