Does charging my phone overnight damage the battery?

No, no damage to your iPhone's battery. Your iphone automatically stops charging when the battery reaches 100%.

I use to charge my iphones overnight since 2009.

As far as your issue is concerned, read this support guide and see if it can help you:

If your iPhone, iPad, or iPod touch won't charge - Apple Support

If the issue still persists, I would contact your most convenient Apple Store or Authorized Service Provider, and have your iPhone (and it's charger) checked : Apple - Find Locations - Location Selector

Regards

Giulio

Ignore the first reply. Every Apple lithium battery device every made has included industry standard SMART lithium battery charging technology. It is not possible to harm the battery by leaving it plugged in because all charging simply stops once the battery reaches capacity.

Howver, all lithium batteries (all batteries really) have a finite life span - they wear out over time and use and will need to be replaced.

But you can safely leave any Apple product plugged in indefinitely without harming the battery. In fact, that applies to every single lithium battery power consumer electronics device that conforms to global industry standards for SMART lithium battery technology.

Yes Alsha, to charge your phone in the night will overcharge your battery.

Let me explain:
When your phone is 100% he 'asks' to put the charger out of him because he is already full. When you overload the phone the change to explode is increasing. Your battery is probably burned.

Can we stop it with the fake b-------? Where did you learn this from? That is completely false.