My iphone battery percentage is misleading? How do I fix this?

[iMore Question]

My iphone will be charged to a 100% and then with about an hour or so of usage will drop to about 70% ish, and all of a sudden it would turn of with an Icon saying I need to charge the battery. And then i'll charge it, it'll turn back on and the battery percentage would be at 80%. Now this doesn't just happen at 70% but it fluctuates to any random percentage of charge. Now you'll say just replace the battery and it'll be fine but I already replaced the battery and i'm still having the same issues. What is wrong with it and what do I need to do?? Can someone please help me.

 

[njlx2016]

Without knowing which iPhone you are using and how old it is, my suggestion would be to contact Apple or bring it into the Apple Store.