I have been running mine continuous on a battery bank I made, its 18650’s 3s2p configuration meaning 12v at 5Ah total power or 60 watt hours…its powered by a cheap charge controller with 2 USB ports and a 40 watt flex solar panel. other battery packs I tested charge by just Micro-USB did not charge enough during the day…I think the 27 watt would work as my 40watt panel is charge by noon even in shade.
https://www.amazon.com/gp/product/B06XWTKYDC/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B07M9BFZBY/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1