This discussion keeps popping up. So here is some real world answers as my job has me out in the field on remote locations daily. Power Inverters are the absolute worse thing you can buy to charge your drone batteries. If you do not leave your car running, you risk killing your Car Battery. An inverter as all of you know changes the DC in the Car too AC. The Electric Charging of a Drone Battery is taking AC Current and Converting it to DC current. So with the Inverter, You are going from DC to AC then from AC to DC. So completely inefficient. A better solution a Much better solution is to get a Battery Field Charger like the Energen Drone Max. You charge it over night and it will charge 4 Phantom Batteries at the Same time and doing that 3 times, or it will charge one Phantom Battery 8 times, you can also charge your controller, tablet or phone. You dont run the risk of killing your car battery or frying you Phantom Battery with a voltage surge off your inverter, Sure it cost way more than a cheap inverter, but didn't just spend $1800plus on your Drone?
https://www.amazon.com/Energen-Dron...pID=41jKiaD8k4L&preST=_SX342_QL70_&dpSrc=srch
https://www.amazon.com/Energen-Dron...pID=41jKiaD8k4L&preST=_SX342_QL70_&dpSrc=srch