Power bank/UPS with MOSFETs?!

[MathCa]

Hello,

I bought 8 nice 21700 batteries (4000 mAh 35A) with 4 PD modules (up to 100w each, but more like 60w max for 3/4) to charge a laptop, use a soldering iron, etc. USB C is cool and it made a super fast charger!

Now I want to put everything in one box that will stay connected to mains most of the time. If the electricity goes out for some reason, I want to automatically get power from the batteries instead of the power supply.

I think you should be able to figure it out easily with this:

(unable to get the image here, see the attachment...)

I don't want to use relays, let alone physical switches!

So I guess I have to use MOSFETs? But what type? Alone? I'm totally lost with this...

Thanks!