I always keep my charger plugged-in and my battery remains fully charged. but sometimes when I restart my laptop it starts charging again and shows the battery is in it's 90's%. My question is should I leave the charger plugged-in so that it reaches 100% again or I plug-out the charger and use the battery to some level and then plug-in the charger?

In simple words, At which level should I recharge my laptop battery? Is it ok to plug-in the charger at 90% charge remaining?

  • Plug it in. Maybe windows doesn't know the real battery %... I've seen very recent windows tablet that wouldn't update the battery life properly. Turning them off when the battery's 100% charged, then waiting a few days (until the battery runs down a little, 20%-30%, plugging it in but not turning it "on" shows the battery graphic - like a cell phone - with the battery closer to half empty) and starting windows has windows thinking the battery's still at 99% or 95% and charging, but the battery % would go down while the battery actually charged, eventually the % would start going up again. – Xen2050 Nov 20 '16 at 7:54

It is okay to plug the laptop into power at any stage, the circuitry is designed not to overheat the battery. However, it is not good for your battery lifespan at all; it is always best to let the battery drop to around 20% and recharge it to 80-90%.

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    I have heard that each battery has some specific cycles. I want to increase the life span of my battery by using as few cycles as possible. If I leave the battery to be used and recharge it again to 100%, it will loose a cycle which I don't want. – Umair Ameen Nov 20 '16 at 6:13
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    Maybe this is true if you have an ancient NiCad battery. Modern NiMH and Li-Ion batteries don't have this issue. See Battery Memory Effect – candied_orange Nov 20 '16 at 6:15
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    My laptop has Li-ion battery and if it is damaged I won't be able to find a new one. – Umair Ameen Nov 20 '16 at 6:17
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    I had some "modern" NiHM batteries in two identical phones, identical batteries. One phone was only charged up & then kept off the charger until the power ran out, that phone's battery was useless after 1 year. The other phone was always left on the charger, it's battery was good for 3+ years. Anecdotal yes, but the more a battery's kept charged (on the charger) the less it's used, and the more theoretical "cycles" it has left. – Xen2050 Nov 20 '16 at 7:44
  • It's like exercise, better to do in short bursts then 0-100 in one go. It exhausts the battery. – Jacob G Nov 21 '16 at 5:33

I've found good documentation on Battery University: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

The most useful parts for you being, probably, the following:

The worst situation is keeping a fully charged battery at elevated temperatures. Battery packs do not die suddenly, but the runtime gradually shortens as the capacity fades.


The question is asked, “Should I disconnect my laptop from the power grid when not in use?” Under normal circumstances this should not be necessary because charging stops when the Li-ion battery is full. A topping charge is only applied when the battery voltage drops to a certain level. Most users do not remove the AC power, and this practice is safe.

Modern laptops run cooler than older models and reported fires are fewer. Always keep the airflow unobstructed when running electric devices with air-cooling on a bed or pillow. A cool laptop extends battery life and safeguards the internal components. Energy Cells, which most consumer products have, should be charged at 1C or less. Avoid so-called ultra-fast chargers that claim to fully charge Li-ion in less than one hour.

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