Battery at 100% plugged in vs. having it from 40%-80% charging all the time.

EvilHamster

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Hi all. I know it has been discussed way, way, way too much. But I am still confused. I have read up on this question quite a lot. But people seem to contradict each other sooo much.

Does anyone know, if it is better to let the Laptop be plugged in all the time, keeping the battery at 100%, or to let it charge to 80%, than disconnect, use it on battery and let it go down to 40%, again charge to 80% and use to 40% etc.

Assuming it makes no difference in effort to the user. Which one is better for long desktop-replacement type use? (Btw. battery is not directly removable. It would void my warranty, so I will not yet do that).

Cheers.
 

velocityg4

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- Discharge the battery to 40-60%.

- Store in a cool dry place. Some people store their battery it the fridge but this leads to condensation issues. While the colder temperatures can make it last longer. The moisture can ruin it. If you do store it in the fridge use a high quality sealed plastic bag and place a fresh pouch of silica desiccant in with it.

- Take it out every few months to charge it, run it down to 40-60% and store again.

- While leaving it in your laptop and using it on battery once a week is better than simply leaving it at 100% all the time. This does increase wear on the battery. The frequent high temperatures will reduce battery life.

http://www.pcworld.com/article/191574/long_live_your_laptop_battery.html
http://batterycare.net/en/guide.html
http://batteryuniversity.com/learn/article/how_to_store_batteries
 
The closer you charge to 100% and discharge to 0%, the more quickly the battery's capacity will degrade over time. If you keep the discharges shallow, you can increase the battery's longevity 5x to 10x.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

When you charge/discharge the battery, you're actually causing tendrils to change physical shape. They grow and fatten up as they charge up (trying to find a video). The closer you charge to 100% (or discharge to 0%) the more physical damage you cause to the tendrils. And the less charge they can hold. Edit: found the video.

http://www.popsci.com/science/article/2010-12/lithium-ion-batteries-swell-and-contort-while-charging-new-study-shows

The problem with leaving the battery at 100% is that Li-ion batteries slowly self-discharge. Many older laptops would charge to 100%, stop charging, self-discharge to 99%, charge back up to 100%, stop charging, self-discharge to 99%, etc. This repeated charging to 100% every hour or so rapidly wore out the battery (the Toshibas were particularly bad about this).

Most newer laptops have adopted several strategies to combat this, especially since non-removable batteries have become the norm. I've seen some or all of these on newer laptops.


  • ■They won't start recharging until the battery's charge has dropped to 95% or 90%. So if you leave the laptop plugged in, it will only top off to 100% every few days. It's still damaging the battery, but because it's doing it once every few days instead of every hour, the damage doesn't significantly degrade the battery for several years.
    ■You can configure the laptop's charging software to limit its max charge. So if you set the max charge at 80%, the laptop will stop charging when the battery reaches 80%, instead of 100%. My previous laptop could do this, and I immediately capped it at 80%. 4 years later when I replaced it, the battery still lasted almost as long as it did when new, despite being plugged into AC power almost the entire 4 years.
    ■Some laptops are designed so the battery mis-reports its capacity. So it's a 44 mAh battery, but it reports its capacity as 40 mAh. So when the laptop thinks it has charged the battery to 100% and stops charging, the battery has actually only been charged to 91% of its capacity. Hardware reporting software like HWInfo will often detect this as battery wear (difference between stated capacity and current capacity). My current laptop reported 5% wear (95% full capacity) when the battery was new. It's been plugged in most of the past year at 100% charge and it still reports just 5% wear.
So if you've got a laptop which doesn't use any of these strategies, then I would manually try to avoid charging it to 100% (especially if it tops off immediately at 99%). But if it's a newer laptop, you're probably just fine with it at 100%. Just discharge the battery at least once a month (not to 0% - that is as bad as charging it to 100%). Maybe once every 4-6 months do a full discharge (Windows will probably auto-sleep at 5% - that's good enough).
 

EvilHamster

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Thank you both for the answers.

It's a brand new Acer E5 15 575G Laptop. It is not the best brand in terms of pure quality, but it is still a very reputable brand. I don't know of any charging software it came with. Are there any general software that can cap the charging?

As I said, I can not unplug the battery without opening the Laptop. After that, I am sure I could, but it would void the warranty. Also, it would be a fairly tricky process, and not something I would like to do every other day.

So removing the battery (which for some reason was half the answers) is not really an option.

As to whether it charges when it is at 99%, I do not know. ASSUMING it does (again, I don't know). Would me running it down to 40% and charging to 80% 2 times a day be better than leaving it plugged in all day? Both seem to be some wear. I can understand that getting it from 99% to 100% is worse than getting it from 79% to 80%. But, it is it also worse than getting it from 40% to 80%?

Sorry, but to make the question a bit shorter. Assuming I have only 2 choices.

1. Having it plugged in at all times (with maybe a discharge to 20% once ever 10 days or so) and 2. always using battery power from 80% to 40%, then charging from 40% to 80%. Which ones is better?

1. or 2.?

Cheers everyone.
 

dudeman509

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We have a fleet of HP laptops at work. They charge themselves to 95-97% in the docking stations.

