Memory Effect Discovered In Lithium-Ion Batteries 157
rwise2112 writes "Lithium-ion batteries have long been thought to be free of the memory effects of other rechargeable batteries. However, this appears to be not the case. Scientists at the Paul Scherrer Institute PSI, together with colleagues from the Toyota Research Laboratories in Japan have now discovered that a widely-used type of lithium-ion battery has a memory effect."
paywall derp (Score:5, Informative)
Re:paywall derp (Score:5, Funny)
No Shit (Score:2, Insightful)
This has actually been theorized for a long time by people that use Li-On batteries and have to charge them frequently. But they've been told 'nope impossible' by the people who make and research Li-On batteries the whole time. To me this is just like the pharmaceutical industry pushing the next opiate as 'non habit forming' and 'extremely safe' only to have it turn out even more addictive and deadly than the last iteration...time after time.
Re:No Shit (Score:5, Informative)
Re:No Shit (Score:5, Interesting)
No one with any actual understanding of batteries said Li-Ion does not have memory.
What was said is that: From a practical perspective, Li-Ion memory is not an issue to worry about.
The article is basically someone who just did a study to confirm what probably every battery manufacture on the planet knew about Li-Ion at least 15 years ago. Longer I'm sure, I just have no experience before that.
What they did was took something they interpreted incorrectly, and then did a bunch of research to disprove some statement they misheard.
This is roughly like me telling you the surface of the earth is flat when you're building a small house, and then having a bunch of morons who overheard our conversion from 3 tables over do a study to determine that no, infact the Earth isn't flat. Of course its not flat, but from a practical perspective to the man building his home, its flat.
Re:No Shit (Score:5, Interesting)
Yes shit. People who "use Li-On[sic] batteries and have to charge them frequently" are simply incurring in an unfortunate characteristic of Li-ion batteries, namely that they have a finite number of recharge cycles, or equivalently, that each recharge cycle diminishes the total charge the battery can hold.*
This has nothing to do with a memory effect.
For comparison, Ni-Cd batteries (as seen for example on power tools) have a strong memory effect, meaning that if you plug them in before they are exhausted, they "remember" the smaller capacity you've used them for, and it takes a number of complete discharge and recharge cycles to restore their full capacity. Of course, all that's needed to fully utilize Ni-Cd is a slightly more expensive charging circuit that fully discharges the battery before switching to recharging, which is why they are widely used in professional applications.
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* Battery-savvy users always keep their mains plugged in on Li-ion devices such as laptops, so that the battery undergoes few recharge cycles and still performs as if it were new when they need it to, even after years of usage. But not after too many years, because Li-ion also have a limited timespan, or equivalently, the total charge they can hold diminishes every second since they leave the factory. Yes, it's a complex world.
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They have their problems, but for charge efficiency and energy density, they're way ahead of the rest. They also don't self-discharge to any great extent. They're doing well on power density now too.
Your alternatives are a memory-laden NiMH battery which wastes 30% of its charge and ha
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Li-ion batteries suck. But they suck ever so slightly less than NiMh batteries, which suck ever so slightly less than NiCd batteries... which makes Li-ion the best of the common technologies available right now.
Battery technology has been improving constantly. That said, it is nowhere near what people want it to be for our increasingly battery dependant lifestyles.
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IBM/Lenovo Thinkpads offer a way in their battery gauge / power management software to prevent recharging until the battery falls below X%. I usually set my users at 85% or 90% as the threshold before charging begins. At which point, it charges from X% up to 100%.
Usually only happens about once every 1-4 weeks, depending on how much they leave it hooked up to the wall out
Re:No Shit (Score:4, Informative)
Man ... living in your head must be terrible, in a world so full of daemons and enemies constantly conspiring against you. No wonder you are a bitter AC.
To my knowledge, both his assertions are accurate. One of them is supported by TFA.
