How can I find out overall health of my iPhone's battery? I'm buying a used iPhone ,so I want to make sure that the phon's battery is not worn out

Hi

What iPhone are you buying battery will last 2/3 years from new

Try and buy with a warranty if you can ask seller to go to apps store download Battery life it will test your battery condition.

Cheers

Brian 🇬-1F1E7;

The only truly reliable method is to have the battery tested at the Genius Bar or an authorized service provider.

There are apps you can download that provide some information about battery condition.