Batteries are also internal (but can be changed via popping off the access panel on the bottom of laptop) - no one does that, of course.

The ones that stay plugged in constantly and have never been undocked or taken home have battery issues at this point where they won't charge or won't hold a charge and/or have had them replaced. The ones that are teleworked with - taken home, run on battery once a week or more - for the most part have no battery issues, and my own still maintains much of its original capacity about a year and a half later.

Avoid putting the battery under a heavy discharge load if at all possible (e.g. gaming or heavy CPU/GPU use). That does create internal wear on the plates.
 

If it doesn't come with software, then it can't do it. The function is actually built into the laptop's firmware, and the software merely controls the firmware's settings. That's how it still works even if the laptop is suspended or turned off but charging.

Since it's brand new, try running HWInfo and see how much battery wear it reports. That should tell you if it's using the third battery preservation strategy. A new battery not doing this should report 0% wear or close to it.

https://www.hwinfo.com/

As to whether it charges when it is at 99%, I do not know. ASSUMING it does (again, I don't know). Would me running it down to 40% and charging to 80% 2 times a day be better than leaving it plugged in all day? Both seem to be some wear. I can understand that getting it from 99% to 100% is worse than getting it from 79% to 80%. But, it is it also worse than getting it from 40% to 80%?
Running the battery from 30%-70% over a few hours is probably better than the battery repeatedly going between 99%-100% for those few hours. But it's worse than leaving the laptop plugged in if it doesn't top off until it hits 95%.

Couple that with the difficulty of keeping the battery between 30%-70%, and this is all more for your peace of mind. Some battery degradation is inevitable. Just adopt the strategies we've all described, and avoid the most dangerous situations, and you should get many years of use out of your laptop.
 

EvilHamster

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Thank you all.

I just ran HWinfo and it reported the battery wear at 11.5%. I had the laptop for less than a week, it was all together at most 10 hours on. Does it mean that it is artificially capped at 90%, in order to save it from too much wear?

In more detail, it reported:

Device Name: AS16B5J
Manufacturer Name: Panasonic
Chemistry: Lithium Ion
Designated Capacity: 62160mWh
Full Charge Capacity: 55034mWh
Wear Level: 11.5%

Current Voltage: 12.626V


In light of this, should I still solely use it on battery power between 40-80%?

Cheers.
 

Nobody can say for sure except the engineer who designed it. But it probably is capped at 90% (the alternative possibility is that you got a refurbished battery). Check the wear again in 6 months, then a year. If it's holding steady or dropping only slightly, then you're all good.
 

EvilHamster

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Thank you... sorry to keep grinding on this, but which one is it,

Option 1 or Option 2?

[1. Having it plugged in at all times (with maybe a discharge to 20% once ever 10 days or so) and 2. always using battery power from 80% to 40%, then charging from 40% to 80%. Which ones is better?]

Cheers.
 

dudeman509

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Option 2 will absolutely create MORE wear on the battery. Li-Ion batteries have a finite number of charge/discharge cycles before their capacity diminishes. You want to cycle it some, but not constantly.

And usually, when it comes down to it, in the long run, even if it is internal, a battery is not very expensive to replace if you have a relatively mainstream laptop. My Dell Studio or a Macbook are some of the exceptions.
 

EvilHamster

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@dudeman509
To be honest, I tend to agree with you from a `common sense' kind of way. But, as you can see (unless I am completely misunderstanding it), the others seems to have the opposite view. That is why I am so confused.


The battery costs about 80 pounds right now. I expect the price to come down, but not under 40 pounds. I will have to replace an other battery in a laptop I bought less than 2 years ago. I think that 2 years is very little for a battery to last and so I am trying to understand what I did wrong. It was also already holding very little charge about a year after I bought it. I think paying 50 pounds a year for batteries is way too much.

The other battery was used with option 1 (mostly plugged in) and had maybe 20-30 full discharges.

I think that a rechargeable battery should last for at least 3-4 years of daily use. After all, smartphone batteries do last me that long. I wonder, if it is maybe because with smartphones I am never keeping it plugged in, but always using it. So maybe option 2 is better??? I am very confused.

Cheers.
 

EvilHamster

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Guys... final answer...
Option 1 or 2????

(Please only answer if you are sure)

[Option1. Having it plugged in at all times (with maybe a discharge to 20% once ever 10 days or so) and Option 2. always using battery power from 80% to 40%, then charging from 40% to 80%. Which ones is better?]
 

velocityg4

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Option 1 is better. As you are using the battery for short periods of time without storing it at 100% for extended periods.

Option 2 would place a lot of load cycles on the battery. It would also add extra heat to the battery as charge/discharge heats a battery up. Realistically, it would be a pain to maintain. There'll be many times you discharge too much or allow it to charge up all the way. The amount of wear would depend on your usage. If you are doing this cycle two times a day the battery would not hold up very long.

The more you drain a battery. The fewer charge cycles it can endure. At 80% discharge you'd get roughly 1/3 to 1/4 to number of charge cycles as the 20% discharge in Option 1.

