
Ask HN: Should I unplug my laptop charger at 100%? - zatkin
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.
======
bkanber
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.

~~~
DavideNL
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".

~~~
JoshGlazebrook
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.

~~~
0942v8653
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.

~~~
epmatsw
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.

~~~
0942v8653
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.

~~~
jmah
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.

~~~
gnicholas
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!

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

~~~
gr8b8m8-88
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
We can try to arrive at an exact answer.

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

------
paulannesley
> 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....](https://web.archive.org/web/20110521104819/http://www.apple.com/batteries/notebooks.html)
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/)

~~~
hvjackson
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
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.

~~~
r00fus
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.

------
brador
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.

~~~
adrusi
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
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.

~~~
cmavr8
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...

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

[http://batteryuniversity.com/learn/article/how_to_prolong_li...](http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries)

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
Finally, a citation, thank you.

~~~
me2in
Thank you too!

------
auganov
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
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.

------
mcculley
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.

------
cjbprime
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
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.

~~~
ignostic
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.

------
mangeletti
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
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

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

~~~
tjohns
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.

~~~
sliverstorm
< 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.

------
tjohns
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
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.

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

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

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

~~~
baddox
One doesn't have to worry about this.

------
t0mbstone
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
Many do. I've had several Windows laptops that want to do this.

------
bluedino
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.

~~~
pingec
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/34801...](https://forums.lenovo.com/t5/image/serverpage/image-
id/34801i9268A10DBD1CEEEF?v=mpbl-1)

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

------
elmar
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.

------
ars
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%.

~~~
jotm
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
it is an option in some power drivers.

------
sean-duffy
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.

------
mwexler
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)

------
singlow
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
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...](http://computer.howstuffworks.com/laptop-battery-
overcharged.htm)

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

------
nashashmi
All my questions have been answered via this link:

[http://batteryuniversity.com/learn/article/how_to_prolong_li...](http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries)

~~~
ignostic
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.

------
archergod
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
:).

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

~~~
vidarh
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
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.

------
geoelectric
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
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.

------
xuancong84
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...](http://softwarerecs.stackexchange.com/questions/10441/laptop-
battery-charging-control-software-for-windows/19426#19426)

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

Chris

------
SamReidHughes
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.

------
JimmaDaRustla
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...](http://chargedevs.com/features/the-challenges-of-battery-state-of-
charge-measurements/)

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...](http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries)

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.

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

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

Heat transfer from the device it's plugged into.

~~~
hurin
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
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
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?

------
brudgers
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.

------
istvan__
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.

------
SuperCynical
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!

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

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

------
lovelearning
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.

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polyx
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
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.

------
dhanush
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...](http://www.reddit.com/r/askscience/comments/1snzg1/is_it_actually_bad_for_the_battery_of_a_laptop_to/)

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

------
yexponential
Tesla e should know this.

~~~
thisispete
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.

------
beachstartup
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.

------
DominikR
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
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%).

------
kazinator
> 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.)

------
webnrrd2k
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).

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

~~~
webnrrd2k
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
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.

