Help Serious battery issue.

[Pranjal98]

I have this phone for like 1.5 years and from last few months I am having a serious battery problem.
Problem- My battery drains unexpectedly like sometimes it is at 75% and would start to drop to 1% and the device will switch off.
Mostly this problem happens at around 50% of battery left. I do charge my phone to 100% but still I can only use it till 50%.
What I have tried- Hard reset of phone.
New batteries.
New charger.

Result- My phone is still malfunctioning with no cure. My phone is not rooted and now is out of warranty period. Would be great if any one helps.

Thanks for reading!!