A lot of people have trouble with the life of laptop batteries because they either. Leave it charged at 100% all the time. They never use the battery. It could go months or years before being unplugged. Others allow it to discharge completely then leave it sitting for days without charging (extremely stressful). Neither scenario usually occur with phones.

Interesting enough. Doing some digging laptops are often rated for 300 to 400 charge cycles while phones are rated for 500 to 600. These counts assume high levels of discharge. Light cycles should greatly improve life. There are a few reasons I can think of the differences in these ratings. It could be any of these or a combination of them.
A. Smartphone and laptop makers use different guidelines for a typical discharge percentage before recharge.
B. Phones use a lower charge voltage per cell than the cells are rated for (increases charge cycle endurance but has lower useful capacity).
C. Phone batteries use a more robust manufacturing process.
 

EvilHamster

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Thank you very much for the answer. I am sorry for asking so repeatedly, it's just that there is sooo much contradicting info out there.

Anyway. Thanks everyone who has taken the time to answer the question.

Cheers.
 

bimmerb0ii

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OPTION 2 IS THE ANSWER. Basic understanding and common sense will lead you to go for option 1, but understanding battery requires more than common sense and a deeper understanding.

I have researched and "googled" a lot on this topic, for my numerous devices at home and interest in the electric car industry. Battery is best charged between 40% to 80%. The damage or wear will come when charging a battery to its full capacity (ie 100%). The battery cells get stressed out and produce heat when reaching its full capacity. This is why chargers (even Quick Charge 2.0/3.0 of Qualcomm and Samsung Adaptive Fast Charging) tend to slow down when you are approaching 80% to 100%.

As for the battery cycle, 1 cycle is charging from 0 to 100%. If you charge say at 40 to 80, then you need to do that 3 times for a 1.2 cycle. Leaving the battery plug in wont do anything much except to top up the battery whenever battery drops. The phone stops charging at 100%, then it will slowly lose 1% over time, then the charger will top it up back to 100%. If this happens 100 times then it is considered 1 cycle. What worries me though is since the constant topping up at almost full capacity, this will hurt the battery cells.

On a different note, I remember having Apple replace my Macbook battery. It went bad before 700 cycles (still under warranty) and they replaced it for free. Then on my wifes macbook the battery went bad at around 1050 cycles (no warranty) and the Apple guy said its time to buy a new battery. According to him a typical macbook battery life is 1000 cycles. On the other hand, my Lenovo and Samsung laptops have "extend battery life" settings that limit charging to 60% (for the lenovo Y580) and 85% (for the Samsung TabPro S). I think these settings are included there for good reason and say a lot regarding battery health.

Also, on my 2015 Tesla Model S (which obviously relies on battery), the everyday driving setting is recommended to stop charging between 50% to 90%. Charging to full 100% capacity is only recommended when you will be doing long driving. This clearly states that battery longevity is best attained when not maxing out battery capacity.

And for anything else, when in doubt, check out batteruniversity.com for all your battery questions.
 

EvilHamster

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I have research quite a bit myself and to be honest... I am not so sure as you. Indeed, I am just more confused than ever. As you can clearly see from this topic, all people are doing is contradicting each other.

Basically, from what I have gathered, it depends on the Laptop. As in, if the battery is not locked at 90% and it drops to 99% fast and tops up to 100% immediately, it is better to use it on battery power. If on the other hand, the manufacturer has locked it at 90%, and it does not drop the charge too fast and only starts to top up when it drops to say 95, or even 90% (of the 90%, so actually 81% of the capacity), than it's better to use the AC.

I am trying to figure it out for this particular model now... mainly on their forum. Still waiting though....
Btw. from what I understand, even if it only starts charging at 95%, the battery will still usually report 100%. This is done so that people don't get confused. That is why often (say on smartphones), when you plug and unplug your phone when it is fully charged, it will now report like 90% or so percent and keep charging. This `overcharge' is an example of this mechanics.

Laptops often can hide this even better, so I am really not sure how this particular Laptop operates...

OOONLY confusion...



Fair enough, but one should consider that one can not keep driving when the car is plugged in, at least not very far. So it's really more of an apples and oranges comparison than anything else.


I tried to read on their webpage, but they are just more confusing. They write a lot, but answer few questions. They basically just write out the results to their experiments, which is very interesting and useful. But they don't really go to the conclusion. At least, not on this issue. At least, I was not able to find it. If you have a link on their webpage answering this question, I am very much inclined to believing them.

Cheers.
 

EvilHamster

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But that's the point. They don't answer the question, not really.

They all assume that one is using the mobile devices in a mobile way... and that in the case of laptops, one can remove the battery.
This question that I am posing, which I think is relevant to a lot of people, is barely addressed on the mainstream websites, which is sooo strange.

I think it is because 90% of the tech journals now-a-days don't actually do anything other than copy and past each others article and comment on the obvious in a given device. Either that, or they are just advertisement in disguise. Few of them, if any, actually even disassemble a product in their review and comment on the real build quality. The most they will say is something like `this is made from carbonfibre or this is made from aluminium or plastic' etc. Which everyone can see. They never comment on the internal build parts, like say the PSU etc.
Oh well.
 
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