Is it a bad idea to keep a MacBook Pro plugged in while charged?
May 16, 2013 8:06 AM   Subscribe

I recently acquired a new MacBook Pro, with a retina display. It's a sealed unit, with no user-replaceable battery, so I'm obviously interested in maintaining the battery life. I noticed that the new T-shape mag safe connector is not very grippy, and falls out all the time. So I called Apple to see whether the constant unplugging/plugging was a bad idea, and the rep actually said at one point that it was a bad idea to keep the laptop plugged in when it was charged (with the green LED showing in the adapter). I confirmed that this was what he was saying. So does anyone know if this is true? Because I've always kept my laptops plugged in, all the time.

I always find battery issues to be very hard to get any clear information about. Thanks for any input.
posted by carter to Technology (13 answers total) 7 users marked this as a favorite
Best answer: Any modern laptop has dedicated circuitry for managing battery level of charge, especially with Li-ion batteries, which are very sensitive to overcharge as well as over-discharge. Keeping your machine plugged-in guarantees it will be able to keep your batteries properly conditioned.

(I have the same machine. It's been plugged in for 99.9% of the last year. Batteries run great when I need them.)
posted by seanmpuckett at 8:12 AM on May 16, 2013 [1 favorite]

Best answer: Here is Apple's official statement on battery use:
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month.
posted by 1970s Antihero at 8:21 AM on May 16, 2013 [1 favorite]

So, while 1970s Antihero's advice is correct, you don't want to run it down every day if you don't have a need to, because there are a limited number of battery cycles.

The short plugging/unplugging you're talking about ist'n a big deal either way, you should just make sure your battery gets mostly discharged a couple of times a month.
posted by mercredi at 8:36 AM on May 16, 2013

Response by poster: Ah interesting, thanks everyone. I'm probably doing it right then, in some sort of intersecting way, as I go to cafes a lot, and with the longer battery life no longer bring the charger with me. So it's not just sitting there at home, but is being cycled to some degree on a regular basis.

I was worried about 'microcycles' between the mag safe popping off, and being re-attached. I agree, seanmpuckett, I would have thought battery firmware would have taken care of this.
posted by carter at 8:39 AM on May 16, 2013

Over the course of about 2-3 years, I rarely unplugged my MacBook. The battery swelled up a bit to the point where it didn't fit perfectly anymore. I don't know if rarely unplugging and discharging was the cause, but I presume it may have been.
posted by Dansaman at 9:25 AM on May 16, 2013

Lithium Ion batteries power Apple hardware and most anything where power density requirements (watts per cubic meter) trumps cost. They are volumetrically efficient and lightweight AND pricey.

Charging and discharging result from chemical changes in an electrolyte. Decreases in capacity come from changes in electrodes, mostly. I'm not sure that a constant float charge would weaken a LiIon battery, and wonder what drives Apple's directive, but it's their product line. There's certainly nothing wrong with using the battery for what it's designed for.... after all, you did buy a portable. Why plug it in all the time? Somewhat defeats a major feature, no?

There's some slight economic incentive, of course, to the profitable sale of replacement batteries, service, and new computers and it's just about right that batteries start to give it up in 2-3 years of normal laptop use, nicely coinciding with performance and feature improvements of great magnitude.

Me? I also plug in my hardware mostly, so that I have a full tank when I don't have no choice but portable. I expect it to die, eventually. By the time the batteries are dying, the box they go in has accumulated enough wear to make that less important. These days, tech is old in a year. If the batts last 3, no problem!
posted by FauxScot at 9:26 AM on May 16, 2013

Just a data point, but I have the same laptop and it's charger is quite grippy magnetically speaking, so maybe you got a bad one. I know that's not that question you were asking but it's an annoyance that you might be able to get Apple to replace.
posted by doctor_negative at 10:59 AM on May 16, 2013

Best answer: doctor_negative: The magsafe 2 connector that came with my retina MBP definitely is less mag and more safe than the connectors I've used on older macbooks. And it does get knocked out during normal non-tripping-over-the-cord operation. And I'm not alone in this. But neither are you. The reviews in the Apple Store seem split between "A butterfly sneezes and it falls out" and "I don't know what you guys are talking about, mine works great!" Since Carter's talking about a new macbook, and mine is one of the first retina models, it seems like it's not a change Apple made, but just variation from unit to unit. Yugh.

I wonder if I (and also the OP) could just get a different charger that does grip tighter, or if it's the macbook side that's lacking in tenacity.
posted by aubilenon at 11:24 AM on May 16, 2013

Also note that the worst thing you can do to a Li-Ion battery is let it sit around empty. That's why new ones always come partially charged.
posted by w0mbat at 11:37 AM on May 16, 2013

I had the same bulging battery issue as Dansaman and was told that was the issue (not unplugging enough). Thankfully it was covered by AppleCare.
posted by backwards guitar at 3:44 PM on May 16, 2013

Bulging and leaking is just what happens when rechargable batteries fail. It's not something you can help, it's inherent to the way they are wired up inside.

In my two modern laptops that have had LiIon batteries, one spent most of its time unplugged, but more or less fully charged. The other one spent nearly its entire life plugged in. The batteries died similar deaths in similar amounts of time.

The biggest thing that causes LiIon batteries to die is their age. They deteriorate slowly from the instant they are manufactured. Besides making sure they are never allowed to remain completely flat for very long, there is very little you can do to extend the life of the batteries. (This is why cheap batteries on EBay isn't always a good plan. They are probably old, and you may not get very much utility out of them.)

I suspect Apple's advice is more social than technical. If you are using your battery regularly, you can tell if/when its capacity starts dropping. If you aren't paying attention and then decide to try and use it on vacation, and find that it dies after 5 minutes, you'll be angry at Apple.

Also, even if keeping it plugged in will shorten its lifespan somewhat, so what? Its job is to a convenient tool. It WILL get worn out, and you might as well get the most efficient usage out of it for you.
posted by gjc at 4:46 PM on May 16, 2013 [3 favorites]

Response by poster: That's a real bimodal distribution in those apple store reviews, aubilenon.
posted by carter at 5:49 PM on May 16, 2013

I learned the hard way that you can really use up a lot of battery cycles if you don't make an effort to keep the charger plugged as much as possible. After having to get a battery replaced on a previous laptop after only a year of use, these days I try very hard to keep my current machine plugged in. Honestly, if I manage to get 2-3 years out of this one before having to replace it, even if it fails due to bulging, I'll be happy.
posted by StrawberryPie at 1:10 PM on June 1, 2013

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