I've had the same problem with the same or similar model. I replaced the unit with a cheap compatible from Amazon witch cost less than a third of the price of a Dell unit. It's still working, lasting longer than the original.
nothing hurting you just having it plugged into walls all the time now 😉 That's if you aren't moving around and just leaving the laptop in the same place.
My Laptop is like six years old now and the battery might able to last 90mins 🙂
I actually wish they would make higher-end "desktop replacements" without batteries in them at all. Use the space for cooling, storage, etc., and give me a laptop that is lighter and less prone to battery failures. I can live without my laptop's 3hr battery life.