[prmoustache]

I would have hooked the smartphone to a small solar panel. The natural daylight cycle would have made sure that the smartphone kept having charging and discharging cycles.

I doubt the traffic hitting it would be sufficient to drain the battery overnight.

[jboynyc]

That's what the project cited as inspiration does: compost.party

[aziaziazi]

an even smaller https://solar.lowtechmagazine.com/about/the-solar-website/ ?