Optimized Battery Charging is not working on my iPhone

You must have the Charge Limit set to 100% in order to use the Optimized Charging option. Also review the information provided in this Support Article when it will not activate. Once the setting is turned on it will take multiple charge cycles to learn your charging behavior and is designed to work in locations where you spend the most time.

About Charge Limit and Optimized Battery Charging on iPhone - Apple Support

ok ok. if you have a new logic bored or new battery not installed by apple you may have this issue. If the device is able to update to ios 18 do it cause you might be able to pair the new battery to the device and not have this issue. If your device isn't compatible with ios 18 there is no way to stop this