Can the body battery calc reset itself?

Not sure I understand the problem, since from the description it sounds that it works as expected (no significant recharge due to high training load, and high stress), but if you want to reset the Body Battery, then simply hard-reset the watch - sync, then press the Light button for some 30s till it completely shuts down (hold the button through the emergency alert, if it comes), wait little bit, and then restart. No worry, no data or settings will be lost with it. [more details]. That will se the body battery at some 50%.

Thanks for the reply. Nope, I dont want to hard reset my watch. I'm asking if a radically different or atypical activity load can cause a kind of recalibration, one that might look like a hard reset has taken place. 

From reading the FAQ, it suggests body battery relates to energy levels. I was at single digit numbers yet I was feeling fine and indeed had enough in the tank to undertake another 6 hours on the bike on consecutive days. I used up nearly all of my battery on day 1, yet apparently next to nothing on the following days. 

Let me pose the question differently; does body battery measure more than simply energy levels? 

plus_ça_change said:

does body battery measure more than simply energy levels? 

I do not know what energy levels you mean, and how you think that they are measured. Body battery uses the HRV / Stress levels and depending on it, it either recharges or discharges the BB level. There is no way to directly measure any "energy levels".

So yes, if your HRV significantly changed, then the BB may be having problems to recharge, and it may take up to several weeks to establish a new baseline. Restarting or resetting the watch may help to get it quicker.

trux said:

I do not know what energy levels you mean

That's sort of my question! What are energy levels?

From   

"The Body Battery energy gauge is a feature that uses a combination of heart rate variability, stress, and activity to estimate a user’s energy reserves throughout the day. It records and displays a number from 5-100, representing the individual’s energy level.

(my bold)

I wasn't questioning how the figure is arrived at (as you and the FAQ mention, HRV is used in the calc) but what it is measuring. The FAQ refers to energy levels - if I take that in simple layman's terms then there was an apparent contradiction between the number given and how I felt, Simply put, I was feeling as though by 'body battery' was fuller than being reported - I certainly felt had enough energy to ride another 90km.

Yes, I think my HRV did change significantly (I phrased it in my op as "out-of-the-ordinary effort") That is why I wondered if a new baseline was being established, triggered by my changed pattern of exercise. Something like what you'd see if a hard reset of the watch was performed. Consequently an accurate number is not reported until the new baseline is established.  

This morning, after a good night's sleep, my body battery is back to 88 and I am told by the app that "it is a good day to take on a project or other activities". Now I don't know whether a new baseline has been established or if what I was seeing was normal functioning but it's left me wondering exactly what the 'body battery' number is telling me. As it stands, I'm not sure how I can effectively use it. I ignored it for 3 days on the basis of how I felt, my own perception of 'body battery' rather than the reported number,

I know the definition, but the energy level is not a physical value and cannot be measured by any sensor. It is virtual value, that (as already mentioned) is being increased when the HRV is high (stress low), a decreased when HRV is low (high stress), or when you exercise (HRV not measured, unless you have a chest strap). 

Thank you for your input.

An article on Android Authority has helped me in my thinking.

https://www.androidauthority.com/garmin-body-battery-1209128/

"We should also recognize the limitations of these tools. The best indicator of recovery, after all, is the way your own body feels. The best way to know whether or not to train on a given occasion is simply to listen to what those systems are telling you."

I think I'll be treating BB as a monitoring tool; of interest but not prescriptive. 

plus_ça_change said:

We should also recognize the limitations of these tools. The best indicator of recovery, after all, is the way your own body feels.

The watches can do more than you sometimes think. For both me and my wife, the values (including body battery) had already sunk low before we even realized that we had covid 19. The watch noticed that we were ill before we felt ill ourselves. The capabilities of these devices are often underestimated.

This! Too many people place too much emphasis on this metric and think it is an absolute indicator of their wellbeing. The data that is used is far from perfect (the sleep data is questionable at best) and people stop listening to what their body tells them.