2016 CX-5 Sport key fob battery died in about a month

[ceric]

That proves me correct. Thanks.

The key becomes active AFTER the car looks for it. Not simply because it is in proximity.

"When the vehicle is triggered...() a signal is sent...."

My understanding was misled by auto-lock (walkaway lock) feature.

 

[7eregrine]

NGL, that one still confuses me.

 

[Conrad 16.5]

Stand corrected.
- from Wiki
The system works by having a series of LF (low frequency 125 kHz) transmitting antennas both inside and outside the vehicle. The external antennas are located in the door handles. When the vehicle is triggered, either by pulling the handle or touching the handle, an LF signal is transmitted from the antennas to the key. The key becomes activated if it is sufficiently close and it transmits its ID back to the vehicle via RF (Radio frequency >300 MHz) to a receiver located in the vehicle. If the key has the correct ID, the PASE module unlocks the vehicle.

I've been saying this for a long while, but no one believed it. It just makes sense.

There's no reason to have the fob continually broadcasting a signal and sucking down the battery. It's listening continually only and becomes active when it 'hears the car calling' to it after the action button is pressed.

 

[txt990]

You could have got low-quality、out-of-date counterfeit batteries. Don’t buy any batteries from that store.

I bought the Duracell CR-2025 (one that died in about a month) from target.

 

[Ranman57]

That proves me correct. Thanks.

The key becomes active AFTER the car looks for it. Not simply because it is in proximity.

"When the vehicle is triggered...() a signal is sent...."

I think not. If the car is parked in close proximity to the fob after X time it will stop pinging the fob so as not to drain the battery. Then you have to press one of the buttons, lock or unlock, I don't remember which offhand, 5 times in rapid succession to reactivate it or it won't unlock with the door button or start unless the fob is held near the start button. It's goofy because the dash will read that the fob battery is low when you get in the car, though in reality it's locked out the fob ping.

Many an owner, including myself, has been fooled into changing the battery because of that warning, while in reality the battery is fine but the car won't open or start until you reset it with the presses. I've learned not to park my car overnight near my side door where my extra fob is on a hook or it will "kill" it every time, but until it shuts down the ping it's draining the battery.

 

[Conrad 16.5]

I think not. If the car is parked in close proximity to the fob after X time it will stop pinging the fob so as not to drain the battery. Then you have to press one of the buttons, lock or unlock, I don't remember which offhand, 5 times in rapid succession to reactivate it or it won't unlock with the door button or start unless the fob is held near the start button. It's goofy because the dash will read that the fob battery is low when you get in the car, though in reality it's locked out the fob ping.

Many an owner, including myself, has been fooled into changing the battery because of that warning, while in reality the battery is fine but the car won't open or start until you reset it with the presses. I've learned not to park my car overnight near my side door where my extra fob is on a hook or it will "kill" it every time, but until it shuts down the ping it's draining the battery.

This the 'sleep function' you're talking about. From my understanding only the newer models with the GIANT-SIZED fobs have this 'feature'.