My s4 recenty seemed to restart yesterday. I said " no problem". But I was wrong. I let it to charge for 7 hours and it was only 70%. And this is not all. After 20 minutes, the battery was 43% and the phone turned off. I opened it and the battery was 0% and turned off again . I checked the battery and it was normal...it didn`t look bigger so I opened the phone again and it was 43% again... It`s draining faster than normally so...I really need some tips.