PSA: Your Touchstone Battery Door Has Magnets in it.

As you know, the Touchstone charger and associated induction back use built-in magnets to align and secure the Pre to the charger. The magnets on the charging “puck” are the more powerful of the sets, but those in the Pre’s back could be strong enough to cause problems if inadvertently placed. I write this post because this morning after I was awakened by my Pre’s daily alarm, I grabbed the phone, killed the alarm, grumbled on the way to my computer (a MacBook Pro that crunches numbers through the night), and then set the Pre on the right palm-rest area (no pun intended) of the laptop. To my bemusement, the computer immediately went into sleep mode. So I pushed the power button on the laptop, it turned back on, and after a second went back to standby. “This is odd,” I said to my empty living room, so I turned it on again. And it turned off again.

Oh wait - that's right, the MacBook uses a magnet to activate sleep mode.  Whoops.  Although the magnets on the Touchstone battery door are fairly weak (far too weak to disrupt a hard drive, one hopes), I imagine that it's possible that they could disrupt other bits and bobs in a way similar to what happened to my MacBook.

The first thing that comes to mind is credit cards and access/ID cards. Every credit card and most state/federal/corporate ID’s have a magnetic strip across the back that can be disrupted by magnetism. Thankfully, since these cards’ magnetic strips only need to be written once, they are what’s called high-coercivity strips and are thus not very coercive to magnetic interference (as tested by Mythbusters). But hotel room key cards are a different story; they use low-coercivity strips to allow easy and quick rewriting for new customers, and are thus prone to failure in the face of magnetism. You or somebody you know has had a hotel key card stop working and the only explanation you (and the front desk) could conjure was that your cell phone had killed it. Most cell phones don’t even have magnets and yet are capable of causing wanton key card destruction, let alone the low-but-powerful-enough magnets in the Touchstone back.

Again, the magnets on the Touchstone Battery Door are very weak, so it's not as if they're a hazard.  Still, any of you have magnetic horror stories, courtesy of your Pre?