Finding a powerbank that doesn't auto shut off with small power draws from a esp/microcontroller is hit or miss, it's not something that is advertised and the threshold can vary wildly. There are workarounds but they can get a little complex if you don't want them to just burn a bunch of excess power.

I've also had bad luck with power banks that can survive outside more than a little while. Not moisture, you can seal that out, but heat and cold seems to kill the batteries.