Quote Originally Posted by WallyWest View Post
Heat.

When a lithium ion battery is at very low voltage, it draws a lot of current. Drawing lots of current produces heat.

Charging it past full also generates heat since the energy that can no longer be absorbed by the cells turns to heat.


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Charging circuits built into all phones prevent this. They stop charging when the battery becomes full. Not to mention the protection circuit that is built-into the cell itself.

You can verify this using a USB ammeter to see the current drop to near-zero (phone powered-on) or zero (phone off) when the batteries become full.

It’s no different from a laptop. You can indefinitely leave it plugged in even after the battery has been fully charged.