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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%?

#81

Post by jotm »

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 pulled out batteries out of working laptops to test just that theory - only a 2006 Toshiba P300 shut down, the rest of them (newer, Fujitsu, Dell and HP) ran uninterrupted. Either they switched faster or more likely, ran off the AC all the time. It's just good design...

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

#82

Post by basch »

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%…

>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.

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

#83

Post by jotm »

ars wrote: post #4

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%.

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...

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

#84

Post by jotm »

robotcookies wrote: post #74

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.

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

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

#85

Post by tjohns »

ars wrote: post #5
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.

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

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.

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

#86

Post by vidarh »

signaler wrote: post #22
JoeAltmaier wrote: post #16

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.

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 in the chances of losing power is reduced (though I have on occasion had both fall out at the same time).

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

#87

Post by JimmaDaRustla »

raphinou wrote: post #69
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%…

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

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).

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

#88

Post by bkanber »

revelation wrote: post #73
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 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.

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.

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

#89

Post by qbrass »

hurin wrote: post #51
kachnuv_ocasek wrote: post #49

Earlier quoted context omitted.

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

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.

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

#90

Post by basch »

tdkl wrote: post #20
cjbprime wrote: post #2

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.

> If you leave it plugged in, you aren't losing cycles Too bad that some batteries wear out even faster this way because of the heat.

the laptop can run, plugged in, without the battery in it.
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