Unrealistic power readings, despite calibration efforts

[IgorB]

For a few weeks now I’ve been trying to calibrate my Powerpod (Ant/BLE). Pairing goes without problems, power goes up when I accelerate or go up a bridge, but the good news ends there. Power is not realistic after the first calibration ride, and using out/back rides and the Analyze-Check calibration feature of Isaac to improve calibration still leaves problems.

I’ve repeatedly reset the device (using Isaac) to start from scratch, and also used a Factory profile provided by Velocomp at this forum – to no avail. I replaced my Garmin GSC-10 sensor with new Garmin magnet less sensors – again no difference. I tried both the standard mount (profile 1) and the out-front mount (profile 2): same problems.

Hoping you can help, here are the steps I followed repeatedly to find the problem. On my rides I tried to keep my RPE and HR the same, because I think the problems relate to the wind sensor.

1- Reset Powerpod; select factory profile 1 (I use the standard mount); set my weight, height, tire width.

2- Attached Powerpod to standard mount on bike (Wilier road bike). 5 minute calibration ride.

3- Following the calibration ride, I did an endurance ride of about 60km. In this ride I included an out/back part, to use in Isaac later to improve calibration. See attached file: 12/27/2016. The wattage in this ride is far too low (around 100W). Considering my heart rate (between 130-140) and RPE, my wattage should have been around 160-200. (Note: at around 1hr-40mins the battery of my HR-monitor was empty – you can see that in the file.) Fyi: my FTP is around 260W with HR of around 172. With an HR of around 135 I should get wattages between 160 and 200.

4- I selected the out/back part of the previous ride to improve calibration using Isaac (Analyze-Check calibration). See attached file: 12/27/2016 OutBack. I sent the updated profile to Powerpod.

5- With the updated profile, I did another endurance ride with HR (around 130) and RPE constant. Average power is now more realistic, but normalized power (205W) seems to be too high. More importantly: the power readings often do not agree at all with my RPE (and heart rate). Best example is between 1hr-5mins and 1hr-11mins, when the wattage is around or over 300W – completely unrealistic. Such unrealistic readings seem to be related with certain wind directions. See attached file: 12/30/2016.

Did I miss something? Hope you can help.

The weird power readings I get during the ride appear to relate to the wind direction. So today I checked the wind port of the Powerpod. I noticed that the underside of the Powerpod (under the port) is not completely closed. The ‘seam’ on the underside is not completely closed under the wind port. See attached pictures. Is that normal? And if not, could that explain my problems?

[IgorB]

And here are the pictures of the 'open seam' on the underside of the Powerpod.

[brock]

I also have that "open seam".

I went through similar frustrations as you and one of two things fixed it:

1) I stopped trying to recalibrate using Isaac between rides and let it do its thing and
2) I switched from Garmin accelerometer-based (magneless) sensors to a Wahoo magnet-based speed/cadence sensor.

I'm curious to see what the Velocomp folks might say about that open seam. I could seal mine up easily enough with Sugru or the like if needed.

[Velocomp]

Sorry, I missed this thread during the holidays.

Your 12/27 out and back ride looks normal, and I can see where your corrected wind scaling factor is obtained. It is pretty high, but not out of range.

Your 12/30 ride shows large headwinds and tailwinds. Is this realistic where you are riding?

By design we leave a small gap in the wind port. This helps drain water that might enter it.

If you want to test the effect of the gap, do a short ride, download it, then put a piece of tape on the outside of the case, where the gap is. Do the same ride again and download it.

Please post some more ride files when you have them.

[IgorB]

Hello John, thanks for your response. Last week I also emailed technical support with my questions, and Tom Gore answered that something seems to be off with my wind readings and proposed that I send my Powerpod back to Velocomp. (He also informed me that the open seam is normal.) So, I was just about to go to the post office.

However, from your message I understand that you would like to have some more information first. And I would prefer to get my Powerpod working with your online support – that might save time (and prevent adventures with avoiding paying VAT again for importing a repaired or replaced product).

