Carry a spare key-fob battery in your glove box.

[JimPghPA]

Something to consider to improve the reliability of your vehicle if you rely on a key-fob to start and run it:

My 2016 Honda CR-V has a removable key built into the key-fob for opening the door if the battery in the key-fob dies. However the electronics of the key-fob are still required to get the engine to start, and also to keep it running. There is a procedure of holding the key-fob next to the start button and then doing the normal start of (pressing the brake pedal and start button at the same time) while the key-fob is next to the start button to allow the key-fob to work if the battery is very low, but not dead. But what if the battery completely dies and you are somewhere where you need the vehicle to run. I have been carrying both of the key-fobs with me every time I use the vehicle since I got it in February, but that is not a good idea because there is the possibility of loosing both of them. So I decided to get a spare new battery for the key-fob and put it in the glove box. There are videos on You-tube on how to replace the battery in the key-fob, and they show that you can use the mechanical key to open the case to access the battery to replace it.

Be aware that the oil from your fingers can conduct enough electricity to slowly discharge small batteries like the batteries used in a key-fob. So it is best to leave a new battery in the package it comes in and not handle it before putting it in storage in your vehicle. Also when you do handle it to put it in the key fob, for maximum useful life you should wear some type of clean plastic or rubber glove or use plastic tools such as plastic tweezers.

Along with the You-tube videos on how to replace the battery in a key-fob, there is a video on how to re-assemble the key-fob if you accidentally allow it to fall apart while changing the battery, and it also shows how to hold the opened key-fob so it does not fall apart in the first place. Do a You-tube search for "How to Replace Honda Key Fob Battery and Reassemble If It Falls Apart".

The battery for my 2016 CR-V is CR2032 and it is a lithium battery so a new one should last about 7 years in storage, although the hot temperatures of being in a vehicle in the summer may shorten that some. So I will probably put a new one in the glove box in 4 years if it is not used by then, so I always have a good spare key-fob battery available, so a dead key fob can never leave me stranded when I venture into remote wooded areas.

You can do some You-tube searches to find key-fob videos for your specific vehicle and find out what type of battery you should carry.

Stay safe everyone.

 

[PimTac]

Don't most cars nowadays alert you somehow when your fob battery is getting low?

 

[Leo99]

You're overthinking this. You don't need a battery in the fob to start the car if it's held against the start button. Once the car is started, it will stay running. Pull the battery from your fob and try it out.

 

[bdcardinal]

Or just change the battery every 2 years or so. They are cheap.

 

[mk378]

Yes if you hold the fob right next to the NFC coil in the car it should power up and read even with completely dead battery.

 

[WhyMe]

my moms 2017 CRV fob battery lasted about 2 years. i don't think they last as long as a fob with a push button. its might be because they are always transmitting even when not close to the vehicle.

her vehicle a message popped up telling her that the battery was low.

 

[JimPghPA]

There is a light on the dash that should light up telling you to change the battery when it is getting low, but I feel safer with a spare in the glove box.

 

[CR94]

It will work held next to the button even with no battery. A battery in the glove box will degrade rapidly if the car is often parked in sun in the summer.
Therefore, I keep my spare fob hidden inside the car without its battery or metal key, keep the metal key hidden under the car (to get into the car and access the hidden fob if I lose the other fob), and keep a spare battery in my luggage on long trips.

 

[Wolf359]

Originally Posted by CR94
It will work held next to the button even with no battery. A battery in the glove box will degrade rapidly if the car is often parked in sun in the summer.
Therefore, I keep my spare fob hidden inside the car without its battery or metal key, keep the metal key hidden under the car (to get into the car and access the hidden fob if I lose the other fob), and keep a spare battery in my luggage on long trips.


Wow, that's super overkill. I just keep my spare fob at home. Never actually lost my car keys as they're attached to my home keys so it's a big pile. Harder to lose when you have a whole bunch and I only keep it in a few places and move it back to where it's supposed to belong so it doesn't get lost. You guys are lucky, my keyfob batteries use 2025 so not as thick and not as much power, lasts around 4-6 months before the voltage gets low and I change them out. I get them from eBay though so I can't decide if the eBay batteries are bad or if it's just like that. Others report not getting as much life out of them too so I don't think it's eBay batteries. Tried lots of brands too, Energizer, Sony, Duracell, Panasonic, etc., but they're all about the same, some batches come with higher starting voltages than other which I think is a function of how old the batteries really are, they're probably really not that fresh.

With fobs costing so much these days, it probably makes sense to buy one of those Tile things on Amazon so you can find your keys if they get lost.

