I was using some 1A charger boards and 500mA USB boost modules before, but with my buddies power bank I ran in some problems. First of all he has an iPhone. He plugged his brand new power bank in and nothing happened. So a bit of googling confirmed our suspicion that apple does something "weird" (meh, who would have known) or at least something of they're own when it comes to charging. Best place to start was this: https://learn.adafruit.com/minty-boost/icharging

So in addition to an LED mod I'll have to work out the resistor stuff. The power bank of my boss had a button that turned on the function for charging an iPhone. Maybe it is enough to shortly put 2V and 2.8V on the D+ and D- rails.

New charger board 0.49 EUR

TP4056 board with DW01 protection for LiPo cell (over and undercharge)

eBay search: (pcm, protection) (lipo, liion, li-ion, lithium) charger

New boost board 1.69 EUR

eBay search: 2A 5V USB boost