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

When my notebook battery is fully charged and on AC power - is the battery life decreasing (because I have heard, that in that case, the battery constantly charges and discharges)?

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marked as duplicate by RedGrittyBrick, Xavierjazz, 8088, Sathya Sep 11 '12 at 4:11

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
I have also heard this. I find it quite inconvenient to constantly have to monitor the battery level to pull the plug before it gets full (for example, while I type, I see the LED is blue meaning it is fully charged). I would think that in this day and age, the battery circuitry and/or the BIOS and/or Windows would be intelligent enough to start and stop charging at an appropriate time, taking these things into consideration instead of leaving the burden on the user. :-| –  Synetech Sep 10 '12 at 22:53

2 Answers 2

This is a tough question to answer because there are often so many other variables to consider. But, all things being equal, let's get to the heart of your question which is an assumption: Is it bad to constantly charge/recharge (otherwise known as "cycle") your battery?

Answer: No (caveat: any modern battery)

There's a persistent concern with (rechargable) battery cycles because of NiMH (nickel metal hydride) batteries. Those are still very prevalent in society (think AA and AAA batteries).

But modern laptop batteries are almost always LiOn (lithium ion) - and even more modern: lithium polymer - batteries. Those batteries are largely immune to the "cycle" effect which plagues NiMH batteries. When laptops first came out with NiMH batteries, people noticed the batteries developing "memory" problems. (i.e. New battery charges to 100%. Then you drain the battery to 90 and recharge. Only charges to 99.5%. You drain again to 85 and then it recharges only to 99%, and so on).

Lithium batteries are largely immune to memory issues. Instead, they just decay as a factor of age and heat. So, Nicole's point about taking out the battery (if possible) is a good one to let your laptop just run on AC power.

Additionally, as noted elsewhere, modern laptops now have smart charging systems to bypass charging the battery when full. Older laptops (of even just a couple of years ago), often did not have this ability.

If you look at Apple's battery information page, you'll see it says its batteries are estimated to have 1000 full cycle lifespan. If you fully charge/discharge your battery four times a week, you'd be at 80% battery life in about four years.

TL;DR: Use AC power if you can. Don't worry about battery cycling. Minimize heat.

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This seems to be a duplicate of Is it better to use a laptop on battery or on AC power? The consensus is that it doesn't make much difference but if you care, you can remove the battery when you're on AC so it's not exposed to the heat thrown off by other components.

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The first disadvantage of removing the battery is the "extra care", so you have to "keep it in mind", and the second disadvantage is that when a notebook is only on AC power, and that power is suddenly lost (for any reason) - the notebook is shutted down, and your work is lost, whereas this cannot happen, when the battery is plugged in. –  Peter Sivák Sep 10 '12 at 23:41

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