Lithium-ion battery tips to maximize the lifespan
The last few days I did some research about Lithium-ion batteries that are used by cellphones, laptops and many other electronic devices. Whenever I get a new device I try to take care of the battery as much as possible. Well, now I figured out I got some things wrong. Heck, most of the people are wrong actually.
There seems to be a lot of confusion about lithium batteries in general. I will try to clear some common misconceptions by writing this article. I have gathered information from several websites, asked some experienced people and will make a compilation about what I learned.
The first charge of your battery
The big first misconception that you might have heard is that you should charge the battery for about 8 hours for the initial charge. This is because of the 'memory effect' in the "old" nickel based batteries. Li-ion batteries are memory-free and don't require overcharging or full discharges. If you battery says it is charged at 100%, it is charged at 100%.
Avoid full discharges, charge more frequently
Because Li-ion batteries do not have the memory effect mentioned above, it does not matter when you recharge your battery. This is the big user friendly advantage of these batteries. In fact, it is even better to avoid frequent deep-discharges.
If the battery cell's voltages would drop below 2.5 volts the internal safety circuit opens and the battery appears dead. Most devices switch off their power before this is possible, but if your battery is discharged and is not used for a few months this could happen because of it's self-discharge rate. It is suggested that you should store batteries at 40% discharge in cool temperatures.
Batteries start losing health through charge cycles and by age. If you would run it down to 50% then charge it, this would count as half a cycle. So charging the battery more often is in fact better because you go through cycles at a slower pace.
However, it is recommended to do a full cycle once a month because continuous partial discharges create a condition called digital memory, decreasing the accuracy of the device's power gauge. So let the battery discharge to the cut-off point and then recharge to recalibrate the gauge.
No need to remove the battery when charged
Some people say you should remove the battery when the power cord is connected. There are smart circuits monitoring your battery that stops the charging when the battery is fully charged. So leaving the battery in with the power cord connected has no detrimental effect on the health of the battery.
However, long time exposure to temperatures higher than 40 degrees Celsius permanently reduces its total charge capacity by noticeable chunks per year.
Conclusion
Charge your batteries when you want, there's no percentage to tell you when to start charging. Charge often and avoid frequent deep-discharges so you go through cycles at a slower pace. Leave your power cord connected as you want, there is no danger. Let it go through at least one charge cycle per month to recalibrate the battery.
http://www.apple.com/batteries
http://en.wikipedia.org/wiki/Lithium-ion_battery
http://batteryuniversity.com