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Should laptops remain plugged in when their battery is 100% charged?

My friend told me that if you leave the AC adaptor plug plugged into the laptop after the battery is charged 100%, it actually over charges it and never cuts off the voltage. As a result, this reduces battery life.

I have Dell n5010 n series laptop with i5 in it. It is a new machine, and I was thinking that how is it possible that huge companies leave a "bug" like this in a laptop that is so expensive.

I think that it never turns off the charging, it actually puts it to float voltage as this is one of charging techniques.

I want to know what, in fact, happens.

marked as duplicate by random Aug 2 '11 at 21:48

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migrated from serverfault.com Aug 2 '11 at 21:37

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Modern notebooks have advanced charging circuits that prevent this from happening.

  • Small but important distinction -- it is the Lithium battery that has the advanced charging circuit built into it. Virtually all Lithium batteries of whatever kind have the charge protection built into them, rather than the laptop. – anastrophe Aug 2 '11 at 22:44
  • No, it's the laptop. The Li-ion battery does have an "electronic fuse" that prevents the battery from being charged after it's reached an unsafe level of DIScharge; this may be what you're thinking of. But the charge regulator is in the laptop. – Jamie Hanrahan Aug 31 '15 at 11:11

I is not a bug, it will happen with any lithium battery, although most modern laptops have special safeties for this problem.

Sony actually has something that makes sure you cannot overcharge it (only charges to 80%), but this means you cannot use 100% capacity of your battery.

Also in my personal experience, I have had several laptops and the only problems I ever had with batteries was with Acer laptops.

It is better to remove the battery when you are going to work for long periods, but as I said I've had Dells Acers MSI and Asus and only the Acers degenerated quickly (which was still 2 years).