My laptop is running Arch Linux and I purchased a battery late last year. However, over the last few weeks, my battery life has declined rapidly (from over 2 hours to less than 1 hour). Over the course of two weeks, the "capacity" (according to KDE) has gone from 99% to 43%.
During the time I owned the battery, I replaced my hard drive with a Samsung SSD and enabled the self-encryption feature. A byproduct of the SED is that the system has to go into hibernation instead of sleep when the lid is closed. As a student, I move my laptop around quite a bit, meaning that I tend to open and close my computer fairly frequently. I am wondering if repeated hibernation could have damaged my battery or caused it to drain more quickly.
At this point, the battery should not be going bad, as I bought it less than 6 months ago. I have tried to keep the battery as healthy as possible, as I unplug the computer overnight, and I avoid draining it to the point of shutdown.