My laptop is ASUS K 551 LB, which has an internal battery. Would the battery's service life be longer leaving the laptop plugged in whenever possible, or running off the battery to regularly run down the charge?

marked as duplicate by bwDraco, DavidPostill, JakeGould, Braiam, studiohack Mar 23 '15 at 3:59

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The battery is most under stress above 90% and under 5%. It also has a limited number of charging cycles, and its health decreases with each one. That being said, the lower the discharge depth, i.e. the difference in stored capacity between when you unplug it and plug it back in, the lower the damage.

According to this website, you would get the longest battery life by always keeping it between 80% and 40%. If your laptop comes with a battery utility that allows you to set charging thresholds, you could stop charging somewhere between 60% and 80%, thus keeping your battery out of the stress zone. In that case, leaving it plugged in wouldn't do almost any damage.

If you don't have access to such a utility, it's probably better to unplug your computer at about 90%, then plug it back it at about 20%, rather than leaving it always plugged it. Of course this is impractical and could become annoying, and you should keep in mind your battery will degrade either way. So the best solution might actually be to use it anyway you want, and should it fail you before you buy your next laptop, just get a new battery, which is usually quite cheap on amazon or ebay.


You have a modern laptop with a Li-ion battery. The best way is to leave it plugged in at all times. This allows the laptop's battery management circuitry the most options, and it's designed to prolong battery life. With the laptop unplugged, there is no choice but to allow charge to leak, whether or not this is good for the battery's life.

Check if the laptop gives you options in its power manager to prioritize battery life. That will give you the maximum possible life.

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    This is generally not true. The best thing to do is to remove the battery when you are not using it. If it's not removable, use software to prevent it from charging past 70-80%. – RockPaperLizard Mar 22 '15 at 19:09
  • @RockPaperLizard If neither charging nor discharging the battery is the best thing to do, then that's what the laptop's charge controller will do. The charge controller is designed by experts who know what is best for the particular setup he has. If keeping it at 70%-80% is what's best, then that's what the controller will do. The controller's job is to keep the battery healthy and the more choices it has, the better choices it can make. – David Schwartz Mar 23 '15 at 0:18
  • Almost every laptop is shipped to keep the battery charged at 100%, despite it not being the best thing for the battery. The user generally has to take explicit action to specify that they want to keep the charge level below 100%. By default, the controller does what the manufacturer specifies, and what they want is for their systems to show a battery that lasts a long time PER CHARGE during tests in order to impress the media and testers. They know that this will reduce the lifespan of the battery, but they also know all reviews will be completed before this is apparent. – RockPaperLizard Mar 23 '15 at 0:24
  • @RockPaperLizard That's why I said, "Check if the laptop gives you options in its power manager to prioritize battery life. That will give you the maximum possible life." – David Schwartz Mar 23 '15 at 0:56

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