[claykin]

I've got a 2019 540i. Car has comfort access. The keyfob batteries seem to last no more than a year before the car reports "keyfob battery empty". Sometimes, not even a year. I've tried both fobs for my car, same issue with both. Dealer tells me this is normal and they offer battery replacement at no charge. Nice, but inconvenient to make a trip to the dealer for a $1.59 battery.

In checking the voltage of the "dead" battery, it's 2.95V, just under the 3V of a CR2032. Yes, I'm aware most CR2032 brand new are 3.1 or 3.2V. Many other products I own using coin cell batteries still work fine until well under the specified battery voltage, rather than just 0.05V below. Sure seems Valeo (Oem of these fobs) did a lousy job with the electronics design.

What's your experience?

[CnSky]

Just buy your own pack of batteries takes 1 minute to change them, 1 year is about normal for most modern BMW fobs.

[PetieD 7]

My key FOB batteries lasted just about 2.5 years. Although, I don't drive my vehicle often, and is in storage during the winter months. BTW, I have comfort access feature as well.

[2022M550i]

How close is the fob to your car when you park it over night? I think if it's close, it may drain the battery quicker as it will be constantly communicating with car.

[Joe-BMW33]

The dealer changed both my FOB batteries in April 2021 (at least that is what my work order says) and I had to replace my main FOB battery at the end of the 2021 summer. I am sure both my FOB's are communicating with the car as my key hooks are in the kitchen right above the garage.

I bet the dealer uses cheap batteries. I swapped a nice Duracell in. We will see, but I'm not going to sweat it for a buck and a half and two minutes of my time.

I do think the "KeyFOB battery empty" message is hilarious. No "KeyFOB battery low" first, just straight to empty it is not "empty".

[PetieD 7]

Originally Posted by 2022M550i

How close is the fob to your car when you park it over night? I think if it's close, it may drain the battery quicker as it will be constantly communicating with car.

I actually purchased two small key fob security protector pouches to prevent/block signals being transmitted while my vehicle is being parked in the garage.

[claykin]

Originally Posted by CnSky

Just buy your own pack of batteries takes 1 minute to change them, 1 year is about normal for most modern BMW fobs.

I did. Takes me 90 seconds, I'm not as fast as you. Lol

[claykin]

Originally Posted by 2022M550i

How close is the fob to your car when you park it over night? I think if it's close, it may drain the battery quicker as it will be constantly communicating with car.

This is not an issue since spring 2018 production. All keyfobs since then go to sleep after 2-3 minutes of sitting still and wake up once moved. The fobs have a simple accelerometer chip in them.

BMW did this to try to thwart relay attacks.

[claykin]

Originally Posted by Joe-BMW33

The dealer changed both my FOB batteries in April 2021 (at least that is what my work order says) and I had to replace my main FOB battery at the end of the 2021 summer. I am sure both my FOB's are communicating with the car as my key hooks are in the kitchen right above the garage.

I bet the dealer uses cheap batteries. I swapped a nice Duracell in. We will see, but I'm not going to sweat it for a buck and a half and two minutes of my time.

I do think the "KeyFOB battery empty" message is hilarious. No "KeyFOB battery low" first, just straight to empty it is not "empty".

If your dealer get their batteries through BMW parts, they should use Varta brand. Varta is a decent brand, however most of the big battery brands get their CR2032 through a 3rd party factory in Indonesia and one or two China makers.

I can sometimes locate energizer brand that are made in Japan.

[Joe-BMW33]

Originally Posted by claykin

If your dealer get their batteries through BMW parts, they should use Varta brand. Varta is a decent brand, however most of the big battery brands get their CR2032 through a 3rd party factory in Indonesia and one or two China makers.

I can sometimes locate energizer brand that are made in Japan.

What the dealer should do and does are two different stories. My dealer should fill up a car that requires 91+ octane on delivery, but they put 87 in every car and they know it.

Anyway, go to Amazon and order a strip of CR2032's from a reputable maker. Most are made in China.

[MauiSteve]

My fob battery was still operating at the 2 year mark. There had been maybe 1 or 2 instances of key not detected warning, so perhaps early sign of weakness. At the time of my 2 year oil service last month the dealer changed the fob battery and left me a brand new battery in the cup holder to install in my other fob at home. Fob battery is Varta and was given to me in the BMW plastic bag with part number 66126912985, and says made in Indonesia.

[SonD]

Im fairly sure that BMW key fobs (in recent times) 'shut down' after a period of some 15 minutes of being laid down and not moved, in an effort to stop 'keyless' theft by cloning signal.
A year from a battery seems not bad to me given how they are used, batteries do discharge by theselves when in circuit, used or not.
I do not know what the battery draw is on a modern key fob with BMW when in use, so difficult to say with any certainty.

[jsf721]

Mine last well over a year. The one I use daily was replaced ny me at about the 2 year mark. I used an energizer battery.

[OmahaDB]

The one downside to selling my side business. I used to buy CR2032 cells, Panasonic or similar good manufacture, in bulk (usually 600 at a time) and paid under a quarter a pop. Never had to go farther than my basement for fresh batteries for most devices. I'm not willing to keep a couple hundred of them on hand now, though.

[Chasta]

Originally Posted by PetieD 7

I actually purchased two small key fob security protector pouches to prevent/block signals being transmitted while my vehicle is being parked in the garage.

I replaced the batteries in both my fobs. Then, I wrapped the spare in aluminum foil and placed it in a clearly labeled Ziploc bag in a kitchen drawer. I tested the fob by pressing on the lock unlock buttons through the foil while standing next to the vehicle and nothing happened. The foil effectively blocks the signal and you probably already have some laying around the house. No need to buy Faraday bags online.

[430Scud]

Originally Posted by Joe-BMW33

What the dealer should do and does are two different stories. My dealer should fill up a car that requires 91+ octane on delivery, but they put 87 in every car and they know it.

Anyway, go to Amazon and order a strip of CR2032's from a reputable maker. Most are made in China.

Most are made in China...even Duracell. But, there is a difference in quality, so reputable maker is good advice. My experience: Bought a strip of them from Ebay (I use them in keychain lights too) and got the same warning as my old batteries. Bought Energizer from the drug store, works perfectly. So that voltage issue mentioned above is legit, and can be a problem for the cheapie batteries. I will reserve the cheapie Ebay lithiums to my keychain lights only.

BTW, Duracell 2032s are on sale at Costco right now. 12 pack is $8.99, normally $11.99. Great deal. Long shelf life (9 years) with lithium batteries, so worth it to buy the 12 pack

[Joe-BMW33]

Originally Posted by 430Scud

Most are made in China...even Duracell. But, there is a difference in quality, so reputable maker is good advice. My experience: Bought a strip of them from Ebay (I use them in keychain lights too) and got the same warning as my old batteries. Bought Energizer from the drug store, works perfectly. So that voltage issue mentioned above is legit, and can be a problem for the cheapie batteries. I will reserve the cheapie Ebay lithiums to my keychain lights only.

BTW, Duracell 2032s are on sale at Costco right now. 12 pack is $8.99, normally $11.99. Great deal. Long shelf life (9 years) with lithium batteries, so worth it to buy the 12 pack

Thanks. Duracell is exactly what I have a strip of at home. Got it from Amazon. I have so many devices that use 2032s