My name is Ankit and I work for the Social Media and Community Team at Dell.
As your system is not working on battery then it seems that the battery is toward the end of it's life.
You can also check battery health in Battery Health Meter.
In order to access BHM, high-light the battery option on the right hand side cornoer of the screen.
Once the option is highlighted, right click on the touchpad & you will get an option for Dell Battery meter.
Open Dell Battery Meter & then look for battery health.
If there will be any failure with the battery, it will be displayed in the box.
Normally the expected life of a battery is 1 year. So if the date of purchase is more than 1 year, you can also buy a new Dell Battery for the system.