 

[Hall]

Originally Posted by bdcardinal
Or just change the battery every 2 years or so. They are cheap.

I bought my sister's G35 that she had dealer-serviced for most of it's life. She gave me the service records and they show every few visits where they replace the key-fob battery at "no charge". Seems minor and not a big deal given how cheap these batteries are but it avoids their customer having it die on them.

 

[Wolf359]

Originally Posted by hallstevenson
Originally Posted by bdcardinal
Or just change the battery every 2 years or so. They are cheap.

I bought my sister's G35 that she had dealer-serviced for most of it's life. She gave me the service records and they show every few visits where they replace the key-fob battery at "no charge". Seems minor and not a big deal given how cheap these batteries are but it avoids their customer having it die on them.


Mercedes does that at the dealer and it's not even mentioned in the work order. I think the service adviser does it. Reason I know is that I had an energizer in there and it came back with a different brand.

 

[Lolvoguy]

I replaced the batteries on my fobs last year.
They were the originals from new.

 

[ammolab]

Leaving an electric fob in a car 100% of the time is not good in some cars. The fob will remain in contact with the car constantly or intermittently. This will shorten the life of your fob AND vehicle battery.

My car horn will honk if I leave a working fob inside as I exit and walk away.

 

[Bud]

No, but my car gives me a message that the battery is low.

 

[ecotourist]

I had to replace the battery in one of the Key Fobs of my 2007 Accord recently. That was the first change and it was not easy. The tiny screw holding it together would not come out and the small screw driver kept slipping on that tiny Phillips head.

Had to put the Fob and the little screw driver in a vice to hold them together while applying lots of torque. Loosened the screw on the other Fob while I was at it.

So if there is a Phillips screw holding the Fob together, loosen it if you have any ideas about replacing that battery in the field.

 

[Wolf359]

Originally Posted by ammolab
Leaving an electric fob in a car 100% of the time is not good in some cars. The fob will remain in contact with the car constantly or intermittently. This will shorten the life of your fob AND vehicle battery.

My car horn will honk if I leave a working fob inside as I exit and walk away.


He said he takes the battery out of the fob so no issues there. You can't even lock the car if it senses the fob in the car on a Mercedes.

 

[earlyre]

Originally Posted by ecotourist
I had to replace the battery in one of the Key Fobs of my 2007 Accord recently. That was the first change and it was not easy. The tiny screw holding it together would not come out and the small screw driver kept slipping on that tiny Phillips head.

Had to put the Fob and the little screw driver in a vice to hold them together while applying lots of torque. Loosened the screw on the other Fob while I was at it.

So if there is a Phillips screw holding the Fob together, loosen it if you have any ideas about replacing that battery in the field.


wow... I've never run across a fastener holding a fob together... but i've only "been inside" of Ford, GM, and Dodge fobs.... all just plastic that snaps together in one way or another...

 

[bbhero]

My battery in my fob lasts maybe 2 years... No where near 7. I bet it is because the key is always searching for my car no matter where I am or where the key is located.

I agree with you about keeping a spare battery around..

 

[JimPghPA]

I removed the battery from one of my fobs and left the other one in the house far away from the 2016 CR-V and mk378 is correct, when the fob is held next to the start button the field generated by the NFC coil in the vehicle energizes a chip in the fob and the vehicle can be started, and moved even without a battery in the fob. So an extra fob battery in the glove box of a Honda CR-V is not really needed.

I wonder if opening the door with the mechanical key activates the NFC coil and it only draws power from the vehicles battery after the door has been opened that way, or if the NFC coil is always active and providing a slight drain of the battery. The vehicles main battery is only a group size 51R with 500 CCA and 85 RC, 85 RC means 25 Amps for 85 minutes, so that is not really a lot to power any small constant load when you consider the vehicle may sit for a week or so without use.

 

[CR94]

Originally Posted by JimPghPA
... I wonder if opening the door with the mechanical key activates the NFC coil and it only draws power from the vehicles battery after the door has been opened that way, or if the NFC coil is always active and providing a slight drain of the battery. The vehicles main battery is only a group size 51R with 500 CCA and 85 RC, 85 RC means 25 Amps for 85 minutes, so that is not really a lot to power any small constant load when you consider the vehicle may sit for a week or so without use.
I once started my Prius with a batteryless fob without first using the mechanical door key, so ...

Overall vampire drain on the battery is about 20 milliamperes, so a couple of weeks would withdraw roughly 7 ampere-hours.