Ask HN: Should I unplug my laptop charger at 100%?

Source: I have a master&#x27;s degree in mechanical engineering in hybrid vehicle powertrains, and a big part of my research was battery technology. I spent some time working with the folks at National Semiconductor learning this, so I have several primary sources.<p>Disclaimer: my knowledge of the field is from ca 2010.<p>1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100% too much.<p>2) Li-ion batteries do not love being at 100% SOC (state of charge). As batteries become more dense, the membranes become thinner. High SOC equates to high chemical potential, which will break down membranes faster. As such, avoid leaving your battery at 100%. This wasn&#x27;t as much of a problem with older batteries with thicker membranes, but is becoming more and more an issue as we try to squeeze every ounce of density out of batteries.<p>3) Roughly 70% SOC is where a battery is happiest, but the whole range of ~30-80% is pretty happy for a li ion cell. Try to keep your battery at ~70% or so overnight, at 50% or so for long sleeps.<p>A good usage pattern: plug in and let charge to 90%, unplug and use for a couple of hours, plug back in at 50% or so, rinse and repeat.

As I sit and look at the replies already coming in, may I just add an enormous [citation needed] to the entire discussion? A question brought on by too many conflicting anecdotes can not be resolved by throwing another unsourced anecdote on the pile.<p>(Incidentally, I&#x27;m at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I&#x27;ve read.)

&gt; For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month.<p>— <a href="https:&#x2F;&#x2F;web.archive.org&#x2F;web&#x2F;20110521104819&#x2F;http:&#x2F;&#x2F;www.apple.com&#x2F;batteries&#x2F;notebooks.html" rel="nofollow">https:&#x2F;&#x2F;web.archive.org&#x2F;web&#x2F;20110521104819&#x2F;http:&#x2F;&#x2F;www.apple....</a> via <a href="http:&#x2F;&#x2F;apple.stackexchange.com&#x2F;a&#x2F;12280" rel="nofollow">http:&#x2F;&#x2F;apple.stackexchange.com&#x2F;a&#x2F;12280</a><p>This could also be useful, but doesn&#x27;t answer the question directly: <a href="http:&#x2F;&#x2F;www.apple.com&#x2F;batteries&#x2F;maximizing-performance&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.apple.com&#x2F;batteries&#x2F;maximizing-performance&#x2F;</a>

Consider the cost of a replacement battery and if it&#x27;s worth the subconcious mental strain this consideration places on you.<p>In short, leave it in because it&#x27;s not worth worrying about.

You should have talked to Google, instead of numerous people.<p><a href="http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_lithium_based_batteries" rel="nofollow">http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_li...</a><p>Summary:<p>Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life.<p>To answer your question: No.<p>Side note: Don&#x27;t blindly trust the manufacturer. Of course Apple wants you to wear out your laptop as fast as possible, once it&#x27;s past the warranty. They&#x27;re a business.<p>Side note 2: Laptops do NOT charge your battery to 100%. Your battery indicator is fake. 100% on your battery indicator is more like 90% in reality. The charger automatically cuts off before it reaches the true 100%, so all of the comments in this thread about 100% being bad are wrong, because no modern laptops will truly let you reach 100%.

Maybe I have bad luck, but I came to accept that every laptop battery eventually becomes a UPS for getting from the desk to bed :-)

This is one of those interesting &quot;mesofacts&quot; that is related to how batteries used to work. It&#x27;s similar to when well meaning people share anecdotes about car maintenance that were only true back when cars had carburetors. These are hard lessons learned that are not necessarily applicable today.<p>It&#x27;s certainly true that the old nickel cadmium batteries were harmed by continuous charging. But nowadays with lithium ion batteries, lots of laptops, batteries, and chargers all have little microcontrollers on them that can be smart about charging and maximizing the lifetime of the battery. The short answer is that you should read the manual that came with your particular system and see what it advises.

No. Your battery degrades each time there&#x27;s a cycle of charge-&gt;use. If you&#x27;re lucky, you can do that a few thousand times before you lose much of your battery&#x27;s capacity. If you leave it plugged in, you aren&#x27;t losing cycles, so you should do that.

