Can BlackBerry Erase Magnetic Card or Electronic Car Key?

CreditCard_Erased_250wMyth or Truth? Can your BlackBerry–or any other cell phone–erase, disable, or otherwise damage your:

  • Credit card?
  • Debit card?
  • ATM card?
  • Gift card?
  • Hotel key card?
  • ID swipe card?
  • Electronic car key?

[ PostScript 2009-02-10: I now have more definitive proof... ]

[ If you already read this article, jump down to end to see my follow-up. ]

What Has Happened to Me

Gift Card Story

Today I went to my favorite grocery store that also has the cheapest gasoline in town. But to get the best price, you have to transfer money to one of their gift cards, then use the gift card at the pump. I have a “rechargeable” gift card that I keep in my wallet solely for this purpose.

So, I have the girl at the checkout put $50 on my gift card while my groceries are being bagged. I realize I’ve already put my wallet away in a zippered pocket of my winter vest, so I just stick the gift card in my pocket. I’ll just have to pull it out three minutes from now when I go gas up my car.

GasPump_250wI load up my groceries and drive across the parking lot to the gas pumps. I park at a pump, swipe my gift card…and it doesn’t work. The pump display says, “Reinsert card.” I swipe the card again–same result. I try it several times, and finally the pump display says, “See cashier.”

Instead, I go to another pump and repeat the process. Same result. It seems the card isn’t working. I guess I should see the cashier.

I put the card back in my pocket where I had it before…but wait…my BlackBerry Storm is in that same pocket. Uh-oh.

(The cashier was able to reprogram my gift card and recover the money on it–whew.)

Hotel Room Key Stories

RoomKey_200w In the last year or so, I have stayed in hotels/motels where the rooms used keys with magnetic stripes on them–much like a credit/debit/gift card.

I remember in three different cities I’ve had these experiences:

Frisco, Colorado

When I first entered my room, I emptied my pockets on the dresser, including my BlackBerry Pearl and my room key card. The Pearl was on top of the key card. The first time I tried to use the card, it wouldn’t work. I took it to the front desk, and they reprogrammed it. It worked after that.

Until the next day, and it happened again. At the front desk, they asked me if my cell phone had been close to it. I said, “yes.” They told me to keep them apart, that cell phones can erase the room key cards.

I kept my room key and my Pearl very far apart after that: no more problems.

Atlanta, Georgia

Basically, the same story. I put my Pearl and key card on the dresser together. The key card quit working after it had been working. I got it reprogrammed and it was fine.

Savannah, Georgia

Do I never learn? Apparently not. Same story as before: Pearl and room key card got close together. Key card quit working. Reprogramming fixed it.

What Others Say

If you research this topic on the Internet, you’ll find people arguing both ways: it’s a myth, it’s a reality.

For example, some argue that the TV show MythBusters “busted” the myth…or did it (if you didn’t see the episode, read the account of the show carefully). They may have proved that an electric eel couldn’t erase a credit card. I’ll definitely rest easier knowing that!ElectronicKey_150w reported that the SideKick 3 cell phone erased a credit card. But that phone apparently has a magnetic latch that will lift a fork. How many cell phones have anything like that?

Maybe slightly more credible than the above is a story reported by Reuters and the LA Times. Reportedly, Nissan North America issued a warning that customers who place their electronic key too close to their cell phones could find the key disabled, and advised them to  keep their car keys and cell phones at least an inch apart. I couldn’t find the original warning supposedly issued by Nissan.

How Could This Happen?

MaxwellsEquations_250w How much do you know…or want to know…about electromagnetism? I’m going to guess that most readers would rather pass on that subject. I do happen to have a degree in electrical engineering, and had to suffer through a year of classes on electromagnetic theory. So, if you’re a reader who wants to lecture me on the subject, please–I don’t need another lecture.

But to keep it simple, the stripes on the back of most plastic cards are magnetic. Information is stored on that stripe magnetically. Electrical and electronic devices, like cell phones, emit electromagnetic radiation. That radiation can, in theory, alter the information stored on the magnetic stripe of a card.

How the radiation from a cell phone might affect an electronic car key is probably a different case. But to keep it simple, let’s just say that an electronic car key might be vulnerable from electromagnetic radiation, too.

The BlackBerry…or the Holster?

How many of you know that the BlackBerry has a holster (the one provided by RIM, or many cases sold by third parties) with a magnet in it? The purpose of that magnet is to signal to the BlackBerry when it is inserted into the holster. Why? Because you can program your BlackBerry to ring/vibrate differently when in the holster than it does when out of the holster.

