Hello,   The batteries have an end of life date based on when they were made.  They will all have to be replaced. If you search this forum you will find others too how have bought batteries thinking they were new when they were actually used.   They start alerting 90 days before they expire.   Wish I had better news for you.  Hopefully, you can get them replaced by the vendor you got them from.   I believe there is an actual date on the assembly.   Regards,    Don
I recently had to upgrade my PS6210's and all of them had critical battery messages. I ordered 6 new batteries and got them replaced. Apparently they were not all seated well enough and some did not charge. Eventually I managed to get all 6 charged and all came up with a status of Good. We have been working on rebuilding our datastores and VM's and now 3 weeks later every single battery is coming up with a status of: end of life critical! Is it likely that we received 6 bad batteries, or is it possible that there might be another explanation? The batteries were initially coming up with similar errors, but once they charged for 24 hours they showed Good. 
EQUALLOGIC PS6210 Controller Batteries