I’ve never heard of this. But I’d replace my battery weekly if it gave me a 20 watt bump.

If you transported the bike via car,plane or donkey cart, that motion seems to keep the PM "awake" and counts into the 300 hr projection. Some folks remove their battery for transport to increase its life. As cheap as they are I'd just replace more often.

Hugh

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Genetics load the gun, lifestyle pulls the trigger.

Do you monitor your Zero Offset?

IME with Quarq and P2M units, low batteries are easy to spot if you're watching the ZO over time.

No - I was not - I am not even sure how to do that. I assumed Power 2 Max was set it and forget it..... Is there a Zero Offset setting somewhere on trainer road? Or would I use my Garmin head for that?

Yes. It's the "calibrate" function in a Garmin.

You need to do a zero offset / garmin calibrate on every power meter before every ride. It has to be done with no load on the pm (you off the bike).

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How does that translate to using an ANT USB stick on a laptop with trainer road? I get it for outdoor rides. I thought that the Power 2 Max meters did a zero every time you stopped pedaling for more than 1 second.....

I've never used trainer road but I would imagine is does the zero offset/calibrate for you when you first connect the pm to the software. But half the reason to do a zero offset before every single ride is to make sure the zero offset value doesn't drastically change. If it drastically changes (you need to remember roughly what the number is every ride), then you have a pm issue (battery issue, water intrustion, etc). It's much easier to detect a pm issue this way than watching your power numbers.

I'm not sure if p2m has the auto zero / calibrate function but that get's enabled on the head unit and I would personally turn it off (in the head unit). I've seen to many issues of it incorrectly assigning a zero offset number when you slowly coast up to a stop sign, stop light, etc. And then your power readings get all wonky and then you have to either coast again for 10-15 seconds to make sure it gets a good re-zero or hop off the bike and do it manually.

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TR has a Zero Offset/Calibrate function.

It has an automatic in-ride ZO that occurs behind the scenes when it detects a zero load on the crank. You won't/can't know the outcome of that reZO. If you do it yourself before each ride, you can look for anomalies like a ZO that has jumped a good bit or one that's gradually changing (ie. battery issues).

Over the life of a power meter battery cost must be about 1-2% of the total cost. Why do people not just change them more frequently?

I only change mine when the low battery notification appears on my Garmin Edge 520.

All that I mean is that if you replaced the battery every season, or at least before your A race you would double the number of batteries you use, but the total cost would be insignificant compared to the investment in a power meter.

Kent

Just laziness because it is a pain to remove a Campy crank from a Cerverlo P2 to properly access the battery cover screws. I ordered 5 more batteries and I will do it more often now.

I change my P2Max batteries at the beginning of the season and just before my last big race so...April and September