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

308 points by zatkin 11y ago

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.

cjbprime 11y ago
No. Your battery degrades each time there's a cycle of charge->use. If you're lucky, you can do that a few thousand times before you lose much of your battery's capacity. If you leave it plugged in, you aren't losing cycles, so you should do that.
- ars 11y ago
  A cycle from say 70% to 80% doesn't wear it out much at all. The problem with leaving it at 100% is that just sitting at full charge wears it out, it's better to just keep it within 40%-80% than to leave it fully charged.
  - deleted 11y ago
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  - jotm 11y ago
    If the indicators are correct, HP's chargers keep the batteries at ~95% (varies between 95-100% all the time). So they're not keeping them fully charged or overcharged, but instead leave some breathing room.
  - ignostic 11y ago
    A 40% depth discharge is going to put way more wear than leaving it at 100%. Unless you want to plug and unplug constantly most users are probably best leaving it plugged while working. If you really want to, you can do a little bit of good by letting it drop to 40=80% during periods of non-use.
- tdkl 11y ago
  > If you leave it plugged in, you aren't losing cycles Too bad that some batteries wear out even faster this way because of the heat.
  - tjohns 11y ago
    Why would there be extra heat if the battery is fully charged? Shouldn't a well designed charge circuit disconnect once the battery hits 100%?
    - tdkl 11y ago
      Emphasis on "well designed". The 500€ laptops I've experienced in the past weren't and you could murder the battery like this in couple months, no matter the brand (HP, Dell).
  - basch 11y ago
    the laptop can run, plugged in, without the battery in it.
rajeshmr 11y ago
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.
- ars 11y ago
  Not 10%! That's terrible for a Lithium battery. Charge it when it gets to 40%.
  - mwexler 11y ago
    Ah, so I can only use 60% of my battery before I have to find a plug? Bummer.
    - zymhan 11y ago
      No, you can use as much as you want. But Li-ion cells will age faster if you deplete them completely, so it's not the best way to keep your battery healthy.
  - alexirobbins 11y ago
    20% is the standard for lithium batteries, but sooner is always better.
  - nashashmi 11y ago
    Actually it has been lab-determined that batteries should be charged once they hit 60%. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...
  - tjohns 11y ago
    Keep in mind many Li-ion batteries have protection circuits that prevent the battery from being discharged too far. I don't know how much reserve they keep on hand, but what your OS reports as 0% charge is almost never actually that low.
ars 11y ago
You should unplug it before it reaches 100% unless you know you'll need the full charge. Letting the battery sit at 100% wears it out more than sitting at 40-80%.
- toomuchtodo 11y ago
  Is there a way to modify the max charge level on apple laptop products?
- zymhan 11y ago
  Source?
- ignostic 11y ago
  It's correct that you'll retain battery capacity better if you store it at 40-80%. But that recommendation is based on long-term storage. It's not right to assume that also applies to in-use products, especially the way people use them. In fact you'd likely reduce battery life because you're putting the battery through a greater depth of discharge (DoD). Assume you let it run from 80% to 60%, you've just gone through a cycle of 20% discharge when you could have kept the DoD at 1%. Also, most modern laptops will run on power once charged, so it's not like an infinite number of 1% cycles. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...
- jotm 11y ago
  Have manufacturers never considered this? If leaving them at 80% was better, they would've configured the adapters to do just that. Unless they really wanted to sell extra batteries, of course...
  - basch 11y ago
    it is an option in some power drivers.
IkmoIkmo 11y ago
It depends and usually it's a good idea to check with the manufacturer.
jerf 11y ago
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. (Incidentally, I'm at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I've read.)
- toxicFork 11y ago
  This is my favorite technology superstition, some citation would help many people sleep easier it seems.
  - 0xdeadbeefbabe 11y ago
    I would easily fall asleep given the right citation.
  - gr8b8m8-88 11y ago
    Statistics and citations today is the Bible quotes / racial stereotypes of yesteryear. Some modern-day pseudo-scientist poster will cite some study that says "80% of chargers waste power if left plugged in at 100% charge" will then draw the logically faulty conclusion that therefore you should unplug your charger. The fact that the statistic study necessary had to ignore extra variables like if you have a lot of stuff plugged in, whether you're drawing power from a set of solar panels on your roof, whether you are using a super-special non-power wasting adapter, etc., necessarily makes the citation not a thought more credible than your great-great grandpa quoting the bible to tell you that you should marry your own race or citing stereotypes that you shouldn't trust your friend because he is Asian. True science, that is, proposing hypothetical models, analyzing results, and admitting no real results can be drawn due to insufficient model complexity, has been thrown out the window by pride and laziness.
    - Lawtonfogle 11y ago
      We can try to arrive at an exact answer. First, we need to start by assuming a sphererical laptop...
kvakvs 11y ago
Its best to consult with your laptop/charger/battery manual. If anything goes wrong, new battery costs like $20. Feel sorry for battery prices for Macbook users, but then their charger is smart enough to help battery survive longer.
deleted 11y ago
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hn_ 11y ago
I just pull the battery out for extended plugged in sessions. Get it to 98%, pull out battery. No need to waste charge cycles.
deleted 11y ago
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JoeAltmaier 11y ago
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.
- signaler 11y ago
  Good advice. The only caveat being this only works for certain laptop models
  - wtallis 11y ago
    And even when it appears to work, it may result in the processor being throttled so as not to overtax the power adapter without the battery available to supplement it.
  - vidarh 11y ago
    Are there really laptops where you can't remove the battery when connected? I've never had one that wouldn't keep running when you pull the battery when on ac. However the reason I know this is the same reason I keep mine in: I've dropped every laptop I've ever owned on the floor multiple times, and I've had one or the other of battery or charger cable fall out at least once for all of them, at least with the battery in the chances of losing power is reduced (though I have on occasion had both fall out at the same time).
    - ggreer 11y ago
      Many laptops (such as all current Apple models) have built-in batteries. I guess you could remove the battery with special tools, but putting it back in may require re-gluing things.
- untog 11y ago
  You could remove the battery Oh, if only that were true...
- nashashmi 11y ago
solve 11y ago
You should have talked to Google, instead of numerous people. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li... Summary: 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. To answer your question: No. Side note: Don't blindly trust the manufacturer. Of course Apple wants you to wear out your laptop as fast as possible, once it's past the warranty. They're a business. 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%.
- zymhan 11y ago
  Finally, a citation, thank you.
  - me2in 11y ago
    Thank you too!
- gburt 11y ago
