Naked Science Forum
Non Life Sciences => Technology => Topic started by: chris on 28/04/2018 09:48:59
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I've recently taken delivery of a new Surface Laptop, from Microsoft. It's actually very impressive and, at about 14h (at the moment), the battery life is the best I have ever had from a mobile device.
(https://img-prod-cms-rt-microsoft-com.akamaized.net/cms/api/am/imageFileData/RW6KQQ?ver=4b2e&q=90&m=6&h=423&w=752&b=%23FFFFFFFF&f=jpg&o=f&aim=true)
But what can I do to keep my battery - and my battery capacity - at its best for the longest time possible?
The accompanying instructions don't say much but they do counsel you not to leave the machine plugged in for extended periods "so that the battery can operate at normal temperature".
But this inevitably means that you are running off battery not the mains most of the time and therefore adding charge/discharge cycles to the battery, which is what causes electrode fragmentation and performance loss.
So what should I do? Run the thing off the mains when possible, or always run the thing off batteries?
And if the latter, should I run the battery all the way down before recharging it, or recharge when it gets to half way, a third...?
And what about storing the machine if it's to be left unused for a period? Store with the cells fully charged, part-discharged, flat?
This seems to be something of a minefield with a lot of misinformation circulating.
What does everyone here think?
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As I understand it, the proper way to treat (and store) the battery will depend somewhat on what type it is (there are many different types of lithium ion batteries that have their own quirks), and whether or not to leave it plugged in will depend on how/when the computer decides to switch between battery and mains.
However, in general, it is typically best to avoid completely discharging or completely (over) charging the battery, and to the extent that it's possible limiting the rates of charging and discharging.
You can think of the battery as an air bladder that has somewhat sticky inner surfaces (or lungs, if you prefer an anatomical model). Inflate it too far and the material will stretch and thin out, increasing the wear and tear and permanently reducing its elasticity. Allow it to get too flat and it will collapse on itself and stick to itself, making it more difficult to inflate again, and possibly causing damage when the innards unstick. Forcing air in too quickly will cause uneven distribution of the stresses, leading to earlier failure, similarly pulling air out too quickly may cause part of the bladder to collapse completely before the pressure can redistribute, again causing uneven stresses that will lead to early failure.
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I am quite surprised that, given that the battery is often one of the most expensive parts of an electronic device, that most devices come with a paucity of guidance regarding the best way to care for it...
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...that most devices come with a paucity of guidance regarding the best way to care for it...
I’m often surprised about that as well especially remembering NiCd where the advice was to regularly discharge fully and many people still think this is the best way to treat a rechargeable battery.
For Li-ion you are best to take a smaller amount of charge out before recharging and to store the battery for longer periods at half charge. Some laptops have a battery management function which keeps the battery at half charge when on mains.
The following gives depth of discharge vs expected cycle life if that helps
Discharge cycles (NMC / LiPO4) Cycle life as a function of
depth of discharge.* A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life.
Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.
100% DoD ~300 / 600
80% DoD ~400 / 900
60% DoD ~600 / 1,500
40% DoD ~1,500 / 3,000
20% DoD ~1,500 / 9,000
10% DoD ~10,000 / 15,000
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No lithium-based pearls of wisdom from anyone...?
I have a cordless electric tooth brush that I got 10 years ago. It came with a cordless charger. I had been leaving the toothbrush on the charge station all the time. After many years of faithful use, one day it appeared the battery was almost dead, with the toothbrush running real slow. The battery was fully charged but had no power. I was going to buy a new battery, but decided to try something.
I unplugged the charger and kept using the toothbrush with the weak battery, until it was fully discharged. I then recharged it to full. I did this a few cycles. To my surprise, the battery now works like new and keeps a full charge. It was almost like only part of the battery was being use, near the full area of the battery. Once I broke that memory, the whole battery reemerged.
My advice is don't keep it plugged in all the time. Allow the battery to almost fully discharge; 10%, before charging. A 90% memory is not bad if it happens.
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@puppypower - but what sort of battery is in the toothbrush? If it's NiCad, those cells respond well to deep discharge and trickle recharge. Lithium ion cells do not...
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Hi...as per my knowledge Inflate it too far and the material will stretch and thin out, increasing the wear and tear and permanently reducing its elasticity. Allow it to get too flat and it will collapse on itself and stick to itself, making it more difficult to inflate again, and possibly causing damage when the innards unstick. Forcing air in too quickly will cause uneven distribution of the stresses
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Hi...as per my knowledge Inflate it too far and the material will stretch and thin out, increasing the wear and tear and permanently reducing its elasticity. Allow it to get too flat and it will collapse on itself and stick to itself, making it more difficult to inflate again, and possibly causing damage when the innards unstick. Forcing air in too quickly will cause uneven distribution of the stresses
Plagiarize much? (I said the exact same thing, word for word several weeks ago, see below with bold added for emphasis)
You can think of the battery as an air bladder that has somewhat sticky inner surfaces (or lungs, if you prefer an anatomical model). Inflate it too far and the material will stretch and thin out, increasing the wear and tear and permanently reducing its elasticity. Allow it to get too flat and it will collapse on itself and stick to itself, making it more difficult to inflate again, and possibly causing damage when the innards unstick. Forcing air in too quickly will cause uneven distribution of the stresses, leading to earlier failure, similarly pulling air out too quickly may cause part of the bladder to collapse completely before the pressure can redistribute, again causing uneven stresses that will lead to early failure.
Perhaps as a first timer, you are having difficulty with the Quote function? I hope you're not a bot or a spammer, because then we would have to ban you :) You can PM me or any other mod if you are having difficulties posting...
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Manufacturers of devices don't care much about how well you look after the battery - it suits them if you kill it within a couple of years and just buy a new device. Personally, I'd prefer to use NiMH for most things and be able to change the battery when it's flat so that I can run them down and leave them flat until I know I'm going to need them again. I managed to keep one laptop battery in almost new condition for eight years, then it died when it was left flat for a few days and became useless. These things really need to be kept on some kind of life-support system. More and more gadgets are being sold with suicidal batteries, and many are for use in gardens - by the time the next spring comes round, most owners will need new batteries because they'll have left them flat for too long and wrecked them. It would be much better if all gadgets had standard batteries so that you could switch the same one from drill to hoover to leaf-blower to bicycle, etc. and stand a better chance of keeping track of which ones are in danger of dying by limiting the number of the damned things. They have become an environmental nuisance.
As for your Surface laptop, it's probably best just to use the battery most of the time and enjoy being free of cables, even if there might be a theoretical way of getting the battery to survive a bit longer. Keeping the battery full charged for long lengths of time is bad for it (which happens if it's plugged too much), and letting it get too low risks killing it by accident if you stop using it for a few days, so you really want to keep it in the middle range, and that gives you little option other than to run it on battery most of the time anyway. Plug it in when you feel it's getting low, but don't be too keen to charge it fully either unless you're immediately going to be running it back down a bit. Every few weeks, run it right down to the point where it wants to shut down and then charge it right up again immediately to remind it of how much capacity it has. This should at least get you good value for money out of the battery.
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reading about the complexities of battery powered devises makes me glad I have never owned a laptop and have always used a mains powered set top