I have my BlackBerry configured with a Notification Profile that I use in business meetings. If my BlackBerry is in the holster, it means I don’t want it to ever ring–because I don’t want a disturbance. But if I take it out of the holster, I want it to ring. I find that a bit easier than changing the profile from Loud to Vibrate, for example.

Could the magnet in the holster (or a case) the culprit? In every case where I had a problem with magnetic cards, my BlackBerry was in its holster!


CardReader_200w There are a lot of facts to consider. Not all magnetic cards are the same.

Some, like credit/debit/ATM and ID cards, are not designed to be “recharged” or “reloaded” or reprogrammed frequently, so are very resistant to damage from external magnetic fields. It seems unlikely that your BlackBerry can harm them.

But some cards, like gift cards and room keys, are designed to have their magnetic information changed frequently, so are thought to be more vulnerable. It just may be true that your BlackBerry or its magnetized holster/case could be a risk to these kinds of cards.

It’s easy to draw premature conclusions. Did my BlackBerry erase my cards? Or were the cards poorly magnetized in the first place? Or did my cards get damaged by something else?

I honestly don’t know. But I’m going to try to keep my BlackBerry away from my gift cards and room keys–just to be sure.

Please leave a comment below about any experience you’ve had:

  • Hard a card erased and suspect your cell phone?
  • Keep your cell phone and cards together all the time and have had no problems?
  • Please give details about your phone and cards!


Since this article spawned some interesting discussion, I thought I’d follow up with more thorough testing that is more conclusive, if not a fully scientific “slam dunk.” Here’s what I did:

Gift Card Exposed to Holster and BlackBerry

1. I started with a new Gift Card and loaded it with a $5.00 balance. 5_dollar_balance
2. I made sure the Gift Card was good by doing a $1.00 purchase of gasoline. 1_dollar_purchase
3. I exposed my Gift Card to my BlackBerry Storm 9530 inserted into its original holster.

The phone was powered on but not on an active call.

4. I tried to make another purchase of gas at the same pump. The Gift Card failed (with same error message as I had seen before). ReinsertCard_200w

OK, that strongly suggests that the combination of phone plus holster damages a Gift Card. If you have any doubt about the strength of the magnets in the Storm holster, check this out:


Next, I used the same BlackBerry Pearl that I wrote about in the article above, without its holster, and transmitting a signal:

Gift Card Exposed to BlackBerry Only

1. I replaced my damaged Gift Card at the issuing grocery store. I restored the balance to $5.00. 5_dollar_balance
2. As before, I made sure the Gift Card was good by doing a $1.00 purchase of gasoline. 1_dollar_purchase
3. I exposed the Gift Card to my BlackBerry Pearl 8130, turned on, and actively on a call (e.g., transmitting a signal). The holster was nowhere present. GiftCard_Pearl_200w
4. As with the earlier test using the Storm, I tried to make another purchase of gas. The Gift Card failed again. ReinsertCard_200w

This time, the holster cannot be blamed. The phone itself–somehow (radiation or internal magnetism)–damaged the Gift Card.

As I noted earlier in this article, Gift Cards and hotel room Key Cards are frequently reloaded or reprogrammed. There is a belief that the magnetic programming is not as “permanent” as with Credit and Debit Cards or ID Swipe Cards. So, let’s test one of those type cards:

Debit Card Exposed to Holster and BlackBerry

1. I used a Visa Debit Card / Check Card / ATM Card and made a purchase in a store: it worked perfectly. DebitCard_Purchase_200w
2. I then exposed (severely) the Debit Card to (a) my BlackBerry Storm, powered on, in its holster, (b) my BlackBerry Storm, actively transmitting on a call, (c) BlackBerry Pearl in holster, and (d) Pearl actively transmitting. DebitCard_200w
3. I then attempted to make a purchase with the card: it worked perfectly. DebitCard_Purchase_200w

No damage to a Debit (aka Check or ATM) Card under any condition!

I realize the test procedures I used still leave interesting questions. I simply don’t have the time to do more extensive testing like you might expect from Consumer Reports or some scientific testing organization. But I don’t know of any better testing done to date.

I think what matters is that my testing provides strong evidence, if not irrefutable proof, that a cell phone in a holster/case with a magnetic latch, or a cell phone alone without its holster/case, can damage a Gift Card.

This testing strengthens my belief that a cell phone with/without a holster/case can probably damage a hotel room Key Card.

Lastly, my testing suggests that Credit, Debit, ATM, and ID Swipe Cards are safe from damage by either a cell phone or holster/case with embedded magnet.

As always, your comments and questions are welcome.