  My understanding (again, uncited, like almost everything in these threads) is that one might /perceive/ a different result than this because the /software/ calibrates what 0 and 100% mean based on observation. If you never observe a zero (or, presumably, a 100%), it might recalibrate incorrectly. Again, this is based on old and uncited knowledge. There's surely someone here involved in writing power management software that could chime in.
- rajeshmr 11y ago
  This link from google says otherwise. https://answers.yahoo.com/question/index?qid=20130825212946AAJnwNY https://answers.yahoo.com/question/index?qid=20130825212946A... Lithium ion batteries do seem to have memory.
paulannesley 11y ago
> 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. — https://web.archive.org/web/20110521104819/http://www.apple.com/batteries/notebooks.html https://web.archive.org/web/20110521104819/http://www.apple.... via http://apple.stackexchange.com/a/12280 http://apple.stackexchange.com/a/12280 This could also be useful, but doesn't answer the question directly: http://www.apple.com/batteries/maximizing-performance/ http://www.apple.com/batteries/maximizing-performance/
- deleted 11y ago
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- JimmaDaRustla 11y ago
  Usually the reason behind discharging fully once per month is because when this happens, the laptop records how much capacity is required to recharge the battery. This will keep your battery % left accurate. The actual preference for getting the MOST DISCHARGES out of a lithium ion battery is discharging it to 50%. This, however, doesn't not to equate to longest battery life (in terms of age) for the use within a laptop/phone. Edit: There is something state of charge estimation models which may rely on this variable to decide how full they'll charge the battery. If you don't fully discharge and fully recharge the battery to update this capacity value, the SOC estimation model might overcharge the battery, thus decreasing the lifespan.
- hvjackson 11y ago
  The fact that Apple no longer has this statements on their website makes me think it's no longer true for their batteries (if it ever was).
  - tjohns 11y ago
    They do have some advice on "long-term" storage here, which is roughly along those lines: https://www.apple.com/batteries/maximizing-performance/ https://www.apple.com/batteries/maximizing-performance/ They don't say what "long-term" is, but monthly seems reasonable to me.
hurin 11y ago
You can control the battery % at which a device will begin and stop charging - so there's no need for this. Idk what all this misinformation is about.
- kachnuv_ocasek 11y ago
  Sure, but the battery gets heated when left plugged in, which is not good for its health.
  - hurin 11y ago
    Why would the battery be heated if it's not charging? You can set a gap - e.g. 80-100% where the battery won't start charging until it drops below 80%. Look at the documentation for your relevant power-management module.
    - qbrass 11y ago
      >Why would the battery be heated if it's not charging? Heat transfer from the device it's plugged into.
      - hurin 11y ago
        I'm not a hardware/electronics guy, but I'm rather skeptical that this is any kind of notable amount - do you have a reference?
        sokoloff 11y ago
        Put the back of your hand (or your bare leg skin) against a laptop that's been in use. My Macbook is noticeably warm (maybe 15*F delta) in normal, non-charging, operation. That's with the benefit of conduction to the free air; I assume the inside delta-T is higher.
        hurin 11y ago
        That's not answering my skepticism to GGP's post - what he is saying is: a non-charging plugged in device has a significantly hotter battery than a non-plugged in device because of thermal-conduction across a non-charging wire?
yexponential 11y ago
Tesla e should know this.
- thisispete 11y ago
  Not sure if it's exactly pertinent, but If I remember correctly tesla recommends draining your battery to 20% then charging back up to 80% when driving on a road trip, but this if mostly for speed of charging. The car battery charges fastest in this half-full range, charging past 80% to 100% is a exponential rate like blowing air into an already full balloon, it gets harder as you reach 100%.. to their recommendation is not necessarily about battery health but more likely about reducing the speed of your mid-trip recharge.
bluedino 11y ago
Lenovo at one time (they still might, I'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. 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.
- icc97 11y ago
  Yep - I have this on my Lenovo.
- vishnuks 11y ago
  The Sony VAIO laptops also have this feature. Sad thing is there is no option for enabling this on Linux.
- pingec 11y ago
  Yeah, I have this on my Yoga 2 Pro. The utility is called Energy Manager - and the setting is "Conservation mode". https://forums.lenovo.com/t5/image/serverpage/image-id/34801i9268A10DBD1CEEEF?v=mpbl-1 https://forums.lenovo.com/t5/image/serverpage/image-id/34801...
- rkda 11y ago
  I'm using a Lenovo now and they still have it. Old Samsung also had something similar, Battery Life Extender, which won't stops charging at 80% even when plugged.
osetinsky 11y ago
Bad UX. One shouldn't have to worry about this!
- baddox 11y ago
  One doesn't have to worry about this.
SamReidHughes 11y ago
Leaving it plugged in has the same effect as removing the battery while it's plugged in (and putting the battery in identical thermal conditions). (Just think: if it were bad, engineering a workaround would be simple.) It'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/discharging to/from 100%, or leaving it unused for long periods of time.
lovelearning 11y ago
I do. From the mains. Not so much to "save the battery", but to reduce power consumption. The charger is still consuming some power all the time it's on, regardless of battery level.
nashashmi 11y ago
All my questions have been answered via this link: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...
- ignostic 11y ago
  Yeah, that's a great starting spot for putting these crazy myths to bed. A lot of a people seem confused about two concepts in the article: ideal storage and depth of discharge. These are two separate concerns. If you try to maintain the ideal storage charge while it's in-use (say 40%), you're going to end up wearing your battery by putting it through unnecessarily deep discharge cycles. Unless you want to plug and unplug every few minutes, you should probably just leave it plugged in.
beachstartup 11y ago
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. when i called apple to replace the battery on warranty because it had started to bulge/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. so at the very least, if you care at all about your warranty coverage, you should probably cycle it normally.
elmar 11y ago
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.
webnrrd2k 11y ago
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's been done to death elsewhere, and is easily answered with a quick search. 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 "useless question" side of things. It's about basic hardware maintenance, and I'm honestly surprised it's gotten 37 points in 22 minutes (so far).
- brudgers 11y ago
  Don't do what you hate. Flag and move on.
- matznerd 11y ago
  Really? Because there doesn't' seem to be a definitive answer here and lots of conflicting information...
  - webnrrd2k 11y ago
    I'm not saying it's a bad question, but I am asking if HN is the place to ask it. There are already lots and lots of answers to this question. Maybe try Reddit, or any of the various hardware forums. People are free to down vote me (and they have) for my opinion -- even though I've been polite and (I think) thoughtful. Even still, my opinion stands: HN is the wrong forum for this kind of question. There are many, many questions that HN isn't the place for... How should I charge my car battery? What's the best electric blanket? Should I use 10 or 12 gauge wire wire for my house? Maybe it would be a good question if the OP had researched it a bit first, and posted "surprising facts about your laptop battery" or something. But just a question about laptop batteries? Each one of these kinds of questions takes away from better quality, thoughtful or surprising content, which is what I like most about HN.
