Is it bad to let your Iphone charge all night?

Does it ruin your battery strenght?

No not at all.

I have heard rumour that leaving your iPhone on charge can expand the battery, which makes the back come off? I dunno, just maybe charge your phone 1 hour before bed just in case this is true.

The phone stops charging at 100% in order to not harm the battery and then goes through charge/discharge cycles to maintain charge near 100%. That's what the modern technology is all about.fixing bugs that can enhance our future