ipod 4th battery indicator issue
I have an ipod touch 4th. I bought it last week from a local store. It was a used one, . I have noticed that when i'm connected to my wifi, downloading and navigating the internet, the battery drain to fast, maybe for 10 minutes, it goes from full to maybe less 20% (i'm assuming because ipod does'nt show the battery in %) . When i turn off my wifi, the battery begin to go up itself. I have searched the internet, and it seems that is a custom problem for ipods. Can anyone show me how to fix this? I'm tired of navigating for 5 minutes, then turning off my wifi, put it so sleep to recover the battery, and then navigating again. Please help!
iPod touch, iOS 6.1.6, 4th