comments on Bosch range assistant

[sjpt]

I have suggested Bosch range assistant on several thread as a very useful (thought far from perfect) tool for estimating range on Bosch and non-Bosch bikes. https://www.bosch-ebike.com/en/service/range-assistant/

One issue raised (below) was the fact you can't put in your power; to which I had responded that the power was implicit in the speed and other factors. I am now adding some numbers to support that.
I've started a new thread as the posts had got rather far off the main topic of the other hub vs crank thread (which rightly had more general interest than I think this one will)

I've taken two cases that represent our cycling; a very upright Raleigh Motus cycled at different not very fast speeds on 'tour' mode, 400wh battery. I've used power estimates from http://bikecalculator.com/ and range assistant estimates. I've said no wind and level (neither of those is typical of our use) to both estimators to make it easier to compare. Tour mode is meant to deliver equal power from rider and motor, so I've split the power 50/50 rider/motor.

Case 1: 10mph => 86w power needed, 43w each. Estimated range 71 miles => 71/10 hrs cycling => 71/10*43wh => 305wh.
Case 2: 14mph =>152w power needed, 76w each. Estimated range 50 miles => 50/14*76 wh = 271wh.

That suggests around 68 to 76% overall system efficiency; with 8% better efficiency at the higher power which seems reasonable.
The figures are close enough that I think they show the range assistant does (indirectly) take account of user input.

Because of the all the other variable factors the system will never get things exactly right (except by occasional chance); but I think the vagaries are more in the +/- 10% range (useful tool) rather than +/- 44% (useless tool)

But I can't find where you input your own power. That's the biggest single factor that affects range. Without it in the algorithm, any prediction could be wildly out. Some people pedal consistently at 200w, others struggle for 50W.

Lets say it calculates a range of 64km (40 miles) and has the 400wh battery. That's 10wh/m or an average of 120w from the motor at an average speed of 12 mph. We have no idea what power they've guessed at for the rider, but lets say 100w, so that range calculation would be based on an average of 220w, but the difference between a 50w (170w total) and a 200w rider (320w total) is nearly a factor of 2. Actually, the tolerance on the calculation would be +/- 44% if they got their average right.

In case of pedantics, I know that's simplified. In practice the 200w pedaller wouldn't be averaging the same speed as the 50w one, but that's beside the point.