Comment removed (Score:5, Insightful)
Re:Small effect big consequences (Score:5, Insightful)
The question is: how big is the effect. Even a small effect will cause significant distortions in battery metering, but if the effect is large enough, it will cause the batteries not to last any where near as many cycles as originally believed. This could really suck for electric car owners. Any '07 Roadster owners out there care to share how well the batteries are holding up?
-=Geoskd
According to what I could read of TFA without paying $32, the memory effect is actually seen just during discharge, as a function of distorting the voltage vs w/hr capacity. The overall w/hr capacity of the battery is not reduced, but the ability to exactly determine SOC is diminished at mid voltage levels.
I am not a chemist, so input from someone with more insight on the exact study would be appreciated.
Re:Small effect big consequences (Score:5, Informative)
Pretty accurate. They see a small deflection on what was commonly believed to be a smooth curve near the previous peak charge.voltage. It does not affect the overall charge capacity of the battery over time (what people commonly think about when "memory effect" is used), just the ability of the charge/lifetime remaining software to make accurate estimates.
For all examples shown, a user would be told they have significantly more charge remaining until near that point, then immediately after it would appear their predicted battery life would drop dramatically, and then it would stabilize again. It makes sense that this would be of keen interest to Toyota and other electric vehicle manufacturers.
If their graphs are as accurate, noise-free and reproducible as the figures lead the reader to believe... then the good news is, this effect can probably be accurately modeled and compensated for now that we know it exists. In that respect, it is a significant step forward for Li charge remaining prediction software.
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I wonder if that's why my G3 ibook battery shit the bed 2 days before I went on vacation that one time. I still got around 4 hours of runtime out of it (I'd checked a couple weeks earlier to be sure I didn't need a new battery) but the charging system suddenly refused to charge it. Of course, it was so old by then that I couldn't even pay full retail for one at the Apple store because they'd stopped stocking them a year or two earlier. I had to suffer without a battery through my vacation and ordered a r
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Re:Small effect big consequences (Score:4, Insightful)
What you experienced was not memory effect, but one or more of the cells failing. Some of them probably would never charge completely up, and the other cells got pushed into over voltage to compensate. If you have cells in series, this is pretty much going to happen sometimes.
Re:Small effect big consequences (Score:4, Informative)
Voltage monitoring should be just one aspect of charge determination. Properly done charge monitoring integrates the electrical charge actually delivered to or taken out of the battery -- as in taking the time integral of the current. The cell voltage should only used together with other indicators (cell temperature!) to determine each cell's health and charge/discharge endpoints (fully charged and fully discharged). The cell voltage should not figure in normal battery "% remaining" indications -- those solely base on the charge taken out of the battery, and the estimation of the 100% charge capacity.
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It does matter because if you properly monitor it, you can not only prevent it from going bad by equalizing the charge on all the cells, but you can also bypass the bad cells. Every modern automotive battery stack has such monitoring and cell bypass. Your electric vehicle will work perfectly fine with a bunch of dead cells. Besides, all this "fancy monitoring" for mobile device battery packs fits in one chip. There are multiple vendors and the market is quite competitive. There is a good reason that charge
can be fixed with software change (Score:2)
According to the first link the issue can be fixed with a software change, and can also be worked around by a full discharge followed by letting the system rest. Doesn't say how long a rest is needed though, depends on the implementation I suspect.
Re:Small effect big consequences (Score:5, Informative)
The question is: how big is the effect. Even a small effect will cause significant distortions in battery metering,
True, and this is what is seen.
but if the effect is large enough, it will cause the batteries not to last any where near as many cycles as originally believed.
Rubbish. It doesn't diminish the battery's capacity, just changes the q-v characteristic DURING CHARGING. Even if it were a large effect, it's still not going to effect total capacity, or estimating remaining charge by measuring voltage during discharge.
Notes regarding this:
1. This effect is shown in LiFePO4, which is commonly marketed as a "safe" chemistry Li-ion. Laptop and mobile phone batteries almost universally use LiCoO, which is not, AFAIK, addressed in this research. The Tesla Roadster also uses either LiCoO or LiMnO (I've seen conflicting reports -- probably because these two have similar electrical characteristics -- and both have much better energy density than LiFePO4), so your plea to Roadster owners seems a little odd...
