In all the years I’ve been road testing cars, I have come to admit that proximity keys are kind of nice. There’s something easy about never having to fish around in your pocket for a key that’s somehow buried itself beneath your wallet and garage door opener, and when you spend time with multiple different key fobs, proximity entry means no hitting the wrong button in the dark. However, beyond potential security issues with some setups, most proximity key fob applications do come with one big downside.
Replacing a key fob battery is a bit of a pain. Not only do dead button batteries mean you have to mess about with a tiny key blade, cracking open a key fob feels like surgery. One wrong move, and suddenly you’ve broken the aged, brittle clips that hold the two halves of the key fob shell together. Also, certain styles of key fob use battery holders that are easily sheared off the board if you have appendages made of ham. Plus, a good button battery is a couple of bucks these days, and that’s just an unexpected nickel-and-dime expense every couple of years.
You’d think by now that we’d have solved the issue of key fob batteries running low. It turns out, BMW did ages ago, but the advent of proximity keys basically killed that feature off. However, hope might not be lost. The digital, connected era means you might already have a rechargeable key fob for your car without even knowing it.
Starting in the 1990s, BMW rolled out a diamond-shaped key with a serious party trick: inductive charging. Yep, the same technology you use to recharge your smart watch. Simply slot the key into the ignition, turn the car on, and inductive charging would juice up the key fob battery on a long enough run, meaning that theoretically, you’d never have to replace a key battery again, so long as you followed the instructions, rotated out both key fobs, and went on periodic longer drives.
When the 2000s rolled around and RFID immobilizer-based contact push-to-start technology rendered physical key blades unnecessary, BMW kept the inductive charging on its base line of fobs. Basically, you’d slide the plastic key fob into a slot in the dashboard, then push a start button to fire up the car. Once in the slot, inductive charging would give the key fob a helping hand so it can theoretically stay charged up.
By the mid-2000s, however, proximity keys were making their way into the mainstream, featuring rolling radio codes and touch pads on door handles that meant you’d never have to remove the fob from your pocket. Obviously, people weren’t sliding these keys into the dashboard, so BMW went with a replaceable button battery once again. That’s a couple bucks every few years, and some hassle to install a new cell.
Of course, going back to button batteries solved an often user-induced issue with rechargeable keys. BMW’s inductive charging keys were sealed, meaning that if the batteries were allowed to run flat, the only way to fix it involved slicing open the fob and desoldering the battery inside to replace it. While some early fobs used according to BMW’s instructions are still functioning nearly 30 years later, some aren’t.
Still, even when proximity keys started to dominate, BMW didn’t give up on rechargeable keys entirely. Remember that hilariously hefty Display Key from the 2010s with its own built-in touchscreen? Yep, in addition to USB charging, it could also charge inductively when set in the car’s wireless phone charger. Probably best that it stayed out of your pocket while driving, considering this monster fob’s about the size of a hamster. That could get uncomfortable on long road trips.
Flash forward to the present day, and the latest sensation is phone-as-key technology, now offered by a huge range of manufacturers from Tesla to Hyundai. Using either Bluetooth Low Energy or Near Field Communication, owners of some modern cars can lock, unlock, and start their vehicles using their phones. Think of it a bit like Apple Wallet or Google Wallet, but for your car. Plus, since your smartphone doesn’t run on button batteries, it means you might already have a rechargeable key fob for your modern car. In some ways, what’s old is new again, although it is quite neat that BMW pretty much solved this common aggravation nearly 30 years ago.
Top graphic images: Thomas Hundal; BMW
Physical keys never run out of battery.
As the owner of a 2024 Chevrolet Trax LS with an actual keyed ignition switch and someone who doesn’t own a smart-phone… (wipes forehead)… Whew!
We also have a 2003 GMC Envoy SLT with key-fobs that still lock and unlock the doors. (no remote start) We bought it used in 2012 and have never replaced the key fob batteries.
Old-school has its advantages sometimes. 🙂
As the owner of a BMW equipped with a display key, it’s not the size of a hamster. It’s the size of a small dog, like a chihuahua.
The Gen 2 Prius key fob would still work after the battery died to start the engine as there was a place to plug it into the dash, bypassing the wireless stuff.
I think every car with a “keyless” system has somewhere to start the car if the fob battery is dead. In my current car it’s in the cupholder, my previous one you’d hold it to the steering column where a normal ignition switch would be.
