My answer to How long should you leave a new smartphone on charge for the first time out of the box?
Answer by Allen He:
They get charged fully from the factory, but who knows how long those batteries have sat on a shelf, then put in a box and sat on a shelf before that phone was sent to you. Charge it fully every night; Lithium ion chemistry prefers partial discharge to deep discharge, so it's best to avoid taking the battery all the way down to zero. Since lithium-ion chemistry does not have a "memory", you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it's ruined". don't let it drop to zero on a regular basis, but it is good to zero out every now and then; stay away from heat.
"Batteries may last longer if not stored fully discharged. As the battery self-discharges over time, its voltage gradually reduces. When depleted below the low-voltage threshold of the protection circuit (2.4 to 2.9 V/cell, depending on chemistry) it will be disabled and cannot be further discharged further until recharged.[clarification needed] It is recommended to store batteries at 40% charge level"
"The need to "condition" NiCd and NiMH batteries has incorrectly leaked into folklore surrounding Li-on batteries. The recommendation for the older technologies is to leave the device plugged in for seven or eight hours, even if fully charged. This may be a confusion of battery software calibration instructions with the "conditioning" instructions for NiCd and NiMH batteries. The software of a typical smart phone, for example, learns how to accurately gauge the battery's life by watching it discharge and leaving it on the charger produces a series of "micro discharges" that the software can watch and learn from."
"They have no memory effect, which means that you do not have to completely discharge them before recharging, as with some other battery chemistries""They start degrading as soon as they leave the factory. They will only last two or three years from the date of manufacture whether you use them or not" "If you completely discharge a lithium-ion battery, it is ruined" -which is why in the wiki link it says it detects where it is and disables itself right!? "Lithium ion chemistry prefers partial discharge to deep discharge, so it's best to avoid taking the battery all the way down to zero. Since lithium-ion chemistry does not have a "memory", you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it's ruined"
but here some tips you may be interested in: