IPhone SE

iPhone discharges very quickly:

Go to settings, battery, battery health. If it is below 85%, it could be the cause. If it is not, open 3uTools on a windows PC. If the cycle count is around 700 cycles or more, it may be bad even if the health is good.

Note: 3rd party batteries often don’t show any degradation under battery health in settings. Judge from the cycle count in this case.

If a battery replacement won’t help:

Your Tristar charging chip has been damaged. Likely due to using a 3rd party cable/car charger. This chip is on the main motherboard. Make sure to only use MFI (Made for iPhone) certified chargers to avoid any future damage.