What happens if you keep on charging your iphone for too long?

I have iPhone SE

Added (1). If I charge it for 14 hours…

Once the battery reaches 100% charge, the phone automatically shuts down charging and the battery starts draining.

It drains the battery

In one session? I doubt it will have much if any effect at all. The best charging practice is to let your battery get as low as possible and then charge to 100%. There's a free app called Power Clean that has charging features(trickle charge, etc) and also show your battery health.

Nothing. IPhones have mechanisms in place to prevent overcharging.

Stops at 100 percent but if plugged in always it could wear on phone non-rechargeable battery life

It's not good for a lithium ion battery to let your battery get as low as possible and then charge to 100%. If you let your battery get too low, it will be damaged slightly. Try not to let it go below about 25% and try really hard not to ever let it drain completely. Also, it's better not to charge it to 100%. Stopping at 90-something percent is a better practice, since damage is likely to occur when the battery is completely charged. (I realize that's impractical for most people. Plugging your phone in at night and letting it charge all night is not terribly harmful.) Granted, you'll get fewer minutes of talk time from your phone if you don't charge it completely, but your battery will have a longer life in terms of how long it provides useable service before it needs to be replaced.

Battery drains faster

Battery gets heated and messed up

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Ruins battery life. Its best to shut down 1 hour per week and not over charge