PC won't shut off unless plugged into a powersource

I have a Dell Inspiron 5759 that keeps restarting if you try to shut it down on battery.

It will shut off if plugged into a power source, but as soon as it is unplugged it restarts.

I believe I have tried all of the suggestions on the message boards I could find, including updating the drivers and BIOS through the Manufacturer’s Website.

If you have any ideas, I would gladly listen. I hate to get rid of this perfectly good computer. Dell just wanted to sell me a new one instead of trying to help.