UPDATE: I Have now used this for three weekends away to charge the Mavic Air’s batteries when away in my Motorhome. It works very well, charges 2 batteries from empty well within an hour, and their behavior (eg flight time) matches that when the stock mains charger is used.
So, I wanted to be able to charge the batteries for my new DJI Mavic Air while away in my motorhome and also from a 12V battery pack when off grid.
DJI’s own car charger was initially hard to get hold of, and cost 50quid, additionally it appeared to only charge one battery at a time and it was not clear whether it would work with the standard quad charging dock. I had also heard rumours that it would not work unless the vehicle’s engine was running!
Enter the Chinese with 2 offerings for 10 and 12 quid delivered with the latter charging 2 batteries at the same time. I ordered mine off eBay and received them about 3 weeks later. These are sold by several sellers, mine came from seller ‘yuthlichi99_uk’ and delivered by yodel with a tracking number. NB. These are now also available from Amazon here and here
I have only had a chance thus far for one charge cycle, but was able to charge 2 batteries and the controller in the van where the input battery voltage was 12.6V.
The connectors fit well and have a pretty pointless cover on them. The DJI batteries themselves will stop drawing power once they are fully charged. I bought both the double output and the single output, I intend to convert the single output to a solar charger using a portable 10W panel. Will take all day to charge, I suspect!
I did try to use them with the stock DJI quad charging dock, but the connector is too fat. It could likely be shaved down to make it fit.
I have a lithium ion car jump start pack which has a 12V accessory socket. I tried this with a pair of Mavic Air batteries and it worked just fine. My pack came from Amazon here.
Disclaimer: as with everything cheap that comes from China, do not use without keeping an eye or rather nose on it!