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

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

#101

Post by bkanber »

JimmaDaRustla wrote: post #95
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%…

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 wi…

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.

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

#102

Post by hurin »

qbrass wrote: post #89
hurin wrote: post #51

Earlier quoted context omitted.

Why would the battery be heated if it's not charging? You can set a gap - e.g. 80-100% where the battery won't start charging until it drops below 80%. Look at the documentation for your relevant power-management module.

>Why would the battery be heated if it's not charging? Heat transfer from the device it's plugged into.

I'm not a hardware/electronics guy, but I'm rather skeptical that this is any kind of notable amount - do you have a reference?

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

#103

Post by JimmaDaRustla »

tjohns wrote: post #59

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 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.

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

#104

Post by gr8b8m8-88 »

toxicFork wrote: post #13
jerf wrote: post #8

As I sit and look at the replies already coming in, may I just add an enormous [citation needed] to the entire discussion? A question brought on by too many conflicting anecdotes can not be resolved by throwing another unsourced anecdote on the pile. (Incidentally, I'm at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I've read.)

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

Statistics and citations today is the Bible quotes / racial stereotypes of yesteryear. Some modern-day pseudo-scientist poster will cite some study that says "80% of chargers waste power if left plugged in at 100% charge" will then draw the logically faulty conclusion that therefore you should unplug your charger. The fact that the statistic study necessary had to ignore extra variables like if you have a lot of stuff plugged in, whether you're drawing power from a set of solar panels on your roof, whether you are using a super-special non-power wasting adapter, etc., necessarily makes the citation not a thought more credible than your great-great grandpa quoting the bible to tell you that you should marry your own race or citing stereotypes that you shouldn't trust your friend because he is Asian.

True science, that is, proposing hypothetical models, analyzing results, and admitting no real results can be drawn due to insufficient model complexity, has been thrown out the window by pride and laziness.

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

#105

Post by therobot24 »

brador wrote: post #47

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.

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

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

#106

Post by adrusi »

brador wrote: post #47

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.

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.

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

#107

Post by DavideNL »

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 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".

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

#108

Post by ggreer »

vidarh wrote: post #86
signaler wrote: post #22

Earlier quoted context omitted.

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

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…

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.

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

#109

Post by TheGRS »

brador wrote: post #47

Consider the cost of a replacement battery and if it's worth the subconcious mental strain this consideration places on you. In short, leave it in because it's not worth worrying about.

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

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

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

#110

Post by coherentpony »

malanj wrote: post #60
jerf wrote: post #8

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.)

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

This isn't remotely related to this discussion.
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