Personal experience:<p>I&#x27;m on an early 2011 MacBook Pro (purchased in March, 2011), which I&#x27;ve used for about 8-10 hours per day, 5 days per week, since the date I purchased it. I have about 6.5 hours remaining at a 91% charge (screenshot for proof <a href="http:&#x2F;&#x2F;cl.ly&#x2F;image&#x2F;1a2d2y2V1J2O" rel="nofollow">http:&#x2F;&#x2F;cl.ly&#x2F;image&#x2F;1a2d2y2V1J2O</a>). I consider this to be pretty good for a notebook that has been used extensively for more than 4 years, which is why I felt like I should share my advice on keeping your battery healthy (I do <i></i>exactly<i></i> this, and have since day one, except when I&#x27;m mobile and actually use the battery - about 2 times per month - today is one of those days):<p><pre><code> 1. keep your notebook plugged in all day while you work 2. unplug your notebook when you power it off at night 3. on Friday, unplug partway through the day, allowing the battery to drain to about 30% by EOD 4. Monday morning, start back at step # 1 </code></pre> The bottom line is, run the charge down significantly 1 (or 2 max) times per week, and let it sit (over the weekend) without a full charge.

AFAIK only macbooks have been designed to bypass battery ( once the charge is 100% ) and directly run on connected power. For other notebooks its best to unplug charger at 100% and connect charger at around 10% to get a longer lifetime of the battery.

I&#x27;ve always been told that the number of cycles was the most important factor in battery life (but not the only one). A cycle is one complete charge+discharge, with partial credit for partial discharges — so discharging to 50% counts as 0.5 cycles. [1]<p>This tells me that leaving your battery plugged in whenever possible is good, since it minimizes the number of cycles you&#x27;re putting on the battery. If you unplug the battery once it&#x27;s fully charged (and proceed to use it), you&#x27;re just subtracting cycles from the battery&#x27;s life.<p>On the other hand, apparently there&#x27;s a cost to letting the battery sit at 100% charge for too long. I don&#x27;t know how long &quot;too long is&quot;, but Apple&#x27;s battery site says this about long-term storage: &quot;Do not fully charge or fully discharge your device’s battery — charge it to around 50%. If you store a device when its battery is fully discharged, the battery could fall into a deep discharge state, which renders it incapable of holding a charge. Conversely, if you store it fully charged for an extended period of time, the battery may lose some capacity, leading to shorter battery life.&quot; [2] Keep in mind this is specifically talking about long-term storage only.<p>Taken together, I interpret all this to mean that it&#x27;s best to leave the laptop plugged in at 100% whenever possible, provided that you&#x27;re <i>occasionally</i> taking it out and using it (so it&#x27;s not &quot;long-term storage&quot;).<p>That said, I&#x27;d love to see some quantitative benchmarks to confirm all this. ;)<p>References:<p>1: <a href="http:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Charge_cycle" rel="nofollow">http:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Charge_cycle</a><p>2: <a href="https:&#x2F;&#x2F;www.apple.com&#x2F;batteries&#x2F;maximizing-performance&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.apple.com&#x2F;batteries&#x2F;maximizing-performance&#x2F;</a>

My experience has been that it depends on the laptop and how it handles the charging. Some will keep trickle charging at 99% so it keeps recharging the laptop frequently. That wears out the battery and usually in a couple years it won&#x27;t hold much charge. Other laptops though wait longer until it falls to say 94% even when you leave it plugged in. This reduces the frequency of recharging and the battery lasts longer.

I wrote a program that monitors battery state for Windows [1], and after a lot of research I concur with the other opinions posted here that leaving a lithium ion battery at 100% for long periods of time is not a good idea.<p>The software I wrote has configurable alerts so a user can get an alert then it&#x27;s reached a certain change level (like 90%) and then again when it drops below a certain level. Users have specifically ask for that so they can unplug without over-charging.<p>[1] <a href="https:&#x2F;&#x2F;batterybarpro.com" rel="nofollow">https:&#x2F;&#x2F;batterybarpro.com</a>

Bad UX. One shouldn&#x27;t have to worry about this!

If unplugging your charger at 100% and letting your battery run to 84% or whatever, and then plugging it back is so good for it, why doesn&#x27;t Apple (or any other laptop manufacturer) just have the power controller do that automatically when your laptop is plugged in?<p>I call malarkey on all of it. I&#x27;ve had my laptop plugged in for years and it sits at 100% most of the time. I don&#x27;t have time to deal with that kind of hassle, even if it is true.

