[drekipus]

I've seen backpacks with a fold out panel. You could probably imagine 3 panels = 90% charge in 1 week with no load.

But that pales in comparison to a phone getting depleted every second day

[BobaFloutist]

But it's not bad for a phone with WIFI, data, and Bluetooth turned off used for GPS navigation while backpacking pretty indefinitely, which used to not really be an option. So that's pretty cool.