2. This effect is caused by starting with discharged battery, charging partially (greatest effect for charging ~50%), discharging completely, then recharging completely. During the final (complete) charge process, the voltage starts at baseline (i.e. full-discharge/full-charge cycle, at the same % charging), increases slightly faster than baseline, so that the voltage difference over baseline peaks at 50% (or whatever state you partially charged it to), then increases more slowly than baseline to arrive at the same voltage when fully charged -- so capacity measured while charging will be overestimated. On the subsequent discharge, however, the q-v characteristic conforms to the baseline -- so capacity remaining will be measured accurately when a device is in use.
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The real question is: is the effect real? NiCd and NiMH batteries don't actually have a memory effect; that's not a real thing, it's just folklore.
NiCd batteries, for example, experience a memory effect if discharged to the same exact level +/- 3% repeatedly MANY times, where the output voltage is not below roughly 1.0V, and the maximum charge is below or exactly 100%. If the batteries are charged with full overcharge or the level of discharge between charges varies by more than 3% or goes below 1.0V, m
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At first the battery would last weeks but after a while a battery would last less than a day and would need to be replaced.
You have completely failed to demonstrate memory effect. All you've shown is that your batteries degraded over time.
Re:Small effect big consequences (Score:4, Informative)
My '08 Roadster (there are no '07 roadsters) has 33k miles on it, and after 4 1/2 years, its battery capacity has been reduced about 8%. I now get 225 miles on a full charge, down from 244 on day 1. That's even better than Tesla's initial projections, actually.
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Thats because you aren't driving it. You're basically treating the batteries in the ideal way judging by time and milage. You'd probably get slightly worse than that if you didn't drive it at all.
Tesla doesn't use LiFePO (Score:2)
And besides that, if you look at the charts, this doesn't cause a loss of capacity, even an apparent loss of capacity. Instead the voltage just reads high during charging. It appears it can foul up capacity remaining estimates, but not actually change the capacity remaining.
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Graphs in linked article show minor effect (Score:2)
In the source article, I notice it's only about a 4 percent total effect on total charge.
So, while not "no memory effect" it's not as bad as the impacts on the other types of battery storage.
Even storage devices like compressed air (PHES) for wind and solar PV systems have only a 70 percent efficiency, so it's still way better than that.
And that type of battery is.... (Score:5, Informative)
LiFePO4.
Cliffhangers in the summary now?
Re:And that type of battery is.... (Score:5, Interesting)
And I wouldn't call LiFePO4 "widely used", it's hardly used at all in the west due to extremely high royalty rates charged by the patent holders. I'd actually love to use LiFePO4 cells for my camping solar setup but the only ones I can find are dodgy Chinese imports with questionable charge controllers.
Ping Battery (Score:3)
I'd actually love to use LiFePO4 cells for my camping solar setup but the only ones I can find are dodgy Chinese imports with questionable charge controllers.
I can't really vouch for their quality because I am far from a battery expert, but Ping Battery [pingbattery.com] is very highly respected among DIY electric bicycling enthusiasts.
Definitely place them in your category of "dodgy Chinese imports", but anyway they're considered to be very reliable among that particular category!
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LiFePO4 batteries are starting to be used in motorcycles. I have a Shorai branded one in one of my bikes. Compared to a conventional lead-acid battery, it is smaller and much lighter. It also has a very limited self-discharge rate which means I don't have to charge the battery when the bike is stored during winter. I do disconnect and bring inside the battery due to the cold weather and parasitic draws.
The downsides that I knew about are that they don't work as well in colder weather and they're not com
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I'd actually love to use LiFePO4 cells for my camping solar setup but the only ones I can find are dodgy Chinese imports with questionable charge controllers.
Hey, they could come in handy if you ever run out of tinder and kindling!
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I've used the 9V and pot scrubber trick to start a fire when both my lighters failed on a camping trip (I wasn't going far enough away from society to pack the parafin encased bluetips which are my backups when my life depends on fire).
