Hacker News new | comments | show | ask | jobs | submit login
Ask HN: Should I unplug my laptop charger at 100%?
308 points by zatkin 987 days ago | hide | past | web | favorite | 237 comments
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.

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.

That's nice to know.

However, i'd rather buy a new battery after 5 years (if my laptop is still fit and the battery is dead), than having to complicate my life and think about when to unplug or charge my laptop multiple times each day for 5 years...

My Macbook air from mid 2011 is currently at 100/6700*5629 = 84% battery health. (6700 = design capacity, gathered from "ioreg -l -n AppleSmartBattery -r".

I agree with you. Instead of optimizing for battery life by constantly checking & adjusting my charging, I'd rather live my life focusing on other things. What I do is super simple: plug it in whenever possible.

Same here. I have no reason to dispute the expert who says Lithium-ion batteries "don't love 100%". Fine, but they don't seem to dislike it too much, either. So far I haven't had any batteries that didn't perform well when they were mostly plugged in, occasionally discharged in mobile use.

I see some similarities to, e.g., medical pronouncements that some particular food increases risk of cancer. It's easy to get alarmed, but there's a big difference between it increasing my likelihood of getting cancer by 0.05% and making cancer, say, (just to illustrate the point) 100 times more likely. The former I would likely ignore and the latter would probably make me give up the food instantly.

I get what you're trying to say, but there's an interesting point to be made here about absolute vs relative risk: imagine for instance your absolute chance of getting cancer was less than 0.0005%

Is your machine even operational? My macbook air from 2011 (with Yosemite) is sluggish to the point of being unbearable to use and just collects dust.

Yosemite is a total mess, but it has gotten slightly better with 10.10.3 (if you are willing to ignore the Photos app, which launches constantly for no reason).

If you are willing to mess with drivers, you may want to try installing Linux. On a 2013 Air, battery life and performance (even graphics!) are surprisingly better with Debian Jessie than with OS X. Of course, it is a newer model than yours, but the drivers will only be more stable and mature with a 2011. Especially if you have 4 GB RAM and you're running into a memory barrier with OS X, you should see a significant improvement.

My Photos app was launching because it got reset at the default action when my iPhone connected. It's possible that's what is happening to you too.

My iPhone and a couple flash drives do this, probably because it thinks my scanner is a camera. Unfortunately I can't stop it from launching (assuming I can disable it in Preferences) until it will actually launch—I have left it beachballing for a very long time and it still has not finished launching, so I just force quit it.

Open the Image Capture application, and you can change the setting at the bottom-left of the window. It seems to get increasingly hidden with each OS release.

This used to be the only place to change the setting—which was ridiculous because virtually no one ever used Image Capture (especially because iPhoto opened by default). But to Apple's credit, you can now also change this preference in Photos. Of course, as the previous poster pointed out, you have to actually wait for Photos to finish launching. But at least it's there now!

If you want to stay on OSX:

Always 'Quit' open apps you don't use, never, NEVER have 2 sessions open at the same time, and try using lighter applications when you can (VLC instead of iTunes for music, Skim instead of Preview for PDFs, Preview instead of Photos for images, etc)

I have to use a 2012 MBP with Yosemite from time to time and if I follow these rules it is definitely bearable.

I recommend VOX over VLC because it has Soundcloud integration and looks nice.

My 2011 11" Air (i7) runs 10.10 just fine. I haven't noticed any slowdown over the past 4 years, although I do disable all the unnecessary transparency and animations Apple keeps adding for seemingly no reason.

By the way, my battery health is also around 85% after 500 cycles and being plugged in and charged to 100% whenever possible.

Switch to OSX 10.9, problem solved. My 2012 rMBP with top end specs is also sluggish on 10.10.3. Not sure what Apple is thinking. On the other hand I am still using my 2003 Panasonic CF 73. It's not quick, but for the limited tasks of automating my DSLR it works perfect.

Define unbearable. Up until 10.10.2 the OS X window server was a bit sluggish. Now it's tolerable for my purposes.

MacBook Pro (13-inch, Early 2011) 2.3Ghz i5, self-upgraded hardware to 16GB 1333MHz DDR3 RAM, Samsung SSD 120GB, caddy with 500GB HD, replaced battery with cheap Chinese, running 10.10.3 like a charm (only my SD-card slot never worked).

