My phone have very bad battery life, i just charged my phone to 92% at night and i turn on airplane mode then i went to sleep. When i woke up my battery become 75% at around 9 hrs from night till morning. I am using the exynos version of s9+
You do not know that your phone has bad battery life. You only know that something has run down the battery while you *thought* the phone was sleeping.
You might have malware running on the phone. Or, some application might be consuming power in many ways. If you use the phones own power saving options to shut down apps that might be running in the background, and you go into the applications menu and force stop anything that might be running, and you run something like GlassWire to make sure nothing on the phone is enabling a radio and reaching out anyway, then you MIGHT have a battery problem.
Or you might just have malware running on your phone, transmitting data all night while you think it is off.
If that is all too complicated for you to followw, then you might want to go to the company that sold you the phone and ask them to do a total reset of it. Install no applications for 48 hours and see how the battery holds up. If it still drains by itself, then have the phone repaired/replaced under warranty.
From what you say, it sounds that you charge your phone, then physically unplug it from the charger and let it stand overnight, which is a safe and sometimes reasonable practice. If that's correct, then there is no question of whether the charger is bad. If you are leaving the phone plugged into a charger, that's a whole other question.
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