Electric power usage on different PAS

[Rexlion]

I've been curious about energy usage in different PAS levels. Today I rode a particular gradual (but steady) incline twice, trying to maintain as close to exactly 10 mph as possible each time. The first run was in PAS 1 (set at 40% power), and the second run was in PAS 2 (set at 66% power). In PAS 1 the motor was consuming about 110 watts. It was harder to keep my speed as steady in PAS 2, so the wattage varied more, but it seemed to still center around 110 or perhaps 120 watts. In other words, achieving the same 10 mph speed with more motor assistance didn't appear to use a significantly greater amount of juice. This was with a hub motor and torque sensor.

Has anyone else tried similar experimentation?

I'm hypothesizing that the greatest battery range penalty from higher pedal assist settings might come from the rider maintaining a higher speed (because pedaling becomes easier); but if one sticks to the same (lower) speed, the higher PAS might not hurt one's range all that much. What do the rest of you think?

 

[HCooke]

I am going to hazard a guess and say that it depends on which brand and/or type of bike you have. Also depends on whether you have cadence or torque assist.

 

[Rexlion]

I am going to hazard a guess and say that it depends on which brand and/or type of bike you have. Also depends on whether you have cadence or torque assist.

That does seem reasonably likely. I can imagine how torque assist would be more likely than cadence assist to exhibit this power-equalizing behavior. I was hoping maybe some others would try the experiment and then we'd have more data from which better conclusions could be drawn.

 

[AHicks]

I generally don't mess with short term tests like that. Too many variables in play over a too short time period/distance for any real accuracy.

Try to maintain a certain set of settings over 2-3 battery charges. THAT will provide a much clearer picture for you. Takes longer, but provides MUCH more accurate info that you can put into practice - or not!

Regarding your question, that's typical for a torque sensing bike. I can't easily see the difference in PAS 1 vs. PAS 2 on the watt meter as much as I feel the differences with my butt meter.... -Al

 

[Rexlion]

I generally don't mess with short term tests like that. Too many variables in play over a too short time period/distance for any real accuracy.

Try to maintain a certain set of settings over 2-3 battery charges. THAT will provide a much clearer picture for you. Takes longer, but provides MUCH more accurate info that you can put into practice - or not!

Regarding your question, that's typical for a torque sensing bike. I can't easily see the difference in PAS 1 vs. PAS 2 on the watt meter as much as I feel the differences with my butt meter.... -Al

And the leg meter!

 

[Stefan Mikes]

Rexlion,
You've made me interested with your experiment. Let us say first, we cannot deny the basic laws of physics.

If you climbed the same hill at the same speed with the same e-bike, the the total energy expenditure (legs + motor) to keep the bike moving shall be the same. The difference being, you might use less leg input and more motor input to achieve the same. Now, without the (leg) power meter you know nothing about the process! Right?

 

[AHicks]

Rexlion,
You've made me interested with your experiment. Let us say first, we cannot deny the basic laws of physics.

If you climbed the same hill at the same speed with the same e-bike, the the total energy expenditure (legs + motor) to keep the bike moving shall be the same. The difference being, you might use less leg input and more motor input to achieve the same. Now, without the (leg) power meter you know nothing about the process! Right?

Stefan, I agree with your thought, but I think that maybe here, it was what the watt meter was showing him?

 

[Rexlion]

Stefan, I agree with your thought, but I think that maybe here, it was what the watt meter was showing him?

Yes, I was monitoring the wattage on the readout. I agree, the power and the work are coming either from one source or the other. And I'm not having to exert quite as much force with my legs in PAS 2 as in 1.

Trying to guess why the wattage seemed so similar, my mind was reasoning thusly:
yes, PAS applies more power in 2 than in 1 for the same pedal torque (via torque sensor),
but I'm not pedaling as hard in 2 as in 1, which sort of tends to offset the above somewhat.

Yet there cannot be any "free lunch" in the system, I suppose.

 

[AHicks]

Yes, I was monitoring the wattage on the readout. I agree, the power and the work are coming either from one source or the other. And I'm not having to exert quite as much force with my legs in PAS 2 as in 1.

Trying to guess why the wattage seemed so similar, my mind was reasoning thusly:
yes, PAS applies more power in 2 than in 1 for the same pedal torque (via torque sensor),
but I'm not pedaling as hard in 2 as in 1, which sort of tends to offset the above somewhat.

Yet there cannot be any "free lunch" in the system, I suppose.

Something to chew on-
The bike's power is controlled by the amount of pressure placed on the pedals, so the amount of power to the motor, especially at lower speeds, is constantly changing during each rotation of the crank. Consider how hard you are pushing on the pedals when the crank is horizontal for instance, vs. the amount slightly beyond that.

Soooo, the bike's controller and instrumentation may be struggling a bit when trying to provide a decent/accurate readout - to the point it may be difficult to see the difference between PAS 1 and PAS 2 on the wattmeter.