Basically if I charge my iPhone 7 (or Apple Watch) to 100% using my wall charger or from my MacBook Air's USB the charge lasts MUCH longer than if I charge from my USB power bank. I've tried multiple power banks and have the same results every time. Same goes for my Apple Watch.
A friend suggested that perhaps it never enters the slow/ trickle charge stage of charging and just does "fast" charging all the way to 100%. If this is true, wouldn't that be an iOS or iPhone hardware issue?
Anyone else experience or notice this?
Also, my power bank has a 5W 1A output and a 5W 2.1A output. Both seem to do the same.
UPDATE: Okay, so far I've done a few tests and am noticing that charging using a 5W source works great and the problem happens when I charge using a 10W source.