In regards to the draining of the battery in the iPhone, why can the iPhone run on "reserved" power, (if the % is shown) you can eaily run it down to 1%, but you need to charge it at least 5% just to switch it on..
Because you should never run a Lithium Ion battery down below 10% if you don't have to. You can actually damage it beyond repair if you run it all the way out to 0%. So on the iPhone when it's 1% it's actually around 5%-10% so that the battery won't kill itself. Do some research on Lithium Ion/Polymer batteries. Here, I'll even give you a link http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
So the reason why you have to charge to 5% (as with most Lithium Ion batteries (laptops whatever)) is because of the danger of destroying the battery if it completely discharges.
