Considerations When Buying a Portable Battery Charger

My Galaxy Note 4 has a big enough battery that I don't need a portable charger for most trips - even cross country flights. But I always pack one, just in case. I'm still using the several-year-old Anker model  I mention in my book about 1-bag packing, but I notice that the device drains quickly (3-4 days) even without use.

Stumbled across this post today about portable chargers and learned that "charge retention" is actually a thing. Blockquote:

"Bateries will start to lose their charge over a period of time.  The ...metric you should look for is how much of its charge is still held over a 1-year period....A low retention charge rate means your battery will begin to hold less and less energy over time, eventually reducing the amount of power it can give to your phone"

Check out the full (and short) article here.