I bought a car charger from Ebay, the connector (at the battery end) wasn't aligned properly and the blades were too thick (when measured with a micrometer and compared to the DJI original) . I never used it because I'd hate the idea of damaging the spring connectors in the battery, especially if the fault manifests itself at 400 feet up and far away
It looks just like that one. The blades on the factory charger are .040 thick. The blades on this car charger are .047. They feel fine slipping into the battery.
The factory charger puts out 17.38 volts and this thing puts out about 17.58.
I believe the charge controller is in the battery itself.