short life of key-fob battery

[Toby]

The batteries in our key-fobs only last two or three months. These are the CR2025 3v batteries. I have one on my desk that measures 3.07 volts. Surely that should be enough but that battery will not start the car or open door locks. A replacement battery works properly. So, what's the problem? Why aren't the batteries lasting longer? Is the car somehow out of tune?

 

[GerryAZ]

I normally get between 1 and 2 years from a high-quality battery in the fob I use on a daily basis. Those lithium button cells will show 3 volts with a meter even when they get weak, but their voltage collapses when the fob transmits. There is also significant difference in the quality of cells you can buy. There is probably nothing wrong with the car, but the fob transmits more because of the wireless entry and keyless switch than an older fob that only transmits when buttons are pressed.

 

[DougWantsALeaf]

Ours average 2 to 2.5 years. We just replaced 1 fob battery from our June 2019 purchase SV+.

 

[HerdingElectrons]

Do you keep your fob within about 20 feet of the car? It may be 'talking' to the car when the car is not used and using up the battery or just lower capacity cells

 

[Toby]

Do you keep your fob within about 20 feet of the car? It may be 'talking' to the car when the car is not used . . .

Interesting thought. When not in use the car is parked in a garage attached to the house. Can the fobs 'talk' to the car through walls?

 

[HerdingElectrons]

To a point yes so I would suggest storing the key further away and see if your battery life is greatly extended because I also get about 12-18 months of life from each coin cell.

 

[LeftieBiker]

Another thing to consider is that the button cell Market is flooded with Chinese counterfeit batteries of poor quality. Those Energizer batteries you are buying May well be not Energizer at all, but counterfeit batteries that go dead in the package or shortly after you put them into something. The best defense against this is to buy Button cell batteries locally, at supermarkets.

 

[Stanton]

Do you keep your fob within about 20 feet of the car? It may be 'talking' to the car when the car is not used . . .

Interesting thought. When not in use the car is parked in a garage attached to the house. Can the fobs 'talk' to the car through walls?

As @HerdingElectrons mentioned, it's all about how close the fob is to the car. My fob batteries last ~2 years, but I suspect the biggest reason for reduced battery life is from leaving the fob near (or even inside) the car on a regular basis.

 

[Toby]

I often leave my key on a hook in a closet on the other side of the garage wall. The location is about 12 feet from the car windshield. If I place a metal plate behind the hook would that help?

The cheap, weak manufacture problem has merit. In all the stores around here the battery display is full of premium names (Energizer, Duracell) , the exception being the 2025 cells which are Reactor. I assume the same supplier hits all the stores. To get around that I got a pair of expensive 2025 from The Source under the name VITAL; different but I don't know if better.

 

[Toby]

BTW, is there a problem when both of us have our keys with us in the car?

 

[jjeff]

I often leave my key on a hook in a closet on the other side of the garage wall. The location is about 12 feet from the car windshield. If I place a metal plate behind the hook would that help?

The cheap, weak manufacture problem has merit. In all the stores around here the battery display is full of premium names (Energizer, Duracell) , the exception being the 2025 cells which are Reactor. I assume the same supplier hits all the stores. To get around that I got a pair of expensive 2025 from The Source under the name VITAL; different but I don't know if better.

Myself and many others on MNL use a 2032 instead of the harder to find, almost 50% less capacity 2025. You can also often find the 2032 in a multi-pack whereas the 2025 is almost always sold individually. I usually purchase a 5 pack of genuine Energizer 2032 batteries from my local B&M big box hardware store(Menards in my case) and they last me a couple of years as many things use the very common 2032. I generally get 3-4 years with my 2032's as again they hold a fair amount capacity than the somewhat thinner 2025.
Note the first time or two you go to close the top on the 2032 you might find it's hard to close, if you can't get it closed try reversing the side you squeeze shut first, that works for me. The good news is after a couple on/off cycles it will click down just like the 2025, or at least both my fobs do now. See the 2032 while the same diameter is a hair thicker, requiring a bit more squeezing to get it closed but the upside is its larger capacity, generally same or lower price, availability to purchase in multi-packs and easier to find, worth using it IMO.
Oh, one way to tell if you are far enough from the car or if your metal idea is good is to push a key on the FOB, if it fails to unlock the doors(or whatever button you pushed fails to respond) you should be good. I used to store a spare FOB in our Leaf for emergencies and found if I wrapped it with many many layers of AU foil, the car wouldn't know the FOB was in the car and I could lock it from outside the car, and also I couldn't start the car without the other FOB nearby. I rarely ever had to replace the spare FOBs battery, maybe every 5 years or so if that. Obviously wrapping the FOB in AU foil isn't practical in your case but maybe as you said, some metal between your FOB and car would do the trick.

