Studying the Slow Decay of a Laptop Battery For an Entire Year 363
First time accepted submitter jradavenport writes "I've been keeping a log of the health of my MacBook Air battery for the past year, taking samples every minute I use the computer (152,411 readings so far!). This has allowed me to study both my own computing/work habits, but also the fascinating rapid decay of battery capacity. Comparing it to my previous 2009 MacBook Pro, the battery in this 2012 Air is degrading much faster."
Survey says... (Score:5, Insightful)
Re:Two Things (Score:2, Insightful)
Re:Survey says... (Score:4, Insightful)
Yea. a change in methodology between test invalidates the results of an experiment. It could very well be that running the battery test every minute is causing his battery to deteriorate.
Re:Laugh (Score:5, Insightful)
Apple get the same batteries from the same places everyone else does. They're as fungible as AAs at this point.
Re:Love my MacBook Air, hate the battery (Score:5, Insightful)
I love the machine but I hate that I cant change the battery myself. I'll have to pay the Apple tax to get this fixed. I am holding out hope for Mavericks though, hopefully the power saving features can breathe some new life into this thing.
If you are willing to unscrew two dozen little screws, the battery swap-out is actually pretty easy according to iFixit. Of course, the battery itself will cost you over $100 bucks new, and Apple only charges about $120 installed, so the only real reason to do it yourself is if you live far away from an Apple Store and don't trust a carrier service with your laptop.
Re:Love my MacBook Air, hate the battery (Score:4, Insightful)
Yes you can, and it's not that hard [slashdot.org].
You know what the hardest part of it is? Going to ifixit, getting the screwdriver, and clicking "checkout now".
8 screws for the bottom cover, and 3 more securing the battery to the case. OK I take it back, the hardest part is possibly removing the bottom cover - Apple does use rather strong clips.
The same is true for everything OTHER than the MacBook Pro Retina 15", which has annoyingly-glued in batteries. I think the 13" is on a carrier frame.
It definitely isn't rocket surgery.
Siiiiigh, the SMC provides an ESTIMATE (Score:5, Insightful)
Calculated battery capacity is an estimate, nothing more, used by power management to decide when the computer should be force-slept, then suspended to disk to keep from damaging the battery (ie, it's not useful to wake up too late from sleep to do the suspend-to-disk.)
The SMC's estimate is just that: an estimate. Errors build up over time, and certain things fake it out a bit. For example, note the capacity, unplug the laptop, use it for 30 minutes, plug it in. Immediately the value will be different. It'll change again when fully charged. Your battery capacity didn't actually change. Even in a perfect world, since batteries have internal resistance, capacity gauges can never be perfect(if you draw at X you'll get less power out than if you draw out at X*0.8), and the battery's capacity varies with temperature. Battery degradation is impacted by temperature as well, so unless you're controlling for temperature of the pack, this was a completely useless endeavor. The only way this would have been useful would've been to cycle several (probably a dozen or more) batteries on lab-grade equipment in a temperature-controlled environment.
The noise and big upward swings alone should tell you that using the SMC's estimate for the purposes of statistical analysis or trending is virtually useless.
The stupid shit I see "enthusiasts" of any product obsess over is absurd. The time wasted on such an exercise far outweighs the impact it possibly could have had on the author (and probably even 9-10 other people combined.) The batteries last for well over 6 hours. Most people using a ultrabook with the battery life of a Macbook Air have plenty of opportunities to charge their machines during the course of a day.
Re:Perfectly valid (Score:5, Insightful)
Yes, because the author insisted that it was the definitive study on how all Macbook batteries behave, so we've got to hold him to that standard. I'll go further: this cad didn't even have this published in Physical Review Letters, much less Science or Nature. He didn't even get it peer reviewed, and... my God, there's no conflict of interest statement! Who was his ethics board?!
Sweet Jesus, I'll bet he isn't even working in a laboratory!
Re:Love my MacBook Air, hate the battery (Score:2, Insightful)
Yeah, I dont want to void my warranty either.
Re:Perfectly valid (Score:4, Insightful)
But he published it, and then Slashdot picked it up, and people are actually interpreting the 'data' and making conclusions. This is how crap like thimerisol=autism gets out there.
Re:Siiiiigh, the SMC provides an ESTIMATE (Score:5, Insightful)
You get around the error in the estimate by looking at a large number of readings. There are plots showing that the style of usage has not changed with time, so I don't see how the downward drift could be caused by something like sampling when the battery is full or when its empty. I am also fairly sure that when you do a full cycle that lets the battery controller recalibrate. The 'study' may not be perfect, but I have never seen a better one (studies on discharging cells at constant currents and temperatures don't tell you all that much about laptops).
Yes temperature is an issue for batteries. But the temperature of a laptop battery is dominated by the design of the laptop, and how much current is being drawn (or charged) to it. Maybe the previous macbook pro was only used in a aircon'ed office and the macbook air is being used in a steel mill, but i think that would have been mentioned.
This study only covers 2 laptops (and only one in high detail), but its worth 10 times all the battery anecdotes that you hear around the web because it contains measurements. I hope some more people try his script, and post the results.
Re:Love my MacBook Air, hate the battery (Score:1, Insightful)
He obviously isn't calliing himself a geek, he admitted to using a Mac running OSX.
Re:Ah, I see the problem. (Score:2, Insightful)
But then what about all the great Hitler jokes?
Re:Love my MacBook Air, hate the battery (Score:3, Insightful)
Those laptops also get hours less battery life. I'd rather have a laptop taht works great for three-four years and then requires a battery change once, than one where I'm swapping out batteries weekly.
I also had Mac laptops back when you could pres a button and remove the batteries. The batteries generally lasted only a year, then were worthless and had to be replaced.. go back to that world? No thanks.