    - wyclif 11y ago
      If the question were about car batteries or electric blankets, I'd agree with you. But it's not; this is about laptop and mobile batteries, which concerns a huge percentage of HN users. That's also why this thread is so active. I'm in the 8-year club here on HN and I don't have a problem with it.
deleted 11y ago
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brador 11y ago
Consider the cost of a replacement battery and if it's worth the subconcious mental strain this consideration places on you. In short, leave it in because it's not worth worrying about.
- therobot24 11y ago
  seriously, i can get a battery for my T410 for ~20$ on amazon, i'm not going to spend my time plugging and unplugging.
  - keithpeter 11y ago
    Agreed. I do leave small laptop on suspend overnight (not plugged in) and then I do use it on the train into work, so a small charge/discharge cycle each day. The big typing box laptop (ancient T61p) is left on and plugged in a lot. May use a timer switch on the wall plug simply to reduce reliance on the overcharge protection in the battery/charger. I think those with devices that have batteries that cannot be replaced may be more concerned.
  - cmavr8 11y ago
    Sure, but do you know what cells these batteries use? They're usually cheap chinese ones, of less than half the rated capacity. A proper replacement will cost much more. I did go mid-way, buying high quality Japanese cells and installing them in a chinese pack. A bit cheaper than a new official battery, but required some work.
- adrusi 11y ago
  Assuming your computer has a replaceable battery, which is not the case always. Replacing a $80 battery is worth it to avoid stress, but replacing a $2000 ultrabook may not be.
  - TheGRS 11y ago
    I would think your ultrabook would be past its manufacturer's warranty anyway at that point anyway and would be a candidate for some sort of DIY battery replacement.
auganov 11y ago
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 :-)
- skizm 11y ago
  Apple ones also? This has happened to several dell and hp laptops I've owned or used long term, but both apple ones still keep charges for close to 3 hours even around 3 years after purchase without replacing the battery.
SuperCynical 11y ago
I'm an electrical engineering student who needed an idea for a school project dealing with reliability. I think I just found my project. Stay tuned!
singlow 11y ago
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 "over-charging". Within a year, the battery had about 50% capacity, and a replacement battery degraded as quickly. 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'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'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't run Windows for more than 1 hour in almost a year.)
- seanp2k2 11y ago
  I'm pretty sure that the charging logic is built into the battery or other dedicated charging circuit hardware. Almost positive that while the OS can say "don't give power to the battery", it can't say "give power to the battery even though the battery says no". Not a great source, but this agrees: http://computer.howstuffworks.com/laptop-battery-overcharged.htm http://computer.howstuffworks.com/laptop-battery-overcharged...
  - singlow 11y ago
    But it can repeatedly recharge the battery from 99% to 100% throughout the whole day - which is not good for it.
  - deleted 11y ago
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DominikR 11y ago
My personal experience with a Lenovo W520 having the battery needlessly inserted for two years (40 hours per week) while connected to the charger: The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger. So if there hasn't been a big change in how laptop batteries work in the last few years I'd recommend removing the battery whenever the charger is connected if possible.
- jotm 11y ago
  I found that fully discharging and recharging such a battery 3-4 times will bring it back to (near) its original levels. I've always had laptops plugged in all the time (desktop replacements) for months at end, with the battery acting as a UPS. When first disconnecting the power adapter, the batteries always discharged much faster than they should. After a few cycles, they went back to normal. I believe that leaving a laptop plugged in all the time is better for the battery than doing complete discharge-recharge cycles (5-100%).
bkanber 11y ago
Source: I have a master'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. Disclaimer: my knowledge of the field is from ca 2010. 1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100% too much. 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'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. 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. 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.
- raphinou 11y ago
  I read batteries wear off when plugged in in hot conditions, which is often the case for a running laptop. Can you confirm?
  - JimmaDaRustla 11y ago
    Heat is a major cause of battery degradation, partially why I don't agree with constantly charging/discharging since it causes more heat. Keep your laptop cool, perhaps even consider battery saving options while plugged in if you find it is generating too much heat. Edit: A running laptop will cause heat, so shut it off when not using it. A plugged in laptop shouldn't create much more heat than a laptop running on battery power, if anything, the battery should be cooler when plugged in and fully charged (assumption made).
  - bkanber 11y ago
    Long term battery degradation happens when its membranes degrade. There are hundreds of variables involved. Temperature IS a variable. But I'm reluctant to outright confirm what you're saying because it may be misleading. Avoiding plugging in when hot could help in some situations, but it won't help in all, so it's not a categorical rule.
tjohns 11y ago
I'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] This tells me that leaving your battery plugged in whenever possible is good, since it minimizes the number of cycles you're putting on the battery. If you unplug the battery once it's fully charged (and proceed to use it), you're just subtracting cycles from the battery's life. On the other hand, apparently there's a cost to letting the battery sit at 100% charge for too long. I don't know how long "too long is", but Apple's battery site says this about long-term storage: "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." [2] Keep in mind this is specifically talking about long-term storage only. Taken together, I interpret all this to mean that it's best to leave the laptop plugged in at 100% whenever possible, provided that you're occasionally taking it out and using it (so it's not "long-term storage"). That said, I'd love to see some quantitative benchmarks to confirm all this. ;) References: 1: http://en.wikipedia.org/wiki/Charge_cycle http://en.wikipedia.org/wiki/Charge_cycle 2: https://www.apple.com/batteries/maximizing-performance/ https://www.apple.com/batteries/maximizing-performance/
- JimmaDaRustla 11y ago
  Battery University typically looks at a discharge as a discharge. For example: Discharging the battery fully might yield 200 cycles, but discharging a battery 50% might yield 500 cycles. Obviously with the 50% discharge, you're only using half the capacity, but when you multiply the number of cycles by the capacity used, you can compare them.
dhanush 11y ago
Your battery's life is all about charge/discharge cycles. Say your battery has roughly ~1000 such cycles. Once you'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. Thus, the longer you can preserve your cycles, the longer your battery will survive. You can also read this thread: http://www.reddit.com/r/askscience/comments/1snzg1/is_it_actually_bad_for_the_battery_of_a_laptop_to/ http://www.reddit.com/r/askscience/comments/1snzg1/is_it_act...
