How to interpret power numbers

[ROJA]

If I wanted to figure out the average amount of power my e-bike is adding, is it right to simply calculate the amount of W-hr used and divide it by the time?

E.g.,
Sample Inputs
Battery capacity = 500 Watt hour
Battery started ride at 100%
Battery ended ride at 50%
Ride lasted 1 hour (60 minutes)

Calculations and Outputs
Battery used 50% * 500 Watt hour * 1 hour = 250W average output
Not reflected = inefficiency / power loss from the battery to the motor and in the motor
(distance traveled doesn't matter)

I know my motor is rated at 250W nominal but I think if I use this calculation, the result will typically be an average output well above 250W and I'm curious if I'm thinking about this the right way

 

[Douglas Ruby]

On the Turbo, the relationship between Eco50 (or any other Eco level) and full Turbo is proportional wrt. distance. If I can go 70+ miles at Eco50, I probably can go 35+ miles at full Turbo. I have not been able to calibrate this to motor power (200W in my case) and battery capacity (691Wh).

If I use time and battery level, I know that I consume about half of my battery at 20 mph in a one hour ride at full Turbo (not including hard climbing). This would suggest a power consumption of around 345Wh from a 200W motor. Hmm...where does the excess go? Heat? Electrical resistance? Mechanical inefficiency?

I can't really figure out the efficiency of our system by merely applying Eco level to motor rating and battery rating. Part of the reason is that it also depends on load and temperature. I am pretty certain that the motor draws more power in hot conditions in full Turbo at slow wheel speed (climbing hills) than it does in cooler conditions when cruising at speed. Since these motors are direct drive, the consumption of our motors depends in part on temperature as well as rpm. And of course, the battery works better in mild temperatures than very cold or very hot conditions.

What I have done is use Strava estimates. I have roughly calibrated my body output on my non e-bike to about 100W-130W and subtracted that from the Strava power estimates. When I do, the notion that I am getting 200W+ of power from my motor at over distance seems well founded.

So I tend to stick with calibrating my distance reserves by experience and planning my rides that way.