DELL Inspiron 7520 not charging the battery

Hi guys i hva DELL inspiron 7520 2 years now and something happend with my charging.
When i put the charging cable the computer is showing ( plugget in, charging ) and like that around few minutes and without touching and doing anything on the computer is showing ( 0% remaining ) and after that again ( plugget in, charging )
Stange is that the computer is not working only on charging cable.
Also strange is when i had a bit battery if a i take out the cable and plug it in again the ac adapter is getting off and the light is shuting down and i have to take out of the electricity and put it again.
But if firs i put the cable in the computer and after that turn on the computer is ok. ( Computer is working but steel not charging)
I thing that can be BIOS driver ?!? but i dont have battery and if i star it and the computer get off then the computer will be totaly fuckt. 

Thanks