Does keyless entry fob drain battery?

BataviaJim

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Is there any problem storing a fob within range of the car? I tested (by locking/unlocking) and the fob reaches the car from anywhere in my house.

I read (but now can't find) where someone said if it's in range, the fob and car communicate continuously, and it can drain the battery either of the car or the fob.

This seems unlikely to me, especially the car battery, but I figured I ask just in case.
Thanks.
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I’d like to know the answer to this aswell. The thought also crossed my mind a while back. I did however just get myself a Faraday RFID blocking pouch for security issues, but I guess if there is also a communications drain issue, it fixes that too
 

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From what I've read, some cars send a continuous signal to the fob & others only send a signal when you touch the door handle or deck lid. I seem to recall there was some advantage or feature that worked with a continuous signal. Maybe some of the vehicles where you wave your foot under the rear bumper & the hatch opens. If your hands are full you can't touch something to activate the signal.

From my understanding, the car sends a coded signal to the fob & activates it. The fob then sends a coded signal back to the car & unlocks the doors. If the fob does not receive a signal from the car then the fob lays dormant.

The relay attack car thefts are done by having one thief at the car who captures & amplifies the car's signal so that it can reach the fob & activate it inside your house. Then another thief outside your house picks up the weak fob signal & amplifies it & transmits it back to the car which in turn unlocks your doors & also can start the car. Then the bad guys drive off with your car. The fob is not needed to keep the engine running.

To avoid car theft if your car is parked outside you probably should keep the fob far away from the car or use a Faraday pouch to shield it.
 

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The fob is not needed to keep the engine running.
Right. I placed my fob into the faraday pouch while driving. and while the instrument panel said fob not detected, the Si kept driving normally until reaching my destination
 
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BataviaJim

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Is there any problem storing a fob within range of the car? I tested (by locking/unlocking) and the fob reaches the car from anywhere in my house.

I read (but now can't find) where someone said if it's in range, the fob and car communicate continuously, and it can drain the battery either of the car or the fob.
Circling back to the original question -- does anyone know the answer? Thanks.
 


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Is there any problem storing a fob within range of the car? I tested (by locking/unlocking) and the fob reaches the car from anywhere in my house.

I read (but now can't find) where someone said if it's in range, the fob and car communicate continuously, and it can drain the battery either of the car or the fob.

This seems unlikely to me, especially the car battery, but I figured I ask just in case.
Thanks.
It sounds like you're talking about 2 different things.

1. Key is close enough to the car for the door handle sensors to unlock the doors: This is only a very short range. Less than 5 feet. The car/key should only be communicating if someone puts their hand on the front door handles or presses the hatch button.

2. Key is within range for the buttons to lock/unlock the car: This is a much longer range and should reach throughout almost any home. Range is probably around 100 feet or more. This communication doesn't happen unless you're pushing the button and will not drain the key fob battery.


If I misunderstood the question, let me know and I'll try to clarify.

If the key is left inside the car, I believe that will drain both car and key fob batteries.

EDITED
 

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It sounds like you're talking about 2 different things.

1. Key is close enough to the car for the door handle sensors to unlock the doors: This is only a very short range. Less than 5 feet. The car/key should only be communicating if someone puts their hand on the front door handles or presses the hatch button.

2. Key is within range for the buttons to lock/unlock the car: This is a much longer range and should reach throughout almost any home. Range is probably around 100 feet or more. This communication doesn't happen unless you're pushing the button and will not drain the key fob battery.


If I misunderstood the question, let me know and I'll try to clarify.

If the key is left inside the car, I believe that will drain both car and key fob batteries.

EDITED
That's sounds correct to me.
 

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According to my dealer this is correct, if left inside the vehicle it will drain.
 
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BataviaJim

BataviaJim

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It sounds like you're talking about 2 different things.

1. Key is close enough to the car for the door handle sensors to unlock the doors: This is only a very short range. Less than 5 feet. The car/key should only be communicating if someone puts their hand on the front door handles or presses the hatch button.

2. Key is within range for the buttons to lock/unlock the car: This is a much longer range and should reach throughout almost any home. Range is probably around 100 feet or more. This communication doesn't happen unless you're pushing the button and will not drain the key fob battery.


If I misunderstood the question, let me know and I'll try to clarify.

If the key is left inside the car, I believe that will drain both car and key fob batteries.

EDITED
Thank you, that's exactly what I was wondering.

My fob locks/unlocks the car (using the fob buttons, not grabbing the car handle) from anywhere in my house that I'd want to keep the fob -- including my bedroom dresser where it usually sits, and the hall closet where I keep the spare.

I was concerned that there might be regular communication between the fob and car that would drain one or the other's battery. Your reply clears it up so I can store the fob where I always have with previous cars.

Thanks!
 

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If it helps, I have noticed that my battery drains faster if the fob is unshielded and the car is unlocked within range of it. I have found that locking the car and then placing the fob(s) into a faraday pouch when not in use helps the battery life in storage longer.
 


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BataviaJim

BataviaJim

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If it helps, I have noticed that my battery drains faster if the fob is unshielded and the car is unlocked within range of it. I have found that locking the car and then placing the fob(s) into a faraday pouch when not in use helps the battery life in storage longer.
A Faraday pouch on Amazon is $30. Wouldn't any metal container do the same, or even aluminum foil?
 

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A Faraday pouch on Amazon is $30. Wouldn't any metal container do the same, or even aluminum foil?
I don't think a metal can or foil will be as effective. Perhaps an old ammo box with a good seal would work, but I can tell you from experience walking around the car with the fob in the pouch that if I'm not very meticulous in closing the pouch the right way, the car still detects the signal from the fob. That sucker is powerful!
 

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A Faraday pouch on Amazon is $30. Wouldn't any metal container do the same, or even aluminum foil?
I've read that wrapping in aluminum foil will work but never tried it. Maybe you have to make sure there are no leaks or openings anywhere. Give it a try & let us know.
 

saiko21

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The best solution is disable auto lock/unlock in vehicle settings and use the remote buttons to lock and unlock. :lol:
 
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BataviaJim

BataviaJim

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I've read that wrapping in aluminum foil will work but never tried it. Maybe you have to make sure there are no leaks or openings anywhere. Give it a try & let us know.
Aluminum foil works. It has to be sealed all around, but that blocked the signal.

I was about 15' away, where I store my spare key. It wouldn't lock/unlock from inside the foil. I pressed the buttons through the foil, and I could hear them click so I know they engaged, but the car didn't respond. I opened one end of the foil and they worked.
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