Laptop battery discharges very quickly after reaching some charge level

Problem description:

The laptop battery discharges very quickly after reaching some charge level. For example, it takes normal time for the battery to discharge from 100% to 75%, but after reaching 75% level it discharges to 0% very quickly. The same failure occurs after recharging the battery again.

Possible cause:

Main battery failure.

Possible troubleshooting steps and repair solution:

This problem is related to the battery failure. Apparently, the battery is getting old and has to be replaced.