Why is my phone battery draining so fast?
There are many factors that can cause abnormal battery usage or just the battery draining so fast. First you need to figure out if this is a software or hardware issue. One example of a software issue for this is that there are too many apps running in the background that are resulting in high battery usages. If it's a hardware issue, it's best to get your physical battery checked or replaced as it may be damaged and could be affecting your phone's overall health. If your phone is a little old, remember that batteries get worn out over time, so don't be too worried as that's completely normal for your phone's battery to drain a bit over the years. If you just got your phone, or noticed unusual battery drain then see some of the solutions below!
What can I do right now to solve this issue?
You can go the device maintenance setting or app to check your phone's battery usage, you should find the apps that are using a lot of battery at the top. In most cases, these apps are system programs that need to be running in the background and you shouldn't turn them off. You may find your other apps as you go along the list that have used a lot of battery, generally they're going to be heavier apps (e.g. social media, editing apps etc.) that you can always disable or completely uninstall. Another way around this is by putting apps you don't always use to sleep, this doesn't force stop or disable the app, however the app may not be able to receive updates or send notifications. This is quite affective by itself, but if you don't want to manually do this to each app, you can turn on power saving mode and adjust some of the battery limitations to help save even more power.
What do I do if my battery is damaged?
If you're certain that it's a hardware issue, then you should check your battery. Take apart the phone and try reconnecting the battery to it's place. Your battery could also be damaged because you're using a high brightness level all the time, you're not clearing unused background apps or you may have accidentally got water through the charging port. Most Samsung phones can resist a bit of water splashing about on the phone, but if water has gone directly through the charging port then your battery could be in a terrible condition. Usually you get a little pop-up message on your phone, saying 'Unplug charger, Moisture has been detected. Unplug the charger and make sure both the charger and USB port are dry' if there's something wrong with the charging port/battery. Have a look on eBay, Amazon or other sites where you can find a brand new battery that is compatible with your phone. You need to make sure you're getting an unused battery for the specific model.
Hope this helps, Sanuka!
