Date de publication : 22 avr. 2014 08:03:52
An interesting explanation to this question from ars technica.
Source and complete article: http://arstechnica.com/gadgets/2011/02/ask-ars-what-is-the-best-way-to-use-an-li-ion-battery/
Question: How do I take care of a Lithium Ion battery to prolong its life? Should I charge it frequently or drain it fully before charging it?
Lithium ion batteries are particular about their operating conditions, and there are a lot of small things that can contribute to better quality of life. Li-ion batteries have a reasonably finite lifespan and can hold only a fraction of their original capacity after a few years, but things like operating temperature, how long the battery spends plugged in, how the battery is used, and the charge cycling you asked about can contribute to how long the battery lasts. If Michael Pollan had to sum up ideal Li-ion battery usage, he might say something like, "Use your battery. Not too much. Mostly for small apps."
One of the worst things you can do to a Li-ion battery is to run it out completely all the time. Full discharges put a lot of strain on the battery, and it's much better practice to do shallow discharges to no lower than 20 percent. In a way, this is like people running for exercise— running a few miles a day is fine, but running a marathon every day is generally not sustainable. If your Li-ion powered device is running out of juice on a daily basis, you're decreasing its overall useful lifespan, and should probably work some charging stations into your day or change your devices' settings so that it's not churning through its battery so quickly.
There used to be certain types of batteries whose "memory" of their total charge capacity seemed to get confused by shallow discharges. This is not, and never was, the case with Li-ion batteries. However, if you are using something like a notebook computer that gives you time estimates of how much longer the battery will last, this clock can be confused by shallow charging intervals. Most manufacturers recommend that you do a full discharge of the battery about once a month to help your device calibrate the time gauge.
One common misconception is that Li-ion batteries will only count charge cycles if the battery is drained completely in one session; another is that the battery counts one charge cycle for every instance the device is unplugged and plugged in again. Neither of these is true—Li-ion batteries actually count charge cycles based on a 100 percent discharge even when it's summed over multiple sessions. For example, if you discharge a battery to 50 percent one day, charge it back to 100 percent, then discharge it 50 percent again the next day, that is counted as one "cycle" of the battery. So shallow discharges, in all these regards, are ideal for a Li-ion battery.
On the other end of the spectrum, keeping a Li-ion battery fully charged is not good for it either. This isn't because Li-ion batteries can get "overcharged" (something that people used to worry about in The Olden Days of portable computers), but a Li-ion battery that doesn't get used will suffer from capacity loss, meaning that it won't be able to hold as much charge and power your gadgets for as long. Extremely shallow discharges of only a couple percent are also not enough to keep a Li-ion battery in practice, so if you're going to pull the plug, let the battery run down for a little bit.
Another thing that Li-ion batteries hate is heat. This somewhat less of a problem for cell phones, but a big problem for notebooks. Even using a battery at room temperature for a year can bring its capacity down by as much as 20 percent, and the interior of most computers is a mite cozier than than that. So in a unfortunate twist of fate, laptop batteries usually spend the most time in the worst possible state: plugged in at 100 percent charge, running at an elevated temperature.
Continue reading at: http://arstechnica.com/gadgets/2011/02/ask-ars-what-is-the-best-way-to-use-an-li-ion-battery/