You can set the output to 4.35V, then add a current limiting resistor, 0.5Ω~1.0Ω1W, the maximum charging current is 1A, and the charging time is difficult to calculate and to be estimated because it is not a constant current load. It takes about 5 hours to fully charge and it can be fully charged in 10 hours. The voltage is 4.35V. If you charge in a limited time, you can set 4.45V and remove it after 5 hours of charging. Do not continue charging for a long time.
Some strong light mobile phones can charge 18650 at 4.65V~4.85V, and they are still in use, but the battery life is unknown. Some portable walkie talkies are also charged at 5V, and the battery voltage is 4.85V. Although the voltage exceeds a lot, the power does not necessarily increase much.
If you use a 5V power adapter and connect itthen to the adjustable voltage regulator board, the input and output voltage drop should not be enough. To get an output of 4.25V, the input must be greater than. 1V, which requires 6V AC adapter or battery power. You can use 5V to directly connect a 0.5Ω 1W current limiting resistor to charge a single battery. It can be fully charged in two hours, and 21 batteries can be charged alternately.