1 part.
In general, many unnecessary but working batteries have accumulated. From old mostly push-button phones.
I ordered myself power controllers and voltage stabilizers for battery on alish. Links will be below.
I paralleled all the batteries, connected the power controller, remembering that someone on YouTube said that these controllers for large capacities are weak and can be connected in parallel to increase power.
So he did, in parallel, two controllers, connected to the battery, and also connected to the controllers an output voltage regulator with a USB connector, and by itself broke the output with a switch. This was the first stage.
2 part
Then I simply increased the capacity of the bank and put in a digital voltmeter. That's essentially all. The power bank was collected in the early summer of 2017, and is still working today. Batteries at the moment, if you measure the return on capacity, they give out 10-15 percent less than the calculated capacity on the nameplates per acb. Of course, the batteries were old at the time of assembly and I still drove them normally like that. In principle, at the moment, the bank has enough for me to fully charge a 3000 mA smartphone, or to my daughter 2 times to charge it with a 2000 mA battery.
References to used components:
ENTRANCE:
EXIT: