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Just heard that if Li-ion battery is kept at 40~60% charged, its lifetime will be longer. Is this correct? If so, are there some applications, respectively for Windows XP, Windows 7 and Ubuntu, that can control charging and discharging of the battery so it is always within some range like 40~60%?

Thanks and regards!

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That is for storage of batteries. If you're trying to keep it that way when you're using the laptop, you're not storing the battery. So what you're trying to do make no sense. – David Schwartz Mar 15 '12 at 10:20
up vote 5 down vote accepted

40%~60% condition is recommended when you're not going to use your battery for a long time. If you bring your battery to a charge level of around 40%~60% and store it in a cold place, this will extend its life. I suggest storing it in refrigerator. It’s a good place but don't set the temperature too low, and remember not to fully discharge it to avoid electrolytic spillage. Here are some laptop battery tips that may be useful.

The biggest factor in battery life, especially for laptops, is the temperature at which the battery is kept. Another important thing is, storage or using at 100% charge is harmful. I think you should read this crucial article about "Lithium-ion battery preservation" for further info.

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Good points. I think your first link might have some older, outdated information. It refers to the "memory effect" and then says that Li-ion batteries are the exception. True, but that suggests that the article was written before Li-ion batteries were the norm in laptops and cell phones. Some good tips, but please ensure that it applies to your hardware before following! – outsideblasts Nov 18 '09 at 8:53
The second paragraph is the most important part of my answer which applies to present-day's systems. The first link is older; true, but I thought it's got useful information and included it in my answer. – Mehper C. Palavuzlar Nov 18 '09 at 13:29

You are right. In fact in EV cars(tesla etc) specialized firmware maintains charge between 30 & 80%. The battery never actually chrages upto 100%. It is also liquid cooled. This is to increase the life time of the battery. So two things are actually important: Heat and 100% charge. Both are harmful. You should not use it always at 100% charge, which is what will happen if you are always plugged in to AC adapter.

There is built in app for Samsung laptops & netbooks called Battery Life Extender which will limit charging to 80% in order to extend battery life. Try and find out if it is available for your laptop.

If you can't find an app, the only option is what I do in my ASUS G53, manually unplug it when it charged to 80-85% and replug when it is 20-25%. BatteryBar is Taskbar widget with modifiable settings for reminding you of ideal range.

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"which is what will happen if you are always plugged in to AC adapter", do you say it is harmful to always keep laptops supplied with power from wall panel? – Tim Mar 15 '12 at 10:50

I think that the 40-60% is for storage when not in use. Otherwise Li-ion batteries' lifetime are limited by the number of full discharge/recharge cycles (if I remember correctly.)

Battery university is a great resource and tutorial for battery issues.

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Unlike other kinds of batteries, there is no ‘memory effect’ with Li-ion systems. Li-ion batteries fail over time regardless of anything else. According to Wikipedia: “At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius, will irreversibly lose approximately 20% capacity per year." – Mehper C. Palavuzlar Nov 18 '09 at 8:30

I always worked with my laptop online, with battery on it. (4 years old now) I used the battery only in airports and in some rare occasions. The battery still have the full capacity, it provide energy for 2 and a half hours, like new.. The number of cycles affects, not keeping on the laptop when online. And if you don't discharge it completely, the effect of aging is even lower. It's true that the battery lose capacity over time even if is not really used, only kept on laptop, but this is really not a concern, because the rate is maybe 5% per year. Temperature is the real problem, but as long as is no more than 26-27 degrees, it's still okay.

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+1, but you could extend it further if you take the battery out of the computer when it is plugged in and not in use. The battery on my laptop reports that it still has some 85% of its original full charge capacity, despite being more than two years old, precisely because I often remove it when my computer is plugged in and it is charged fully enough for me. – bwDraco Oct 11 '12 at 15:48

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