mwexler 11y ago
There seem to be 2 main ways people use laptops in my unscientific "asking of my friends" survey: Plugged in for long periods, or unplugged for long periods. It seems like the vendors should have solved for both of those. 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'll forget where you last put the cord!) and "you'll have to buy a new battery... and they aren't cheap" if you stay plugged in. 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. Sorry, didn't mean to evoke this earworm: https://www.youtube.com/watch?v=8zLx_JtcQVI https://www.youtube.com/watch?v=8zLx_JtcQVI
kazinator 11y ago
> 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. Hi Zatkin, General advice: please study the materials hosted at the following great "Battery University" website: http://batteryuniversity.com/ http://batteryuniversity.com/ The charge and discharge protocols which are best for battery life and capacity depend on the kind of battery. Certain batteries benefit from being cycled, like NiMh and NiCad. It's not that important for lithium, IIRC. 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. (I could use a refresher myself; I'm going to study the materials on that website.)
robotcookies 11y ago
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'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.
- jotm 11y ago
  I've noticed that, too - I thought it's a safety feature to not overcharge the battery and kill it prematurely.
JimmaDaRustla 11y ago
A few things: 1. A lithium ion battery charger is smart, it will not overcharge or harm your battery in any way keeping it charged. 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. 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/recharge regularly to stay accurate. Not important for actual capacity you get out of your battery. 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. 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: http://chargedevs.com/features/the-challenges-of-battery-state-of-charge-measurements/ http://chargedevs.com/features/the-challenges-of-battery-sta... My recommendation: Don'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. Battery technology has changed a lot since I worked in the industry - they're always advancing and changing. There are many resources to keep yourself well informed: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li... 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'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.
deleted 11y ago
[deleted]
istvan__ 11y ago
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.
Osiris 11y ago
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. The software I wrote has configurable alerts so a user can get an alert then it'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. [1] https://batterybarpro.com https://batterybarpro.com
- james-skemp 11y ago
  Slightly OT, thanks for this software. When I picked up a new Windows tablet I was looking for a better battery indicator and found BatteryBar Pro. I don't personally use that feature, but it was something that I liked. The feature to show remaining battery and charge time is what I really enjoy about it.
  - Osiris 11y ago
    I'm glad you've found it useful. Let me know if you have any suggestions or feedback.
mangeletti 11y ago
Personal experience: I'm on an early 2011 MacBook Pro (purchased in March, 2011), which I'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 http://cl.ly/image/1a2d2y2V1J2O http://cl.ly/image/1a2d2y2V1J2O). 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 exactly this, and have since day one, except when I'm mobile and actually use the battery - about 2 times per month - today is one of those days): 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 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.
- cerberusss 11y ago
  One disadvantage is that you miss all Power Nap features: https://support.apple.com/en-us/HT204032 https://support.apple.com/en-us/HT204032 In my opinion, you don't miss all that much except for the following features: * Software updates download * Time Machine performs backups * Spotlight perform indexing
mcculley 11y ago
This is one of those interesting "mesofacts" that is related to how batteries used to work. It'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. It'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.
sean-duffy 11y ago
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't dealt with for us by some control chip is a conspiracy that laptop manufacturers purposely limit the battery's life by not including this functionality. Which I suppose isn't hugely far fetched, but I'd still find it hard to believe.
mikelyons 11y ago
Good to know, I used to believe that deep discharges were good for the battery ... I wonder who told me that!
polyx 11y ago
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.
- cerberusss 11y ago
  Exactly, that's my method as well. Although I have to say it's not so much a necessity rather than a preference for new and shiny. Hardware is so powerful nowadays.
facepalm 11y ago
Supposing it would matter, why wouldn't laptop manufacturers include some 0.01$ part that switches off the charger as needed?
t0mbstone 11y ago
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't Apple (or any other laptop manufacturer) just have the power controller do that automatically when your laptop is plugged in? I call malarkey on all of it. I've had my laptop plugged in for years and it sits at 100% most of the time. I don't have time to deal with that kind of hassle, even if it is true.
- jccooper 11y ago
  Many do. I've had several Windows laptops that want to do this.
geoelectric 11y ago
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's only off for the suspend portion). After 201 full charge cycles in ~2 years (trickle charging at 100% takes awhile to equal one cycle) I'm still at 95% battery life. My take is that, at least for MacBooks, it doesn't make nearly as much difference as not letting your computer sit in a hot car a lot and other standard battery hygiene things.
yellowapple 11y ago
From a technical perspective, yeah, you probably should unplug your laptop at around 70-80%, since that'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't universally available, though. From a realistic perspective, though, I've found that (in my experience) to be marginally beneficial; the slight benefit to battery health it had afforded to me wasn't worth the hassle.
archergod 11y ago
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 "ON". after 3.5 yrs HP/laptop software show indication of "END of life" 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't work as long and by the time 5yr is complete it works only 20-30 minutes. But isn't it that good life for batteries anyways? and yes my charger were hot enough to cook :).
brudgers 11y ago
From the Help and Support for the ThinkPad X201 Tablet: 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.
cmavr8 11y ago
Wrote a small script to easily put my Thinkpad battery to storage mode (50-70% SOC) and back to full charge: https://gist.github.com/cmavr8/204132a008d4ebabce94 https://gist.github.com/cmavr8/204132a008d4ebabce94 Also one (lame) for bat stats on linux: https://gist.github.com/cmavr8/bdf591d8dc66290ae87a https://gist.github.com/cmavr8/bdf591d8dc66290ae87a
- cmavr8 11y ago
  They're not well tested but seem to work. Let me know if you have improvement suggestions that are easy to do. Chris
xuancong84 11y ago
In general, the battery health problem should be handled by the manufacturer, not by user. That's why Lenovo is doing a very good job. However, if you still insist on doing it by yourself, take a look at my hardware-level solutions at http://softwarerecs.stackexchange.com/questions/10441/laptop-battery-charging-control-software-for-windows/19426#19426 http://softwarerecs.stackexchange.com/questions/10441/laptop...

