I suggest making bigger/higher wattage (60w +) foldable solar panels. Like ones with integrated Anker power banks (10k-20k mah) and USB PD charging capabilities. that would be awesome and I’m sure I (and many others) would buy it. It would be very useful for off-grid applications like on a boat or camping!
I’d be interested in this product if it existed
Solar panels with integrated power banks are tricky. Heat can shorten the life of battery cells, and you’re basically laying the battery in the sun which is generally a no-no. By keeping the solar panel separate from the battery, you can keep the battery in the shade while the solar panel basks in the sun.
An Anker solar panel would be fantastic! I second having that separate from (but connectable to) the battery bank.
If you’re looking for a basic (5V) solar panel, Anker has one available here: https://www.amazon.com/Anker-Charger-PowerPort-iPhone-Galaxy/dp/B012YUJJM8/
These have been tried and failed.
Bigger folding panels cannot be held at an angle to face the sun, they flop around, collapse. So the bigger panels are not folding or fold a little and lock and allow a stand to face the average sun direction, they are more for base camp to not be moved often. On a boat you have a rigid panel which can lock tilted to the latitude.
Folding panels around the 20W are common, they fold into 3 panels and a rock, stick, bag, can prop the middle panel and it stays in place.
As @TechnicallyWell correctly says, batteries age faster in heat, their ideal temperature is body temperature like in a pocket, if you place inside a solar panel which is under the sun they will get too hot and fail faster. The integration also makes it heavier which fights the collapsing problems with folding panels. So you need a sufficiently long cable to be both in shade and away from damp from battery to panel.
The current solar and battery technology means a 20W folding panel weighs 420g, and in good conditions gives 10W, so a few hours of good sun you’re looking at 30Wh/day. A 70Wh Powercore is 290g, or 100Wh 420g, so you can carry 3 days of solar energy for the weight of solar. So it only takes a a modest % of sun not being perfect to make carrying batteries more reliable source than sun.
On volume, a solar panel is the size of about 200Wh, so the weight of a larger backpack has to be factored.
So the watershed point is around a week, beyond this you’re lighter to carry solar than simply more batteries, that’s quite a long trip, and so you do see solar on long off grid trips.
I find I pass a power socket no more than 3 days apart so what I focus on is a fast recharging battery, I can ingest 3 days of gadget power needs in 6 Hours. If I’m expecting to be off grid for longer I carry two Powercore and charge both in parallel.
I own 3 solar panels, I use them for longer camping trips in very rural trips but that’s so rare I find focus on picking the best size and charging speed Powercore is more reliable.
I own Anker 21W panel but can’t find a photo, this is from a similar product I preferred as it has a pouch to hold things to keep together, I store the battery in the pouch but put it in shade, usually behind the propping item.