Thoughts on best power meter

tbar23

Member
Hi all - I have a bit of an obsession with bike data. I'm an engineer, and engineers have a hard time knowing that they are having fun without the data ;)
One of the things that I found very appealing about the Specialized ebikes is that they broadcast the data from their torque sensor and cadence sensors to generate power data. If I'm going to be assisted by a motor, I would like to know how much power I am generating vs the bike. With that said, I am investigating the best option for a power meter for my new Stromer ST2S.
I have Garmin Vector pedals on one of my other bikes, but the LOOK-compatible cleat is not an awesome option for a commuter bike.
I like the idea of a crank arm or spider-based power meter.
The ST2S appears to have an FSA Gossamer Megaexo-based 52T single-speed crankset. If I'm looking at things correctly, the bottom bracket is a British 1.37"x24T.
The seemingly integrated chainguard is throwing me a bit.

Any thoughts on easiest way to get a power measurement on my bike?
 

J.R.

Well-Known Member
Region
USA
Don’t think I understand this.
Thomas is referencing the Cycle Analyst, which measures and adjusts all sorts of things an ebike is doing. For all I know it can't be setup on a Stromer, and your looking to measure what you are doing. I use a Garmin activity tracker that tells me a lot about my personal performance. It doesnt measure my torque or cadence, and I think that's what you're looking for. We've had discussions here about power meters, but I've yet to see anyone say they've mounted and use one. When I was commuting long distance everyday I seriously considered one, I found the stats I got from the Garmin to satisfy me. Heartrate, speed, distance, gps tracking of elevation etc... Experience helps, just knowing what the ebike can do and what I've been able to do without it, add the metrics I get with an activity tracker and that was enough. I definitely understand your curiosity though. Knowing one's cadence and watts would be interesting.
 

fooferdoggie

Well-Known Member
Thomas is referencing the Cycle Analyst, which measures and adjusts all sorts of things an ebike is doing. For all I know it can't be setup on a Stromer, and your looking to measure what you are doing. I use a Garmin activity tracker that tells me a lot about my personal performance. It doesnt measure my torque or cadence, and I think that's what you're looking for. We've had discussions here about power meters, but I've yet to see anyone say they've mounted and use one. When I was commuting long distance everyday I seriously considered one, I found the stats I got from the Garmin to satisfy me. Heartrate, speed, distance, gps tracking of elevation etc... Experience helps, just knowing what the ebike can do and what I've been able to do without it, add the metrics I get with an activity tracker and that was enough. I definitely understand your curiosity though. Knowing one's cadence and watts would be interesting.
cadence is easy if your garmin can handle ANT+ or bluetooth you can get a caddice sensor that will connect to it and its not expensive.
 

tbar23

Member
Thanks. I may try hooking up my Vector pedals for a test ride. Cadence is easy but not what I’m looking for.
 

JRA

Well-Known Member
The 850c display I have on my Open Source TSDZ2 has that info and more but it took some doing by a community to make it happen....

Screen Shot 2020-12-21 at 6.42.37 PM.png


It is nice to see how much effort you are putting in to inspire you to get with it and PHDI
 

linklemming

Well-Known Member
The 850c display I have on my Open Source TSDZ2 has that info and more but it took some doing by a community to make it happen....

View attachment 74812

It is nice to see how much effort you are putting in to inspire you to get with it and PHDI
Do you find the human power accurate? It seemed about 1.5x to 2x higher than expected when I used it.

Back when I was playing with my opensource tsdz2 in early 2019, I focused alot on the code that calculated human power. In the end it was a simple cadence/crankarm length/force calculation. Of course its not that simple in the bigger picture as you have to scale it due to not having constant pressure throughout the pedal stroke and it wasnt clear to me how fast the torque sensor was being sampled (of course the sw does this but the hw delay in the low pass filter was pretty big). In the end I was just going to scale the human power but decided to just set the assist levels lower.
 

linklemming

Well-Known Member
Thomas is referencing the Cycle Analyst, which measures and adjusts all sorts of things an ebike is doing. For all I know it can't be setup on a Stromer, and your looking to measure what you are doing. I use a Garmin activity tracker that tells me a lot about my personal performance. It doesnt measure my torque or cadence, and I think that's what you're looking for. We've had discussions here about power meters, but I've yet to see anyone say they've mounted and use one. When I was commuting long distance everyday I seriously considered one, I found the stats I got from the Garmin to satisfy me. Heartrate, speed, distance, gps tracking of elevation etc... Experience helps, just knowing what the ebike can do and what I've been able to do without it, add the metrics I get with an activity tracker and that was enough. I definitely understand your curiosity though. Knowing one's cadence and watts would be interesting.
Im pretty sure a CA3 could be setup on a stromer since it uses its own torque sensor on the rear dropout.

You could use a BB based torque sensor and a CA to read human power. You would have to tap into battery power somehow and Im not sure how easy that would be on a stromer.

That being said, it would be fugly....doable but fugly.

I have a BB based torque sensor and CA on a DIY build and LOVE the human power readouts. I do rides on that bike targetting human power levels and find I get more of a workout (which is the whole point for me)
 

J.R.

Well-Known Member
Region
USA
Im pretty sure a CA3 could be setup on a stromer since it uses its own torque sensor on the rear dropout.

You could use a BB based torque sensor and a CA to read human power. You would have to tap into battery power somehow and Im not sure how easy that would be on a stromer.

