A 50Ah 12V deep cycle car battery would give you at most 600Wh. This RPi's max draw is 12.5W, but an average draw is 6W is probably reasonable. So that battery alone would get you at most `600 watt-hours / 6 watts = 100 hours` of run time (minus some voltage conversion loss and other imperfections). Then just hook up some solar to charge the battery and assume at least 25% loss. ~70W should probably be enough even for a Chicago winter. The RPi might actually idle at around 1W making it even easier.
All that said, there might be a better solution for you if 99% uptime offline personal Wikipedia is your only goal. And IIAB isn't really optimized for high availability I assume. (just get a local copy of Kiwix on your phone+laptop? Or a cheap dedicated tablet for Kiwix would probably cost less than the battery+solar setup)
All that said, there might be a better solution for you if 99% uptime offline personal Wikipedia is your only goal. And IIAB isn't really optimized for high availability I assume. (just get a local copy of Kiwix on your phone+laptop? Or a cheap dedicated tablet for Kiwix would probably cost less than the battery+solar setup)