My portable USB phone charger’s LCD screen broke today, so i decided to tear it apart and use its 11,200 mAh battery for the server UPS. I also recently built a 3D printer, so I designed a case to hold the components to my budget Ebay UPS.
I decided to refine the schematic the same for the USB UPS, because the boost converter was prone to dropping out early, and therefore the battery was never 100% usable.
The new schematic uses a TP4056 1A Lithium Ion charger with a DW01 Battery protection IC and the MT3608 DC-DC boost converter (capable of boosting a voltage as low as 2V up to 5V with 2A of output current). 3A rectifier diodes and a large capacitor are used to smooth the transition between mains sourced 5V power and battery power.
The whole circuit can be assembled for less than $8. (The high quality super capacitor being the most expensive part)
In testing, the Mini-Sever can now run for just shy of 4 hours off of mains power.