Yes, mine still runs smooth, that's why i always buy the fastest model (processor) available, it's more expensive when buying but usually saves money in the long run. (i have the 1.8GHz Dual-Core Intel Core i7)

my macbook 2008 running os x 10.7.5, 128gb ssd and 4gb ram is still fast enough and gets the job done. It's even faster than the latest middle to low end windows PC's (dual boot with windows 7)

MBP 2009 here... works as good as new. Only upgrade was a SSD for the hdd. Still only 4GB RAM. Wouldn't want to do much video/graphics processing but everything else is fine.

Mid-2010 MBP upgraded with SSD runs perfectly on 10.10.3

Same here, only boots extremely slow (I have the original HDD but 8gb memory)

You should really upgrade to SSD. Makes a huge difference (easily 5-10X speed-up for many tasks).

I run Windows on mine and it runs fine (late 2010 13", 4GB model). Only use it when travelling though.

Agreed. I do avoid leaving my laptop plugged in overnight, but I'm also not too careful about leaving it plugged in during the day. I'll often pop the charger out when I notice the battery at 100%, but I'm not going to lose sleep if I forget about it or operate slightly sub-optimally.

I have a Lenovo Yoga Pro 2, it's got an app that manages this for me. I turn on "conservation mode" and it keeps the charge at 55%-60%. The only negative here (and it would be there with doing it yourself) is that if I run out without the charger I'm essentially at 1/2 capacity.

Could you clarify how you arrived at 84% battery health? After the command "ioreg -l -n AppleSmartBattery -r" I see DesignCapacity, but where does the other number (5629) come from? I'd like to compute battery health myself...


  ioreg -l -n AppleSmartBattery -r | grep -i capacity
gives me

  "MaxCapacity" = 8329
  "CurrentCapacity" = 8002
  "DesignCapacity" = 8440
I'm guessing MaxCapacity or CurrentCapacity (I'm at 100% charged on a ~1 year old MBP, so I don't know which number is appropriate)

Your battery percentage is going to be:

    100 / DesignCapacity * MaxCapacity
Or, in the way that makes way more sense to me:

    MaxCapacity / DesignCapacity * 100
Which, with your results, yields something to the effect of:

It's kind of (read: very) dirty looking, but you can get the same result with:

    echo $(ioreg -l -n AppleSmartBattery -r | grep MaxCapacity | awk '{print $3}') / $(ioreg -l -n AppleSmartBattery -r | grep DesignCapacity | awk '{print $3}') \* 100 | bc -l

    ioreg -l -n AppleSmartBattery -r | awk '/MaxCapacity/{mc=$3};/DesignCapacity/{dc=$3};END{print 100*mc/dc}'

mine is at 103.211

He's just dividing the current battery capacity by the 'new' battery capacity. You can just let a program like Coconut Battery do it for you.

Coconut Battery is nice. You can let it take snapshots and compare it with other batteries online. You can view my battery health here http://ccbonline.coconut-flavour.com/index.php?bid=d78a6c124.... I try to unplug at 100% and recharge it at 10-20%. Once per month I drain it all the way to 0%.

After reading this thread I try to keep my battery at a 50-80% charge :)

Except when I do some CPU intensive stuff like compiling or rendering, then it is being charged thought the process.

Just another data point: I'm at 77% (4431/5770) on an April 2010 MBP. I tend to leave it plugged in when possible, and often run it far down when not near an outlet. I take it that's about the worst I can do, but the convenience has seemed worth it.

On ubuntu, you can do something similar with

    upower -i /org/freedesktop/UPower/devices/battery_BAT1 | grep capacity | awk '{print $2}'
You can see all of your power options with

    upower -e

On Debian:

    bc -l <<< "100 * $(cat /sys/class/power_supply/BAT*/energy_full) / $(cat /sys/class/power_supply/BAT*/energy_full_design)"

Agreed. My mid-2012 Macbook Pro Retina has been plugged in @ 100% nearly all the time it's been in use. Pretty much the only time it's not plugged in is when traveling. Battery is at 7845/8460 CurrentCapacity/DesignCapacity or 93%.

I treat the 2012 MacBook Air I use at work the same way. It's plugged in all the time, and it stays in the office. I think its capacity is 95% or higher.

Same but slightly worse, mine is generally always plugged in.

100/8460*7633 or 90.22%

With thinkpad acpi modules you can write scripts to automate this. https://wiki.archlinux.org/index.php/Tp_smapi

Could you elaborate on how you arrived at the "5 years" lifespan for batteries having charge state of 0-100%?

