Thanks for the ref, and only to clarify... There is no evidence that letting the battery die even once does anything toward promoting good battery health or extending its ability to take a "full charge". I will also say that doing so even a few times will have little perceptive negative impact, but the fact is, a Lithium Ion (or Ion Polymer) battery has only so many cycles available to it before the battery has lost its capacity to a certain percentage. So, unless you're using the battery for reasons OTHER than to simply discharge it, you're OK. Now, if you are using the battery simply to discharge it and then fully recharge it ("cycling"), believing it will somehow magically extend the battery's ability to hold a certain level of current, you are wasting your time, the money spent on the electricity, the lifespan of your phone AND the battery's effective lifespan.
Originally Posted by Snow02
There is however plenty of evidence in studies done in many laboratories and under strict testing conditions that prove allowing the battery to discharge below certain thresholds, or charging beyond certain thresholds will at the very least impact the battery's life by reducing its capacity by stressing the battery.
Truth is, all batteries have a finite number of charging “cycles”, simply due to their design. However, Lithium-Ion batteries also have a lifespan dictated by when they were manufactured. In fact, Lithium-Ion batteries start dying the moment they leave the assembly line! Lithium-Ion batteries left on a shelf at the manufacturer will actually be able to hold less charge as time goes on, even if not being used or charged, and after 3 years will effectively be able to hold only about half of their original rated charge, so even if you DON'T cycle the battery, it will eventually die. For this reason, manufacturers try to move their inventory of Lithium-Ion batteries quickly to prevent them from degrading over time while not in the consumer's hands.
I still do stand by the assumption that Motorola is well aware of the battery's characteristics and has put more conservative thresholds in place that show the battery at 100% charge when its voltage has reached possibly 4.2V or slightly less (commonly considered a safe "full charge" voltage), to further extend its lifespan, and showing 0% when the battery is at no less than 3V or slightly higher (again commonly considered a safe "minimum charge"), and also to extend its lifespan. In other words, Motorola has put in place "Buffer Stops" to protect you from yourself, or to prevent you from doing damage to the battery - no matter how small, so although doing the "cycling" or "deep discharge" while in the phone MAY not damage the battery perceptibly, there is no evidential benefit whatsoever to doing it, so why would anyone?
In fact, to charge beyond 4.3V for prolonged periods of time can result in both permanent damage to the battery effectively reducing its capacity to take a charge, and if allowed to continue can ultimately cause the battery to explode. Just that information alone and the risk of liability I am sure has Motorola taking a very conservative position with regard to its charging protocol and engineering. Furthermore, storing a LI or LIPO battery for extended periods of time with a full charge can also reduce it's lifespan, and again not so much for liability but for battery claims, I suspect Motorola has taken the conservative position as well.
As for discharging, anything below 2.7V can cause the battery to go into a state of "Sleep mode" rendering it completely unresponsive to a standard charger, and although it may be able to be "revived" with an expensive battery rejuvenation device manufactured by Cadex for example, it may ultimately be beyond recover and completely destroyed. Further, if a battery remains below 1.5V for even beyond a week, it can develop "shunts" internally which would effectively short the battery from inside. If a battery in this state were attempted to be recharged, it could result in becoming excessively hot and unstable. So not to be repetitive, but Motorola has certainly protected the phones' batteries from such damage and potential resultant harm.
Ref: Battery University - Charging Lithium-Ion Batteries
and: Battery University - How to prolong Lithium-based batteries
Here's an excerpt from Wikipedia as well (which ironically cites the link above):
Prolonging battery pack life
Avoid deep discharge and instead charge more often between uses, the smaller the depth of discharge, the longer the battery will last
Avoid storing the battery in full discharged state. As the battery will self-discharge overtime, its voltage will gradually lower, and when it is depleted
below the low-voltage threshold (2.4 to 2.9 V/cell, depending on chemistry) it cannot be charged anymore because the protection circuit (a type of electronic fuse) disables it.
Lithium-ion batteries should be kept cool; they may be stored in a refrigerator.
The rate of degradation of Lithium-ion batteries is strongly temperature-dependent; they degrade much faster if stored or used at higher temperatures.
Here's another reference (maybe not a popular one here, but still...),:
"You can also recharge a lithium-ion polymer battery whenever convenient, without the full charge or discharge cycle necessary to keep nickel-based batteries at peak performance. (Over time, crystals build up in nickel-based batteries and prevent you from charging them completely, necessitating an inconvenient full discharge.) "
And even with all this info and more available, there are still people out there who will profess to be experts and give advice that is completely contradictory to the lab tests. For instance: