Does solar really work? Or we got fooled

Nope, you misinterpret that. It states clearly that the battery is NOT charged as long as the watch is ON:

"Der Akku einer eingeschalteten Uhr mit Solar-Ladelinse wird bei Sonneneinstrahlung nicht im herkömmlichen Sinne aufgeladen, wie als wenn Sie die Uhr mit einer Stromquelle verbinden. Die Akkulaufzeit wird jedoch deutlich verlängert, wenn die Uhr das Sonnenlicht empfängt. "

They say that the battery is not charged like connecting it with a conventional power supply. It only extends the battery life.

The last sentence makes it even clearer:

"Erhält eine ausgeschaltete Uhr Sonnenlicht, wird der Akku wie über eine Stromquelle aufgeladen, jedoch deutlich langsamer."

It says, that the battery is charged by sunlight like connected to a power supply if it is OFF, but much slower.

I confirm that a 7 series garmin (tactix 7 pro for me) can charge in the sun with a power saving setting. Ie stock watch face, no seconds display, no wrist heart rate, no pulse ox, no wifi or bluetooth..

Today in Alsace (France) we saw the sun appear from around 11.30 am until sunset.

So I left my fenix tactix 7 pro in front of the French window in my living room from 11:30 a.m. to around 3:30 p.m. (after the sun is hidden by the roof of the neighboring house).

She was at 58%. She had 137klux/h. I turned it off and on again it went to 59% and there at 8:50 p.m. it is still at 59%

Last summer when during my teleworking days and there was much more sun than now and I put it in front of the windows, it could receive 350 to 400klux / h it could have gained 3% battery.

I understand that garmin doesn't put this forward, but it would still be nice if they added the percentage increment without having to turn the watch on and off each time.

Frequently Asked Questions About Power Glass Solar Lens | Garmin Customer Support

The last statement is not compatible with the suggestion that the watch will NOT CHARGE WHILST ON

bluefish said:

Is the BATTERY (itself) charged (RECHARGED) even when the watch is on ? Very clear answer: YES

And that's exactly NOT stated there. I (as a german) wonder how you come to that misinterpretarion.

They clearly state that the battery is not charged or recharged as long as the device is on. Especially the last sentence and the reference to the power supply leaves no more doubts.

The real implementation of the Fenix 7 may be different but this support site is very clear and consistent.

mcbit said:

The last statement is not compatible with the suggestion that the watch will NOT CHARGE WHILST ON

The last statement doesn't say that the battery is getting recharged, it only says that the battery is not discharged anymore. 

Garmin never claims that the solar lens recharges the battery as long as the device is on. They only claim that the battery is not discharged anymore if the solar power is sufficient. Lasting indefinitely means "solar power = current power requirement of the watch".

I don't know their implementation of the internal power supply. It could be that:

1. The battery supply from the solar lens is only active while the device is off. As long as the device is on, the solar power is in parallel to the battery. Similar to the dual powered calculators. The effort to collect a very, very small amount of energy at very rare times could be too costly.

2. They have an intelligent internal power supply which doesn't waste more power than it collects from the solar lens even during bad light conditions but they don't want to promise anything because this recharging times are very, very rare.

If you read my earlier post, you will note that `! have seen with my own eyes a Fenix 7 increase its remaining battery life whilst ON. Nowhere doe Garmin say that it will not charge whilst on. The increase in charge that my friend experienced from 30 mins to 5 hours represents an increase of around 0.125% if you consider a 15d battery life to be the norm. Unless your watch is almost fully discharged this is an increase you will not see either as a percentage or in days remaining under normal conditions, but an increase in charge none the less..

You will note in the previous paragraph, the conditions under which the watch will not accept a solar charge

There are two different things:

1. What Garmin states (at the german support site) - and there is really no doubt about it - that it's not (re-)charged as long as the device is on. They added the note/comparison with a power supply to make it more clear and from a technical point of view it's not comprehensible to interpret that in any other way.

2. What is really implemented. This may differ from Garmins statement and it may differ from device to device.

However, if you really observe a re-charging while the device is running - be happy. But don't expect that from your watch, nobody promised that to you.

And that is exactly as I understand it. It's never going to significantly charge my watch, and I don't expect it to, as I'm pretty much always connected to external sensors and whilst cycling I use my Garmin head unit as an external display and the data is broadcast from my watch. As stated earlier, I'm more than happy with the 10ish days life that I get including around 10 hrs of activity, so solar charging doesn't bother me one way or the other. I only chipped in to mention the fact that I have first hand experience of Fenix 7 Sapphire battery life increasing during solar exposure.