Why use Power Match?

Mobile Apps
#1

Can someone please explain the intent for the Power Match feature?

I have a Stages SB20 Smart bike with Erg mode and individual power meters on each crank. Do I need to use Power Match on a bike that presumably has accurate power measurement?

Turning Power Match on give me wildly inconsistent values. If pedal very slowly during calibration, I get power offsets of +/- 10w. If I pedal fast during calibration, I get offsets more like +/- 200w.

Turning Power Match off gives me incorrect actual wattage readings in TrainerDay. It will show Actual 130 watts (top right) for an Erg Target (top left) of 200 watts. The bottom bar on the display shows an indication of an offset of +70w . At the same time My Garmin head unit, monitoring via Ant+, will show 200w.

Thanks!

#2

Powermatch is a function to eliminate a discrepancy between Trainer reported Power (often not accurate at all) and the Power read from a real Power Meter. The app reads the power from the power meter and compares to the target that was sent to the trainer. If there is a difference, the app sends an offset target value and tries to match the Power Meter with the intended target.
I don’t have any experience with the Stages bike but since it has a Power Meter incorporated, I think that same functionality is already implemented in the bike itself. And probably it goes nuts when another app also tries to correct the resistance. Hence the strange behaviour you experience.
In the second case with PowerMatch off, I think you will need to use the option of doubling singel sided Power. Bluetooth has limited support for double sided power. Some models send both signals L/R over one channel, others only send L-Power.
So bottom line, try PowerMatch=Off and Double single sided power=On.
In the end, if the app keeps you on target and you record on your Garmin, it doesn’t really matter what the app reads. It would just maybe be confusing when looking at it.
Maybe both modes even work ok when you use Double Single Sided Power. Or check if Stages allows to send both L/R power over one channel in BlueTooth. My Favero’s do that - Both channels over ANT+ and the sum of both over Bluetooth.

#3

I think your answers are in here:
https://support.stagesbike.com/en/support/solutions/articles/11000087112-using-erg-mode-with-zwift-or-trainer-road

#4

Thanks for the comprehensive reply.

The Stages bike has several configurable power reporting options.

  1. Use BT or Ant+ to send power data directly from individual cranks on separate channels.
  2. Use BT to send L:R data from both cranks over a single BT connection.
  3. Use BT or Ant+ to relay L:R data from both cranks through the Stages Bike head unit.

Rumour has it that Stages will eventually add the normal resistance-based freewheel power reporting mode to presumably allow the bike to be used if both crank power meters have failed. Based on your description, this will be the only time that Power Match should be considered.

I currently use Option 3 with TrainerDay. I use my Garmin 520 to simultaneously monitor Ant+ broadcasts from the bike’s head unit. Now that I understand the reason for Power Match, I will see if I can now find an explanation for the incorrect actual wattage readings shown in TrainerDay. It is not simply a multiple of the expected value. It is always a consistent fixed offset from the correct value…

Thanks again.

#5

Hello, also, since you have dual pedals and we only connect to a single pedal you likely need to click on the setting to double the power in our app so it is trying to power match 50% of your power to your full power from your smart trainer which might cause problems. This should resolve your issue. Also it sounds like option #2 might also do the same thing. If it does not let us know.

#6

You’re welcome.
If possible keep ANT+ with both pedals separated. That will give you L/R balance information on your Garmin. And for Bluetooth use L-R over a single connection. That will be more accurate compared to double single side.
I think we can safely assume that an indoor bike at that price has those possibilities…

#7

Thanks for checking in.

Power Match: Off + Double Side: On seems to do the trick!
I did some testing this afternoon. Lots of interesting data.

Here’s the Stages SB20 Smart Bike sequence that works reliably:

a. Use Add Devices +: Connect to only SB20 Smart Bike
(this option relays cadence & L:R power meters through the bike’s head
unit via a single BT connection)
b. Power Match: Off
c. Double Single Side Power: On
d. Stages Bike: Toggle power Off/On
e. Restart TrainerDay (iOS)
Target and Actual Power display is now correct in TrainerDay. Yea!

