Thanks for posting. Apologies that your system is not performing as expected.
How old is your system? Batteries only last about a year to a year and a half depending upon the number of charge/discharge cycles.
Have you run a systems diagnostics? Please run Dell SupportAssist paying particular attention to the Battery Health tests. Make a note of any error messages encountered and post back.
Here is information from the Dell knowledge base you may find helpful:
If you still require assistance and the system is under warranty, you may contact me privately. Be sure to include your personal information (name, address, telephone, email) and your computer's service tag number in your message. Thanks.
If there is no warranty, then you could contact our Out of Warranty team to get a quote for a paid service request.
Thanks btw, I supposed I found the reason why.
It says underpowered adapter, may affect performance in BIOS.
(Also, I just bought the laptop.)