308 points by zatkin 11y ago

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.

cjbprime 11y ago

No. Your battery degrades each time there's a cycle of charge->use. If you're lucky, you can do that a few thousand times before you lose much of your battery's capacity. If you leave it plugged in, you aren't losing cycles, so you should do that.

ars 11y ago
A cycle from say 70% to 80% doesn't wear it out much at all. The problem with leaving it at 100% is that just sitting at full charge wears it out, it's better to just keep it within 40%-80% than to leave it fully charged.
- deleted 11y ago
  [deleted]
- jotm 11y ago
  If the indicators are correct, HP's chargers keep the batteries at ~95% (varies between 95-100% all the time). So they're not keeping them fully charged or overcharged, but instead leave some breathing room.
- ignostic 11y ago
  A 40% depth discharge is going to put way more wear than leaving it at 100%. Unless you want to plug and unplug constantly most users are probably best leaving it plugged while working. If you really want to, you can do a little bit of good by letting it drop to 40=80% during periods of non-use.
tdkl 11y ago
> If you leave it plugged in, you aren't losing cycles Too bad that some batteries wear out even faster this way because of the heat.
- tjohns 11y ago
  Why would there be extra heat if the battery is fully charged? Shouldn't a well designed charge circuit disconnect once the battery hits 100%?
  - tdkl 11y ago
    Emphasis on "well designed". The 500€ laptops I've experienced in the past weren't and you could murder the battery like this in couple months, no matter the brand (HP, Dell).
- basch 11y ago
  the laptop can run, plugged in, without the battery in it.

rajeshmr 11y ago

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.

ars 11y ago
Not 10%! That's terrible for a Lithium battery. Charge it when it gets to 40%.
- mwexler 11y ago
  Ah, so I can only use 60% of my battery before I have to find a plug? Bummer.
  - zymhan 11y ago
    No, you can use as much as you want. But Li-ion cells will age faster if you deplete them completely, so it's not the best way to keep your battery healthy.
- alexirobbins 11y ago
  20% is the standard for lithium batteries, but sooner is always better.
- nashashmi 11y ago
  Actually it has been lab-determined that batteries should be charged once they hit 60%. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...
- tjohns 11y ago
  Keep in mind many Li-ion batteries have protection circuits that prevent the battery from being discharged too far. I don't know how much reserve they keep on hand, but what your OS reports as 0% charge is almost never actually that low.

ars 11y ago

You should unplug it before it reaches 100% unless you know you'll need the full charge. Letting the battery sit at 100% wears it out more than sitting at 40-80%.

toomuchtodo 11y ago
Is there a way to modify the max charge level on apple laptop products?
zymhan 11y ago
Source?
ignostic 11y ago
It's correct that you'll retain battery capacity better if you store it at 40-80%. But that recommendation is based on long-term storage. It's not right to assume that also applies to in-use products, especially the way people use them. In fact you'd likely reduce battery life because you're putting the battery through a greater depth of discharge (DoD). Assume you let it run from 80% to 60%, you've just gone through a cycle of 20% discharge when you could have kept the DoD at 1%. Also, most modern laptops will run on power once charged, so it's not like an infinite number of 1% cycles. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...
jotm 11y ago
Have manufacturers never considered this? If leaving them at 80% was better, they would've configured the adapters to do just that. Unless they really wanted to sell extra batteries, of course...
- basch 11y ago
  it is an option in some power drivers.

IkmoIkmo 11y ago

It depends and usually it's a good idea to check with the manufacturer.

jerf 11y ago

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. (Incidentally, I'm at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I've read.)

toxicFork 11y ago
This is my favorite technology superstition, some citation would help many people sleep easier it seems.
- 0xdeadbeefbabe 11y ago
  I would easily fall asleep given the right citation.
- gr8b8m8-88 11y ago
  Statistics and citations today is the Bible quotes / racial stereotypes of yesteryear. Some modern-day pseudo-scientist poster will cite some study that says "80% of chargers waste power if left plugged in at 100% charge" will then draw the logically faulty conclusion that therefore you should unplug your charger. The fact that the statistic study necessary had to ignore extra variables like if you have a lot of stuff plugged in, whether you're drawing power from a set of solar panels on your roof, whether you are using a super-special non-power wasting adapter, etc., necessarily makes the citation not a thought more credible than your great-great grandpa quoting the bible to tell you that you should marry your own race or citing stereotypes that you shouldn't trust your friend because he is Asian. True science, that is, proposing hypothetical models, analyzing results, and admitting no real results can be drawn due to insufficient model complexity, has been thrown out the window by pride and laziness.
  - Lawtonfogle 11y ago
    We can try to arrive at an exact answer. First, we need to start by assuming a sphererical laptop...

kvakvs 11y ago

Its best to consult with your laptop/charger/battery manual. If anything goes wrong, new battery costs like $20. Feel sorry for battery prices for Macbook users, but then their charger is smart enough to help battery survive longer.

deleted 11y ago

[deleted]

hn_ 11y ago

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

deleted 11y ago

[deleted]

JoeAltmaier 11y ago

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.

signaler 11y ago
Good advice. The only caveat being this only works for certain laptop models
- wtallis 11y ago
  And even when it appears to work, it may result in the processor being throttled so as not to overtax the power adapter without the battery available to supplement it.
- vidarh 11y ago
  Are there really laptops where you can't remove the battery when connected? I've never had one that wouldn't keep running when you pull the battery when on ac. However the reason I know this is the same reason I keep mine in: I've dropped every laptop I've ever owned on the floor multiple times, and I've had one or the other of battery or charger cable fall out at least once for all of them, at least with the battery in the chances of losing power is reduced (though I have on occasion had both fall out at the same time).
  - ggreer 11y ago
    Many laptops (such as all current Apple models) have built-in batteries. I guess you could remove the battery with special tools, but putting it back in may require re-gluing things.
untog 11y ago
You could remove the battery Oh, if only that were true...
nashashmi 11y ago

solve 11y ago

You should have talked to Google, instead of numerous people. http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li... Summary: 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. To answer your question: No. Side note: Don't blindly trust the manufacturer. Of course Apple wants you to wear out your laptop as fast as possible, once it's past the warranty. They're a business. 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%.

