Battery Capacity, dropping fast + unstable

[QE2]

Had the battery switched out under Apple Care, when it died completely about 11-12 months ago.

Almost immediately after the replacement was installed (days after), the battery fell from it's 100% capacity reading, down to 95-96%. I contacted Apple to mention this, and they made a case ref, and said to monitor the situation.

Well it's been shifting unstably around the 90s, but has just recently nose dived into the 80s, while left in sleep mode for a day or so.

I did a total system rebuild awhile back, so would have to delve into my backup for the full log. However I've attached an image showing the recent drop, and would like to know why I've never had a battery thats operated at 100%?

 

[nickandre21]

i think you should try using it on battery power rather then keep it on charge most of the times and see if it goes down more further take it back to apple. Cause 37 charge cycles in 11-12 months seems low, let the juices keep flowing atleast let it run on battery once a week if not 3 times a month.