Hi there phoenix140,
Thanks for taking the time to reach out to us here in Apple Support Communities! We understand your iPhone battery is draining at night while you're not using it. We're glad you're here, and we can provide some guidance.
It's possible that background activity could be contributing to this behavior. You can turn that off in Settings > General > Background App Refresh. Learn more here:
About the battery usage on your iPhone, iPad, and iPod touch
Also, you can work through the suggestions in the link below to optimize battery life on your iPhone:
Maximizing Battery Life and Lifespan
We hope this information is helpful. Don't hesitate to let us know if you have any more questions.
Take care!