You could also make key fobs rechargeable with usb C or wirelessly. Or make a dock for it in the car like ferrari does but make it charge
Take note: only use your phone as a key if it’s actually using the phone’s built in key system, like apple carkey. One that just use their app and bluetooth are generally unreliable as shit
Jokes on you. BMWs of the e9x/e8x key era pictured that have the inductive charging system do NOT also have Comfort Access, which was BMW’s proximity key system. And later ones 2 and 3 series keys don’t have it either, just replaceable batteries. I guess the top of the line nonsense still did.
The Comfort Access keys use an easily replaceable coin cell. I have one of each, my 328! wagon has Comfort Access, my 128i convertible does not. I have replaced the battery in the 328!’s keys once each in 14+ years from new. The 128i’s keys still hold a charge, but it’s only a matter of time before the stupid things need to be either surgically cracked open and the soldering iron gotten out, or fairly expensively replaced. The battery in them is NOT meant to be user replaceable, as you note. One of the few occasions where I agree with the “German overengineering” complaint.
Another neat feature of BMW keys (I am sure lots of other premium cars have this too) key memory. The driver’s settings are stored in the key, so each driver can have the car automatically adjust various things to the key. And it stores a good bit of service history that the dealer can read too.
I LOVE having Comfort Access, and cheerfully ponied up the $500 that BMW charged for that option in 2011.
Absolutely disagree with the keys having a memory feature, especially as the keys are proximity keys. Hear me out- the keys are normally in some type of bag coming along with you (purse, etc) and there’s no reason to take them out. If you and your driving partner decide to switch drivers (not uncommon for my wife and I), you’re stuck with their settings. There’s already multiple memory settings for the seats and multiple driver profiles. The keys just make things confusing.
-2023 X5 45e owner, hates key memory
You are welcome to disagree. It works great for me. They probably made it worse in the later cars, like pretty much everything. Works a treat in my 2011s. For the one with CA, you don’t have to put the key in the slot, whichever key unlocks the car is the settings set that is used, so obviously it can tell which key is being used. Wasn’t a problem when my mother and I were travelling around Europe together in my ’16 M235i. She always had the 2nd key in her bag.
No thanks. My fob batteries last at least 4 or 5 years in my experience and I’ll take replacing a 2032 battery every 4 years over having to get my key out of my pocket every single time I drive the car.
Now, if they were to stick a USB C port on my fob I wouldn’t be mad, although it sounds like the rechargeable BMW fobs are a bit of a nightmare when the battery inevitably dies. I hope at some point right to repair laws mean no more devices with batteries permanently soldered in, but I’m not going to hold my breath.
They absolutely are a PITA when they inevitably croak, and it’s stupid. It takes 30 seconds to replace the 2032 battery in the otherwise identical Comfort Access key. They could have at least made the rechargeable battery easy to replace too, given they already made an all but identical key that has a hatch in it!
“Permanently soldered” is an oxymoron. It might not be easy to get to them, but I’d wager there’s a way they can be repaired, just like solar watches, toothbrushes, etc.
The only thing I really like about having proximity keys on my Volt is the ability to lock/unlock by pushing the button on the door handle. Otherwise, regular fobs, or even just manual locks have never bothered me. I have to replace the batteries CONSTANTLY on my Volt key
Replacing button batteries in fobs is not that big of a deal at all. Full disclosure: I replace them several times a day at work, so maybe it’s just practice?
Someone literally came in to have 2 replaced as I hit enter on that lol
Yeah, I’m not a fan of keyless entry. There’s a time and place for it (everyday life,) but when you’re venturing somewhere remote, you’d better hope it doesn’t go flat on you – Like when your rental Land Cruiser’s keyless fob starts goes flat half way along the Gibb River Road.
My BMW still has a metal blade key and locks too. The right way to do it. And it starting the car has nothing to do with the proximity stuff, it still has the slot in the dash, you can stick the key in and start it even with the battery removed.
I assume all cars have a way to read the key with a dead battery, although JLR would be the ones to fuck that up
So take a backup.
A couple of bucks a year? I wish! Both of the fobs for my wife’s 2015 VW Sportwagen TDI eat a battery every few days! And it is not because they are nearby and in constant communication with the vehicle, because the batteries in the two fobs to my 2015 VW Sportwagen TDI do not experience this issue, and they are identically situated. Neither VW service nor a specialty keyfob business can figure out the problem. We have bought hundreds of the damn batteries by now, and they all start out holding a proper charge. By the end of the week, the dashboard messages (“Key not in range”) start, and the little LED stops flashing when pressed. Time for a(nother) new battery. Grrr…
Based on the comments, the BMW keys fixed some problems but caused others.