Lenovo at one time (they still might, I&#x27;m not sure) included a piece of software that allowed the user to optimize charging for battery life. Basically, it would stop the battery from reaching 100% of a charge.<p>Great idea, except that if you forgot to turn this feature off and had to leave, you might leave the house with just 60% battery life.

It depends and usually it&#x27;s a good idea to check with the manufacturer.

Personal experience with IPAD 1, 4 years using it every day with full discharges every day more than 1,000 charge cycles. When new full battery lasted 9 hours after 4 years lasts 8 hours.

You should unplug it <i>before</i> it reaches 100% unless you know you&#x27;ll need the full charge.<p>Letting the battery sit at 100% wears it out more than sitting at 40-80%.

Surely laptop technology has advanced beyond the point of us having to manually manage battery health? The only reason I can imagine for people assuming this isn&#x27;t dealt with for us by some control chip is a conspiracy that laptop manufacturers purposely limit the battery&#x27;s life by not including this functionality. Which I suppose isn&#x27;t hugely far fetched, but I&#x27;d still find it hard to believe.

There seem to be 2 main ways people use laptops in my unscientific &quot;asking of my friends&quot; survey: Plugged in for long periods, or unplugged for long periods. It seems like the vendors should have solved for both of those.<p>From the previous answers to this item, it would seem that most vendors focused on long life unplugged (6 hours! 10 hours! So long, you&#x27;ll forget where you last put the cord!) and &quot;you&#x27;ll have to buy a new battery... and they aren&#x27;t cheap&quot; if you stay plugged in.<p>While part of me finds that hard to believe, another part wonders if this is just a part of the wonderous circle of (battery) life. Luckily, the conspiracy part left the building, or he would have said that the evil vendors do this on purpose to keep a steady cash flow.<p>Sorry, didn&#x27;t mean to evoke this earworm: <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=8zLx_JtcQVI" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=8zLx_JtcQVI</a>

I know that this was an issue on my ThinkPad W700 with Linux installed. In Windows, the Lenovo drivers would automatically manage the charging level to preserve battery life, but in Linux it would overheat when plugged in for extended periods of time, and I suspect that it was &quot;over-charging&quot;. Within a year, the battery had about 50% capacity, and a replacement battery degraded as quickly.<p>My current ThinkPad w540 does not seem to do this in Linux, so I suspect that either Linux or Lenovo has solved the problem, but I haven&#x27;t really investigated what happens. I leave my ThinkPad plugged into a dock most of the day at the office like I did with the W700, but it&#x27;s battery still has almost full capacity a year later and can still keep it running for 5+ hours on a full charge. (Linux could never get the 7+ hours that it can get under Windows and I haven&#x27;t run Windows for more than 1 hour in almost a year.)

All my questions have been answered via this link:<p><a href="http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_lithium_based_batteries" rel="nofollow">http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_li...</a>

Just sharing my thoughts. I have HP Laptop for 5yrs. I use that for 10hrs a day for 5 yrs, very rarely I use it with batteries I would say 95% of time my battries were 100% and power charger is connected and remain &quot;ON&quot;. after 3.5 yrs HP&#x2F;laptop software show indication of &quot;END of life&quot; for battery though to test I run my laptop on batteries and they work for full 3hrs as they used to work when new. but after another 6 months, i.e. 4yrs it won&#x27;t work as long and by the time 5yr is complete it works only 20-30 minutes. But isn&#x27;t it that good life for batteries anyways? and yes my charger were hot enough to cook :).

You could remove the battery when its charged and stay on the cord. Because battery life is heat-related. And leaving a charged battery in the laptop when you have a cord is chewing up lifetime without benefit.

Just for anecdotal sake, my work laptop stays plugged into a charger about 22 hours a day most days, and is only off charger for the occasional meeting or to come home with me for a night (where it&#x27;s only off for the suspend portion).<p>After 201 full charge cycles in ~2 years (trickle charging at 100% takes awhile to equal one cycle) I&#x27;m still at 95% battery life.<p>My take is that, at least for MacBooks, it doesn&#x27;t make nearly as much difference as not letting your computer sit in a hot car a lot and other standard battery hygiene things.

