Most solar panels on portable products are a top-up, not a power source. Panel area times about 150 watts per square metre gives the maximum it can physically produce. If the label claims more, the label is wrong. And an honest panel still needs days to fill the battery.
Every booth had a panel on it. Camping lights, floodlights, power stations — all with a small black panel folded on top and a number on the box.
100W. 200W. 300W.
There is one thing you can check at the booth, with a tape measure, in about thirty seconds.
The panel can only be so big
A monocrystalline solar panel produces roughly 150 to 200 watts per square metre of panel area. That's not a market number. That's the physics of the cell.
So take the panel, measure it, and multiply.
A folding panel around 0.35 square metres — roughly the size of an A2 sheet — tops out near 50 watts. If the label says 100W, the label is describing something other than the panel.
This is the only solar specification you can verify with a ruler.
The arithmetic of charging
Say the panel really is 100W. A rated wattage is measured under standard test conditions: full sun, directly overhead, panel at 25°C.
In the real world — angle, haze, heat, dust, a bit of shade from a tree — you get 60 to 75% of that, and only during the few hours around midday.
So a 100W panel delivers something like 100 to 150 watt-hours across a good day.
Now the battery. A small power station is around 300Wh.
300 ÷ 120 is two and a half days of good sun, assuming nothing goes wrong, plus charging losses.
That is not a power source. That's a top-up.
> The panel is real. The number on the box usually isn't.
Which is fine — if you say so
Solar on a portable product is genuinely useful. It keeps a battery from going flat in storage. It adds a few hours of runtime on a camping trip. It makes a light work when someone forgets the cable.
None of that is "solar powered".
The returns start the moment the listing says "solar powered" and the buyer expects to run a fridge off it in the woods. What he gets is a panel that adds a bit each day, and a product that dies on day two of a trip.
Write "solar compatible", not "solar powered". It's the same product and a different return rate.
> Two and a half days of good sun to fill this. On a good day.
What to ask
- "What are the panel's dimensions?" Multiply them out. If the maths doesn't reach the label, stop there.
- "Charging time from empty, in standard sunlight hours?" Not "how long to charge". Hours of sun.
- "What's the battery capacity in watt-hours?" Amp-hours alone tell you nothing without the voltage.
- "Does the manual say 'solar compatible' or 'solar powered'?" The second one is your return rate, in writing.
Straight answers
Are these panels fake?
Usually not. The panel is a panel. The wattage on the box is measured under conditions the product will never see, and sometimes it isn't measured at all.
Can I run a device entirely from solar?
Yes, if the panel is several times larger than the battery. On a product you can carry, it isn't.
Is solar worth paying for at all?
Yes — for keeping a battery topped up and extending runtime in daylight. No — as the reason the product works. It's the same trick as a 4K label on a kids camera.
The honest part
Solar isn't a scam, and the engineers who build these products know exactly what the panels do.
The gap isn't in the technology. It's in one word — "powered" instead of "compatible" — and in a wattage number that was measured somewhere the product will never be.
The panel isn't useless. The claim usually is.
> Guzhen, Guangdong. Every booth had a panel on it.
— Damon, Founder
