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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Low Key Fob Battery Question...
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      05-07-2013, 09:39 PM   #1
dbs600
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Low Key Fob Battery Question...

How does placing the key fob near the steering wheel column help 'charge' it?

It does so wirelessly!?
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      05-07-2013, 11:06 PM   #2
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It isn't rechargeable. Replace the battery if it's low.
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      05-08-2013, 12:12 AM   #3
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Not sure, but my remote completely stopped working the other day; I believe the battery needs to be replaced (2.5 years old). Called BMW Assist (forgot I had BMW Remote on my iPhone) to unlock my doors. Car wouldn't start with the key in the car and I was told to place the remote near the steering column. Didn't work first couple of attempts, but after keeping the remote there for a little while (2 minutes?), and reattempting, the car started. Key has worked since, but I'm bringing in the car for service tomorrow and will ask them to replace the battery. Anyone know if the battery is covered under warranty?
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      05-08-2013, 12:20 AM   #4
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There was a thread on this recently. As I recall, most dealers will replace as a matter of course at service interval. Shouldn't be a problem. I think when the battery is dead, the back up for ignition is to hold near the sweet spot on the steering column. It starts the car, but does not charge the non-rechargeable battery.
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      05-08-2013, 08:38 AM   #5
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Quote:
Originally Posted by dbs600 View Post
Not sure, but my remote completely stopped working the other day; I believe the battery needs to be replaced (2.5 years old). Called BMW Assist (forgot I had BMW Remote on my iPhone) to unlock my doors. Car wouldn't start with the key in the car and I was told to place the remote near the steering column. Didn't work first couple of attempts, but after keeping the remote there for a little while (2 minutes?), and reattempting, the car started. Key has worked since, but I'm bringing in the car for service tomorrow and will ask them to replace the battery. Anyone know if the battery is covered under warranty?
You could have use your mechanical key to open the door as well The steering column has a Proximity Reader in it, it will read the chip in your key fob and let you start up your car. Key fob battery are not cover under warranty, but some dealers will change it for free, some will charge you just for the price of battery and some will chrage you full price, parts and labor.
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      05-08-2013, 09:41 AM   #6
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Originally Posted by The X Men View Post
You could have use your mechanical key to open the door as well.
OMG, you're absolutely right; how stupid of me!

Otherwise, thanks for your replies, gentlemen. I'm just wondering what's occurring when the remote doesn’t work, but placing next to the steering wheel brings it back to life; maybe these charge up as well - but only for a short amount of use thereafter?
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      05-08-2013, 08:41 PM   #7
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Quote:
Originally Posted by dbs600
Quote:
Originally Posted by The X Men View Post
You could have use your mechanical key to open the door as well.
OMG, you're absolutely right; how stupid of me!

Otherwise, thanks for your replies, gentlemen. I'm just wondering what's occurring when the remote doesn’t work, but placing next to the steering wheel brings it back to life; maybe these charge up as well - but only for a short amount of use thereafter?




No. As the previous poster said, there key fob contains a passive RFID chip.

Normally, the key fob transmits the secret information by way of a small, low power, RF transmission.

This way, you can keep the key fob in your pants pocket. The key fob silently listens for a request from your car after you pull the door handle, for example.

Once the key fob receives a request (listening takes far less battery power than transmitting), the key fob returns, among other things, the encrypted value if your key's ID. Then, in near real time, your vehicle evaluates the response from the key fob and ensures the decrypted value matches the expected value in the car's key database. Every key has their own ID. The key fob has the capability to handle non-key related functions, such as the number of miles on your vehicle.

So long as your key fob has battery power, your key fob can convey its secret value in response to an active request from your car.

When the battery gets too low, the key fob conveys this condition to your car. In turn, a warning is displayed on your dash.

Now, at some point there may not be enough energy in the battery to power the transceiver. That's ok! A battery is not necessary! Since the RFID can be determined passively, you do not need power. All you have to do is place the key fob in close proximity to the car's reader. There RFID reader's location is marked on the steering wheel for your convenience. Just hold the key fob next to the reader and depress the start button. The RFID value is read and compared in a similar manner as an actual transmission. However, it may lack some level of full encryption used in a transmitting environment.

This does not mean there is no encryption. It just may be less than that used by the transmitter.
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      05-08-2013, 09:59 PM   #8
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Quote:
Originally Posted by BMWrules7 View Post
Now, at some point there may not be enough energy in the battery to power the transceiver. That's ok! A battery is not necessary! Since the RFID can be determined passively, you do not need power. All you have to do is place the key fob in close proximity to the car's reader. There RFID reader's location is marked on the steering wheel for your convenience. Just hold the key fob next to the reader and depress the start button. The RFID value is read and compared in a similar manner as an actual transmission. However, it may lack some level of full encryption used in a transmitting environment. This does not mean there is no encryption. It just may be less than that used by the transmitter.
Wow; YOU ARE THE MAN, BMWrules7!

Clear and easy to understand; exactly the explanation I was looking for!

Much Thanks! Happy Motoring!
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