The battery's health dropped to below 30% within 6 months, and the warranty is out.
It was quick and straightforward fix, all thanks to the guide from you guys.
Good battery send by you guys, it was better than 100% health when I first use it. One week down and it dropped to 97%. I'll monitor from here on.
MacBook Air 11" (Mid 2011/Mid 2012) Battery
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air