Confused about estimates with respect to power

[stijn konijn]

Starting with the fastbike profile and entering a couple of standard routes I use regularly, after adjusting weight it turns out using 350W for bikerPower yields a pretty good estimate of travel time, and it also scales well to longer routes.

However this 350W (and the reported 1kWh for 'Energy per 100km') seems to be almost a factor 2 less than reality based on a crude estimate based on my bike's battery capacity (1kWh) and distance it can actually do with a full charge on those routes (about 50km), and that's without counting the amount of power I put on the pedals myself.

Where could this difference come from? I realize there are losses in the battery/motor but is that enough for a factor 2? Maybe wind isn't calculated in?

[Poutnik Fornntp]

With the total weight set correctly, I assume the real and model rolling and air drag resistances differ.

Dne 21. února 2024 14:44:35 stijn konijn <deathwill...@gmail.com> napsal:

Starting with the fastbike profile and entering a couple of standard routes I use regularly, after adjusting weight it turns out using 350W for bikerPower yields a pretty good estimate of travel time, and it also scales well to longer routes.

However this 350W (and the reported 1kWh for 'Energy per 100km') seems to be almost a factor 2 less than reality based on a crude estimate based on my bike's battery capacity (1kWh) and distance it can actually do with a full charge on those routes (about 50km), and that's without counting the amount of power I put on the pedals myself.

Where could this difference come from? I realize there are losses in the battery/motor but is that enough for a factor 2? Maybe wind isn't calculated in?

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[stijn konijn]

Would that mean the default C_r and S_C_x are not super suitable defaults?

[Poutnik Fornntp]

Speaking from custom trekking bike perspective, consider them just a ballpark values, as especially rolling drag highly depends of road surface.

I approach the biker power just as the effective mean value, including breaks, to match known and estimated ETA for longer known routes. E.g. I use for myself for multihour travelling with luggage the power 85 W.

For ebikes, match the power to fit ETA as do not care much about matching real power.

Or, you can experiment with drag coefficients for profile power matching both ETA and real power.

Dne 22. února 2024 13:18:30 stijn konijn <deathwill...@gmail.com> napsal:

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[stijn konijn]

> I approach the biker power just as the effective mean value, including breaks, to match known and estimated ETA for longer known routes.

Yeah that's exactly what I do as well, it's like one of the main reasons I use brouter, I was just wondering why the numbers seem so far off. Will check if I could somehow estimate drag etc.