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Which is actually a very uncommon form of li-ion battery. Military drones use it, the batteries are taken out of service after just a few charge cycles.
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Thanks for spoiling the story for me. Now I guess I'll have to read something else.
Wrong description (Score:5, Informative)
I don't know about Lithium batteries but NiCad cells exhibit a second plateau which gradually gets more difficult for the charge system to punch through. The usual cure is a couple of heavy charge/discharge cycles.
Don't think I want to try that with Lithium though!
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Laptop batteries, anyone? (Score:5, Interesting)
I've always wondered why they say that Lithium Ion and Lithium Polymer batteries don't have a memory effect, when even laptop batteries based on those technologies die after several years, and NOT because of charge cycles. I'm talking about the ones that stay plugged in most of their lives, charging. Maybe its the lack of charge cycles that kills them? But to say Lithium batteries have no memory effect has always been ludicrous to me.
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Batteries should be stored in a cool location. Keeping a battery in your notebook for long periods of time when running off of AC subject it to high temperatures and a shortened lifespan.
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"
Batteries should be stored in a cool location. Keeping a battery in your notebook for long periods of time when running off of AC subject it to high temperatures and a shortened lifespan.
"
Nope, that's not the reason.
Typically, a new laptop owner does the following.
Buy new laptop
Install battery (if it's not already)
Place on desk.
Plug in to AC power.
Use for 5 years or less, and never move it from that spot.
In other words, the battery is NEVER used.
I've seen it personally with the last 3 business laptops I've
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I've seen it personally with the last 3 business laptops I've had (hp, lenovo, dell) as well as the past four personal laptops i've sold to people. Those that actually use the battery down to zero at least once a month? Batteries last forever.
That's true for older technologies, but not true for lithium-ion. They will lose capacity no matter what you do. They'll lose it faster when fully charged and at higher temperatures, but they'll always lose capacity.
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The battery is used. If there's a power blackout, the laptop keeps on going. The desktop, DVD player, cable box, satellite box, and plasma TV have all gone out and go back into their respective boot-up sequences.
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What? AC is completely correct, and you failed to even address their comment in any meaningful way, except that, yes, I too have noticed occasional deep cycling seems to help preserve battery capacity.
Heat deteriorates li-ion batteries - and being in a laptop with a cpu, HD, etc all running at max because they're on AC subjects them to lots of heat.
Being held at 100% charge also wears out li-ion batteries, there's a reason that a Prius strives to keep it's batteries between 40 and 60% charged most of the t
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Seriously? Sweet! What brand? I may have to look to them next time I need a rechargable gadget of some sort.
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I remember such software
it nailed your hard disk for 3 hours causing that to fail
Re:Laptop batteries, anyone? (Score:5, Interesting)
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I'll put it simply the designers are too cheap to simply put a timer circuit/code in place to stop charging the damn battery because it's already as charged as it's going to be....
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With modern charge controllers, there is no overcharging of any sort -- a charged battery pack is not being charged anymore, that's it. Only after it self-discharges a bit -- enough so that it's detectable -- will it be topped up. The problem you have of course is that the battery pack is still treated as a whole and while charge controllers in mobile device battery packs will detect voltage on individual cells, still very few have the electronic bypass switches needed for cell charge equalization and cell
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I don't see how plugged-in laptop batteries dieing has anything to do with a memory effect. Lithium-Ion batteries when stored lose capacity depending on how much they are charged and how high the temperature is. At the relatively high temperatures of a laptop and kept at near 100% charge they can lose as much as 40% capacity per year. This is a known fact and has nothing to do with what is called memory-effect. The summary talks about a specific (and not widely used as I understand it) kind of Lithium batte
Re:Laptop batteries, anyone? (Score:4, Informative)
Okay, first up let's define memory effect: Memory effect is NOT a battery dying. Memory effect is the tendency for a battery to stop charging/discharging at a set level if you regularly fail to completely charge/discharge it. It develops a 'memory', and thus falsely acts as though it's fully charged or discharged before it actually is.