That was just a personal estimate, obviously if the battery health is for example at 75% you also lose 25% of 'the time' to work without plugging it in... so if that becomes a problem when traveling i might want to buy a new one. For others this might not be a problem of course.

Ok. I was wondering if the breakeven is set as 5 years but if the cycle of tilt to full makes the life shorter for the battery, then it may not be worth it. I agree that if I've to weigh battery life vs my time, I would go with the latter.

So what my laptop should do automatically is to stop charging once it hits ~90%, and start charging again when it hits ~40%. And the OS should give me an easy-to-reach option to "charge to 100%" for when I'm about to make a trip. Why hasn't anyone implemented this yet?

I have this as "conservation mode" on my Lenovo Yoga Pro 2, and probably all new Lenovos.

See Siracusa's analysis of this suggestion.


TL;DR: good idea, but people will forget and become shitty when their laptop isn't at 100% when they go on a trip.

My Sony VAIO had this 7 years ago.

Yeah my thinkpad did this from the same vintage but that was only on Windows. I think quality of battery management on other Operating Systems is varied...

My ThinkPad E530 (1 year old) has this, it's part of Lenovo Power Manager. Again, only on Windows (it doesn't charge at all in Ubuntu, which I've never managed to get to the bottom of)

Macbooks have also done this for, like, forever, but more with the top few percent than 10%-60%

Yeah, it lets it drop to about 97% before it starts charging again. That doesn't really count, although I guess it's nice.

Yes this is not real battery care-taking. Ubuntu does it by default like that (I guess linux kernel in general). Although the low and high thresholds (97 and 100% resp.) are adjustable.

You're right. Someone should have done it in each OS. In linux it's just a matter of echo-ing a few numbers to the write "files". I just made a script to do it, see my other comments here if interested.

This assumes the battery percentage displayed is the SOC. This might be the case for laptops or small appliances where manufacturers are happy to trade long battery longevity for a small gain in time to empty, but the Model S for example has gap of a kWh+ and will simply not charge or discharge the battery fully, to avoid these cases where a very low of very high SOC damages the battery.

Correct. I, of course, am talking about battery cells, and not battery systems. It is up to the reader to understand the specifics of their use-case and apply this information appropriately.

>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.

My thinkpad has a mode for keeping a healthy battery that stops charging at 90%, then trickle charges to keep it there (it also allows for fine tuning of this behavior)

Yes my Samsung Serie 7 (now Ativ Book 8 I think) has the same feature (stops charging at 80%) and I think my previous Sony Vaio also had something like that..

I use it on my Samsung given that I don't really need +5 hours without plugging anyway.

excellent - what software does this? Built into the OS or a separate application?

On ThinkPads this can be (or maybe used to be) configured in one of the preinstalled ThinkVantage utilities (Power Manager). But I believe that the whole charging logic itself is really in EC firmware and this application is only user interface for that.

As an aside: the mechanism works in slightly different way (at least on all of my 4 thinkpads of different generations). There are two thresholds, maximum battery capacity when charging can start and capacity when charging stops, the aforementioned application even seems to have some kind of logic to set these thresholds according to battery aging.

Also, trying to keep Li-ion cells charged to constant state of charge is not good for their lifespan. What is commonly known as trickle-charging (charging by infrequent, short but large pulses of current) is actively discouraged by most cell manufacturers, sometimes even citing safety reasons.

It's definitely a separate app. Lenovo has various versions of "Power/Energy management" apps available depending on the specific model of the laptop. Not sure about other manufacturers though.

From experience, it's a separate app but manufacturer specific. Haven't had much luck looking for a generic app.

Why don't device manufacturers code this kind of thing into their power/battery drivers?

Is it possible they do, and the battery level indicator you're looking at is lying to you?

I don't know, but there seems to be not very much incentive to invest a lot of R&D dollars on this problem from a manufacturer standpoint:

* Devices marketed on how long they last on a single charge, but much less often on how quickly the battery degrades * Batteries are a later upgrade upsell opportunity * I would not be surprised to learn that a significant number of device upgrades start as simply wanting a better battery (but why not upgrade at the same time)

This is often the case. Not all the time, but lots of devices have started doing this.

This is definitely the case for the Prius, even from 2004. I really doubt higher-end manufacturers like Apple wouldn't do the same since they control the entire stack.

I'm not sure I'd want my battery to be "that" smart, safety measures coded into the power/battery drivers (which would be present on the battery itself, not main OS drivers) sounds about right. Optimizing and things like that I rather leave up to the OS, or even an APP (as long as it cannot do anything dangerous).

