The panels are quite rigid. This thing is supposed to be attached to your backpack open to the sun. I believe they have aluminum backing to which the crystalline is glued - so quite impact resistant while folded.

The surface of the crystalline is covered with some epoxy like material, which is quite soft, so it might be scratched, they were protected with a film out of the box, which you need to remove before use. But IMO that's not a big deal as far as you have just isolated scratches slightly diffusing the sunlight.

The panel is positioned as weather proof, so you can leave it under the rain without worrying at least. I believe you can dunk it without a problem, just dry it out well before use.

Regarding the battery life and Li-Ion batt.packs. I'm standardized on AAs. I have plenty of them, I can find plenty later. Most of my electronics is taking AAs. The smartphone can be powered directly from the solar panel if necessary with even dead stock Li-Ion battery. Or from the AA pack powered by any AA or AAA size batteries. After all, the solar panel can charge 12V car batteries too. No 12V charging controller integrated though, so - only manually.