If you noticed that the notification LED on your Samsung Galaxy S6 at the top left constantly flashes, but you will find no reason for this, then this has probably to do with the following setting or function: energy saving mode
Is the power saving mode activated on your Samsung Galaxy S6, then it starts, if a certain percentage of the battery level is undercut. A value can be specified as a percentage of battery charge. Suppose, you have here a value of 50% indicated, then this means that the red notification LED starts blinking when your battery level falls below 50% and the power saving mode is activated.
The LED lamp of your Samsung Galaxy S6 merely point out that the defined value of the battery charge state is undercut.
If you interfere with the flashing LED notification on your Samsung Galaxy S6, then you can turn this off as follows. Pull down the status bar on your smartphone. Now tap once long on the shortcut "power saving ". It now open the settings of the power saving mode. Then tap at "Start energy saving mode" and then set the value to either "immediately" or "At 5% battery charge".
The notification LED of your Samsung Galaxy S6 will now no longer blink regularly, but only from a battery level of 5%.
You know now, why the LED of your Samsung Galaxy S6 has constantly flashed red.