While this can ruin a battery, a number of techniques have been developed to rehabilitate such batteries to restore full function.
However, batteries don't just wear from charge/discharge cycles. They age over time as well. Alkaline and Lithium primary cells are especially resistant to this, but until very recently LiIon rechargeable cells were very, very vulnerable to this, losing 10% or more of total capacity just sitting on a shelf in a cool warehouse at 70% charge(the ideal situation for them).
Sitting in a hot laptop being kept at 100% is much worse than ideal, you could be losing 30% or more per year in that scenario.
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being kept at 100% is much worse than ideal
This is at the heart of my laptop battery experience. My laptop is rarely off AC power. When I had the charger set to stop charging at 100% (and to recharge when 90%), my battery life greatly improved. OId battery dropped 60% in reported capacity in less than 2 yrs; new battery is barely down 30% in the following 4 years.
I call it Chinese electron torture for your battery -- drip, drip, drip.
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The new battery might be using the improved technology as well, but you'd probably save even more life if you can set the charger to recharge at 60% and stop at 80%.
After that it's a fight against heat. Keep the battery under 70F and you'll slow it's degradation even more.
Then again, 30% in 4 years might be slow enough for your purposes.
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The problem with most batteries is that the designs are cheap and the cells are not individually controlled with bypass switches. Then you have a pack with just one bad cell and the whole pack is "bad". All the rechargeable battery pack failures I've seen were of this kind: one weak cell with all the others having lots of life in them. The bad cell issue is self-exacerbating: as soon as a cell has higher internal resistance than the others, it will always get overcharged and over-discharged, accelerating t
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Holy shit someone is wrong on the Internet.
Each cell supplies a certain amount of voltage. Lead-acid, carbon-zinc, and alkaline batteries supply 1.5V per cell. Remove a cell and the voltage potential drops, which plays hell with electronics not ready for that big of a fluctuation. For example, when a car battery loses a single cell, it usually can't start the engine--it definitely can't when it's cold. Sensitive electronics may have some very odd issues with different input voltages. It's possible to
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Remove a cell and the voltage potential drops, which plays hell with electronics not ready for that big of a fluctuation.
I don't know what kind of electronics don't use flexible switching power supplies these days, but yeah, if the latest you've seen is stuff from the 80s, then you might have had a point. These days a laptop power supply might use a battery with a total voltage anywhere between 12 and 30V, but all the heavy power consumers besides screen backlight and hard drive actually run on a couple of Volts. The power supplies for many of today's electronics wouldn't even notice if a cell drops out -- everything will ke
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Power supplies can be flexible at a nominal performance reduction when outside of the "sweet spot" and zero parts cost, if you just design them properly. Most laptops are extremely flexible and will work just fine over a supply range that spans 10V. You'll notice that for many laptops the external power supply provides a voltage much higher than the internal battery. There's just one internal power supply that can take either voltage, there's no extra step-down stage just for the external input. The design
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Tell that to all those designers who make power bricks that take anywhere between 90 and 240 VAC on the input. Tell that to all those designers whose laptops happily run over a 10V or larger input supply range, by design. In other words: you have demonstrably no idea what you're talking about. None whatsoever.
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Portable electronics use switching regulators almost exclusively since that's the only way to step down voltage without wasting lots of energy as heat. That's also the only way to step the voltage up -- whether the regulator uses inductors or capacitors as the energy storage buckets.
Sure there are small low drop-out regulators here and there, but the "low drop-out" is the key: those are the linear regulators that can do the job with just a couple tenths of a volt of overhead. You'll most likely not have an
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I've always wondered why they say that Lithium Ion and Lithium Polymer batteries don't have a memory effect, when even laptop batteries based on those technologies die after several years, and NOT because of charge cycles. I'm talking about the ones that stay plugged in most of their lives, charging. Maybe its the lack of charge cycles that kills them? But to say Lithium batteries have no memory effect has always been ludicrous to me.
