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

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

#181

Post by geoelectric » Mon, May 04, 2015, 9:09 PM UTC

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.

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

#182

Post by misframer » Mon, May 04, 2015, 9:09 PM UTC

ingsoc79 wrote: post #146

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".

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.

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

#183

Post by plq » Mon, May 04, 2015, 9:11 PM UTC

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%…

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?

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

#184

Post by epmatsw » Mon, May 04, 2015, 9:12 PM UTC

0942v8653 wrote: post #169

JoshGlazebrook wrote: post #125

Earlier quoted context omitted.

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 w…

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.

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

#185

Post by jules » Mon, May 04, 2015, 9:16 PM 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.

Do you have a citation for that?

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

#186

Post by justifier » Mon, May 04, 2015, 9:18 PM UTC

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%…

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?

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

#187

Post by neilyadig » Mon, May 04, 2015, 9:18 PM 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.

Mid-2010 MBP upgraded with SSD runs perfectly on 10.10.3

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

#188

Post by gpvos » Mon, May 04, 2015, 9:29 PM UTC

misnome wrote: post #164

gpvos wrote: post #115

Earlier quoted context omitted.

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?

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.

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

#189

Post by 1qaz2wsx3edc » Mon, May 04, 2015, 9:29 PM UTC

ingsoc79 wrote: post #146

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".

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%.

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

100/8460*7633 or 90.22%

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

#190

Post by webnrrd2k » Mon, May 04, 2015, 9:35 PM UTC

matznerd wrote: post #99

webnrrd2k wrote: post #45

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…

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.