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They're definitely a real product. Popular with campers; someone was selling a backpack with integrated solar panels.

Achieving those numbers does require the panel to be aimed at the sun and the sky to be clear, though; cloud or off-axis aiming drops the efficiency dramatically.

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They aren't worth the money or the weight. You are almost always better off bringing the equivalent in spare rechargeable batteries. I've written an article on it:

https://www.reddit.com/r/flashlight/wiki/solarcharging

4.9oz or .139 kg: https://www.amazon.com/LightSaver-Roll-up-Solar-Charger-Batt...

Works well on sunny days if you adjust it to point directly at the sun, and it charges in 6-8 hours.

While that is extremely light, it still weighs as much as 3x18650. Breakeven point would be after four days of perfect 100% utilization of solar power.

Is it practical even then? I'd gladly carry a few extra batteries so that I don't have to sit around camp and keep adjusting the panel every hour.

$100 isn't practical for most people either.

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