I mean it's one thing if my OS can control the charging cycle to some extend, whether Apple can install drivers (and bad guys bad stuff) on my Battery "smart" board.

It may seem like a big leap now, but I bet someday (or perhaps even now, why do people place tape on their webcams otherwise) it could become a problem.

But of course, to my knowledge so far Apple is doing a pretty good job in keeping Macs and OSX kind off secure (don't quote me on that), however than again I don't want OSX to become as restrictive as iOS or I'll have to switch to Linux t get my dev-tools working. (not a fan of that personally)

Granted device manufactures are pushing devices out every year or two, and it's in their best interest to offer the longest battery life possible, there is no incentive or evidence present that manufactures are limiting the maximum charge to prolong battery life.

Having read similar perspectives I was always annoyed that there was no way to essentially pause the charging and perhaps run via trickle charge at a set percentage, so if I'm tethered to a desk for a week I could keep the battery at 70% and then choose to bring it to 100% if I expect a long day away from an outlet. Perhaps this is not plausible for some reason? Would it be control required at the battery firmware level? (Referring to an Apple laptop for example)

The only concerns I have with this advice is the heat generated by constantly draining/charging the battery will degrade the life, plus constantly cycling will degrade the battery in other ways as well.

If a charger could be tweaked to charge the battery slowly and not overcharge it, that'd be the ultimate solution.

SOC is relative to the application, but it is possible many applications nowadays purposely operate within a specific SOC and not exactly 0-100%. We need an Apple battery engineer in here to confirm ;)

Edit: You already acknowledged this elsewhere.

Temperature, temperature gradients, heat, membrane potential, charge/discharge speed, etc, are all variables in long term battery life, along with dozens of others.

So I'm reluctant to agree or confirm with any sweeping statement about a single variable (in this case, heat generated by charging), because it may be true in some cases but not in all. And it also depends on the specific battery.

Most likely, for most laptops, for most daily use-cases, and a charging pattern of 90-50-90 in 2-3 hours, I'd rather take the slightly increased temperature than keep the battery at 100% for that time period.

But again: it depends. On so many things.

Edit: also, either case (keeping at 100% for 3 hours vs 90-50-90 for 3 hours) is better than keeping at 100% 24/7. So no harm done if you can't decide which is better. Just A) don't plug in all day long and B) don't go crazy with the heat and you'll be fine.

The Thinkpad power manager mentions the issue and comes with different modes to maximize the battery lifespan.

Quote: "If you primarily use your computer with the AC adapter attached and only infrequently use battery power, battery deterioration may occur faster if the battery is constantly charged at 100%. Lowering the charge thresholds for your battery, periodically resetting the battery gauge, using Maximum Lifespan mode, or using Battery Health Mode will help increase its lifespan."

That's insightful, thanks.

But how do I know the battery reports honest numbers? If all these years spent dealing with hard disks tought me anything, it's that what's being reported by the device could be totally different from the reality :)

Perhaps some brands charge a premium for a "long lasting" battery whose only actual difference from a regular one is a firmware hack that keeps it at %80 charge? Can I actually know this?

That reminds me of over-provisioning in SSDs


If I was going to do this, it would be at the laptop end, because that's were I'm sitting.

How long until the power plug, or the receptacle in the laptop, wears out?

How expensive is labor to fix the receptacle, compared to the cost and convenience of replacing a battery?

Unless the OS manages this for me (and maybe it does behind my back?), I'm not going to bother. But many thanks for the interesting writeup.

I read batteries wear off when plugged in in hot conditions, which is often the case for a running laptop. Can you confirm?

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.

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).

On Linux and ThinkPads you can use acpi_call to set these tresholds https://wiki.archlinux.org/index.php/Tp_smapi#2nd_Option (the old tp_smapi way ceased to work about four years ago).

tp_smapi still works fine on my T61?

I meant laptops released four years ago.

It'd be nice if the battery controller/charger had the intelligence to make these optimizations transparent to the end user. So present them with 100% or whatever, but in actuality, the battery is at 90%, most of the time it's plugged in, and so on.

I thought this was actually standard operating procedure for laptop batteries (or really, anything using lithium batteries). Similarly, 0% is actually more like 5 or 10%.

If you actually deep discharge a lithium battery to 0%, think they'll sometimes have problems taking a charge again. You see this occasionally when someone has taken to 0% on the meter, then let it self-discharge on the desk for a long time.

