This is just a brief tutorial on how to repair your DJI Spark/Mavic batteries once the dreaded PF flag is enabled by the BMS on the battery, which leads to the battery not being able to charge or be used. My drone might be a couple of years old, but has not flown that much, so I couldn't believe that the batteries were done for. So after doing some research, I found this way to be easiest and quickest method of resetting the PF flag on the BMS, using a CP2112 HID USB to SMBus/I2C adapter circuit board from China and a CCTV power supply with adjustable DC output voltage and the DJI Battery Killer software.

CP2112 HID USB to SMBus/I2C adapter board on E-Bay:
https://www.ebay.com/itm/295631975983...

Dropbox link for DJI Spark wiring diagram and DJI Battery Killer software:
https://www.dropbox.com/sh/wl4ibgn9pq...

All credit to mixeysan for his incredible software.