zymhan 11y ago
Finally, a citation, thank you.
- me2in 11y ago
  Thank you too!
gburt 11y ago
My understanding (again, uncited, like almost everything in these threads) is that one might /perceive/ a different result than this because the /software/ calibrates what 0 and 100% mean based on observation. If you never observe a zero (or, presumably, a 100%), it might recalibrate incorrectly. Again, this is based on old and uncited knowledge. There's surely someone here involved in writing power management software that could chime in.
rajeshmr 11y ago
This link from google says otherwise. https://answers.yahoo.com/question/index?qid=20130825212946AAJnwNY https://answers.yahoo.com/question/index?qid=20130825212946A... Lithium ion batteries do seem to have memory.

paulannesley 11y ago

> 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. — https://web.archive.org/web/20110521104819/http://www.apple.com/batteries/notebooks.html https://web.archive.org/web/20110521104819/http://www.apple.... via http://apple.stackexchange.com/a/12280 http://apple.stackexchange.com/a/12280 This could also be useful, but doesn't answer the question directly: http://www.apple.com/batteries/maximizing-performance/ http://www.apple.com/batteries/maximizing-performance/

deleted 11y ago
[deleted]
JimmaDaRustla 11y ago
Usually the reason behind discharging fully once per month is because when this happens, the laptop records how much capacity is required to recharge the battery. This will keep your battery % left accurate. The actual preference for getting the MOST DISCHARGES out of a lithium ion battery is discharging it to 50%. This, however, doesn't not to equate to longest battery life (in terms of age) for the use within a laptop/phone. Edit: There is something state of charge estimation models which may rely on this variable to decide how full they'll charge the battery. If you don't fully discharge and fully recharge the battery to update this capacity value, the SOC estimation model might overcharge the battery, thus decreasing the lifespan.
hvjackson 11y ago
The fact that Apple no longer has this statements on their website makes me think it's no longer true for their batteries (if it ever was).
- tjohns 11y ago
  They do have some advice on "long-term" storage here, which is roughly along those lines: https://www.apple.com/batteries/maximizing-performance/ https://www.apple.com/batteries/maximizing-performance/ They don't say what "long-term" is, but monthly seems reasonable to me.

hurin 11y ago

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

kachnuv_ocasek 11y ago
Sure, but the battery gets heated when left plugged in, which is not good for its health.
- hurin 11y ago
  Why would the battery be heated if it's not charging? You can set a gap - e.g. 80-100% where the battery won't start charging until it drops below 80%. Look at the documentation for your relevant power-management module.
  - qbrass 11y ago
    >Why would the battery be heated if it's not charging? Heat transfer from the device it's plugged into.
    - hurin 11y ago
      I'm not a hardware/electronics guy, but I'm rather skeptical that this is any kind of notable amount - do you have a reference?
      - sokoloff 11y ago
        Put the back of your hand (or your bare leg skin) against a laptop that's been in use. My Macbook is noticeably warm (maybe 15*F delta) in normal, non-charging, operation. That's with the benefit of conduction to the free air; I assume the inside delta-T is higher.
        hurin 11y ago
        That's not answering my skepticism to GGP's post - what he is saying is: a non-charging plugged in device has a significantly hotter battery than a non-plugged in device because of thermal-conduction across a non-charging wire?

yexponential 11y ago

Tesla e should know this.

thisispete 11y ago
Not sure if it's exactly pertinent, but If I remember correctly tesla recommends draining your battery to 20% then charging back up to 80% when driving on a road trip, but this if mostly for speed of charging. The car battery charges fastest in this half-full range, charging past 80% to 100% is a exponential rate like blowing air into an already full balloon, it gets harder as you reach 100%.. to their recommendation is not necessarily about battery health but more likely about reducing the speed of your mid-trip recharge.

bluedino 11y ago

Lenovo at one time (they still might, I'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. 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.

icc97 11y ago
Yep - I have this on my Lenovo.
vishnuks 11y ago
The Sony VAIO laptops also have this feature. Sad thing is there is no option for enabling this on Linux.
pingec 11y ago
Yeah, I have this on my Yoga 2 Pro. The utility is called Energy Manager - and the setting is "Conservation mode". https://forums.lenovo.com/t5/image/serverpage/image-id/34801i9268A10DBD1CEEEF?v=mpbl-1 https://forums.lenovo.com/t5/image/serverpage/image-id/34801...
rkda 11y ago
I'm using a Lenovo now and they still have it. Old Samsung also had something similar, Battery Life Extender, which won't stops charging at 80% even when plugged.

osetinsky 11y ago

Bad UX. One shouldn't have to worry about this!

baddox 11y ago
One doesn't have to worry about this.

SamReidHughes 11y ago

Leaving it plugged in has the same effect as removing the battery while it's plugged in (and putting the battery in identical thermal conditions). (Just think: if it were bad, engineering a workaround would be simple.) It'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/discharging to/from 100%, or leaving it unused for long periods of time.

lovelearning 11y ago

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

nashashmi 11y ago

All my questions have been answered via this link: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...

ignostic 11y ago
Yeah, that's a great starting spot for putting these crazy myths to bed. A lot of a people seem confused about two concepts in the article: ideal storage and depth of discharge. These are two separate concerns. If you try to maintain the ideal storage charge while it's in-use (say 40%), you're going to end up wearing your battery by putting it through unnecessarily deep discharge cycles. Unless you want to plug and unplug every few minutes, you should probably just leave it plugged in.

beachstartup 11y ago

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. when i called apple to replace the battery on warranty because it had started to bulge/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. so at the very least, if you care at all about your warranty coverage, you should probably cycle it normally.

elmar 11y ago

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.

webnrrd2k 11y ago

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's been done to death elsewhere, and is easily answered with a quick search. 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 "useless question" side of things. It's about basic hardware maintenance, and I'm honestly surprised it's gotten 37 points in 22 minutes (so far).

