ok, this has been bugging me for these last few years and i must tell people what no to do with lithium batteries so here i am to help many of those who don't know this. Important: DO NOT EVER DISCHARGE COMPLETELY YOUR PHONE/NOTEBOOK BATTERY. So, as you may notice, it really is as the post says, so i will give an explanation in advance. Back in the days where all the mobile phones started, like nokia, samsung, etc... they used those first batteries Ni based... Same is true for those batteries you find in your apple wireless mouse and toys. These batteries must be discharged completely because they have memory cycles and if you charge them when they're at half they will memorize it and lose capacity. However lithium batteries (you use them in your phones and notebooks today) don't use the same techonology. As you may know, they're lithium batteries, and they have a lifetime of "x" cycles. Why is that? well, for each cycle the battery loses a bit of it capacity percentagen due to the low voltage resulting in damaging cells in the battery. i think cells is the correct word. Q: So, what happens if you discharge it completely? A: Your battery will have very low voltage, and that will result in overheating your battery, consequently damaging a lot more cells than it should in normal usage. So that's why you should never discharge a battery completely, either it's your phone or notebook or whatever device you have with lithium technology in battery. I'm robotics engineering expertise, and work a lot with radio controled devices, so we investigate a lot for battery solutions, that is one of the basics usage for lithium batterys. There are some lithium magnesium batterys being developed that will not suffer from this problem, but they are currently very expensive for commercial use in masses. Tip: Charge your batteries when they are close to 10% at maximum, and if you will not be using your device for a long time, keep it stored with the battery around 50%. having max charge or low charge is bad for the battery. I Hope this information helps everyone... Sorry if my english doens't satisfy you, it's not my native lang.