Here is a little cost savings tip for you.

I was able to secure 2, 180 watt chargers with identical specs to the ones DJI is now selling at a computer recycle center.  I paid 12 dollars each and just move the connectors from the old ones.  They Charge from 10% to 100 in just about 50 minutes.

Could you send us pictures and more information, specs, i will like to follow your steps and create something to charge, thanks in advance!