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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 tim

by bkanber 11y ago

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

raphinou 11y ago
I read batteries wear off when plugged in in hot conditions, which is often the case for a running laptop. Can you confirm?
- JimmaDaRustla 11y ago
  Heat is a major cause of battery degradation, partially why I don't agree with constantly charging/discharging since it causes more heat. Keep your laptop cool, perhaps even consider battery saving options while plugged in if you find it is generating too much heat. Edit: A running laptop will cause heat, so shut it off when not using it. A plugged in laptop shouldn't create much more heat than a laptop running on battery power, if anything, the battery should be cooler when plugged in and fully charged (assumption made).
- bkanber 11y ago
  Long term battery degradation happens when its membranes degrade. There are hundreds of variables involved. Temperature IS a variable. But I'm reluctant to outright confirm what you're saying because it may be misleading. Avoiding plugging in when hot could help in some situations, but it won't help in all, so it's not a categorical rule.
revelation 11y ago
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.
- bkanber 11y ago
  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.
basch 11y ago
>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.
- piyush_soni 11y ago
  Time to write an app to do that (possibly only for rooted phones), someone?
  - JimmaDaRustla 11y ago
    That's assuming that devices don't already operate in this range of SOC within device...which I wouldn't believe to be true.
    - piyush_soni 11y ago
      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.
- gpvos 11y ago
  > or set your power drivers to do it for you. Pray tell me how. (Macbook Pro 2010.)
- zo1 11y ago
  It already exists. E.g. The Dell laptop I currently own already has it as part of some or other pre-installed software.
JimmaDaRustla 11y ago
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.
- bkanber 11y ago
  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.
DavideNL 11y ago
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".
- bkanber 11y ago
  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.
  - tertius 11y ago
    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.
- rexf 11y ago
  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.
  - hsitz 11y ago
    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.
sigmar 11y ago
>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)
- BorisMelnik 11y ago
  excellent - what software does this? Built into the OS or a separate application?
  - m3Lith 11y ago
    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.
  - dfox 11y ago
    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.
  - rkda 11y ago
    From experience, it's a separate app but manufacturer specific. Haven't had much luck looking for a generic app.
- Guillaume86 11y ago
gpvos 11y ago
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?
- silverlake 11y ago
  My Sony VAIO had this 7 years ago.
  - IE6 11y 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...
    - SmellyGeekBoy 11y ago
      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)
- tertius 11y ago
  I have this as "conservation mode" on my Lenovo Yoga Pro 2, and probably all new Lenovos.
- misnome 11y ago
  Macbooks have also done this for, like, forever, but more with the top few percent than 10%-60%
  - gpvos 11y ago
    Yeah, it lets it drop to about 97% before it starts charging again. That doesn't really count, although I guess it's nice.
deleted 11y ago
[deleted]
aqme28 11y ago
Why don't device manufacturers code this kind of thing into their power/battery drivers?
- shocks 11y ago
  Is it possible they do, and the battery level indicator you're looking at is lying to you?
  - bkanber 11y ago
    This is often the case. Not all the time, but lots of devices have started doing this.
  - r00fus 11y ago
    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.
  - dwg 11y ago
    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)
- nosuchthing 11y ago
  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.
- lawry 11y ago
  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)
BorisMelnik 11y ago
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.
- Guillaume86 11y ago
  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.
- ElijahLynn 11y ago
  Having an employee micromanage this will actually cost you more money over time.
zobzu 11y ago
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.
- bkanber 11y ago
  Li-ion batteries do not have a memory effect. LiFePO4 do, however.
tgb 11y ago
> 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!
deleted 11y ago
[deleted]
jules 11y ago
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?
- bkanber 11y ago
  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.
  - jules 11y ago
    Do you have a citation for that?
    - bkanber 11y ago
      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.
  - wyclif 11y ago
    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.
mibollma 11y ago
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."
mc32 11y 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.
- geoelectric 11y ago
  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.
  - mc32 11y ago
    Yeah I thought so too. The parent comment seemed to indicate otherwise.
a3n 11y ago
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.
plq 11y ago
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?
- omribahumi 11y ago
  That reminds me of over-provisioning in SSDs http://en.wikipedia.org/wiki/Write_amplification#Over-provisioning http://en.wikipedia.org/wiki/Write_amplification#Over-provis...
justifier 11y ago
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?
chx 11y ago
On Linux and ThinkPads you can use acpi_call to set these tresholds https://wiki.archlinux.org/index.php/Tp_smapi#2nd_Option https://wiki.archlinux.org/index.php/Tp_smapi#2nd_Option (the old tp_smapi way ceased to work about four years ago).
- eertami 11y ago
  tp_smapi still works fine on my T61?
  - chx 11y ago
    I meant laptops released four years ago.
waffl 11y ago
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)
swah 11y ago
> 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...
cwe 11y ago
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.

