Thanks for reaching out to the Apple Support Communities! It sounds like you are having issues with the battery usage on your iPhone SE. Check out this article with steps to take for Maximizing Battery Life and Lifespan . Using Low Power Mode is a great step to start with, and this article will allow you to adjust other device settings. Once the adjustments have been made, test the phone through regular usage to see if you notice any changes in the battery performance.
Have a great day!