Hi @longoman ,
Check that the battery is being detected in Device Manager. Here’s a [https://www.cnet.com/how-to/how-to-fix-a-windows-10-laptop-thats-plugged-in-but-isnt-charging/|link] that may help
If it is and the above didn’t resolve the issue, create a [https://www.windowscentral.com/generate-battery-report-windows-10|Win 10 battery report] and check the status of the battery.
If the battery is faulty and needs to be replaced, here’s the [https://topics-cdn.dell.com/pdf/inspiron-15-5578-2-in-1-laptop_service-manual_en-us.pdf|service manual] for the laptop, taken from this [https://www.dell.com/support/home/en-au/product-support/product/inspiron-15-5578-2-in-1-laptop/docs|webpage].
Go to p.14 to view the necessary pre-requisite steps and then the procedure to remove / replace the battery. Usually batteries have model numbers printed on them. If you search online using the model number of the battery you should get results for suppliers of the part.