. It can only run three hours on battery power when in fact the design spec for its 4-cell battery is between four and five hours of mobile usage.
I am of the opinion that battery runtime figures stated by manufacturers are rather optimistic. Those tests are usually done with a bare Windows install, and as such have lower CPU and RAM usage compared to real-world usage.
With background tasks like a virus scanner or even Windows Update, coupled with software that can utilize all processor cores (i.e. Chrome browser), battery life is expectedly shorter than what the manufacturer claims.
Unless, of course, the issue is reduction of the battery's capacity. Lenovo's Power Manager software can show the battery's designed capacity and its actual capacity (as of the last full charge).