 

[Stanton]

I often leave my key on a hook in a closet on the other side of the garage wall. The location is about 12 feet from the car windshield. If I place a metal plate behind the hook would that help?

That's too close; the metal plate thing is a waste of time (RF travels in all directions).
+1 on the 2032: I use those as well (they don't fit everywhere, but they fit in the Leaf fob).

 

[HerdingElectrons]

I often leave my key on a hook in a closet on the other side of the garage wall. The location is about 12 feet from the car windshield. If I place a metal plate behind the hook would that help?

The cheap, weak manufacture problem has merit. In all the stores around here the battery display is full of premium names (Energizer, Duracell) , the exception being the 2025 cells which are Reactor. I assume the same supplier hits all the stores. To get around that I got a pair of expensive 2025 from The Source under the name VITAL; different but I don't know if better.

You would be better off leaving the key in the car because it would take less energy to 'talk' to the car when the fob is inches away vs feet away if you are unable or unwilling to keep the fob 20-30' away so there's no communication possible


And one or two keys has no ill effect other than consuming two coin cells and the inevitable scenario when the other key is left in the handbag & you try to lock the car

 

[Stanton]

You would be better off leaving the key in the car because it would take less energy to 'talk' to the car

Not advised: that will kill the battery just as quickly. The idea is to prevent the key from communicating with the car at all for longest battery life.

 

[jjeff]

I often leave my key on a hook in a closet on the other side of the garage wall. The location is about 12 feet from the car windshield. If I place a metal plate behind the hook would that help?

That's too close; the metal plate thing is a waste of time (RF travels in all directions).
+1 on the 2032: I use those as well (they don't fit everywhere, but they fit in the Leaf fob).

Do note though my AU foil around the FOB did result in the vehicle not knowing the FOB was inside the car, maybe that was because the foil(and many layers) completely encapsulated the FOB?
I do know RF is hard to stop though, I seem to remember copper may be good for stopping it but I didn't have easy access to sheets of bendable copper which is why I used aluminum foil, something I did have easy access to and low and behold it worked. I do have many square feet of bendable Pb sheets, although I'd rather not work that much with lead, isn't it supposed to be not that good to touch? do you think Pb would also be a good RF stopper?

 

[Learjet]

Without more details from the OP it's hard to say his/her batteries only last XXX months consistently....what was the cars build date and time on first set of batteries....how many sets have they used since?...if only one replacement set, it could have just been a bad set as mentioned.

Like everyone has said, I got @ 2 years from the cars build date on my first set of Fob batteries.

Also, if you carry them in your pocket all day...how often are you keeping a button depressed accidently.

 

[Toby]

Without more details from the OP it's hard to say his/her batteries only last XXX months consistently....what was the cars build date and time on first set of batteries....how many sets have they used since?...if only one replacement set, it could have just been a bad set as mentioned.

You're right, of course. The car is a 2018 Leaf which we bought secondhand in 2019. Now that you mention it I think the batteries that were in the fobs when we bought the car lasted the longest although I never kept a record. For the sake of expedience let's say they lasted a year; my wife's failed first and mine about 2 weeks later. Since then, replacement batteries have only lasted 2 to 3 months. As you suggested it may be a bad batch or, maybe, a cheap, poor quality brand.

jjeff wrote, "Myself and many others on MNL use a 2032 instead of the harder to find, almost 50% less capacity 2025." I have a multi-pack of Energizer 2032 which I purchased for something else. I tried to install one in place of the 2025 but there didn't seem to have room. I'll try again next time one fails.

I have moved my key farther from the garage and want to see if that helps.

Thanks, everyone, for your input. It's a big help.

 

[Nubo]

Do you keep your fob within about 20 feet of the car? It may be 'talking' to the car when the car is not used and using up the battery or just lower capacity cells

Interesting but if that's a thing, the range for that must be shorter. My fob hangs on the wall just inside the garage entrance door, and the car is parked about 5 feet from there so the fob is about 8 feet from the car, and my fob batteries last from 1 1/2 to 2 years. The range for keyless entry recognition seems to be about 3 or 4 feet from the handles.

 

[Toby]

Interesting but if that's a thing, the range for that must be shorter. My fob hangs on the wall just inside the garage entrance door, and the car is parked about 5 feet from there so the fob is about 8 feet from the car, and my fob batteries last from 1 1/2 to 2 years. The range for keyless entry recognition seems to be about 3 or 4 feet from the handles.

Thanks for that. I hung my key-fob on its usual hook in the house and then tried to start the car. This message came up, "NO KEY DETECTED".

 

[cwerdna]

Approximately, where you located?

If you have any Daiso stores near you, they should have 2 packs of Mitsubishi-branded CR2025 batteries for $1.50. +100 on what Leftie said about counterfeits. I wouldn't be surprised if most of the "brand name" coin cell batteries sold on Amazon by random 3rd-party resellers are counterfeit.