Inspiron 754 - BATTERY issues after only 1 year!?

Hi everyone, 

I bought a Dell laptop (Inspiron 754) in late 2015 in the US. After about a year the computer started acting weird. It would restart all of the sudden, the battery was really weak. I contacted Dell just to find out that the warranty JUST expired! 

Here's some details: 

• The diagnosis went well, everything passed the system "test". Even the battery (so weird)
• When i unplug the charger while connected to the laptop, the computer shuts down.
• When i connect the laptop with the charger,i can start/turn on the computer but it will randomly shut down, sometimes after 2 min and sometimes 4 hours.

The 1 thing that all of the sudden changed, the same day my computer started with this issue is THE charging overview bar in the corner of the screen (task bar/toolbar?) It keeps saying the same %.
It says " 72% avaliable (plugged in charging)". Another thing i tried to take a closer look at was the Dell Power Manager lite, it tells me that the battery health is "excellent".

I am not sure to do here. i guess i have two options. 1) Get someone professionel to look at my laptop OR 2) Buy a new computer , either way it is probably gonna cost a lot of money! It makes no sense that i have problems with this laptop after ONE YEAR! I would expect a little more from computers in 2017! i mean come on....we send people to space and build self-driving cars but most electronics we buy can't last more than 1-3 years. .what ..

Have someone experienced the same? 

Maria