Actually overcharging your Li-Ions and Li-Pos is bad news. It shortens the life of your battery. You can't trickle charge them, so as you use the device plugged in, the battery discharges to some threshold, where the battery controller starts charging it again. So even if you leave it plugged in 24x7, if the battery is plugged in, it will discharge and then recharge at some frequency.
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anybody with an iThingie can tell you that (Score:1)
and I wish you didn't have to hack your way in to replace them.
Ha ha... (Score:2)
It pays to charge your batteries based on your instinct and tradition "just in case" instead of just believing and falling for claims that are only to be proven false later...
Well, I'm set, because I always let my phone nearly die before charging it. That's sure as hell not gonna change now.
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Nice. Because that's the worst thing to do to a Lithium-ion, for example.
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I have a Makita LXT drill and screwdriver and I've been beating the crap out of them, running the batteries down each time until the performance drops low enough to make me have to switch. No problems so far, even though I've had them 3 years or so. I'm drooling for the new brushless versions, but seriously I have no reason at all to replace what I have -- they work great in spite of using brushed DC motors.
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Are you sure? I thought it was letting them *totally* die that was a problem. I've noticed deep-cycling them (to 10%) occasionally, maybe once every month or two, seems to do them good, not that I've done any rigorous testing, just noticing how changing behavior patterns seem to affect them.
Of course the biggest benefit was when I disabled "maximum performance mode" when connected to AC. Battery-saver mode gives me plenty of performance 99% of the time, and the lack of lap-roasting heat and a roaring fan
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Nice. Because that's the worst thing to do to a Lithium-ion, for example.
You tell that to my phone, which after a full year and a half is still capable of running as long as it could when I bought it. Actually, it was lasting a day or less when I first bought it (largely due to a battery-guzzling bug that I found out how to solve), but now a whopping seven days. Lots of tweaks to reduce power draining too, but it's still running the same stock OS on the same battery it came with.
By comparison, many of my friends leave their laptops and cell phones plugged in 100% of the time t
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The worst thing you can do to a lithium ion battery is to leave it fully charged. That's the quickest way to wear it out. (aside from the obvious over charging and over discharging)
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the question is, how shitty is your device? Any decent device will just lie to you about charge status.
Keeping a cell phone or laptop plugged in 100% of the time, especially during use, is the fastest way to degrade the battery life.
the question is, how shitty is your device? Any decent device will just lie to you about charge status.
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Modern laptops and top-end cell phones from Samsung, LG, and Motorola do this. Plug in your phone, pick it up, and start talking. It gets really hot. It also stays properly charged. It doesn't tell you it's 100% charged when really it's shut the charger off and is currently 80% charged. Note that the ideal charge under this condition is 70% or below--note that the Tesla won't charge the battery above 80% unless instructed.
Ideally the device would just shut off the charger and keep it below 80%. That
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Yes, they found it to be acceptable. You come home and keep your car plugged in, it stays at 80% charge, an 8% drain is not a problem. You throw in a 30A breaker and hook up the 10kW charging station and plug your car in. That was the use case. The use case for the Model S is not "refuel at the end of the week" because it takes 8 hours to refuel and if you suddenly need your car it's got 50 miles on it and you need to go 75.
It made sense in that configuration to drain the battery. I'm pretty sure the
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Forget the batteries... (Score:1)
Discombobulating multiple issues (Score:3)
First of all of LiFePO4 are not commonly used in any of our portable gadgets.
Second memory effects we are seeing in our gear are illusions based on memory effects in the electronics that help figure out capacity. Deep cycling lion batteries works to clear these effects as what you are actually doing is resetting the "gas gauge" to synchronize with reality of the battery.
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First of all of LiFePO4 are not commonly used in any of our portable gadgets.
Lithium Ion != Lithium Iron ... i.e. WTF are you bringing up LiFe for? Not part of this conversation.
Second memory effects we are seeing in our gear are illusions based on memory effects in the electronics that help figure out capacity. Deep cycling lion batteries works to clear these effects as what you are actually doing is resetting the "gas gauge" to synchronize with reality of the battery.
Actually, you have that backwards.
