So the 18650 cells are not serviceable. You could do it if you really want to but it is not designed to unfortunately. But after using it for over a year now I can say it’s the best powerbank I ever had and I think it’s worth the price. If supports a lot of charging standards for phones and other devices which I have rarely seen in other powerbanks. The 100w output and passthrough works flawlessly and also having a variable DC output is nice for diy stuff. Still have 99% health on all cells. I got mine for 180€ and the regular is 240€ I think. So wait for a sale from shargee if you want it 
Edit: about the people saying you can get this on Ali express or do it yourself → I have yet to see one with this features on Ali. Lots of people saying this about this powerbank, so just my few cents.