Try enabling adaptive battery saver in settings. Also check to see if your apps are running in the background and enable them to enter sleep mode if they are. That will help save batety power. You can search for both settings in the settings search box.
Ive been usin adaptive battery and mostly use medium power saving and i still dont know what to do since ive literally tried all battery settings and i have no idea what to do. Also is this a frequent thing since i cant find issues like this anywhere else.
i was thinking since whatsap was in the backround for 13 hrs would that be the problem since ive read if you put whatsapp to sleep when you are not using it you wont get any notifications. Any ideas?