Inspiron 15 3000 goes off when it's unplugged

Did you get it new or used? If used--the battery is dead. Ignore the 87% evaluation. Either buy a dell replacement battery or remove the battery and use the adapter alone. Try that to see if it works. 

If it is a brand new computer from Dell, contact Support for warranty service. When posting your model name, use the complete name and number. There are many Inspiron 15 3000 models. If yours is the original 3000, there are no Dell batteries available from Dell. Try Parts People.

Thank you for your message. Please try the steps suggested by Mary G.

If the system is under warranty, I can help you with the warranty claim.

For my reference, please click on the message tab next to your avatar– click “New Message” & search for my Dell username (Sreejith R) & send a private message with the service tag, registered name & email address.         

How to locate the service tag