So: some more information and questions.

1- In November/December I have been riding in moderate to moderately strong winds – around wind force 4 Beaufort (around 24 km/h) but not stronger than that. I guess that is wat you see in my 12/30 file? Still, the power readings during this ride were often completely unrealistic, like between 1hr-5mins and 1hr-11mins, as I wrote in my previous post, which means that the Analyze-check calibration feature did not have the desired effect. Should I calibrate during rides when the winds are less strong?

2- You say that my 12/27 out/back ride looks normal. However, from information on this forum and in the Isaac manual, I understand that the blue (wind) ‘icicles’ should not be consistently below bike speed, and that is the case in this out/back file. Can you explain? Moreover: in the full 12/27 ride, blue ‘icicles’ are mostly below bike speed, and sometimes extremely so. Does this not indicate an improper wind calibration? (As I understood from the information under ‘Garbage in, garbage out’ in the manual?) Isn’t this why Tom Gore emailed me that something seems off with my wind readings?

3- Attached to this post three files: two rides directly after a new initial calibration. One on 1/6, with power readings that are too low and blue wind ‘icicles’ mostly under bike speed (in the beginning and end of the rides extremely so). One ride on 1/10, also with unrealistic low power readings. (For example, between minutes 27 and 32 I was riding with moderate headwinds and crosswinds. Power fluctuated between 55W and 100W, speed around 27 km/h. Doesn’t seem correct.) The complete 1/10 ride was out/back, however the first 5 minutes are missing because of the initial calibration. Therefore, with Isaac I cut part of this file, a complete out/back segment: also attached as 1/10 Outback. (When I use Analyze-Check calibration on this file, I get a wind scaling of 4,560. Isn’t that a bit high?)

4- Can I conclude that the initial calibration doesn’t work?

5- Is this useful information for you? Or should I post a few ride files based on 1 initial calibration?

Lastly: before the ride today (1/10) I reset and set up (my weight etc) the Powerpod. After my ride (with initial calibration and then the ride of which I have attached the file) I used Isaac to check the profile settings on my Powerpod. When I click on ‘Get from Device’ under the Aero/Wind scaling/Fric/Etcetera settings, I should get the values that have been set after initial calibration – is that correct? If that is correct, it is interesting that these values are exactly the same as the values (Aero, Wind scaling, Fric, ectera) that were set after resetting and setting up. Does that mean that the initial calibration does not have an effect on these settings? Or did I misunderstand something?

Thanks for the support.

[IgorB]

Brock, thanks for your response. I already replaced my Garmin GSC-10 sensor - bought new magnetless Garmin sensors, hoping it would fix my problems. It didn't. And I understand from this forum that both sensors, except older GSC-10 types, should work.

As for stopping to use the Check calibration function: my initial calibrations left me with unrealistic low power numbers. Moreover: the check calibration function is advertised as a useful feature - so I should work, shouldn't it?

Maybe my initial calibration doesn't work. Or maybe the Powerpod will calibrate itself further after a few more rides?

[Velocomp]

Brock, thanks for your response. I already replaced my Garmin GSC-10 sensor - bought new magnetless Garmin sensors, hoping it would fix my problems. It didn't. And I understand from this forum that both sensors, except older GSC-10 types, should work.

As for stopping to use the Check calibration function: my initial calibrations left me with unrealistic low power numbers. Moreover: the check calibration function is advertised as a useful feature - so I should work, shouldn't it?

Maybe my initial calibration doesn't work. Or maybe the Powerpod will calibrate itself further after a few more rides?

Please see my (late) response above.

[IgorB]

Hello John, thanks - I already responded to your response - see above.

[Velocomp]

Hello John, thanks for your response.

I looked at your ride files. Sorry to say, but I think Tom is correct; we need to replace your PowerPod. The wind sensor is operating unreliably.

You won't need to pay any VAT on the repaired unit.

[IgorB]

Ok, I'll send my Powerpod back to you for replacement. Looking forward to riding with a working one.