Weird behavior with Powertap P1 Pedals

power-meter

#1

My Setup

I use TR with powermatch. I have a Wahoo KICKR and a Powertap P1 pedals.
Also, at the same time I connect my Garmin unit to my P1 pedals. I know…don’t ask…I know you can send the Workout to GC directly from TR using Ride Sync. I like recording the workout using my Garmin unit. Primarily I do this because the Garmin will calculate VO2 only if you use the Garmin unit to record the workout

The behavior,

for the last few weeks I notice my Garmin always read 10 or so less watts than what TR was reading. Couldn’t figure out why until I decided last night to remove the battery from my right P1 pedal. The result, the power recorded in TR matched the power recorded in my Garmin.

Putting the whole connecting the Garmin Unit to the power meter at the same time connected to TR aside, this makes me wonder if Trainerroad is managing the power readings from the Power Meter with is dual correctly. is the trainingroad app having a difficult keeping up adjusting the resistance on the Wahoo KICR. Specially when people don’t have good L & R power balance.


#2

P1s only send left sided power over bluetooth.


#3

thank you. I did not know that. that makes completely sense

them makes me wonder what TR does that Garmin doesn do, and which one is more accurate then


#5

Well, that is disappointing. I was under the impression Powermatch is the only thing we needed to worry about to have consistency outdoors vs indoors.

There isnt clear documentation about this.

This whole time I have been using my P1 pedals via BLE indoors but ANT+ outdoors because that is what the Garmin Unit uses.

so this whole time I though my Garmin was the one who wasn’t reading correctly, but sounds like because my Garmin reads from both pedals, then is more accurate. I guess I can solve the discrepancy by switching to ANT in TR as well

if that is the case TR should make it more clear to users about this.


#6

To the best of my knowledge, the BLE single-side reporting limitation, is a common one for most apps and most dual-sided power meters. The issue exists in Zwift for sure and I think in other apps as well.


#7

This is a PowerTap issue, not a TrainerRoad issue. No matter what recording device you pair with the P1 pedals, if you use BLE you will see this exact same behavior


#8

Well this explains a lot, I tried to use my Power Tap P1 dual pedals with TR as well over BLE and was unaware of the single sided issue. Good to know.

Now if I could just get the right pedal to stop chewing through batteries that would be great. Anyone know if the BLE issue would also lead to something like 3x battery usage on the right side vs the left? Perhaps the right pedal is constantly trying to pair over BLE and that takes more power than a paired pedal?


#9

That is a question likely better directed to PowerTap.


#10

Sounds like in order to get more accuracy I need to switch back to ANT+. This was very helpful.

I was also unaware of the single sided issue.


#12

How often are you changing them?

I agree with @mcneese.chad about talking to PowerTap about this - but for me, one of the huge plusses of the P1 pedals is that AAA batteries are cheap and last me a month. I swap out both batteries on the 1st of the month every month. Probably slightly more often than I need to change them but the total cost for 24 AAA batteries/year is pretty small in the grand scheme of things and this way I never have to worry about them dying on me


#13

Looks like I will start using my ANT+ dongle and a laptop, again.

So, @mcneese.chad, if I do switch back to using the ANT+ dongle to pick up both P1’s, would you advise redoing the Ramp test, if it was originally done using BLE?


#14

This is interesting because I just discussed some drop out issues with TR concerning my P1’s and they stated in that conversation - “We only connect to one pedal which relays the data and we hide the other one for pairing.” This statement wasn’t specific to blue tooth vs. ANT+. I was surprised by it because I had never heard that or read that previously. Even if it is a PowerTap limitation/issue - I would think TR would point that out as it creates some really wonky results going from outdoor to indoor.

Also note on the AAA batteries, after confirming my particular issue wasn’t TR related, I turned to PowerTap who advised to only use Lithium Ion batteries (unhelpful reminder in my case). They stated that alkaline batteries actually deform under load and can cause problems with the caps. Further, they are also much more prone to leaking which would be an issue. Just wanted to pass this reminder along since it sounds as though some folks are perhaps using alkaline.


#15

that was exactly my point earlier. I understand that this is not a TR issue, but you would think that the limitations of BLE would be widely known and published somewhere


#16

Well certainly not monthly. I got them in May but we had a very rainy summer (like records for both days of and total rainfall) and I’m a wimp who doesn’t ride in the rain. I’ve changed the left pedal one time but I’ve changed the right pedal 3 times.

At no point in time have the battery indicators been anything other than green and near full (looking in the PowerTap app). It’s like the right one goes from 3 out of 4 bars to won’t connect with nothing in between.

Yeah I’ve been using Energizer E^2 Lithium batteries. I had my right side die on a ride and could only get alkaline at the convenience store so I rode home with one but changed it out as soon as I got home.


#17

Regarding the battery indicator on TR, there is another issue. my right pedal ran out of battery but trainerroad didn’t indicate that. Only noticed because my garmin did alert me - Garmin uses ANT+

again we go back to the same thing which make sense. When you use BLE, you don’t know what is happening with the right pedal that includes battery status


#18

I don’t think that would be necessary, unless you have a significant imbalance, especially at over-threshold efforts. I think you can do the typical self-evaluation in workouts and adjust FTP as needed if you think it’s off by a bunch.

Otherwise, I’d just train along and you will retest at some point in the near future, with the full dual-reporting via ANT+.


#19

@mcneese.chad There is definitely and issue with P1’s and Powermatch going on - at least in my case. After reading this thread, I did my workout yesterday and as usual since getting my P1’s I was heading towards failure as my heart rate kept climbing during the first sweet spot interval even though I had manually adjusted my FTP down 15 watts. After barely getting through the first interval, I turned off my P1’s in Trainerroad and let my Kickr control the rest of the workout. The next two sweet spot intervals were completely manageable and well within the appropriate heart rate range which was on average 12-15 bpm lower than the first interval. I tracked my P1’s outside of TR the rest of the way and they tracked consistently, albeit about 10 watts higher along the rest of the intervals.

This has been going on for months. I have checked in with TR and been going through the run around with both Kickr and Powertap. Everyone says it’s not them, but the test yesterday was pretty convincing it’s a TR issue. My L/R balance is usually around 47/53 so if it were simply doubling my left, the workouts would actually be slightly easier than if it were based off my true FTP, however that is not the case. Every workout has been near impossible requiring VO2 max efforts to do simple SSB1 workouts. To get through them at a normal SS effort level, I have to downgrade the intensity so much that I actually get no training effect and have watched my FTP plummet from test to test.

I will ride again today using the Kickr and tracking the P1’s with my Garmin to see if the results are the same. if they are, I am relieved to have finally figured this out. At the same time, I am furious to have just found out this information as I have spent thousands at this point in Dr. visits, tests, CAT scans, diet modifications, etc. to try and pinpoint why every “easy” workout is so hard and why I keep getting sick.

Knowing it’s a left only set up with P1’s doesn’t fully answer the question, but at least it got me to turn off the Powermatch and eliminate that issue.


#20

I have found with my P1 pedals that even when I get a low battery warning on my Garmin I have a least 60-90 minutes of battery life left.


#21

Going forward I am going to connect to my P1 using ANT+. I actually my FTP test is next week. I don’t expect FTP increase because the discrepancy I was seeing.

I actually my last two workouts felt more difficult. My HR is higher. So using BLE had a difference of 10 watts difference or close to that

So @rb42, in your last workouts, did you use ANT+?


#22

I have an identical setup, P1 and kickr 18 using powermatch, and have had zero problems.