Passtrough Power Bank Designs

This is a collection of thoughts and links for power bank designs
Modifying USB Battery (Portable Power Banks) to charge while charging (to use as ups)
Wiring of a passthrough charging circuit

a solution for 1-cell UPS offered by Maxim
MP2690:All-in-One, 2.5A Battery Charger w/ 2.1A Boost Current
Can i connect Power source in parallel with power bank output to keep Uninterruptible power supply)

Proper usage of Lithium charger based on TP4056
How can I use two TP4056 with two li-ion batteries, but single load?
ATtiny85 based Lithium-Ion Battery Power Bank DIY Power Bank Motherboard Circuit
DC-DC Boost Buck Adjustable Step Up Step Down Automatic Converter XL6009
1.8V-5V to 3.3V DC Step Down Step Up Converter 100mA
0.9-5V To 5V DC-DC Step Up Power Module Boost Converter 480mA