The batteries have degradation. The electronics are wrong because they remember capacity based on the charge/discharge cycle of the battery when it was new. Over time it degrades, this is not memory, its just degradation ... wear. When you 'deep cycle' the battery, all you are doing is allowing the device to actually see how the battery is currently performing rather tha
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Lithium Ion != Lithium Iron ... i.e. WTF are you bringing up LiFe for? Not part of this conversation
Please RTFA.
Actually, you have that backwards.
The reverse of what I said would be memory effects in batteries which is not occuring.
The batteries have degradation. The electronics are wrong because they remember capacity based on the charge/discharge cycle of the battery when it was new. Over time it degrades, this is not memory, its just degradation ... wear.
Normally it is a simple loss of synchronization rather than meaningful change to capacity. The most common issue stems from self discharge not being accounted for over prolonged periods of nonuse.
When you 'deep cycle' the battery, all you are doing is allowing the device to actually see how the battery is currently performing
Thanks for agreeing with me.
rather than how it was expected to perform a hundred charges ago.
It is more complicated than this.
Pitty A123 died then eh? (Score:2)
Tell me when there is a problem with cobalt lithium batteries.
Memory free batteries don't exist (Score:4, Insightful)
And I expect never will. All batteries have various flavors of memory. The only question is, does the memory effect cause enough of a problem to make it worth addressing the issue to extend battery life.
You worry about memory in a NiCad because the process that causes the memory is easily reversible (partially), and the battery itself is still functional.
If the memory effect of Li-Ion only effects ... say 1% of the total capacity before the rest of the chemical processes break down and cause the battery to 'wear out' than it has memory, but from a practical perspective the memory is irrelevant.
There are all sorts of batteries that would appear 'memory less' at first glance, but thats only cause they are so shitty in other ways that you don't get to the point of noticing the processes that cause memory to start happening.
Until a battery is 100% energy efficient, its going to have memory, so never.
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modern NiCad don't exhibit the memory effect. there are other effects such as depression and aging, but not memory.
So much stinking bullshit here (Score:2)
People who keep their laptops on AC are NOT killing their batteries by keeping the system on AC. The batteries are being killed by the fucking design of the laptop's charging circuit! Bonehead charging systems will keep trickle charging the battery even when they shouldn't! The end result is shortened battery life. In effect the laptop was designed to kill the battery prematurely.
Properly designed charging systems do not do this. If you bought a cheap-ass laptop you can expect it to chew up batteries
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nope, it was first introduced by Duracell and then re-used by Energizer, and only in the US at that. In Europe we've only had Duracell's.
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The Duracell Bunny campaign was launched in 1973 and predates the Energizer Bunny, which was created in 1989.
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Degradation with time and usage != memory effect. Memory effect is a specific kind of degradation due to partial charging or discharging. For example if you recharged a NiCd battery that was only down to 50% charge you would immediately and permanently reduce it's total capacity, hence the tendency of those "in the know" to drain the batteries completely before recharging them.
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There's a difference between the memory effect and the battery wearing out. It is known that a lithium battery will wear out. They even wear out while in storage. Especially when warm and fully charged.
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It won't, because they're not using iron cathodes.
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Because you're treating your batteries like shit.
Lead Acid batteries (like you car battery) are pretty fucking hard to kill outside of the environment your car subjects them too (heat is a bitch), even that, how many times have you warranty replaced your car battery?
NiCads are relatively resilient. You can certainly hurt them, but you have to do 'known bad' things that every manual and charger label probably has written on it. Don't drop them below 1.2v per cell, keep them cool during charging (heating me
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'94 Ford Taurus SHO stick, daily driver for about 15 years: I replaced the battery about the middle of every Texas summer- yeah, heat kills, but still, in spite of buying 60+ month batteries. Had a vampirism problem with a faulty alarm that took out two in one year, but other than that, eating batteries was just the price I paid for the enjoyment that car gave me.
Strangely enough, I am using an ACER notebook now that I keep plugged in probably 80% of the time that I use it (and, yes, I know better, I just