…or we just pick up the original purpose again.
I own the X4 OpenPPG, batch 3. built my own battery with 18650 cells, and I am located near Hannover/Germany (going often to Austria for free-flying).
The battery is a 13S20P setup.
I shared the build process with lot’s of photos here: 13S15P Battery Pack Build
and the upgrade later with a new aluminum case here: Follow up post: Case for 13S20P Li-Ion Battery Pack
Let me know if you want to know more.
I did not have any plans of selling my unit. But honestly, I am not flying it very often, so I guess if the price is right, everything is for sale 
What would you be willing to offer?
Feel Free to DM me.