I change the battery in my proximity key roughly every 2 years. Haven’t had any issue with it, and changing a battery every 2 years is miles easier than messing with a key fob or key every day.
The rechargeable keyfob battery in BMW keyfobs deserves it’s own dedicated hell which I’m confident is awaiting.
Only someone who has not had to deal with one can say anything positive about them with a straight face.
Also, only the cars without Comfort Access have them. The ones that require the fob to go in the slot. The Comfort Access ones are regular replaceable ones.
The batteries eventually fail. For a very long time, they were not sold separately- just with a new fob around them. Given that they are soldered on the circuit.
They are BMW-specific. They are a variation of a commercially available battery (VL2020), but have the solder legs at 90 degrees rather than at 180.
To this day, they are gray imports. No serious distributor has them. Even Mouser only has standard VL2020s, not the BMW keyfob ones.
The first batches of batteries that appeared on Chinese sites with the correct pins/legs orientation seemed to be old stocks, as they overwhelmingly didn’t hold charge and came precharged at 2.5v rather than 3v. An E60/E61 keyfob will not emit any signals below 2.95v.
Fresher batches seem to be available now, at prices above $15.
So once the remote in your keyfob dies (the ignition is a separate circuit that is not battery dependent, so the car will still start) you have to check if you have a signal going out at all. Which would be easy as remotes have LEDs that blink when they emit a signal, right ? Yeah, about that… nope.
Then, you’ll have to try and charge it. Because it could be the coil in your keyfob slot that is dead, not the battery. So you’ll try every electric toothbrush charger known to man.
Then you’ll crack open the keyfob to measure the voltage at the solder pins. Then order the battery. After a few orders, you’ll buy a keyfob signal tester for 20 bucks, because sanity matters, then will test the keyfob with 3v constant fed at the pins. Then order more batteries. Find one that works.
Desolder old one. Solder new one. Test. Hear that confirmation beep at the tester. Wipe tears of pride and joy.
Test keyfob. Realize that the diversity antenna has croaked as well. Replace. Realize the wire loom at the trunk lid is cut as well. Fix.
Enjoy your working keyfob. Then rinse repeat with the second keyfob that was a spare and never used, so – left to discharge and dies.
While reading the article I kept wondering what the process would be like when the battery eventually fails, and now I know. It doesn’t look good.
I for one appreciate Toyota using an old school watch battery in my key fob.
Everybody uses standard 3V flat batteries. Even BMW in their other keyfobs, outside of this monstrosity.
It’s an awful thing when any sane troubleshooting attempt will be blocked from the beginning.
Knowing what I know after what I went through-a keyfob signal tester is mandatory to remain sane with these.
Buuut…
Have I mentioned…
All testers are Chinese, but are not made equal 🙂
The ones with the huge LCD display only catch US BMW signals randomly or not at all. They catch everything else as stated in the manual.
The older looking ones with just LED indicators catch everything. Ask me how I know 🙂
Single use batteries are under rated when it comes to low-drain devices. I kept a Logitech MX1100 mouse working for more than 15 years because it took AA cells.
Aw, man! That process sucks. I’m sorry you had to go through all that.
I just had to change the battery in my Kia Telluride fob. I took the “emergency” key blade out of the fob and used it to pry open the case—which the case was designed to accommodate. A CR2026 button battery was right there, in a little holder, not soldered to the board. I happened to have the right battery on hand (my wife’s Prius uses them, too) so I popped the old one out, slid the new one in, and closed the fob. Snap-click! And I’m done. The whole process took less than 5 minutes—including watching the YouTube video that told me how to do it.
100% agree. Non-Comfort Access fobs are ridiculous. When my fob battery died, I assumed an easy replacement because that would make sense for drivers who buy less car tech on purpose. Plus “German comfort” is a contradiction. This proves my YouTube-informed decision about limited skills/tools/patience. With my MacGyver tech relative too far away, I sucked it up with choice words and simply bought another. Lesson learned needing to ask something so ridiculous when purchasing the ultimate driving machine. Such an inane design.
I rotate my non CA keys for my 1-series precisely to extend the life of them. Both still fine at 15 years old and they will still hold a charge for months, but it’s only a matter of time. You can noticeably tell that the battery gets low when you don’t drive much for a while because the range for unlocking gets shorter and shorter. After a good long drive it will work across a parking lot.
