So I have a Huawei p8 Lite (battery not removable) and my battery lasts for 3 hours normal but at night when I go to sleep, the battery is empty if I'm 100% has been for 3 days so in the morning it only takes 3 hours I have mine Put your phone back to factory settings and have optimized my phone so that it saves power is almost no difference.
Presumably, the reception of the mobile signal at your place of sleep is bad, which then sucks on the battery.
How can I stop this
You can't exhibit there, you have to see where the reception in the apartment is better.
Somewhat expensive.
Store the smartphone for a night near the wireless router.