There are few reasons for this problem.
1) If you are using the device for a long time, the capacity of the battery may have fallen. Usually this is due to charging the phone too often. Also, according to a research, if you charge the phone up to 80 percent, it will suffer very little damage. I would recommend the Accu Battery application to do these checks and tests. When you download the application you can learn battery health as a percentage.
2) The battery may be short-cycle due to excessive processor usage. If the applications that you use are tiring of your phone, they will consume a lot of charge.Also applications such as facebook in the background cause very high charge consumption.
3) If your phone is at a new level and there are no problems at the top, distress may be a virus. The best way to clear the virus is return to factory settings of the phone. Before you reset it, you can do a scan with the avast and malwarebytes programs and get rid of it without resetting.
4) Although it seems rare, the problem may be caused by your android version. Check for updates. If you started to experience this problem after a new update, try to return to the old version.
I hope your problem is solved.
It depends on the type of activities you engage in with your mobile phone and the battery capacity.
There are sometimes we run numerous tasks on a single phone which enables us to minimize more than 2 applications and this drains down the phone battery.
Also, there are some activities that we engage in which enables the phone to heat up and this affects the battery life.
The phone battery can also be easily drained whenever you engage in charging and using your phone simultaneously. This really affects the battery life and makes it reduce it's duration.
Let's try as much as possible to avoid activities that can affect the battery life to enable the phone last longer.
Thanks for reading and I hope this helps.