Battery drained suddenly Nitro 5 AN515-54

Jervi

i have a nitro 5 AN515-54, used for few months, not even one year,

Lately, when its battery gets to 20%; it shows me a message to plug the charger, then shuts down
it doesnt even give me time to plug it, (that's the first case)
Second case; lets say i was working on laptop and battery was 70%, i close it , it goes to sleep 
then few hours i open it back; it gives me a message of a really low battery then it shutdown it self

note: this laptop was working fine before

What should i do, for real :"{

sri369

What changed? Is there any windows process, like search, kicking in when laptop is idle? Are there any USB ports being supplied with power when laptop is off?
I would suggest a battery calibration here...

Charge it to 100%. Leave on charge for an additional 30 mins. Put on some video so laptop does not go to sleep, and let it run all the way down until it goes to auto hibernate/shut down. And then keeping it turned on, connect charger and keep it charging until it goes to 100%.