Yeah I thought so too. The parent comment seemed to indicate otherwise.

A lot of laptops allow for various trickle charging modes. Generally they stay charged between 90 and 100% (charges to 100 then wait until 90), some allow for charging to 80.

In my experience there can be memory effects when fully capping at 80% over the years, though.

Li-ion batteries do not have a memory effect. LiFePO4 do, however.

This is exactly the pattern I've fallen into with the Apple Watch. It charges so fast, and my usage hasn't been that extreme. I charge it during showers and my son's bedtime, and I'm good to go.

Exceptional. Armed with this info, this will surely save me a ton of money over time, especially if I can get my employees to adopt this reasoning. I've been dying for this answer for years now.

Having an employee micromanage this will actually cost you more money over time.

Depending of the type of work your employees do, it might be frustrating. If you need CPU power you'll not get the full speed when unplugged.

Also unplugging/replugging is annoying, get a brand/model that already has the charging cap option and just ask to enable it.

> plug in and let charge to 90%, unplug and use for a couple of hours, plug back in at 50% or so

Well isn't this what computers are good at? I thought modern computers had a microcontroller for doing this...

> 1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100% too much.

Great. Another reason to avoid barely-one-day batteries on phones. They'll die sooner!

>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.

or set your power drivers to do it for you.

> or set your power drivers to do it for you.

Pray tell me how. (Macbook Pro 2010.)

It already exists. E.g. The Dell laptop I currently own already has it as part of some or other pre-installed software.

Time to write an app to do that (possibly only for rooted phones), someone?

That's assuming that devices don't already operate in this range of SOC within device...which I wouldn't believe to be true.

Yes, I didn't (/don't) know about that. I believed the charging cycle would have become intelligent by now, but thought then this whole thread wouldn't come up if that was the case.

this sounds like a problem begging for a software solution.. any reason this sort of functionality is left to the user stead automated by the device?

What if you're mostly using the laptop near a power outlet? Wouldn't it be better to keep it plugged in to avoid charging/discharging the battery at all?

No. Leaving a battery at 100% is bad for the battery's life. Just as bad as deep cycling all the time. Even if your laptop is stationary, knock the charger out once a day and let it run on battery power for a bit.

I'd like to see some supporting info on this. It's not that I don't believe you— what you say sounds plausible enough, it's just that I'd rather understand why this is so.

Do you have a citation for that?

Check out Chester Simpson's work from Natl Semiconductor. I don't have a DOI available for you unfortunately, but Simpson is a great starting point.

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.)

This is my favorite technology superstition, some citation would help many people sleep easier it seems.

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.

We can try to arrive at an exact answer.

First, we need to start by assuming a sphererical laptop...

The perfect is the enemy of the good.

The question is simply "what do we know about this problem" not "what is the absolute unquestionable universal answer."

Also your comment has some interesting points but starting off by comparing statistics and citations to bible quotes and racial stereotypes isn't going to win you much support.

I would easily fall asleep given the right citation.

It's difficult to argue the idea that any manufacturer of a device containing a battery cell would not engineer the system for the proper balance of longevity, capacity, and durability to result in acceptable quality to customers.

If I were running a social network like this, I'd post questions with definitive answers like this one, see who voted up / wrote the wrong answers, and then block those people from voting / commenting again for a long time period.

Do that enough times, and you'd quickly have the smartest site on the Internet.

This thread literally has people posting links to Yahoo Answers.

Well, after you divide the total IQ to the zero remaining posters, you can choose what value you want for the mean.

Obligatory (and analogous) XKCD: https://xkcd.com/927/

This isn't remotely related to this discussion.

> 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.... via 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/

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).

Indeed. From my understanding, while this is still technically true, they have replaced the need for users to do anything with chips in the batteries themselves which shut off recharging when they're near 100%.

That's why if you pay attention you'll often see your battery % go from 97%-100% and then back down to 97%. It is reporting as "charging" but in reality it goes idle to let the battery de-charge a little.

They do have some advice on "long-term" storage here, which is roughly along those lines:


They don't say what "long-term" is, but monthly seems reasonable to me.

It specifically calls out recharging it to 50% every six months, so I assume it's a month+ kind of long term.

Also Apple seems to indicate that storage in a deep discharge state is far more damaging than storage at near-capacity based on the wording.

So if you're in doubt, charge it before you store it.

