True..
I understand that the spare battery is probably easier, overall. Nevertheless the conversation surrounded using a solar charger, not if you have access to a spare battery.
Besides, when I have been on camping trips, Disney, golfing GPS software, etc. they will crank through a battery (or a spare too). A solar charger sure is a nice way to keep your battery charged, until the sun goes down. THEN you have the spare battery for events in the evening.
IF you have need of a solar panel, I was providing input to the topic.