Battery drains very fast

First, before we proffer any solution, we need to know the problem.

Before the battery drains, does the phone gets hot in any way?

If your phone gets hot, then maybe the problem is from the phone board.

But if your phone does not gets hot before battery drains, then it is obvious that the fault is from your phone battery.

The solution therefore is for you to change your battery to an original one. The same problem might persist if you don't purchase a good battery, please take note.

I wish you the best.