Bookmark and Share

About the author

This entry was contributed by Kelly Carter
84 entries have been written by this author.

24 comments on this post

Jan 31, 2009 - 06:01:36

I also had a room key get erased by my BB Pearl. The key worked several times when I first arrived, but eventually stopped functioning. The desk clerk gave me the same advice about not putting the key in the same pocket with the phone. Sure enough, there was no problem after ensuring that the two were kept separate.

Jan 31, 2009 - 08:01:50

Father Sticha,
Thanks for sharing your story.

Xandrex says:
Feb 1, 2009 - 09:02:51

yes I had the same trouble with magnetic keys in hotel : worked the first two days.
In some countries (ike France), people can stick coins to the back of their Blackberry. It’s practical for always have money for a coffee at the coffee machine :)

your conclusion is very interesting, about the difference between permanent / transient data. I’m making a talkback on blackberry’s support community forum.

Feb 1, 2009 - 10:02:04

Merci beaucoup for that interesting feedback.

Dave says:
Feb 1, 2009 - 02:02:21

Kelly, another nice, well thought out, informative blog post. Enjoy your work. Thank you for sharing.

Feb 1, 2009 - 04:02:41

Thanks for the feedback. It’s nice to hear a kind word.

Cute kids!

OddyOh says:
Feb 2, 2009 - 08:02:22

Thanks for this timely post…I hadn’t thought about the magnet on my holster, until I got some loose change stuck to it! I’ll be keeping the phone and my wallet in different pockets from now on.

Feb 2, 2009 - 01:02:32

I just tested my Storm holster, and it picks up paper clips and some other random metal I had in my desk drawer at work. I may add some photos of this to the article later.

johno says:
Feb 2, 2009 - 03:02:21

I heard this at yesterday’s SuperBowl party. I doubt very much it has much to do with the RF from the Blackberry.

In the 80s I was an engineer for an outfit that manufactured mag-card debit systems for vending applications. Monetary values were stored right on the card (pre-online days) so erasures were a constant concern and we conducted numerous studies and field-evaluations addressing erasures and other issues.

By far, the most common cause of a card becoming unreadable was inadvertent contact with a magnet. They’re everywhere. If your blackberry holster has a magnet, that would be my guess as to the cause of erasures. To change / erase data on even a low energy stripe requires a field density unlikely to be generated by a cellphone type unit. If it did, you’d be picking paperclips and thumbtacks off of it every time you picked it up. With the proliferation of cheap, very strong NIB and other rare-earth magnets used in all kinds of not always obvious places, the inadvertent clobbering of mag-stripes continues to be a problem.

Of course, other problems can stem from poor quality card stock and/or mag-tape, poorly maintained equipment (worn/dirty heads etc). Hotel cards in particular seem to suffer from these issues. Being throwaways which only have to work a few times, the quality of the stock varies a lot from place to place. Dirty cards are another biggie. Wiping the stripe briskly on your pants-leg does not ‘re-energize the stripe’ as some will attest but it can clean some of the wallet-gook off of the stripe so that the read head makes better contact with the stripe.

This has all the earmarks of an urban legend in the making – like the old stories of eel-skin wallets erasing cards. We actually conducted a formal study to investigate customer problems with eel-skin wallets and indeed, found a significant number of erasures on wallets with magnetic catches. What was unexpected is that not all of them caused problems. It wasn’t until we reviewed videotapes of the subjects using the equipment that we found that only the wallets with the magnet part of the catch on the flap caused problems and this was due to the magnet flapping against the card when it was taken in and out of the wallet. Despite the proximity to the card (2-3mm), when the magnet was mounted on the outside of the wallet, no problems occurred.

Kelly, your comment about drawing premature conclusions is spot-on. Without examining the cards with instruments, its difficult to know exactly what’s going on. I suppose one could do a brief personal study. The next time you check into a hotel, keep the cards separate and safe. Confirm that they both work reliably in the lock. Then take one and rub it with your blackberry, send an email with it sitting on the card,put it in the holster etc. Try them both again and see what happens. Please post the results.

And apologies to all if this turned out to be the lecture you dreaded. I get that way but thanks anyway for the trip down memory lane (and for reminding me how glad I am not to be in the magcard OR vending business any more)


Feb 2, 2009 - 11:02:06

Your comment is fantastic, and I know it took quite a bit of your valuable time to type up, so I appreciate it greatly. I, too, agree with your suspicions that poor-quality cards, dirty cards, or magnets are more likely responsible. Your report of videotaped subjects, wallets with magnets, etc. was especially interesting. I have actually been thinking about doing a little experiment that is at least a modest attempt at a scientific test. I’m just so busy, and I have such a backlog of stuff to do on this site! But I’ll try. Thanks again for your great reply to the article.

johno says:
Feb 3, 2009 - 01:02:44

You’re welcome. Thanks for the kind words but I would be remiss in taking credit for time spent if I didn’t point out that while I was formulating my ‘tome’, your one paragraph reply to OddyOh pretty much covered the issue.

