@BackpackATL
This is the USB multimeter that I would recommend as it will give you very detailed information.
Best Power Bank for Thru-Hiking?
Other than Anker, I also prefer RAVPower Solar Power bank. It has 3 output so I can charge 3 device at once up to 5V/6.4a.
Can you report back with how this setup actually worked for you on the trip?