DIY Anker PowerHouse

I have some laptop pulled 18650 laying around and when the Anker PowerHouse (or any other powerbank with ac outlet) came out I really liked the idea.

I searched the internet but couldn’t find any buildlog or similar for this kind of project. Since I don’t have much knowledge about electronic parts I don’t know where to start.
I’d like to have at least one 230 volts ac and 2 usb outlets built in.
What kind of electric circuit do I need to convert 3.7V DC to 230V AC? Is this even possible or do I have to build multiple battery packs that i use in serial?

I really like to hear your thoughts.

There are DC to AC converters for lead batteries
Those work OK with 3S battery packs when it discharges it stops at 10.5V which is for Lithium batteries 70-80% empty and good for the cells life
If the converter has also thin leads to battery for voltage reading you can adjust the voltage it monitors with an OP amplifier
or check the board if you find the sense input reading the battery voltage and modify it to reduce the cutoff to 9V

If you build such a battery pack you need to select the capacities for the pack so that each parallel cells have the same capacity as the ones in series

For laptop pulls dont drain more than 3A from them, so you need more parallel for more power

You can use lithium with them, but you need a balance charger to charge the battery pack

Yeah that could work. I’d need a BMS to balance the cells.
I have 18 cells with similar tested capacity with the same manifacturing date. I could use these in 6p3s config.