Finally, I don't think there's anything on that page that says you shouldn't keep your laptop plugged in when it's at 100%. I would be very surprised if they didn't have some cycle-conditioning going on. I have both a 2008 unibody and 2010 MBP, both essentially remaining plugged in for years. I don't think the battery life is abnormally low for their age, they still are capable of several hours of usage on battery.

Or they're trying to bolster sales of their warranty initative: Apple Care

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.

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.

I think an environmentalist just died a little bit after reading this.

But yes, this is the only sweeping statement that could be universally applied. Anything else is just anecdotal and something to talk about at the next happy hour.

seriously, i can get a battery for my T410 for ~20$ on amazon, i'm not going to spend my time plugging and unplugging.


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.

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.

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.

Even if it's not made to be user-replaceable, surely it can be replaced by someone with the right skills and tools for much less than the full replacement cost of the entire device.

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.

Isn't battery warranties usually 1-year long? A device would have minimum 2-year warranty in Europe so you can find yourself in the middle...

Apple charges something like $120 for changing the battery out. Not worth the stress to micromanage that, really not. It’s never about $2000.

You should have talked to Google, instead of numerous people.



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%.

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.

Finally, a citation, thank you.

Thank you too!

This link from google says otherwise.


Lithium ion batteries do seem to have memory.

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 :-)

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.

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.

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.

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.

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.

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.

> 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.

the laptop can run, plugged in, without the battery in it.

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%?

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).

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). 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.

One disadvantage is that you miss all Power Nap features: 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

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've pulled out batteries out of working laptops to test just that theory - only a 2006 Toshiba P300 shut down, the rest of them (newer, Fujitsu, Dell and HP) ran uninterrupted. Either they switched faster or more likely, ran off the AC all the time. It's just good design...

Not 10%! That's terrible for a Lithium battery. Charge it when it gets to 40%.

Actually it has been lab-determined that batteries should be charged once they hit 60%.


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.

< 40% is not "too far", it's just outside the optimal standing charge range for battery longevity, which studies have found is 40-80%.

In other words you can use your battery from 100% all the way down to shutdown- but the more time it spends in the 40-80% range, the longer its service life.

Ah, so I can only use 60% of my battery before I have to find a plug? Bummer.

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.

20% is the standard for lithium batteries, but sooner is always better.

I've often popped the batteries out of ThinkPad's when they are full and just ran on the wall wart. I don't know if they bypass automatically, but you can certainly just pop the battery out yourself.

10+ year old lenovos run when the battery is yanked. as do toshibas and dells.

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. ;)


1: http://en.wikipedia.org/wiki/Charge_cycle

2: https://www.apple.com/batteries/maximizing-performance/

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.

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.

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

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

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.

I'm glad you've found it useful. Let me know if you have any suggestions or feedback.

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

One doesn'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'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.

Many do. I've had several Windows laptops that want to do this.

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.

Yeah, I have this on my Yoga 2 Pro. The utility is called Energy Manager - and the setting is "Conservation mode".


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.

The Sony VAIO laptops also have this feature. Sad thing is there is no option for enabling this on Linux.

Yep - I have this on my Lenovo.

It depends and usually it'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.

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.

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%.

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.


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...

it is an option in some power drivers.


Is there a way to modify the max charge level on apple laptop products?

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.

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.

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%).

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

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.)

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...

But it can repeatedly recharge the battery from 99% to 100% throughout the whole day - which is not good for it.

All my questions have been answered via this link:


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.

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 :).

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.

You could remove the battery

Oh, if only that were true...

Good advice. The only caveat being this only works for certain laptop models

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.

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).

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.

This is exactly what I do. When I am plugged in to a desk and do not intend to move for longer than 3 hours, i take the battery out.

For maximum effect, remove it at 40-70% and store the removed battery in the fridge.

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.

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...

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.

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

Also one (lame) for bat stats on linux: https://gist.github.com/cmavr8/bdf591d8dc66290ae87a

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


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.

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-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_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.

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.

Sure, but the battery gets heated when left plugged in, which is not good for its health.

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.

>Why would the battery be heated if it's not charging?

Heat transfer from the device it's plugged into.

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?

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.

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?

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.

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'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!

Supposing it would matter, why wouldn'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 "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.

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.

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.

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_act...

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.

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.

> 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/

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.)

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).

Really? Because there doesn't' seem to be a definitive answer here and lots of conflicting information...

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.

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.

Don't do what you hate. Flag and move on.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | DMCA | Apply to YC | Contact