7x Solar -How many Lux hours to add 1 % to battery charge?

At 37 days you have a net average loss of 2.7%, which means that in order to replace that every day (to maintain current charge) you'd need 476k Lux hours every day. Even if you could squeeze your battery to 50 days, you'd still need 345k Lux hours per day. 

(100/37 - 100/28) / 3 hours = 0.29% solar charge at 50K lux.

To run in smartwatch mode forever it would require 12.3 hours sun at 50K lux (100/28 / 0.29%).

But note I believe watch shows 50K already as 100% even though it can charge higher. 

With perfect conditions it could be 4x higher according to pocketnav. test for the 6x (and I've seen tests showing 1% for the 6X).

although it is winter around my place, i tried to test the solar charging with the watch in low power mode during a few days, while not using the watch. I noticed that the watch showed no change in battery life. It stayed on 91%. I expected a gain and i saw a gain as soon as i pugged my watch into my pc to check a update. It showed 94% immediatly. So maybe its an other software bug?. 

You're right. You'd need 467 lux hours PLUS the already assumed 150 lux hours per day.

So yes, in only smartwatch mode (no battery saver or sensors turned off), you'd use 3.57% battery per day, so you'd need 617 lux hours per day to have unlimited battery. 

If you use sleep mode with everything turned off but the wrist heart rate sensor (44 days at 100%) 8 hours per day, you'd use 3.138% per day, so you'd need 542 lux hours per day for unlimited battery.

36k lux hours isn't very much, that's only 1/4 of the solar energy needed to achieve Garmin's battery specs of 28+9 days in smartwatch mode. You would need 150k lux hours per day to achieve 28+9 days.

In order to sustain your current battery % indefinitely, you would need to get 28+28 days (rather than 28+9), which requires something like 600k lux hours per day. And even then, you wouldn't GAIN battery percent, you would just stay at your current % indefinitely. You would need more than 600k lux hours per day to gain more battery % than the watch used that day.

That's not to say the solar charging isn't great, or isn't useful. It is. It certainly does make the battery last a lot longer. I just don't want people to have unrealistic expectations that you'll be able to put your watch out in the sun and watch the battery recharge as if it were plugged into a charger, because that's never going to happen.

You are a real Garmin fan, i think Garmin is all about marketing. Atually they fool people. The watch does not count much more then arm movement. Garmin is also not open about what they offer. As an example, there is no info about how solar actually works. There is also no insgiht in any masurement in the watch in a way you would be able to calculate it yourself.

I think Garmin is misleading consumers since a long time. They offer no more then counting arm movement. But they cell with the marketing you are familair with.

Ohhh you are very correct. How could i've missed that. 150k should be counted every 37 days, to gain 9 additional days.

Sorry for misleading claculations. 

I am experiencing the same ( i live in Singapore  so we have 32 degree sunshine every day) and its not making a difference to the % power or the days remaining - i only have the device a week on Thursday but expected the solar power function to make more of a difference to be honest!?!?

From my personal experience, 180 klux per day give 1% of battery gain and half of a day remaining.

Starting from 100% battery (and 28 days remaining) on march 2nd, after 13 days I have still 72% battery (and 21 days remaining) with 7 gps activities (running for 40 minutes at least).

without the solar charge, I should have 15 days remaining and not 21. 

I have been collected an average of 138k per day in 2 weeks.

One day I saw the battery percentage increased of 1% with 200k (more or less) in 4 hours under direct sun.

switching off and switching on after the sun bath does the trick to see the real gain.