You cannot over charge the battery.
.. leave it charging all night ...
Many people do with No adverse effects.
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).
From here > http://www.apple.com/batteries/iphone.html
so u mean that it is okay to leave it charging at night
Yes it is safe to leave the iPhone charger connected all night--providing, of course, that you don't take a lightning strike or other electrical circuit anomaly that can actually damage the charger/iPhone during the night
The iOS charging circuits will actually stop the charging process and let the battery discharge a little bit from time to time. Apparently this helps in battery life.
I'm sorry but no, you are all wrong. Let me explain why:
Overheating any battery degrades it. The battery will heat up while being left on charge and this WILL degrade it.
Thus, unless you are leaving your phone in a cool room, it will will heat up overnight and it will slowly damage it. This is most noticeable with laptop batteries. Furthermore, when you overcharge a battery and it keeps discharging a little and recharging you are continually cycling your battery and this DOES degrade your battery. Consider your battery like an oiled machine. That machine is garanteed to run for x amount of cycles, just like a hard drive is or any other thing. Every time you charge your battery you are degrading it, leaving it plugged in so it is continually recharging and decharging is shortening it's life span.
Take the samsung laptops for example. They have built in a function that allows you to stop your battery from charging over 80%, this is because if you leave it plugged in you will degrade your battery. By capping it off at 80% they have a greater time to slowly overcharge and slowly decharge the battery. This means they are using substantially less charging cycles than they would be if it was capped at 100%.
You guys should not be giving out advice. Might I also point out that since I was playing a lot of games while charging my phone and letting it get hot I have noticed a substantial decrease in my battery life even when not playing games anymore. This proves my point.
I'm sorry but no, you are all wrong. ...
We are not.
.... The battery will heat up while being left on charge ...
Once the battery is Fully Charged... the Charging process ceases.
Thus, unless you are leaving your phone in a cool room, it will will heat up overnight and it will slowly damage it. ...
Not true. See above...
...Might I also point out that since I was playing a lot of games while charging my phone and letting it get hot I have noticed a substantial decrease in my battery life even when not playing games anymore. This proves my point.
That proves nothing in regard to leaving the iPhone on charge overnight.
Can You Overcharge Your iPhone Battery?
Apple products use lithium batteries, which are rechargeable, so you can plug your device in and let it charge for multiple uses. The lithium battery uses a trickle charge at the end of charging, so you don't need to worry about overcharging your battery by leaving the phone plugged in once it has reached a full charge.
Lithium batteries like the type in your iPhone are different from nickel batteries. Phones that use nickel batteries are particular about how the phone must be charged, and often the phone must be fully discharged to preserve battery life. Nickel battery phones are also prone to overcharging. With a lithium battery in your iPhone, you don't need to worry about when to plug your phone in to charge, and you can charge the phone at any point without damaging the battery capacity.
Type of Charging
Apple's iPhone uses two types of charging when you plug in your phone. For the first two hours that the phone is plugged in, the battery charges quickly so that it reaches 80 percent of the capacity, and your phone retains that charge if you need to use it immediately. If you leave the phone on the charger, the battery continues to charge at a trickle charge, which uses just a small amount of charge to continue charging up the battery until it is fully charged.
Your phone tells you when it has finished charging, by switching the icon from a charging icon to a charged icon. The charging icon looks similar to a lightening bolt, while the icon that displays when the phone is fully charged looks like a plug. Leaving the phone plugged in once the charged icon is present won't overcharge the battery; the battery stops accepting the charge.
While overcharging is not a concern, you must still be aware that the iPhone battery has a limited lifespan. After 400 charges, the phone holds a charge of only 80 percent of the battery's capacity. A charge is counted as a full discharge and recharge, so partial charges over a period of days can add up to one charge cycle. If your battery is no longer holding a charge, you may need to take the phone to an Apple service provider for a new battery.