brudgers 11y ago
Don't do what you hate. Flag and move on.
matznerd 11y ago
Really? Because there doesn't' seem to be a definitive answer here and lots of conflicting information...
- webnrrd2k 11y ago
  I'm not saying it's a bad question, but I am asking if HN is the place to ask it. There are already lots and lots of answers to this question. Maybe try Reddit, or any of the various hardware forums. People are free to down vote me (and they have) for my opinion -- even though I've been polite and (I think) thoughtful. Even still, my opinion stands: HN is the wrong forum for this kind of question. There are many, many questions that HN isn't the place for... How should I charge my car battery? What's the best electric blanket? Should I use 10 or 12 gauge wire wire for my house? Maybe it would be a good question if the OP had researched it a bit first, and posted "surprising facts about your laptop battery" or something. But just a question about laptop batteries? Each one of these kinds of questions takes away from better quality, thoughtful or surprising content, which is what I like most about HN.
  - wyclif 11y ago
    If the question were about car batteries or electric blankets, I'd agree with you. But it's not; this is about laptop and mobile batteries, which concerns a huge percentage of HN users. That's also why this thread is so active. I'm in the 8-year club here on HN and I don't have a problem with it.

deleted 11y ago

[deleted]

brador 11y ago

Consider the cost of a replacement battery and if it's worth the subconcious mental strain this consideration places on you. In short, leave it in because it's not worth worrying about.

therobot24 11y ago
seriously, i can get a battery for my T410 for ~20$ on amazon, i'm not going to spend my time plugging and unplugging.
- keithpeter 11y ago
  Agreed. I do leave small laptop on suspend overnight (not plugged in) and then I do use it on the train into work, so a small charge/discharge cycle each day. The big typing box laptop (ancient T61p) is left on and plugged in a lot. May use a timer switch on the wall plug simply to reduce reliance on the overcharge protection in the battery/charger. I think those with devices that have batteries that cannot be replaced may be more concerned.
- cmavr8 11y ago
  Sure, but do you know what cells these batteries use? They're usually cheap chinese ones, of less than half the rated capacity. A proper replacement will cost much more. I did go mid-way, buying high quality Japanese cells and installing them in a chinese pack. A bit cheaper than a new official battery, but required some work.
adrusi 11y ago
Assuming your computer has a replaceable battery, which is not the case always. Replacing a $80 battery is worth it to avoid stress, but replacing a $2000 ultrabook may not be.
- TheGRS 11y ago
  I would think your ultrabook would be past its manufacturer's warranty anyway at that point anyway and would be a candidate for some sort of DIY battery replacement.

auganov 11y ago

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 :-)

skizm 11y ago
Apple ones also? This has happened to several dell and hp laptops I've owned or used long term, but both apple ones still keep charges for close to 3 hours even around 3 years after purchase without replacing the battery.

SuperCynical 11y ago

I'm an electrical engineering student who needed an idea for a school project dealing with reliability. I think I just found my project. Stay tuned!

singlow 11y ago

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 "over-charging". Within a year, the battery had about 50% capacity, and a replacement battery degraded as quickly. 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'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'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't run Windows for more than 1 hour in almost a year.)

seanp2k2 11y ago
I'm pretty sure that the charging logic is built into the battery or other dedicated charging circuit hardware. Almost positive that while the OS can say "don't give power to the battery", it can't say "give power to the battery even though the battery says no". Not a great source, but this agrees: http://computer.howstuffworks.com/laptop-battery-overcharged.htm http://computer.howstuffworks.com/laptop-battery-overcharged...
- singlow 11y ago
  But it can repeatedly recharge the battery from 99% to 100% throughout the whole day - which is not good for it.
- deleted 11y ago
  [deleted]

DominikR 11y ago

My personal experience with a Lenovo W520 having the battery needlessly inserted for two years (40 hours per week) while connected to the charger: The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger. So if there hasn't been a big change in how laptop batteries work in the last few years I'd recommend removing the battery whenever the charger is connected if possible.

jotm 11y ago
I found that fully discharging and recharging such a battery 3-4 times will bring it back to (near) its original levels. I've always had laptops plugged in all the time (desktop replacements) for months at end, with the battery acting as a UPS. When first disconnecting the power adapter, the batteries always discharged much faster than they should. After a few cycles, they went back to normal. I believe that leaving a laptop plugged in all the time is better for the battery than doing complete discharge-recharge cycles (5-100%).

bkanber 11y ago

Source: I have a master'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. Disclaimer: my knowledge of the field is from ca 2010. 1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100% too much. 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'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. 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. 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.

raphinou 11y ago
I read batteries wear off when plugged in in hot conditions, which is often the case for a running laptop. Can you confirm?
- JimmaDaRustla 11y ago
  Heat is a major cause of battery degradation, partially why I don't agree with constantly charging/discharging since it causes more heat. Keep your laptop cool, perhaps even consider battery saving options while plugged in if you find it is generating too much heat. Edit: A running laptop will cause heat, so shut it off when not using it. A plugged in laptop shouldn't create much more heat than a laptop running on battery power, if anything, the battery should be cooler when plugged in and fully charged (assumption made).
- bkanber 11y ago
  Long term battery degradation happens when its membranes degrade. There are hundreds of variables involved. Temperature IS a variable. But I'm reluctant to outright confirm what you're saying because it may be misleading. Avoiding plugging in when hot could help in some situations, but it won't help in all, so it's not a categorical rule.

tjohns 11y ago

I'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] This tells me that leaving your battery plugged in whenever possible is good, since it minimizes the number of cycles you're putting on the battery. If you unplug the battery once it's fully charged (and proceed to use it), you're just subtracting cycles from the battery's life. On the other hand, apparently there's a cost to letting the battery sit at 100% charge for too long. I don't know how long "too long is", but Apple's battery site says this about long-term storage: "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." [2] Keep in mind this is specifically talking about long-term storage only. Taken together, I interpret all this to mean that it's best to leave the laptop plugged in at 100% whenever possible, provided that you're occasionally taking it out and using it (so it's not "long-term storage"). That said, I'd love to see some quantitative benchmarks to confirm all this. ;) References: 1: http://en.wikipedia.org/wiki/Charge_cycle http://en.wikipedia.org/wiki/Charge_cycle 2: https://www.apple.com/batteries/maximizing-performance/ https://www.apple.com/batteries/maximizing-performance/

