Battery replacement, bad readings?

Hey everyone,

Just a couple of days ago I replaced the old battery of my XPS 9560 with a new one. I charged it up normally and ever since I have been noticing some issues I hope you can help me figure out.

Yesterday, I was using the laptop as usual and before leaving for lunch I put it into Sleep mode (this was around 1 pm, the battery had ~55%-60% of power remaining if I remember correctly). I didn't use the laptop at all until around 5:30 pm. When I came back to it and pressed a key on the keyboard, the laptop turned on and then immediately entered into hibernation mode. When I tried turning it on again, the battery indicator turned solid amber (which means the battery was completely depleted if I'm right) so I charged it up again. Hours later, I booted into the BIOS and checked the battery health status. BIOS says it's excellent. Once the battery was fully charged again, I used the laptop for a bit and it had ~90% of charge left when I turned it off.

Today, as a test, I turned on the laptop and battery was still around 90%-85% (I don't really remember, I know it had roughly the same amount of charge left). I stopped using the computer for ~2 / ~2 1/2 hours. When I turned it on again, it had (according to Windows at least) ~60%-55% battery left... and then it suddenly dropped to 5% which made Windows enter into Battery Saver mode.

I booted into the BIOS and again it said battery health is excellent. Ran all diagnostic tests and no problems were found. I just installed the Dell Power Management app and just changed the battery settings to "Primarily AC Use" to hopefully help battery life.

Anything else I should try / may have overlooked? Bad battery calibration maybe? Any other possible issue?

Thanks in advance for your help.