The other evening my wife mentioned that she thought the fob for her 2016 Hyundai Tucson needed a new battery since the driver’s door wasn’t as responsive any more. I had some CR2032 batteries handy and went ahead and replaced hers. In the process, it occurred to me that I’ve owned my 2009 Corolla for 9 years and I’ve never replaced the battery in the key. For all I know, it’s the original battery. Granted, I don’t have keyless ignition and the other various gewgaws hers does but 9 years seems like a long time, not that I’m complaining. Google says 4-6 years on average: https://www.testingautos.com/car_care/key-fob-battery.html Anyway, I’m curious; what’s the longest life you’ve gotten from a key battery?
I have never replaced a battery in the key for my 1991 Honda CRX. 
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The batteries last longer in older cars. I got about 3 years from the battery in my 2015 Accord EX-L key fob. It doesn’t seem long compared to my 1998 Buick Regal, with battery replacement at about 8 years. They serve different functions though. The Accord fob does everything the Buick fob does, but it never leaves my pocket. I touch the inside of the door handle and it opens. I push a button under the truck lid and it opens. I can start the car remotely. It even locks when I walk away if I want. It’s no wonder the battery life is short.
I will probably replace the batteries in our 2017 fobs in the net year. Some cars give you a low battery fob warning.
Before I started my practice of leasing a new car for my wife, she had a 2008 Chrysler Pacifica that we bought new. When we traded it in August 2016, the key fob battery had never been changed.
I haven’t paid much attention. I think my secondary key for my 16 yo truck still has the original battery. But I never use it. The primary has has 2 or 3 batteries and a replacement case and button covers. I changed batteries a few times on our old Saab in 15 years in each key.
2000 Dodge Stratus my wife bought new april 2000 with 2 fob’s baterry’s still going strong in june 2015 when it got totaled.
I don’t really keep track and I’m not interested in seeing how long they will go, but I think it was 3 years on the Acura when I got the message to replace the battery.
Now on the remotes for the garage door openers I’m a little more concerned and replace them all about every year. I have one on the snow blower and was caught out in the cold once with a non working remote. Luckily someone was home to unlock the door. I’ve taken other precautions since like key pad and lock box but still it’s easier to replace a few batteries ahead of time.
Now that brings up what happens if your car battery goes south and the electrics don’t work. My BIL has a Jag and was saying he had to call the company to find out how to get into the car trunk when the battery went. Turns out there is some kind of a secret key access by the tail light or something to open the trunk. Things are getting complicated.
Original batteries in both fobs for my 2003 Camry still working when sold a month ago…
I’m at 6yrs for the fob battery for my 2015 Forester, I’ll buy a new battery just to have since it’s simple to change
It might be more of a range issue than just not working. I know with a good battery I can hit the auto start from half way across a parking lot but not with an older one.
I suspect you’re correct. Mine only operates the doors/trunk/panic alarm so I’m usually pretty close anyway. For all I know the battery could be half dead already.
The fob for my 96 Lincoln still has the original battery and it still works for some strange reason. I would have thought it would have needed to be buried a long time ago.
I have that on my Accord, too. I like the reminder. I wonder if the alert is a result of the signal read, or if it is time based. I replaced both of my son in law’s Accord fob batteries recently. The alert was on for his primary fob and then I tried his backup fob. The replace alert was on for it too.
We’ve replaced the battery in my wife’s 07 Lexus twice. I’ve replaced the battery in my 14 Highlander just once. They last a long time.
I bought my 2005 Outback in 2010, have not changed the battery yet, don’t know if it is the original one from 2005, but at least 10 years.
We traded in my wife’s 2003 Jeep Liberty last year and AFAIK the separate fob still had the original battery. Dunno where the 4-6 years thing comes from but I’d guess probably from people who sell CR2032 batteries.
Some cars give you a warning. Why take a chance and find out yours doesn’t. Change it after 5 years.
That’s true of vehicles with keyless ignition and such like my wife’s Hyundai but not older ones like my Corolla. The only negative (pun unintended) to a dead key battery in my case would be having to actually put the key in the door instead of unlocking it remotely. Lord help me if I ever get so lazy that’s a big deal.