That being said, it would be fugly....doable but fugly.

I have a BB based torque sensor and CA on a DIY build and LOVE the human power readouts. I do rides on that bike targetting human power levels and find I get more of a workout (which is the whole point for me)
I think with the amount of sensors, several battery terminals, mobile network connectivity it would be near impossible to get a CA3 to work on a Stromer. It's one of the best ebike computers, but given the proprietary tech of Stromer and the lack of information available on the system, I can't see anyone willing to try with such an expensive ebike. Of course the minute one says that a YouTube video shows up to prove it wrong😖
 

JRA

Well-Known Member
Mr. Lemming, quite frankly I don't get that scientific about it. I just ride, but with the info that is there I do notice that it goes up with effort and down with less effort on the human and motor side. Heck I have never even gotten the speedometer to work and don't use the odo either. I've been using a TS since '18 with the stock display that I pay even less attention to. The only reason I mentioned it is that it seemed to address the OP's needs although it would probably never be of use. What can I say....cabin fever?
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
I may try hooking up my Vector pedals for a test ride.
That's a logical thing to do. You actually do not need the power meter on your Stromer for the whole time; that would be enough if you tested your performance from time to time. I was obsessed with the same data as you and could take the benefit of riding my Specialized e-bike. Once I determined my own leg power, I lost interest, focusing more on the cadence. That is measured by two e-bikes of mine (Specialized and Giant). Once I discovered I got used to spinning at the cadence >80 consistently, I lost my interest in this datum, too :) Now, I only check the net ride time and distance. And the battery level, of course.
 

linklemming

Well-Known Member
I think with the amount of sensors, several battery terminals, mobile network connectivity it would be near impossible to get a CA3 to work on a Stromer. It's one of the best ebike computers, but given the proprietary tech of Stromer and the lack of information available on the system, I can't see anyone willing to try with such an expensive ebike. Of course the minute one says that a YouTube video shows up to prove it wrong😖
Actually to just have the CA measure the newly added BB torque sensor (and nothing else) would only require that the CA get battery power
 

linklemming

Well-Known Member
That's a logical thing to do. You actually do not need the power meter on your Stromer for the whole time; that would be enough if you tested your performance from time to time. I was obsessed with the same data as you and could take the benefit of riding my Specialized e-bike. Once I determined my own leg power, I lost interest, focusing more on the cadence. That is measured by two e-bikes of mine (Specialized and Giant). Once I discovered I got used to spinning at the cadence >80 consistently, I lost my interest in this datum, too :) Now, I only check the net ride time and distance. And the battery level, of course.
I actually really like the human power meter on my CA. I like to target rides to be at specific power levels. Sure, after 30+years riding, I kindof already know this(same as HR monitor) but its nice to come home after a ride and see how much power I put into the ride. I find I work harder when doing this as well. Yeah, it may get old after awhile but its always there if I want to look at it.

I have seen my fitness increase as a result of targeting ever increasing power levels during rides
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
I actually really like the human power meter on my CA. I like to target rides to be at specific power levels. Sure, after 30+years riding, I kindof already know this(same as HR monitor) but its nice to come home after a ride and see how much power I put into the ride. I find I work harder when doing this as well. Yeah, it may get old after awhile but its always there if I want to look at it.

I have seen my fitness increase as a result of targeting ever increasing power levels during rides
Well, if I had to, I would immediately buy a HR armband and set my Vado to "assist me to keep me at given HR". It seems more practical. (I'm finding it difficult to watch the bike display or the smartphone for the whole time during the ride, as observing the road in front of me is more essential). The reason I'm not buying the Polar armband is I don't want to be totally "robotised" by the e-bike ;)

As tbar23 correctly stated, Turbo e-bikes produce any information you need, including your average, weighted average and maximum power post-ride. But he rides a Stromer.
 

tbar23

Member
Thanks for all of the interesting comments. I just finished swapping my Vector pedals onto my Stromer this morning, and I'll try to get out for a test ride at lunch. I also appreciate the additional info on CA. I'll have to investigate, though I suspect I will come to @linklemming's conclusion. I'm also looking into power2max crank-based power meters as an option. I think one of their FSA options might cleanly replace the stock Stromer crank.
I will admit that I don't track the data quite as much as I used to, but I have been a fan of the https://www.xertonline.com/ training platform, and that platform works best when you feed it a steady stream of your own human power.
 

Johnny

Well-Known Member
There are people who use power meters on their stromers. You have probably come across this video.

He is also a forum member I believe and he is using a powertab p1's.

So far I am trying to resist buying an external power meter but Power2Max NGeco seems interesting.

Too bad Stromer is not letting riders access/store power data. It seems inconvenient/redundant to get an expensive power meter when you already have the data available.
 
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tbar23

Member
Click on me.

Being silly here but so often a simple Google search has enlightened and taught me something.
Yep, super-helpful post @Thomas Jaszewski. That was the first thing I did - and nowhere did I find information on power meter options for a Stromer.
Now, if you had included your most recent post "I use a CA3 and shunt for best results. By taping into the power leads.", I would have had a bit more context for what you were thinking.
However, that still doesn't solve the initially posted problem of "I would like to know how much power I am generating vs the bike".
The shunt approach may give some (indirect) idea of how much power the motor is producing, but it certainly won't give any indication of how much power the human is producing.