Battery drain iOS 12.4

My iPhone SE battery was replaced a year ago and it’s been fine until the update. After updating the phone to iOS 12.4 I charged the phone to 100% yesterday and 5 minutes later it was down to 89%. Today I stopped charging at 44% and 5-10 minutes later it’s down to 30% without any use, other than anything going on in the background. It seems to be settled at 30% for now, so it’s immediately after a charge that the problem seems to occur. What’s going on?

Start by going to Settings>Battery>Battery Health and see what it says. Is it below 80%? If so, time for a new battery. If not, look at Settings>Battery to see what apps are using up all the power.

Thanks Idris. I’ve already done that. The battery is at 92% battery capacity. The main app use is 33% listening to audiobooks on Audible (as background activity as it’s sending Bluetooth to a separate speaker), but the strange one is Safari at 31%, because I’ve not used Safari on the phone as I have my iPad with me at home.

I closed all the apps and restarted the phone, which went from 14% at shutdown to 20% after the restart!

l’ve now fully charged the phone and it’s still reading 100%, so I’m hoping the restart did the trick.

If it is the original battery that shipped with your phone maybe it's time to replace it.