After reading some of the stuff / forums etc I found while searching on the subject this morning, I think I can say that your readers are well served.


Stephen M says:
Feb 18, 2009 - 01:02:03

I just did a test with my BlackBerry Curve 8900, and I was able to pick up coins with the BlackBerry itself, owing to the magnet that is in every cell phone speaker. It was probably this magnet that erased the cards, not the EM from the phone. Whether the phone rings or vibrates, there is likely an electromagnetic field being generated or enhanced.

Feb 18, 2009 - 05:02:15

Stephen M,
You may very well be right. I didn’t think further testing was warranted (nor did I have the time!) since the point is that HOWEVER IT HAPPENS…IT CAN HAPPEN. Thanks for your comment!

Jake says:
Feb 19, 2009 - 01:02:54

The speaker magnet does seem like it could be the culprit. Perhaps a test with the phone off so there’s no EMI (probably have to pull the battery to get it to be really off with a BB).

Maybe somebody should submit this to MythBusters and see if they’ll do the more extensive testing…

Deeno says:
Mar 11, 2009 - 05:03:11

Set wy BB9530 Storm on my laptop next to the mouse pad…….my monitot shuts iff. Remove it….the monitor comes back on. Anyone else have incedental interactions with electrincs?

Mar 11, 2009 - 01:03:37

Now that’s odd. After doing a little research, here are a couple of things you can try. (1) Maybe the monitor is thinking it needs to power down to save energy. See if you can find a way in Windows Power Options to disable the monitor shutting off. (2) Maybe the monitor is thinking the refresh rate is too high and shutting down. See if you can change the video refresh rate to something slower, like from 75 Hz to 70 Hz. Please let me know if by miracle one of those fixes the problem. In any case, thanks for sharing this very strange phenomenon.

Pat W says:
Apr 27, 2009 - 02:04:56

I found this site while trying to find an answer to my cell phone problem. I have a Samsung a 737 cell phone and am using a DLO leather case made for a Blackberry with a magnetic closure. When I open the case to answer a call my phone will hang up on about 90% of the calls and I get a missed call message. This never happens if the phone is not in the case. The disconnect happens immediately, before I even remove the phone from the case – seems to be related to seperating the two magnets.

Apr 29, 2009 - 05:04:39

That’s odd. I don’t know if it’s the magnet or if the case is squeezing the phone and pressing a button. Thanks for sharing.

tazu says:
Jul 6, 2009 - 11:07:46

myth busters tested it and its nto possible to vipe data off the cc or any card.
it required really strong mag , and its not easily available

Jul 6, 2009 - 09:07:03

Myth Busters’ test was not like mine at all. It’s true that a very strong magnet is required to erase a credit card. My test proved that a weak magnet like that found in a BlackBerry case or the phone itself can easily erase a gift card, but not a credit card. If you re-read my article in full, you’ll see the difference. Thanks for reading and commenting on the article.

Hagen von Eitzen says:
Aug 10, 2009 - 06:08:48

@ Deeno:
I suspect that the laptop might use a magnet to determine whether the laptop is closed or open (and switch of VGA when closed). In that case magnetic effects from the cell phone might have “simulated” closing the laptop (reminds much of Data sending a sleep command to the Borg in StarTrek…)

Aug 10, 2009 - 09:08:37

Yes, I think you’re right. When I gave my original answer, I somehow overlooked that Deeno was using a laptop. I thought it was a standalone monitor. I need to slow down and read more carefully. Your answer was much better. Danke!

Wendall says:
Aug 24, 2009 - 11:08:12

We use ID cards for students and have found that all cards are not equeal. There are HICO and LOCO cards. HICO is what credit cards are encoded with and LOCO are what a lot of hotel/generic uses are encoded with.

There is a good article on wikipedia on mag cards which explains the differences.

We have also found that our printer is set to encode by default in the HICO format but we had bought LOCO cards. Most of the time the printer would write the data but there was a HIGHER than normal rate for the cards to be ereased.

Aug 27, 2009 - 07:08:30

Thanks so much for that enlightening information. I can’t tell you how many people wrote me that I was dead wrong about what I saw with my own eyes. Info like what you just provided helps substantiate my findings.

Sorry, comments for this entry are closed at this time.