You can check the number of "cycles" your Batterys have gone thru by checking in the APP. For my
Air 2S batteries ( for Example) I get an average of 200 cycles before they die WITH GOOD CARE. If your numbers are close its time for them to go ( You Should seriously consider saving the cases and not actually throwing out the battery. IF they are indeed newer and they have stopped working they have probably been subjected to Heat OR the biggest reason for dead Batteries --Someone has stored them for too long fully charged or not charged at all-- (Both BAD ) no matter what they say about self discharging.
The drone needs to be switched on to read the charge count via the app, with dead batteries it would be impossible.
That said and it would be a bit tedious, if the OP processes their txt flight logs with csvview
the side window shows
a) the charge count against "batteryLoopNum" and
b) the battery serial number against "RECOVER:batterySn".
EDIT forgot
c) the battery "production date" against "batteryProductDate"
This would perhaps be the quickest way to process the logs for themself and to get this info for free.
You can read the charge count from the csv down loaded from
DJI Flight Log Viewer | Phantom Help
but there is a 10 logs per 2 days or similar, with that.
Airdata can give counts but I think they are based on the number of times AIrdata has detected the battery being charged.
Alternatively and if it is permissable to say so, if the OP PM's me logs I can run my log book program on them and should be able to get the charge counts with one single program run.
This was one of the things it was
designed 'cobbled together' to do.
If it is not permissible to offer that, then would a mod either tell me and I will delete the offer or would they delete the relevant bits of this post.