KPREN

Quote:
Originally Posted by 2old View Post
AFAIK, motor wattage is pretty much what a motor can produce continuously without overheating. As intimated above, the manufacturers are fast and loose with their values, and some individuals report putting two or three times the designated amount into a motor (probably for a limited time). I've never had a problem with my 1000w motor with a 30 amp controller and 52V battery (theoretically 1,500 or so watts).

You know I pretty much try to avoid going where you are shoving me but you put your boot on my head. Just know that I do respect your opinion. Kevin could have been more diplomatic. That said I will side mostly with Kevin on this one The highlighted line above is what is commonly referred to as duty rating, normally associated with Grid cycles and voltages E bikes are not on grid. In the e bike world, the regulations rule, not the power companies. The regulations are written as motor output wattage at the end of the drive shaft. A whole new driver of motor ratings and introduces a real can of worms to understand.

Here is how the regulations affect the BBSHD. The battery draw of a BBSHD at 52 volts is likely to be at or above the 1,500 watts you quote but not motor power output. The max motor output you are likely to get from that is a maximum of around 1,170 or 1,080 watts (48 volts) motor output, at the manufacturers reference points. Bafang BBSHD I think is 130 crank rpm at around 15NM @21 deg C. That is max design by the manufacturer, not a duty rating. The motor was designed to output 1080 watts at 130 rpm but Bafang knew it would never be pedaled that fast. At a more reasonable 90 rpm the BBSHD will put out about 750 watts at 48 volts with a power draw of 22 amps and around the magic number of 28 mph on most bicycles.
Here again, max as designed by Bafang has more to do with the regulations than with a duty rating. . Bafang's reference points and design parameters were set to produce a motor of a certain diameter and weight. to operate on a designated voltage and be supplemented by a human.. You must understand that if the rpm is not at 130 rpm (too fast for me to pedal but not to fast to throttle) then the motor is not putting out those wattages
As an extreme example, Your battery may be putting out 1.500 watts when you first hit the throttle at a stand still but the motor wattage output is near zero because the motor speed is near zero.
Technically speaking, electric motors are not even rated in watts but in watt hours. Perfectly legal, even in EU

Bottom line is that Bafang designed the BBSHD to have pedal inputs in the range of 350-500 watts with corresponding battery inputs of 465-665 watts. and a possible 750 watts at 90 rpm

If you want to go fast and contribute pedal power inputs with high powered motors on bicycles then you need to go with a large diameter hub motor, with a large diameter chainring. Mid drives are self limiting as pedalecs. Its actually tough to sustain 750 watts on a mid drive while contributing pedal power input. but very doable with throttle only and low gearing. I have climbed hill with a heavy load using low gearing and ghost pedaling to get the rpm way up. I can get more power than I can by adding in my own pedaling power.

The whole damned e bike power thing is very complicated with so many factors involved that the possibilities are nearly endless. The regulators could have been nice and just given us a speed limit instead of a max motor output limit and greatly simplified things. Imagine cars and semis having the same motor output limit. That is what you have with road bikes and cargo bikes.

How far can the possibilities go? You can build a controller to give you 160 NM of torque out of a 250 watt nominal mid drive bike. Look for that in e mountain bikes in the near future. Battery power draw would spike some where's in the 1,500 watt range without exceeding 250 watts output. Enough to get you over a technical rock climb. The controller would be expensive with lots of controls. The writers of the e bike regulations knew they were throwing in a speed governor, but not a fun governor when they wrote the regs as motor output power. E bike manufactures still have not taken full advantage of what those regulations offer and the regulations are better than 20 years old. Still too many grid thinkers.

A disclaimer.: This whole e bike power thingy is complicated enough that I don't fully understand it enough to explain it to an 8 year old. I am likely to go back and say" Why the hell did I write that" about this post. Some of my sentences might not make sense to you or to me later but they were a best try right now. I am too damned old to invest enough time to fully understand it.. Trying to explain these abstract concepts is a rabbit hole for ragging opinions and therefore against my better judgement to post this but WTF I have been on this for two hours and therefore my editing likely sucks. I am going to have a beer. knowing that I will likely hate my post later.