Do you reckon? In that case, taking an average and adding 150W for a healthy but untrained rider in a hurry, we have a round kilowatt.Bonzo Banana wrote: ↑10 Mar 2024, 11:35am This continuous rating doesn't work, a Bosch mid-drive motor climbing a long hill for 5 minutes just uses it's maximum power for those 5 minutes which could be in the region of 800-900W.
By my calculation (I have a spreadsheet, populated with data for cycling equipment and verified against rider performances): given a 70kg rider, 22kg of e-bike plus clothing, 0.55m2 frontal area, 1.15 drag coefficient, 0.008 tyre rolling coefficient, 95% transmission efficiency and 1000W... it should be possible to maintain the full permitted speed of 25kmph up most hills and only be slowed when the gradient gets steeper than 1:9.
Is there anyone with a Bosch mid-drive e-bike out there who can do that? Or do less steep hills also slow you down a bit? Do tell us the steepest hill you can ascend at full permitted speed. From that we can work out the truth of how much power these mid-drives actually deliver.
Meanwhile over on Strava we know there's a bit of a fuss about e-bikers taking KOMs from muscle-bikers, without fessing up to using E. But this seems to be mainly in America, where even Class1 e-bikes can do 20mph with up to 750W of 'assistance'. But if there's anyone over here logging segments on an EU-legal e-bike, do tell us on which climbs you beat the best muscle bikers - and by how much.
As I may have mentioned before, we are happy to have a few e-bikers join us on our Matlock CC social rides, one of whom has a high spec Bosch mid-drive. We're a load of old coffin-dodgers so she can beat most of us up the steep hills, but one or two can hold her off if they try. Given our age and distinctly also-ran ability, none of us will have anything like the power of a top pro, on which one can find quite a lot of useful data here. I think I max out at 200W these days, but I guess some of our number may be good for 300W. Putting the data for their bikes into my spreadsheet and comparing likely outcomes, I agree that the e-bike must be giving more than 250W of assistance when Jan puts it on 'Turbo' mode up a hill, but it doesn't look like more than twice that.
For the time being I'll assume that Bonzo Banana is talking about electrical power consumption, which is a whole lot easier to measure, can often be read most conveniently off the handlebar control unit of an e-bike, but isn't the same thing at all. Electric motors are not 100% efficient and only get near it when spinning at just the right speed. So the conveniently indicated power is always more than the actual assistance you're getting, which may be even less than half that. Quite frankly, it makes almost as much sense to measure the power of a human cyclist by counting the calories he eats! And without sight of their methodology, I'd be very surprised if Americans are daft enough to measure the power of e-bikes that way.
There is some illustration of my earlier point here. The Bosch Gen 4 CX can actually push out 600 watts at 70 rpm - which is several times the power that one might expect an ordinary rider to be able to generate - but the motor is rated at 250 watts. Smoke, mirrors and marketing …