Hey applexcodeEthan,
We see that you're experiencing issues with your battery life after updating your device to iOS 15, and we'd like to help!
How long has it been since you updated your device to iOS 15? We ask you this because after a major software update, your iPhone battery may be consumed faster than it normally would. After a software update, your device will continue to reindex all your apps and documents silently from the background.
Please take a look at our article here for more information: iPhone Battery and Performance
If you continue to experience issues with your battery life, we recommend that you apply the tips that we offer from our maximizing battery life article, and observe your battery within 48 hours to see if there are any improvements: Maximizing Battery Life and Lifespan
We hope this helps!
Best regards.