Talking of power banks, there are ones that typically take 4 AAs and provide USB output, to charge phones and the like.

Eg (just first found on amazon.com)

https://www.amazon.com/POW1-EMERGENCY-PORTABLE-BATTERIES-SMARTPHONES/dp/B0168O5GOG

Also a handy battery holder.


Edited by Ren (11/17/19 05:10 PM)