Ask HN: Should I unplug my laptop charger at 100%? • Hacker News Board

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

#211

Post by lnanek2 » Tue, May 05, 2015, 1:20 AM UTC

rajeshmr wrote: post #3

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 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.

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

#212

Post by sokoloff » Tue, May 05, 2015, 2:19 AM UTC

hurin wrote: post #102

qbrass wrote: post #89

Earlier quoted context omitted.

>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.

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

#213

Post by ChristianBundy » Tue, May 05, 2015, 4:04 AM UTC

jffry wrote: post #173

johnymontana wrote: post #167

Earlier quoted context omitted.

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...

running 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:

    98.68%

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

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

#214

Post by wyclif » Tue, May 05, 2015, 5:10 AM UTC

bkanber wrote: post #174

jules wrote: post #153

Earlier quoted context omitted.

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.

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

#215

Post by wyclif » Tue, May 05, 2015, 5:20 AM UTC

webnrrd2k wrote: post #190

matznerd wrote: post #99

Earlier quoted context omitted.

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, man…

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.

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

#216

Post by jen729w » Tue, May 05, 2015, 5:23 AM UTC

gpvos wrote: post #115

bkanber wrote: post #58

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%…

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?

See Siracusa's analysis of this suggestion.

http://atp.fm/episodes/33-a-30-minute-skip-button

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

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

#217

Post by archergod » Tue, May 05, 2015, 6:27 AM UTC

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 :).

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

#218

Post by gnicholas » Tue, May 05, 2015, 7:56 AM UTC

jmah wrote: post #205

0942v8653 wrote: post #202

Earlier quoted context omitted.

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!

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

#219

Post by DavideNL » Tue, May 05, 2015, 8:14 AM UTC

JoshGlazebrook wrote: post #125

DavideNL wrote: post #107

Earlier quoted context omitted.

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".

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.

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)

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

#220

Post by DavideNL » Tue, May 05, 2015, 8:26 AM UTC

myth_buster wrote: post #172

DavideNL wrote: post #107

Earlier quoted context omitted.

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".

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.