Since we can't control the discharging condition and rate most of the time, and today's design often stick the battery to a heat source. Since I am no expert i

Since we can't control the discharging condition and rate most of the time, and today's design often stick the battery to a heat source. Since I am no expert in chemistry, I rather point to an article here: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li... Basically, the capacity degrades over charge/discharge cycles. The reason is pretty simple to explain, because you can't really operate the batteries in perfect condition, it always get worse while discharging and charging it. The other conclusion of that report points to the fact that depth of discharge is related too. So instead of using it from 100% to 0% (actually 0% doesn't mean nothing left, it just means the phone can't operate on that voltage), recharge as soon as you have a plug.