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Old 12-16-2014, 03:09 AM
 
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We have a Toyota Avalon with push button start and have been told the fobs must be kept at least 30 feet from the car, or it will drain the battery because it is always communicating. Does this sound logical? We keep the keys in the kitchen right next to the garage, and it's less than 30 feet.
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Old 12-16-2014, 03:21 AM
 
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If it is not designed well, that is possible, especially if it is an aftermarket product which was added to the vehicle.

Vehicle manufacturers usually (not always) take more care to design things so they don't have problems.

You can put the FOB in a tin box with a tin cover and it will not be able to communicate. Read about that here...

http://en.wikipedia.org/wiki/Faraday_cage
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Old 12-16-2014, 03:28 AM
 
Location: Raleigh, NC
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No that doesn't make any sense.
The radios in these devices consume a very very small amount of power, (which is why their range is 20 feet, not 20 miles).
It's very similar to using a bluetooth earbug with your smartphone. The earbug's battery is TINY, and still lasts for hours of use and days of standby, but it's only good for a very short distance.

If the car/fob has the Hands-Free door locking feature then the fobs probably send out regular signals if so the car can 'hear it coming.
The way I understand it, car designers use fobs with a plain replaceable battery for cars that use tiny amounts of power for the fob, and if the fob needs more than that, they design the fob to have a rechargeable battery that auto-recharges whenever it's in the start-socket.

So either way, don't worry.
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Old 12-16-2014, 03:34 AM
 
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Quote:
Originally Posted by Billy_J View Post
If it is not designed well, that is possible, especially if it is an aftermarket product which was added to the vehicle.

Vehicle manufacturers usually (not always) take more care to design things so they don't have problems.

You can put the FOB in a tin box with a tin cover and it will not be able to communicate. Read about that here...

Faraday cage - Wikipedia, the free encyclopedia

There are no aftermarket products on the car. All factory.
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Old 12-16-2014, 03:46 AM
 
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Then I guess it depends on who told you this. If it was a person from the car dealership, factory, etc., then they probably know what they are talking about.

Being a dealer, they would have people come in and say their batteries were quickly dying. Then they would investigate the problem and issue a "warning" or "fix" for the problem.

I would let it sit where it is (FOB) and see how soon the battery goes. If it lasts a long time, then not true or far enough away to not be a problem.

P.S. This would be like holding down a button on a TV remote control constantly. The batteries in the remote would not last very long. But if no buttons are being pressed, then the batteries can last for years. The computer chip in the remote goes to "sleep" - a very energy saving mode. With the car FOB, it would be the car in effect "pressing" a FOB button [activating it/keeping it from going to "sleep"].

Someone could test this by removing the FOB batteries and rigging up an amp meter between the FOB [test] batteries and the FOB. See what the amperage draw is when the FOB is near the car. And what it is far away (sleep).

Last edited by Billy_J; 12-16-2014 at 03:55 AM..
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Old 12-16-2014, 05:23 AM
 
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BillyJ- I know a lot of people that keep their car keys in the kitchen near the garage. You would think the car manufactures would know this and not design them this way. FYI somebody from AAA said this about the fobs, not the dealer.
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Old 12-16-2014, 09:29 AM
 
Location: Ohio
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Were they referring to the car battery or the fob battery?
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Old 12-16-2014, 09:41 AM
 
Location: New Market, MD
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We leave our car keys maybe about 10ft from the car (3 of them) and never had battery drain problem. We drive cars everyday so maybe that makes some difference but we don't need to hide them.
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Old 12-16-2014, 09:45 AM
 
Location: Seminole County, FL
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Quote:
Originally Posted by alpha_1976 View Post
We leave our car keys maybe about 10ft from the car (3 of them) and never had battery drain problem. We drive cars everyday so maybe that makes some difference but we don't need to hide them.
I only had to replace my fob battery once (at 120k miles) and I don't particularly keep the keys close to the car...
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Old 12-16-2014, 10:02 AM
 
Location: OH>IL>CO>CT
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Apparently there is some truth to the issue.

Read page 99 of the owner's manual at:

http://www.toyota.com/t3Portal/docum.../sec_03-02.pdf

where it talks about the battery issues. Both the fob and the car have battery-saving modes depending on the specific circumstances. Such as,
"The electronic key has been left in an area of approximately 6 ft. (2 m) ofthe outside of the vehicle for 10 minutes or longer."
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