How my iPad crippled my MacBook Pro

When I got home one recent evening, I still had some work to do, so I fired up my MacBook Pro after dinner. It was very slow, which is not how the three-year-old laptop usually performs. Our IT department was switching Exchange servers, and it had been restoring all our archived email to our local computers. From there, the archives could then be moved to the new server when the switch occurs. That slowed down all our systems at the office, and I figured that was happening on my home MacBook as well.

What I didn’t know is that my iPad had essentially crippled my MacBook, and that slowdown was the first sign of that problem.

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The next day, the slowness persisted, to the point where Photoshop couldn’t even save files — it would time out, either freezing or crashing as a result. Everything else — Mail, Safari, Chrome, TweetDeck, Keynote, Word — crawled along. I spent six hours doing all the things that seemed to make sense to troubleshoot the problem. I ran the Disk Utility to see if my drive had failed; it was fine. I booted from an external drive. I tried older versions of OS X on external drives. I tried different versions of Photoshop — same problem.

Activity Monitor (a utility similar to Windows’ Task Manager that Apple includes with OS X) showed that the OS X kernel — no matter what OS X version I had booted into — was using 70 to 80 percent of my CPU time, versus the normal 5 to 10 percent. I saw no rogue apps; in fact, app resource usage was normal. I was stumped.

My brain flashed to viruses, which can slow PCs to a crawl. I’ve been using a Mac as my primary computer since 2008 (thanks to Windows Vista), and I’d never used antimalware software on them. But I remembered what viruses could do to the PCs I had used before then, so I got an antivirus app and ran it. It turned up no viruses.

I finally did a Web search. (No, I don’t stop to ask for direction, either.) The Apple forums had several reports from people with the same sudden, persistent slowdowns and excessive kernel usage. The culprit: a failed MacBook battery. I checked the Battery status menu in the OS X menu bar, and it showed a zero charge and the message “Replace Battery Now.” Uh-oh. Although OS X helpfully tells you when your keyboard or mouse battery is running low, it doesn’t provide that proactive notification when your battery is failing, though a warning appears in the Battery status menu that none of us really checks.

My MacBook Pro is an early-2011 model, so the battery is not user-replaceable. (On older models, replacing the $100 battery is a two-minute operation anyone can do.) I went to the Apple website and made an appointment to bring it in to my local Apple Store the next day. I figured I’d have no MacBook for a day or two in the course of repairs. Fortunately, I got it back within the hour, with a new battery installed, for $129 including labor. My MacBook ran normally again.

The Apple tech, Zack, told me OS X uses the battery even when the MacBook is powered from an electrical outlet to boost the graphics subsystem. As Intel engineers informed me a couple years ago, Apple is a master at squeezing out the most from the standard PC hardware components it uses because it takes full advantage of the control it has by designing the entire system. Intel’s Ultrabook effort was in fact an attempt to provide Apple-like optimized integration to PC makers, who weren’t making the effort.

The problem with such a highly integrated approach is that when one component fails, everything else is affected. A dead battery on a PC laptop, or even an older MacBook, would not have had such consequences. I know that from both my pre-2008 PCs and my now-retired 2008 MacBook Pro.

My battery died catastrophically — its storage capacity was 1.7 percent of normal, Zack told me. That’s very rare, and when the battery drops that low, the MacBook has to work much harder to do its normal job. When you’re running solely on battery power, the Mac automatically adjusts its resource usage in ways that aren’t that noticeable unless you’re doing intensive operations. When you’re plugged in, the MacBook goes full throttle.

My slowdown occurred because without the battery the MacBook couldn’t go full throttle, causing the kernel to churn. That’s why the kernel usage in Activity Monitor shot up. Newer MacBooks are designed to operate on battery only, but not on electrical mains only.

What does any of this have to do with my iPad?

Zack said my battery had been cycled — completely discharged and recharged — only 16 times during the three years I’ve owned the MacBook Pro. It should have been cycled dozens of time, perhaps even 100, over such a period. Such cycling is critical to battery health; if you don’t cycle the battery roughly every month, the dreaded memory effect occurs, causing the battery to calculate that it has less capacity than it does. The reasons have to do with the chemistry of some batteries, including the lithium-ion batteries commonly used today. In any event, the lack of cycling caused the battery’s memory effect to kick in at an obscenely high level that essentially killed the battery.

That was the iPad’s fault. I got my first iPad in 2011, not longer after I got the MacBook Pro. It didn’t take very long before I stopped carrying the laptop with me, whether on business trips or to the living room. I’m iPad-only when on the go. That means my MacBook Pro is always plugged into mains power. The only time it had discharged is when I accidentally pulled off the magnetic power cord or the very, very few times I’d used the laptop as a laptop.

My iPad’s battery is quite healthy, as is the battery in my 2011-era iPhone. The iPad and iPhone fully cycle at least weekly from my normal use. (No, their batteries don’t last a week. I tend to top them off each evening, but there’s usually at least one day each week where I drain the batteries to below 20 percent, which allows the battery to cycle.)

If I were using the MacBook Pro as a laptop, the battery would have been able to periodically cycle. But because I used the MacBook as a desktop, it didn’t, causing the catastrophic battery failure that showed up as a superslow system. My next home Mac will be a Mac Mini, but that’s easily a year or more away. Until then I’ve put a reminder in my calendar to cycle the MacBook Pro’s new battery each month. (You can check the cycle count in the Power section of the Hardware pane in the System Information utility.)

I’m doing the same at work, since that mid-2012 MacBook Pro also never goes anywhere and thus never cycles. In fact, it’s cycled only twice in the year I’ve had it! Fortunately, the memory effect on that battery has been minimal, so I’m in no immninent danger of a repeat catastrophe.

But cycling a battery is not easy on a MacBook. Apple’s hardware is too good at not using power. For example, I left my office MacBook Pro unplugged for two days when I was out of the office, hoping to run down its battery to cycle it. When I got back, it still had a 75 percent charge — so much for that cycling attempt.

You might think you could just unplug a MacBook periodically while working to run down the battery. But doing so causes the MacBook to stop sending its video signal to any external monitor (to save on battery life, of course), which means you need to open the lid and use the built-in LCD instead of an external monitor. I use large monitors at both home and work, and losing access to them while my MacBook is discharging is not a reasonable option.

[UPDATE: Since I wrote the article, I’ve found a trick that seems to work to let me cycle the MacBook Pro’s battery while still using it with my monitor: Open the MacBook’s lid before disconnecting the power cable. Then the screen stays on and continues to mirror to my external monitor as well.]

Apple should think about a way to build automatic cycling into its MacBooks, since it’s so hard to manually cycle the battery. Because so many of us use iPads as we once used MacBooks, Apple has created an unexpected risk. After all, MacBooks make up the lion’s share of Apple’s Mac sales, whether or not they’re used as laptops. It needs to find a fix that people can embrace.

The iPad is a wonderful device, which is why people like me use it exclusively away from a desk. But it shouldn’t lead to our Macs being crippled.

This article, “How my iPad crippled my MacBook Pro,” was originally published at InfoWorld.com. Read more of Galen Gruman’s Mobile Edge blog and follow the latest developments in mobile technology at InfoWorld.com. Follow Galen’s mobile musings on Twitter at MobileGalen. For the latest business technology news, follow InfoWorld.com on Twitter.