4 batteries, all properly cared for, never left in the extreme cold or heat. About 30 charges. Within 1 week all 4 are swollen and cannot be used. All of them are from production date 2018.9.

There are problems with some batteries from 2018. I had read that somewhere. Contact DJI. They want to have a video and usually refund the batteries.

I have 3 batteries dated  10/2018 and have never in 6 months had a problem. They have all had about 30 odd charges. There definitly seem to be some dogy ones according to this forum before that date. I also do not go below the last bar <20% if I can help it, whether that makes any diff I do not know.

It seems a bit strange that 4 batteries after 12 months decided to swell on the same day/week , were they all stored in the same place ? Could something have caused this , it would seem plausible if one battery swelled a year after purchase but 4 in the same week owned by the same person, not saying it’s your fault but it’s an amazing coincidence you’d have to say .
Maybe their programmed to die after 12 months, I still have old mavic 1 batteries 3 years in perfect condition .

There seems to be a lot of complaints about the MP2 batteries doing this recently even on the Mavic pilots forum there were some complaints about this. Wonder what Dji has to say about this and if they are really replacing these batteries which do not fall under the 6 month warranty.

Hi KerryG, we are so sorry for the troubles, please contact our support team www.dji.com/support with the serial numbers and the picture of the swollen batteries, we will do our best to help.

The advice they gave me for my 3 Mavic 2 Pro batteries were to purchase 3 new batteries ($477.00  aka, 1/3 of the cost of the drone). Makes me wonder what Apple would do if I only got 21 charge cycles out of my iPhone.  In the future, I’ll only purchase 1 battery at a time and not spread my flights around multiple batteries.   

The 3 of my lipos i own are from 9/18 and all 3 are good

You are not alone.

What response did you get from DJI?

Same problem here on 3 batteries after about 20 charge cycles each. Opened a case with DJI. They are aware there may be a problem with a batch of batteries and are working to determine how to address my problem. Batteries are made July and August 2018. It has only been about a week. So far DJI has been responsive and fair about it IMO...