Doubling the pedal value is important. Other devices/apps like Garmin and Stages Link app appear to do this automatically. I did some single leg tests. All record 0W for a period of time when pedalling right leg only. This is odd. Connecting directly to either crank eliminates this issue - see below.

Anyways: Problem fixed. Thanks!

There are other BT connections available for the individual crank power meters. They can also be made to work with TrainerDay.

No SB20 Bike + One Power Meter:

a. Use Settings > Add Devices +: Disconnect SB20 Bike & connect one individual crank Power Meter
b. Settings > Account & Additional Settings > Double Single Side Power: On

TrainerDay can use this combination to get a valid power reading. Without the SB20 Bike connection, TrainerDay obviously can’t control bike resistance. This connection is more useful for things like single leg tests.

You can alternatively connect the SB20 Bike + one Power Meter:

a. Use Settings > Add Devices +: Connect SB20 Bike & one individual crank Power Meter
b. Settings > Account & Additional Settings > Double Single Side Power: On

Power display also works properly. TrainerDay appears to take the single side power meter and ignores the relayed value from the SB20 head unit. Nice but this combination consumes two BT connections with minimal incremental value.

#8

Good advice. I am still trying to figure out the differences in the individual Bike and Power Meter data streams. The data from only the SB20 Smart Bike connection is likely the best in most scenarios.

The SB20 Bike and Sensors support:

2 BT Connections to Bike - Dedicated bi-directional connections. Once 2 bike connections are established, the bike stops listing itself as a BT endpoint until a connection is freed up.

1 BT Connection per Power Meter 1 dedicated uni-directional connection per Power Meter.

**Unlimited Ant+ Connections for Bike and Power Meter **

So far I managed to get 10 different listeners to different Ant+ streams. The Bike connection use bi-directional Ant+ FE-C. This means multiple apps can control the bike if you are not careful. When beginning a new training session, I start TrainerDay first (BT-1), then the Stages Link app (BT-2) and then Garmin 520 (Ant+ FE-C). This sequence seems to allow TrainerDay to control the bike without interference.

I have worked in the communications and software industry for 40 years. Setting up my Stages Bike was challenging for me. I have no idea how most people deal with this level of technology. It does explain some of the problems however :(

#9

Wow, that sounds like some crazy options and glad you have it working!!! :slight_smile: Yeah I have worked in the software industry too for 30+ years and this bluetooth with lots of different devices has been challenging for us.

#10

IMHO Smart Bikes, like mine, are still in the early adopter phase. Smart Trainers are a bit further along. None of them have their software working perfectly. Resistance modelling is good but I think all smart bikes/trainers have difficulty replicating heavy-duty sprinting experiences. Similarly, I am not convinced that Erg Mode (as implemented by the Smart Bike/Trainer software) is as good as were are lead to believe. Erg resistance to rapid acceleration feels very wrong to me. I think great Erg behaviour is still an iteration or two away.

I also empathize with you: Platforms like Android, iOS, Windows and MacOS create a very challenging test environment. I think you are right to stick with iOS and Android for trainer control - for now.

Peloton does a better job serving consumer-level users by building both the hardware and software. 3rd party software control of smart bikes/trainers will take a bit longer. Please don’t get discouraged. Products like TrainerDay are several orders of magnitude more useful than the Peloton-style alternatives.

#11

Your thoughts/comments are right on from my perspective. The software and hardware platforms seem to be effectivly pushing people to indoors, COVID is helping that as well. I don’t see hardware / software doing what outdoors does any time soon.

Performance cycling is very convient inside (no stop lights, traffic…), outside it’s easier to just enjoy yourself with bouts of performance. I believe the outdoor market can and should go more in the direction of the “top tube sticker” for performance cycling and less in the direction of being glued to the computer screen. I am working on a viable solution for this. Even taking the polarized approach and doing 1 day a week of strict very hard interval session indoors and ta lot of outdoor forcus on easy rides is a good approach from my persepctive.

I also feel that ERG mode is one tool in the toolbox. I do also feel spin bike style (Peloton) training is another tool in that toolbox, especially in my case where my wife won’t let me keep bikes in our apartment so I have an M3i spin bike (she likes it too). It’s nice because it is 100% silent. Generally I like it.

Thanks for your thoughts and compliment “orders of magnitude…”