JimmaDaRustla 11y ago
Battery University typically looks at a discharge as a discharge. For example: Discharging the battery fully might yield 200 cycles, but discharging a battery 50% might yield 500 cycles. Obviously with the 50% discharge, you're only using half the capacity, but when you multiply the number of cycles by the capacity used, you can compare them.

dhanush 11y ago

Your battery's life is all about charge/discharge cycles. Say your battery has roughly ~1000 such cycles. Once you'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. Thus, the longer you can preserve your cycles, the longer your battery will survive. You can also read this thread: http://www.reddit.com/r/askscience/comments/1snzg1/is_it_actually_bad_for_the_battery_of_a_laptop_to/ http://www.reddit.com/r/askscience/comments/1snzg1/is_it_act...

mwexler 11y ago

There seem to be 2 main ways people use laptops in my unscientific "asking of my friends" survey: Plugged in for long periods, or unplugged for long periods. It seems like the vendors should have solved for both of those. 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'll forget where you last put the cord!) and "you'll have to buy a new battery... and they aren't cheap" if you stay plugged in. 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. Sorry, didn't mean to evoke this earworm: https://www.youtube.com/watch?v=8zLx_JtcQVI https://www.youtube.com/watch?v=8zLx_JtcQVI

kazinator 11y ago

> 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. Hi Zatkin, General advice: please study the materials hosted at the following great "Battery University" website: http://batteryuniversity.com/ http://batteryuniversity.com/ The charge and discharge protocols which are best for battery life and capacity depend on the kind of battery. Certain batteries benefit from being cycled, like NiMh and NiCad. It's not that important for lithium, IIRC. 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. (I could use a refresher myself; I'm going to study the materials on that website.)

robotcookies 11y ago

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'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.

jotm 11y ago
I've noticed that, too - I thought it's a safety feature to not overcharge the battery and kill it prematurely.

JimmaDaRustla 11y ago

A few things: 1. A lithium ion battery charger is smart, it will not overcharge or harm your battery in any way keeping it charged. 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. 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/recharge regularly to stay accurate. Not important for actual capacity you get out of your battery. 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. 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: http://chargedevs.com/features/the-challenges-of-battery-state-of-charge-measurements/ http://chargedevs.com/features/the-challenges-of-battery-sta... My recommendation: Don'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. Battery technology has changed a lot since I worked in the industry - they're always advancing and changing. There are many resources to keep yourself well informed: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li... 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'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.

deleted 11y ago

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istvan__ 11y ago

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.

Osiris 11y ago

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. The software I wrote has configurable alerts so a user can get an alert then it'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. [1] https://batterybarpro.com https://batterybarpro.com

james-skemp 11y ago
Slightly OT, thanks for this software. When I picked up a new Windows tablet I was looking for a better battery indicator and found BatteryBar Pro. I don't personally use that feature, but it was something that I liked. The feature to show remaining battery and charge time is what I really enjoy about it.
- Osiris 11y ago
  I'm glad you've found it useful. Let me know if you have any suggestions or feedback.

mangeletti 11y ago

Personal experience: I'm on an early 2011 MacBook Pro (purchased in March, 2011), which I'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 http://cl.ly/image/1a2d2y2V1J2O http://cl.ly/image/1a2d2y2V1J2O). 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 exactly this, and have since day one, except when I'm mobile and actually use the battery - about 2 times per month - today is one of those days): 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 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.

cerberusss 11y ago
One disadvantage is that you miss all Power Nap features: https://support.apple.com/en-us/HT204032 https://support.apple.com/en-us/HT204032 In my opinion, you don't miss all that much except for the following features: * Software updates download * Time Machine performs backups * Spotlight perform indexing

mcculley 11y ago

This is one of those interesting "mesofacts" that is related to how batteries used to work. It'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. It'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.

sean-duffy 11y ago

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't dealt with for us by some control chip is a conspiracy that laptop manufacturers purposely limit the battery's life by not including this functionality. Which I suppose isn't hugely far fetched, but I'd still find it hard to believe.

mikelyons 11y ago

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

polyx 11y ago

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.

cerberusss 11y ago
Exactly, that's my method as well. Although I have to say it's not so much a necessity rather than a preference for new and shiny. Hardware is so powerful nowadays.

facepalm 11y ago

Supposing it would matter, why wouldn't laptop manufacturers include some 0.01$ part that switches off the charger as needed?

t0mbstone 11y ago

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't Apple (or any other laptop manufacturer) just have the power controller do that automatically when your laptop is plugged in? I call malarkey on all of it. I've had my laptop plugged in for years and it sits at 100% most of the time. I don't have time to deal with that kind of hassle, even if it is true.

jccooper 11y ago
Many do. I've had several Windows laptops that want to do this.

geoelectric 11y ago

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's only off for the suspend portion). After 201 full charge cycles in ~2 years (trickle charging at 100% takes awhile to equal one cycle) I'm still at 95% battery life. My take is that, at least for MacBooks, it doesn't make nearly as much difference as not letting your computer sit in a hot car a lot and other standard battery hygiene things.

yellowapple 11y ago

From a technical perspective, yeah, you probably should unplug your laptop at around 70-80%, since that'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't universally available, though. From a realistic perspective, though, I've found that (in my experience) to be marginally beneficial; the slight benefit to battery health it had afforded to me wasn't worth the hassle.

archergod 11y ago

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 "ON". after 3.5 yrs HP/laptop software show indication of "END of life" 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't work as long and by the time 5yr is complete it works only 20-30 minutes. But isn't it that good life for batteries anyways? and yes my charger were hot enough to cook :).

brudgers 11y ago

From the Help and Support for the ThinkPad X201 Tablet: 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.

cmavr8 11y ago

Wrote a small script to easily put my Thinkpad battery to storage mode (50-70% SOC) and back to full charge: https://gist.github.com/cmavr8/204132a008d4ebabce94 https://gist.github.com/cmavr8/204132a008d4ebabce94 Also one (lame) for bat stats on linux: https://gist.github.com/cmavr8/bdf591d8dc66290ae87a https://gist.github.com/cmavr8/bdf591d8dc66290ae87a

cmavr8 11y ago
They're not well tested but seem to work. Let me know if you have improvement suggestions that are easy to do. Chris

xuancong84 11y ago

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