18650 protection board limitations Answered

Hi There

I've been lucky enough to stumble across a large quantity of brand new 2600 - 3300mAh 18650 cells and I'm wanting to find some DYI projects to put them to good use. 200W flash light, electric Go Kart or a basic power wall comes to mind. However first things first Ill be needing to build them into a packs and connect them to protection modules but Ive got a few questions:

Protection modules come in so many flavors. 2S - 3S - 4S - 5S - 5S5P and bigger.. Do you choose the module based on how many cells you have in total and then just use a DC-DC converter to get the required voltage? Or do you try to get as close as possible to the voltage needed in series first and then find a module that suits? What is the most versatile configuration?

Can I connect 5S5P pack to a 5S module? Can I keep increasing in parallel with no consequences? Like for example can I connect a 5S15P pack to a 5S model and expect the module to be able to balance and charge the pack back up? I understand there are Amp draw limits to watch out for too. The module I was looking at is below.

https://www.ebay.com/itm/191978019369

Also this module requires a charge voltage of 21 volts at no more than 5Amps. Where would I be able to find a charger like that? A laptop power brick maybe?

Any guidance would be great as I'm keen to learn as much as possible!

Thanks in advanced!