Can you overcharge an iPhone? Is it bad to leave it plugged in after it's fully charged?

Hello ~Yes…you are correct and it cannot be overcharged. Charging will stop automatically when the battery is fully charged and start again if and when required due to ongoing battery usage. Take a look at this excellent user tip written by a most knowledgeable poster here in our forum *Lawrence Finch *

https://discussions.apple.com/docs/DOC-9732

~Katana-San~

Joshua342 wrote:

Thanks. That gave a lot of information, but still didn't answer my question.

My common sense says that the iPhone's computerized charging system is advanced enough to be able to stop charging the battery when it reaches 100% as to not overcharge it, but I've never read that anywhere, so I'm looking for that documentation. Thanks

The computerized charging system is the “U2 Tristar” microcircuit. It is used by every product in the world that uses Lithium batteries, and for the same reason; it can’t overcharge the battery. If you dig through enough documentation you can find somewhere that Apple states it, but the fact that Apple recommends charging overnight (with Optimized Charging enabled) should be sufficient evidence.

Hello ~Take a look here :

About Optimized Battery Charging on your iPhone - Apple ...

Charge the iPhone battery - Apple Support

Batteries - Maximizing Performance - Apple

~Katana-San~

Joshua342 wrote:

Can you overcharge an iPhone? Is it bad to leave it plugged in overnight after it's fully charged?

You can’t overcharge any iOS device; the charger is built into the phone and stops charging at 100%. The absolute best way to slow the decline of battery capacity long term is to enable Optimized Battery Charging (Settings/Battery/Battery Health) and charge the device overnight, every night. The battery will fast charge to 80%, then pause. During the nighttime pause the phone will use mains power instead of battery power, allowing the battery to “rest”, and thus reducing the need to charge the battery quite as often. The phone will resume charging to reach 100% when you are ready to use your phone; it will “learn” your usage pattern. If you enable iCloud Backup (Settings/[your name]/iCloud - iCloud Backup) the phone will back up overnight also, assuring that you can never lose more than the current day’s updates.