> I later learned that if you use a portable solar panel battery pack, let the pack charge and then plug in your phone. Don't plug a near-dead solar panel battery pack into your phone and let. There's something about the low-voltage trickle-charge that can be terrible for electronics. I'm not an EE, so I don't understand the details. Perhaps someone else can explain it better.

I'm interested in learning more about this. I recently got a USB solar panel (with no battery). I wonder if it has anything to do with voltage dropping way below USB spec (which I've seen when the panel can't provide the current the device wants, which seems to be pretty easy when the panel is small and/or not in full sun).