From a technical perspective, yeah, you probably should unplug your laptop at around 70-80%, since that&#x27;s where the current battery tech is happiest. An even better option would be to use software to limit charge to 70% unless you manually tell it to fill up; this isn&#x27;t universally available, though.<p>From a realistic perspective, though, I&#x27;ve found that (in my experience) to be marginally beneficial; the slight benefit to battery health it had afforded to me wasn&#x27;t worth the hassle.

In general, the battery health problem should be handled by the manufacturer, not by user. That&#x27;s why Lenovo is doing a very good job.<p>However, if you still insist on doing it by yourself, take a look at my hardware-level solutions at <a href="http:&#x2F;&#x2F;softwarerecs.stackexchange.com&#x2F;questions&#x2F;10441&#x2F;laptop-battery-charging-control-software-for-windows&#x2F;19426#19426" rel="nofollow">http:&#x2F;&#x2F;softwarerecs.stackexchange.com&#x2F;questions&#x2F;10441&#x2F;laptop...</a>

Wrote a small script to easily put my Thinkpad battery to storage mode (50-70% SOC) and back to full charge: <a href="https:&#x2F;&#x2F;gist.github.com&#x2F;cmavr8&#x2F;204132a008d4ebabce94" rel="nofollow">https:&#x2F;&#x2F;gist.github.com&#x2F;cmavr8&#x2F;204132a008d4ebabce94</a><p>Also one (lame) for bat stats on linux: <a href="https:&#x2F;&#x2F;gist.github.com&#x2F;cmavr8&#x2F;bdf591d8dc66290ae87a" rel="nofollow">https:&#x2F;&#x2F;gist.github.com&#x2F;cmavr8&#x2F;bdf591d8dc66290ae87a</a>

Leaving it plugged in has the same effect as removing the battery while it&#x27;s plugged in (and putting the battery in identical thermal conditions). (Just think: if it were bad, engineering a workaround would be simple.) It&#x27;s fine to have the battery sit at 100% for short periods of time. The damage you get around the 100% number is from charging&#x2F;discharging to&#x2F;from 100%, or leaving it unused for long periods of time.

A few things:<p>1. A lithium ion battery charger is smart, it will not overcharge or harm your battery in any way keeping it charged.<p>2. In terms of discharging a lithium ion battery - they are not susceptible to memory like ni-cd and ni-mh batteries, so regular discharging is not required.<p>3. Apple and other companies will suggest discharging your lithium ion battery fully. The reason being that a complete discharge followed by a full recharge will update an internal counter which records the capacity of the battery. The capacity decreases over time, so your battery charge indicator will need this full discharge&#x2F;recharge regularly to stay accurate. Not important for actual capacity you get out of your battery.<p>4. There is a recommendation that in order to get the MOST NUMBER OF DISCHARGE CYCLES out of a lithium ion battery, you should only discharge it to 50%. I put MOST NUMBER OF DISCHARGE CYCLES in bold because it is important to know that this is the most important factor in the life of your battery - you do not need to discharge the battery to 50% in order to get a longer life, but if you do need to discharge it, 50% discharge is optimal to avoid any damage by over-discharging. If you discharge your battery EVERY day because you charged it to full, you are going to severely decrease the lifespan.<p>5. (Edited in) Laptops and phones use a State of Charge estimation model to decide how full the battery is. Depending on the device, the manufacturer may suggest fully discharging and fully recharging the battery so that the estimation model understands the capacity of the battery and avoids overcharging: <a href="http:&#x2F;&#x2F;chargedevs.com&#x2F;features&#x2F;the-challenges-of-battery-state-of-charge-measurements&#x2F;" rel="nofollow">http:&#x2F;&#x2F;chargedevs.com&#x2F;features&#x2F;the-challenges-of-battery-sta...</a><p>My recommendation: Don&#x27;t discharge when it is full. Only discharge when you need to. Charge it at 50% if possible to avoid over discharging. KEEP IT COOL - heat kills batteries lifespan as well.<p>Battery technology has changed a lot since I worked in the industry - they&#x27;re always advancing and changing. There are many resources to keep yourself well informed: <a href="http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_lithium_based_batteries" rel="nofollow">http:&#x2F;&#x2F;batteryuniversity.com&#x2F;learn&#x2F;article&#x2F;how_to_prolong_li...</a><p>Edit: All applications and devices are different. My recommendation might not be the best - some have suggested avoiding keeping your battery at 100% constantly, whereas my suggestion assumes that the charger won&#x27;t harm the battery by overcharging. For example: battery is at 100% on the device, but in actuality it is sitting at 90% state of charge in the context of lithium ion technology.

