Recent content by mcdenny

A quick test showed Pm max on the display to be about 250 watts at about 40 cadence. Very hard to hold a steady low cadence. The Spec data shows 210 watts for 40 cadence and 255 watts for 50 cadence so the very short test is in the ball park with Spec's chart.

Just went for a quick ride to be sure - selecting "Motor Power Mechanic" for the display. In 100/100 tune it's easy to keep motor power maxed out. I rode for about 1/2 mile lightly dragging the brakes to keep speed in check. Motor power mechanic was almost always above 300 watts with max I...

The Spec app specifically defines Pm mechanical as one of the data items you can put on the display. In my experience the highest number I've seen while riding is a little over 300 watts. The .fit file resulting from recording a ride has a field called "motor power (watts)" that maxes out at...

John, any update?

I have a new SL2 5.0. About 4 weeks old, 60 ish miles. Does exactly the same thing. Happened 2 times this week. Maybe related, the LBS swapped the stock handlebar for a new one with more rise. I helped the mechanic do it. It is quite tricky to get the two wires for the light and display...

Well it took awhile but here's my final answer from a couple of weeks of recording test rides, downloading .fit files, massaging the raw data and charting Pr vs Pm in many tune settings. Spoiler: the data doesn't remotely agree with our assumptions based on the Spec tune tables. I'll post the...

Straight line is almost as good a fit

And here's the new efficiency function based on the Pm max electrical vs cadence shown in the prior post. A lot less curvy, as you suggested it ought to be.

New info regarding efficiency. Thanks @mschwett for suggesting getting a lot more low cadence 100/100 data. Big surprise to me anyway, at 100/100 and Pr above 85 watts the controller does NOT just dump in full voltage regardless of cadence. Just as with Pr vs Pm, there is a linear ramp up to...

Not at all, just ride the brakes.

The Spec mechanical power vs cadence is significantly curved. If you accept that the electrical power input is constant across the same cadence range then the efficiency curve is going to have the same shape. PS, I’m taking my bike in to get the new 2” more rise handle bar this afternoon and...

You can see the spec chart has a good bit more curvature. I did my best to match the spec chart in my spreadsheet to figure out an efficiency vs cadence function to use to adjust all my Pm electrical to Pm mechanical..

For reference here's the Spec charts for torque and Mechanical power

I haven't tried that experiment but your statement is correct - It isn't designed to work at that low rpm that means it's less efficient at that low rpm. It makes sense, The controller applies voltage against the resistance of the windings but the rotating winding themselves generate a current...