Notebook's Battery is not calibrated. Operates at 0% for an hour
All I can say is re-calibrate the battery. here's how :)
have a way to keep track of time. this can be done with a stopwatch or even a phone (IOS & android both have that function built in, android has an app called stopwatch, IOS 7-9 has it in the clock app).
charge the battery all the way to 100% (simple enough)
take note (on a piece of paper preferably) of how long the computer estimates the battery will last (this will make the later steps easier)
tweak the battery settings so the display will never shut off and set the critical and low battery actions to none
open the stopwatch app (or just get it out if you have a physical one) and start it the moment you unplug the battery being sure to not touch the computer and ignore all battery low and battery critical notifications.
stop the stopwatch as soon as the computer shuts off and record that time.
calculate the difference between the 2 times
do steps 1-7 once more so you have 3 results (a. the computer's estimate, b. test 1, c. test 2)
charge the battery once more and record the computer's new estimate and compare it to the 2 tests, hopefully the computer's estimate will be more accurate then before.
The reason the battery get's un-calibrated is because the is a little microchip in the battery compartment that measures the voltage of the batteries (which are only a set of 18650s by the way).
I don't know if that's entirely correct, but if you need more info, check out this video by "the 8-bit guy" (formerly "the IBook Guy") (https://www.youtube.com/watch?v=iy9Mp1vik-s).
If you need a new battery, you can try rebuilding one. the same guy from the previous video also did a video on this topic (he's doing it to an I-Book G3 Clamshell, but the same technique can be done to almost every other laptop battery) (https://www.youtube.com/watch?v=VrDnTXqoqjM)
hope this helps :)
According to this answer on the Dell community page, you should start expecting battery performance to decrease starting around the 18 month point.
Here is Dell's laptop battery FAQ. They also say that you should expect it around the 18 month point.
In the future, disabling the critical battery action might be a bad decision, as lithium ion batteries actually function better if they don't fully discharge.
Also, here is some information on prolonging battery life.
All this is to say, you should expect some degradation to your battery life. As for the calibration of the battery, this page gives a fairly good explanation of the process. In short, fully discharge and then fully recharge.
Sheer conjecture on my part, with no factual backup and supported only by personal experience: older batteries seem to suck at being calibrated.