iPhone SE battery suddenly draining fast

Epicshamrock wrote: "Yes. Original battery.

it shows Max battery is 81%..."

81% is not healthy and is to be expected in a 5½ year-old battery as a result of age and use. Batteries can degrade gradually and then suddenly. Have the battery replaced and all will be well:

iPhone Battery & Power Repair

About genuine iPhone batteries

(Articles found by searching Apple's Knowledge Base.)

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Epicshamrock ~ Which model of SE is it?...

iPhone SE (1st generation) released in 2016

iPhone SE (2nd generation) released in 2020

iPhone SE (3rd generation) released in 2022

Settings > General > About > Model Name

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Have you updated to iOS 15.4.1?

Epicshamrock ~ Does your iPhone SE 1st generation still have its original 5½ year-old battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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