by bkanber 11y ago

raphinou 11y ago

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

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

revelation 11y ago

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.

bkanber 11y ago
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.

basch 11y ago

>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.

piyush_soni 11y ago
Time to write an app to do that (possibly only for rooted phones), someone?
- JimmaDaRustla 11y ago
  That's assuming that devices don't already operate in this range of SOC within device...which I wouldn't believe to be true.
  - piyush_soni 11y ago
    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.
gpvos 11y ago
> or set your power drivers to do it for you. Pray tell me how. (Macbook Pro 2010.)
zo1 11y ago
It already exists. E.g. The Dell laptop I currently own already has it as part of some or other pre-installed software.

JimmaDaRustla 11y ago

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.

bkanber 11y ago
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.

DavideNL 11y ago

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".

bkanber 11y ago
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.
- tertius 11y ago
  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.
rexf 11y ago
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.
- hsitz 11y ago
  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.

sigmar 11y ago

>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)

BorisMelnik 11y ago
excellent - what software does this? Built into the OS or a separate application?
- m3Lith 11y ago
  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.
- dfox 11y ago
  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.
- rkda 11y ago
  From experience, it's a separate app but manufacturer specific. Haven't had much luck looking for a generic app.
Guillaume86 11y ago

gpvos 11y ago

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?

silverlake 11y ago
My Sony VAIO had this 7 years ago.
- IE6 11y 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...
  - SmellyGeekBoy 11y ago
    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)
tertius 11y ago
I have this as "conservation mode" on my Lenovo Yoga Pro 2, and probably all new Lenovos.
misnome 11y ago
Macbooks have also done this for, like, forever, but more with the top few percent than 10%-60%
- gpvos 11y ago
  Yeah, it lets it drop to about 97% before it starts charging again. That doesn't really count, although I guess it's nice.

deleted 11y ago

[deleted]

aqme28 11y ago

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

shocks 11y ago
Is it possible they do, and the battery level indicator you're looking at is lying to you?
- bkanber 11y ago
  This is often the case. Not all the time, but lots of devices have started doing this.
- r00fus 11y ago
  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.
- dwg 11y ago
  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)
nosuchthing 11y ago
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.
lawry 11y ago
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)

BorisMelnik 11y ago

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.

Guillaume86 11y ago
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.
ElijahLynn 11y ago
Having an employee micromanage this will actually cost you more money over time.

zobzu 11y ago

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.

bkanber 11y ago
Li-ion batteries do not have a memory effect. LiFePO4 do, however.

tgb 11y ago

> 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!

deleted 11y ago

[deleted]

jules 11y ago

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?

bkanber 11y ago
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.
- jules 11y ago
  Do you have a citation for that?
  - bkanber 11y ago
    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.
- wyclif 11y ago
  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.

mibollma 11y ago

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."

mc32 11y 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.

geoelectric 11y ago
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.
- mc32 11y ago
  Yeah I thought so too. The parent comment seemed to indicate otherwise.

a3n 11y ago

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.

plq 11y ago

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?

omribahumi 11y ago
That reminds me of over-provisioning in SSDs http://en.wikipedia.org/wiki/Write_amplification#Over-provisioning http://en.wikipedia.org/wiki/Write_amplification#Over-provis...

justifier 11y ago

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?

chx 11y ago

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

eertami 11y ago
tp_smapi still works fine on my T61?
- chx 11y ago
  I meant laptops released four years ago.

waffl 11y ago

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)

swah 11y ago

> 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...

cwe 11y ago

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.