"Lux hours" doesn't mean anything

Locked-N-Loaded said:

What is a "lux hour"?

Lux hours, also known as solar irradiance hours or solar insolation hours, are a measure of the amount of sunlight that falls on a particular surface over a given period of time. It is a metric commonly used in the context of solar charging because it provides an indication of the amount of energy that can be harvested by a solar panel.

The basic idea behind lux hours is that the amount of energy available from the sun varies depending on a number of factors, including the time of day, the season, and the weather conditions. By measuring the amount of sunlight that falls on a surface over a given period of time, we can estimate the total amount of energy that can be harvested by a solar panel during that time.

To calculate lux hours, we need to measure the amount of sunlight that falls on a surface (in units of lux) and then multiply that value by the length of time that the sunlight is present (in units of hours). For example, if a surface receives an average of 1000 lux of sunlight for 10 hours per day, we would say that it has received 10,000 lux hours.

Lux hours can be a useful metric for estimating the performance of a solar charging system, as it provides a more accurate measure of the actual energy available from the sun than simply looking at the amount of sunlight in a given day. However, it's important to note that lux hours are only one factor to consider when designing a solar charging system, and other factors such as panel efficiency, battery capacity, and charge controller performance must also be taken into account.

Circular icon just shows the immediate relative lux value (with no sections being no lux and all sections being “max” lux).

It just helps to offset discharge... it doesn't actually charge the watch in any meaningful way unless you turn off all of the features that make the watch worth purchasing.

No offense, but you just made my point for me... Nobody understands {nor ultimately cares) about this depth of an explanation.

The solar charging functionality is sold as a way to potentially increase battery life. Period. That's it's selling point & intended purpose.

But this is represented to the user as "lux hours". That representation has zero indication of how much you improved your battery life (by adding charge or reducing discharge - even that's not clear).

People understand battery life in percentages or hours. 23 hours or 15 minutes or 13 days is meaningful.

Even Garmin tech support doesn't have any idea how it translates to a meaningful number to the user.

A typical American won't understand KPM until you convert it to MPH or KM to MI. So, how can "lux hours" not be converted to minutes or hours or seconds? Definitions universally understood.

I earned 90.1k lux hours today. Tell me, what did that do for my battery life (by adding charge or reducing discharge)? Is 90k a lot or a little even? You can't. Apparently, nobody can. It's a number that means nothing to anyone but a scientist in the field. I mean look at your explanation. I understand the science. BUT in those terms, it still doesn't answer the main question... How much battery life did I gain (by adding charge or reducing discharge)? Who cares about the "efficiency" of a solar system if the system can't demonstrate to you how you benefited.

Locked-N-Loaded said:

I earned 90.1k lux hours today. Tell me, what did that do for my battery life (by adding charge or reducing discharge)?

It's not that simple. It essentially depends on how much power is currently required. Are you recording an activity, are you using GPS, which GPS systems have you activated, etc

Understood. But again, it underscores my exact point... The metric as no obvious value. What's it telling us?

Now, the watch could do the calculations as to what you're running currently, it's power usage (vs) the accumulated "lux hours" and report that in a meaningful number. It's math. Do you slow battery use by 5% and that translates to 20 extra minutes? Who knows. 

As is, what does it mean? Who cares if you have 90 or 10 or 150 lux hours when there is no idea what that even means to the battery life. Reporting "lux hours" literally means nothing.

There's no way you can't be getting my point.

Ps - until it's explained, I bet no one knows that the solar panel is not adding power - despite the fact that is exactly what everybody understands solar panels to be doing. But that it is, in fact, just mitigating burn rate. According to you, if my watch is doing nothing but sitting in the sun, it will not generate added battery life.

Locked-N-Loaded said:

Now, the watch could do the calculations as to what you're running currently, it's power usage (vs) the accumulated "lux hours"

You can have already collected the Lux by lunchtime, but only need more energy later when you start an activity in the afternoon. How should the watch know in advance how much energy you will need later?

Locked-N-Loaded said:

According to you, if my watch is doing nothing but sitting in the sun, it will not generate added battery life.

 If you don't record any activity, put it in power-saving mode or switch it off and make sure that the watch can dissipate enough heat, it will also be charged if there is enough sunlight. Whether the watch is charged or only discharged more slowly depends on the energy required.

It should be a constantly changing real time number like every other reported number.

If I'm running, and I'm using GPS, medium screen brightness, heart rate monitor, whatever.. on the same "lux hour" screen should be a real time read out of say:

"Battery life added: 4%" or "battery percent added: 5%" - that number would be a real time constantly changing number based on the current lux hour (vs) current battery draw. It's not rocket science. It's just a real time calculation of power in vs power out knowing the only "power in" can come from the solar panel.

Ps - Ask yourself... If you have this feature, and you look at "lux hours" what do you think? What does it tell you? How does it inform you in a meaningful way? Do you think more lux mean more battery life saved? Why? What would make you think that based on seeing that number? Ultimately, it tells you nothing of use as is.

Why do you think that? The lux hours page wouldn't tell you that. That seems like speculation. You don't know how much, if any. It's only telling you the solar panel received sun input. That doesn't mean any actual battery benefit was gained. If so, what? How much?

Do you get my point? What's the point of reporting "lux hours" versus a meaningful real world number people can understand. 90 lux hours is useless. It tells you nothing as it has not relationship to any number people understand.

Locked-N-Loaded said:

If I'm running, and I'm using GPS, medium screen brightness, heart rate monitor, whatever.. on the same "lux hour" screen should be a real time read out of say:

"Battery life added: 4%" or "battery percent added: 5%"

As already mentioned, you will never achieve a charge during a GPS activity. Under these conditions, the consumption is higher than the energy provided by the cell. In this case, the solar cell supports the battery and it discharges more slowly.