Hello all,
I have a question with regards to some Mavic 2 batteries. One was obtained with a brand new/old stock Mavic 2 pro drone. As I expected, the battery was dead and would not start charging when placed on a charger . The Battery Killer software ( at least in my hands ) was not able to bring it back . 16v was applied while checking with the software and it looks like all the cells are like 0 to .15 volts . Should I waste any time on it? The other thing I’m seeing is with 3 other batteries I have …they all charge and give 4 LED lights . When placed in the drone they all say only enough power to RTH. Within the app under battery …all cells are showing NA instead of voltages . I tried making sure they all had updated firmware using DJI assistant and a PC and refresh firmware and after about 78% completion a message pops up about being unable to update the battery . Any hope for them ?
Thank You in advance,
Brian
Hi @bdschmidt, it looks as though you’re quite new here 
Why not nip over to the Introductions category to say hello and tell us a bit about yourself 
Do they offer enough power to actually take off?
If so, I’d take off, hover (stay low!) for 30 seconds, give it a quick straight up full power blast for a second to make sure there’s some good current draw going on, then land and upload the flight log to Airdata.
If you can then share the Airdata flight logs here it will give us better insight than the DJI GO4 app 
Hello… yes very new here. I’m a veterinarian here in the states. Have acquired a bunch of drones. The batteries in question do not permit taking off. Even after getting off a charger and showing all 4 green LED’s. I got them from another pilot knowing they had this problem.
Hi Brian, welcome from the Heart of Merrye Olde England 
What size vet are you? (Long rubber glove up a cow, or cute little rodent size?)
I’ve got a Mavic 2, but have never had a problem with the batteries. Put one on charge and leave it, it may come around, but may take more than a few hours.
Started as mixed animal in 1982 … in 1991 went 95% small animal with some equine but for the last 20 yrs been strictly small animal.. Practice limited to surgery . I I have accumulated a bunch of Mavic 2 series drones and accessories , mostly from people who crashed them and got out of it. I have repaired them all I including a couple salt water casualties. I revived some batteries recently via the DJI Battery Killer app.I thought maybe that would help me when I bought the 3 that my initial post was about. I got all 3 for 20 US dollars figuring I didn’t have much to lose in trying.
No, if the cell had gone below 2.5v then permanent damage has been done
Most lipo chargers will not charge a cell that has gone below 2.5v
You can take a risk and try to recover them 
You will need a smart charger, and will need to use NiMh or NiCad setting to bring the cell up to 3v then charge with the lipo setting
This is very dangerous as the internal resistance of the cells will be very high and I would only do this outside
Remember your house 
is more important