DELL XPS 17 L702x Battery Percentage Not Increasing

I purchased a Dell XPS 17 L702X a year ago (runs on Windows 7 - it's the OS it came with).
It has the 9 cell battery (not sure if that is its entire name) which was the highest upgrade when I purchased the laptop.

The battery percentage is NOT increasing when I charge the machine. It says that it's charging, but the battery life will not show that it increases in percentage.
Today it went from 2% to 1%. A day ago it was on 4%.

I only started noticing this when I found the battery symbol saying "battery low" every time I unplug the laptop's charger.
If I remove my charge, the battery percentage drops. If I plug it back in, the computer charges, but the battery percentage will not increase.

This has been going on for a while now.

Edited to include this sentence : I even charged the laptop for an entire night and when I turned it on, battery life did not increase.

I right-clicked on the battery sign and selected "Dell Battery Meter". I switched the tab to "Battery Health" and it says that the battery is performing normally.

What's wrong and how do I solve the problem?

There is a black sliding switch on the laptop's back that I slided by accident a long time ago. I'm not sure if that does anything.
I tried sliding it again when I discovered this problem, but it does not trigger anything... :/ (it does not fully slide to the end)

 

I have the exact same problem, same computer same config.. I know the problem isnt my AC adapter (tried in a friend computer and it charged the battery)..

Have u ever gotten a solution? Thanks!