I gave it a go a few years ago. It seemed like all the solar battery chargers I could find were for lead acid. So I got one of those batteries you'd find in a UPS and a panel. Initially it was working alright but the battery very quickly degraded to the point the pi would run out of power every night. Realistically just a waste of resources unless you are doing it purely for fun.
Isn't fun the main point of artisanal technology projects like this? Did you really expect to save money by using solar at such a micro scale where you get precisely none of the economics of scale? Besides, lowtechmagazine also goes offline from time to time: https://solar.lowtechmagazine.com/about.html#often
It seems like your battery perhaps wasn't big enough, or you haven't taken enough measures to engineer your system. This certainly isn't plug-and-play without getting an enormously oversized solar and battery setup.