You can control the battery % at which a device will begin and stop charging - so there&#x27;s no need for this. Idk what all this misinformation is about.

From the Help and Support for the ThinkPad X201 Tablet:<p><pre><code> To maximize the life of the battery, do the following: Use the battery until the charge is completely depleted--until the battery status indicator starts blinking orange. Recharge the battery completely before using it. The battery is fully charged if the battery indicator shows green when the AC adapter is plugged in.</code></pre>

Generally speaking the best for the modern batteries in our laptops is to be charged between 20 - 80 %. I think Apple fiddles with the 100% and it is not the actual 100%. I am not able to find a credible source to confirm this. Ideally you would want to remove the charger when your battery is around 80% and reconnect it when it hits 20%. This can be done with some of the PC vendors easily.

I&#x27;m an electrical engineering student who needed an idea for a school project dealing with reliability.<p>I think I just found my project. Stay tuned!

Supposing it would matter, why wouldn&#x27;t laptop manufacturers include some 0.01$ part that switches off the charger as needed?

I just pull the battery out for extended plugged in sessions. Get it to 98%, pull out battery. No need to waste charge cycles.

I do. From the mains. Not so much to &quot;save the battery&quot;, but to reduce power consumption. The charger is still consuming some power all the time it&#x27;s on, regardless of battery level.

IMO, I dont really care about it that much. You will probably want to change laptop after 2 or 3 years anyway, during this time battery degradation should not be a massive issue.

Your battery&#x27;s life is all about charge&#x2F;discharge cycles. Say your battery has roughly ~1000 such cycles. Once you&#x27;ve exhausted the cycles, your battery is typically running on bonus power. Whatever performance you get after this is extra and cannot be relied upon.<p>Thus, the longer you can preserve your cycles, the longer your battery will survive.<p>You can also read this thread: <a href="http:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;askscience&#x2F;comments&#x2F;1snzg1&#x2F;is_it_actually_bad_for_the_battery_of_a_laptop_to&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;askscience&#x2F;comments&#x2F;1snzg1&#x2F;is_it_act...</a>

Good to know, I used to believe that deep discharges were good for the battery ... I wonder who told me that!

Tesla e should know this.

i used to have a macbook that i used as a desktop in clamshell mode. i left it plugged in all the time. i never took it anywhere.<p>when i called apple to replace the battery on warranty because it had started to bulge&#x2F;swell dangerously and not hold charge, they had me open up the system information panel to see how many cycles it had been through, and it was hilariously low, like, 4. they refused to warranty it.<p>so at the very least, if you care at all about your warranty coverage, you should probably cycle it normally.

My personal experience with a Lenovo W520 having the battery needlessly inserted for two years (40 hours per week) while connected to the charger:<p>The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger.<p>So if there hasn&#x27;t been a big change in how laptop batteries work in the last few years I&#x27;d recommend removing the battery whenever the charger is connected if possible.

&gt; I have talked to numerous people and there is no set consensus on whether I should be unplugging my laptop charger when it is fully charged.<p>Hi Zatkin,<p>General advice: please study the materials hosted at the following great &quot;Battery University&quot; website: <a href="http:&#x2F;&#x2F;batteryuniversity.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;batteryuniversity.com&#x2F;</a><p>The charge and discharge protocols which are best for battery life and capacity depend on the kind of battery.<p>Certain batteries benefit from being cycled, like NiMh and NiCad. It&#x27;s not that important for lithium, IIRC.<p>Some batteries benefit from priming: treating the battery in a certain way when it is brand new, so it lasts longer and performs better over its lifetime.<p>(I could use a refresher myself; I&#x27;m going to study the materials on that website.)

I hate to sound like an ass, but I think I need to say something anyway... Is this the kind of question we want at HN? It&#x27;s been done to death elsewhere, and is easily answered with a quick search.<p>I know there can be a fine line between a good, thought-provoking question and a useless one, and, to me at least, this seems too far on the &quot;useless question&quot; side of things. It&#x27;s about basic hardware maintenance, and I&#x27;m honestly surprised it&#x27;s gotten 37 points in 22 minutes (so far).