Here's a pretty trivial question:
I've replaced the batteries in my 2014 remotes a number of times, and each time I note that BOTH remotes suffer battery failure at the same time.
Yesterday I tried to use one remote and got the "smart key not found" message. So I grabbed the other remote, which worked, but gave the "smart key battery low" error. The batteries are kept in different places, used about the same amount, and last many months; but when they fail, they fail together.
My refrigerator water filter lights the "replace filter" light on the same week every year, so I'm sure it is just on a timer. Is the "low battery" warning on the XF also on a timer?

You may now return to more critical issues...

 

Mine have failed within days of each other also after about a year or so, they transmit all the time so Jag recommends storing them at least 16ft. from the car when not in use.

 

Thanks, should have thought of the fact they both transmit all the time. That's the reason I have to hang the key on the far wall of the garage, and never put a motel key in the same pocket. Still wonder about two different batteries in two different transmitters kept in two different places - expiring within hours of each other. But many more important things to wonder about...

 

Not to be argumentative, but I park my 2013 XF in a locked garage, so I leave the key fob in it when I'm home. I've owned the car over a year and just now got a low battery message. I guess this would point toward the message being on a timer, rather than the transmitter always being active.
Did you ever figure it out?
Megan

 

Well there are a couple of factors.
As Big Will has stated the fobs are proximity aware, so if you are within (i think) 5 meters or so the fob will keep communicating.
There may be a weird behavior with the fob when it is within the vehicle.

I have also found that when replacing the battery on the fob that the contact points can become mashed down a bit, making intermittent contact, I tend to pull them up a bit when I change out the battery.

 

Here's something interesting...I just replaced the battery in only one of the 2 key fobs, and still got the low battery message when using that same fob. I will replace the other one tonight and let you know if I still get the message (when using either fob)
Also, I always assumed the proximity sensor worked similarly to a tv remote; i.e. only transmitting when activated by a button push or polled by the car (when you open the door, push ignition, etc)
Is this not accurate? How inefficient, if not.