UPDATEI contacted Panda Podium to share my test results with them. They informed me that they would be looking at the issue with Nexga and get back to me, which took less than a day. Nexga determined that the issue was likely hardware related. A replacement unit was set to me.
I'm very happy with the customer service, there was no beating around the bush, lame excuses or denying of the issue.
TLDR of the rest of this post: the new power meter is very accurate, it auto-calibrates at shutdown and doesn't seem to drift much (once settled), but the USB cover retainer is very fragile (I immediately ripped it). I'll also reinstall the first unit at some point to test again how it behaves after I acquire a better understanding of the second unit's behavior.
I'll divide my observations in 5 sections:
- USB cover
- App and firmware update
- Auto-calibration, offset drift and logs
- Test (Tacx Neo 2T vs. Nexga S1)
- Conclusion
1. USB coverThe first thing I managed to do after unboxing the new unit was to rip apart the USB cover. I don't believe I was a brute, but maybe I was. However, whether I was or wasn't careful enough, I believe the design is fragile. The rubber cover is retained by a small protrusion of the cover itself.
Picture of the intact one on my original unit:
2. App and firmware updateThe new unit came with firmware 1.6, so I updated my original unit from 1.5 to 1.6. There was also an update to the Android app. Because of the firmware update, I decided to wait before installing the new power meter and test first unit some more.
3. Auto-calibration, offset drift and logsBefore diving into the data and logs, there is a weird behavior with the "Time" column within the log files. The hours change from log extraction to log extraction, as if the time zone changed. One log can have correct time stamps that I can match with my recorded activities (used for tests), then the next log will have all or some time stamps offset by x number of hours, then the next will be even more offset, to the point where the time stamps (at least the first half) in latest log extraction of the first unit are offset by about 3 days. It is therefore much harder to understand the data and match it to test results.
First unitLooking at the logs of the first unit a few days after updating it's firmware to 1.6, I noticed that the offset seemed to be much more stable, but that was in fact mostly caused by the auto-calibration feature now working (from 2026-09-12 in the logs). The unit auto-calibrates when it goes to sleep.
Log sample that shows the behavior (green = auto-calibration then sleep, yellow = manual calibration, red = sleep without auto-calibration):
I did two tests on the trainer during that time period with the first unit, which yielded good results. The second test was started on September 14 without calibrating the unit, which was, I believe, about 3h after the last auto-calibration, than manually calibrating the unit midway. I'm unsure where the test falls in the log because of the time stamp issue described above. See results in the next section.
Looking at the logs of the first unit, it auto-calibrated only 3 times before updating the firmware to 1.6.
After the update and while it was mounted on the bike, it has auto-calibrated 10 times and failed to do so only once.
After it has been disassembled from the crankset, it has not auto-calibrated once over 3 days (about 15 "power on" --> "sleep" cycles) and the offset has drifted from 0 to -116, with a low of -143 after about 2 days.
Second unitThe second unit already had a very long log history starting from mid August when I received it (over 700 lines, including many manual calibrations). I assume it was tested for a while, therefore already activated unlike the first unit which had no log entry before I first charged it.
I was worried that things wouldn't be better with this unit at first as it drifted quite a bit over the 3 days that went by between delivery and installation.
Note that it does not appear to have auto-calibrated before installation, but I'm not sure as the time stamps are again offset and hard to follow.
Log sample (received around line 719, first manual calibration lines 722-723, probably installed around lines 751, first auto-calibration lines 754-756):
As the second unit was activated before being shipped out to me, I can see the offset drift before, during and after transportation (by plane).
Looking at the log entries, it appears that transportation had a significant effect on offset drift. It also took several days for the unit to stabilize. The first unit also appear to have become more stable with time, but less so than the second unit.
There is about 150 "power on" --> "sleep" cycles between the last calibration before transportation and delivery, which were very likely caused by movement during transportation. Offset started at 16 on the first cycle, went to over 800 a week later and was in the 600s when delivered another 3 days later.
The power meter being sealed, I suspect that pressurization has a significant effect on the sensors and that it takes a few days for the pressure to equalize and offset to stabilize.
If that is the case, this factor would have to be considered if traveling by plane with your bike and when testing the meter. I did test the first unit only 1 or 2 days after it left the plane, which may have affected the results.
The offset of the second unit however, now that it has stabilized, seems to drift far less than the offset of the first unit does.
About 2 days (46 hours) after the last calibration, the offset has only drifted by -6.
Remember that the first unit drifted by -116 over 3 days, with a low of -143 after 2 days.
This could confirm that the first unit does indeed have a hardware problem. I do intend to test it again at some point.
Test (Tacx Neo 2T vs. Nexga S1)First unitThis test was done about 3h after the last auto-calibration (offset was 32 at power on), than manual calibration was done midway.
Complete test:
ERG steps 3h after last calibration:
ERG steps right after calibration:
Second unitThe first test was done 15h after the last calibration (offset was -16 at power on) than calibration was done midway (which did not have an effect on the results).
ERG steps 15h after calibration only:
For the second test, I don't know when the last calibration was made before starting it (probably not very long before).
Full test:
ERG before sprints:
Sprints:
ERG after sprints:
Conclusion- Great customer support from Panda Podium
- First unit is probably defective as the offset still drifts significantly, although less than during the first days (when I first tested it)
- First unit may now be usable even for long rides if calibrated at the start
- Second unit has much less offset drift, but did drift quite a bit during the first days following delivery
- Second can be used without really worrying about calibration
- Second is VERY accurate when compared to Tacx Neo 2T
- Offset drift seems to be affected by plane transportation (effect of pressure?)
- Auto-calibration works when unit is installed since firmware update 1.6
- USB rubber cover can too easily be ripped apart