Stupid, pointless, bullshit gimmick for no reason other than they could. One of the few BMW features I really hate. Thankfully only one of my pair lacks Comfort Access, so I only have two of these stupid things not four.
Anyone remember the keys that had the built in lights? They pre-dated keyfobs altogether. I had a couple of 30’s that had them. You press the button on the key and it lights up so you can see the keyhole.
Yup. Somehow, my E30 still came with the 2 original keys, one still working.
https://www.ebay.com/p/1626635169
Had one, never used it.
Bonus points for a easy to locate lock cyl.
The big problem with replacement batteries (pretty much all of them) is they never last as long as the original ones. I mean I have had button batteries last for years, and when they finally die I replace them and the replacement lasts for months at best.
Could be more an issue of the fob having a short/using more power then which is what really caused the battery to die originally. I’m still using the original battery in my 2006 (non-proximity) fob…
I have 2 of the keys mentioned (a 2005 and a 2001 BMW) and they both work fine. I was really talking about the newer fobs that have replaceable batteries.
This really never should have gone away.
The first time I drove a car with a proximity key, it took me about 10 minutes to figure out how to start the damn thing.
My ’98 BMW has the inductive charging key, and it still works! It’s probably the only original part that still does!
“The first time I drove a car with a proximity key, it took me about 10 minutes to figure out how to start the damn thing.”
And how did that make you feel Bob?
This is so good.
The Mini Coopers (also BMW) had the same system in those keys, but it was near impossible to open them to do battery surgery.
BMW has always been pretty innovative with keys. I love how many options we have to use our 330e. It has 2 traditional fobs, but we can also use our phones as keys, or it also came with a proximity wallet card that doesn’t ever need a battery. I usually use the standard key fob, but its so nice to just use my phone and not have to run back into the house for keys if I’m outside and decide to run an errand or something. It’s a feature I use at least a couple times a week. The only downside is that I have to remember to lock the doors by tapping my phone on the door handle when I get out of the car… where the fob will automatically lock them when I walk away.
I lost my Mercedes’ “keyless go” fob…unfortunately they had a really bad era of the batteries failing in a matter of weeks not months. So apparently their answer was just to discontinue the supply of keyless go fobs for older applications. Thanks…
FWIW a batteryless key fob still works to turn the car on. In Mercs it uses induction energy (same as the recharge of the key above) to excite an IR transmitter and RFID in the fob itself. So even if your fob battery is dead, you still use the key as normal to start the car. Of course like most cars there is also a physical key for the door locks.
BMW discontinued their older key/fobs (shown above on the pic with 32 on it, used in early 2000s cars) this year. Now if you lose your key you can only get a manual one to replace it. Side note, all keys are made in Germany and you have to have one shipped. They can only program 10 total keys for your car before you have to replace the EWS system so a new batch of 10 can be made for the car. You get 4 keys with the car, so that means you’re capped at 6 more keys before the car is essentially bricked – for the vast majority of cars still left with this systems a EWS replacement is more than the car is worth.
I have 2 BMWs that use that key.
Those keys were on an intergalactic backorder for about a year, but they are back. They’re quite a bit more expensive now, but we can get them. I work at a large BMW parts department. For a while there, there was no ETA or any info whatsoever so there’s a chance the people you talked to thought they were permanently discontinued.
I knew about the backorder, but heard (on BMW forums) that the replacement they eventually got was the manual key and the fob key was NLA. How much more are we talking, because they were already expensive, if they went up significantly they are probably worth more than many of the cars they operate.
What kind of BMW do you have if you don’t mind me asking? There’s a few different part numbers depending on the chassis for a nearly identical key, but the majority (E46, E85, E83, E53 etc.) are a part number that ends in 748. We’ve just recently been able to fulfill those backorders that were placed over a year ago.
Each dealer has slightly different pricing, I think pre-backorder they were around the $320ish range and now they’re up to mid to high $400s. Customers think we raised the price on our own, but BMW themselves rose prices across the board. Some of the newer cars are up to over $800 for a key.
I have an e46 and an e83.
Every proximity key car I’ve had from several manufacturers has had an “emergency space” to set the key so you could drive with a dead fob battery.
And I noticed on my annual service from Mercedes-Benz that one of the included items is “change key fob battery”. Now I need to remember to bring both key fobs next time!
Annual!? LOL my w212 key fob battery lasts like 6 weeks, common problem unfortunately. Luckily harbor freight sells the button batteries super cheap. Pretty wasteful though.
Are the keys kept close to the car? If so, I wonder if they might keep communicating.
It’s probably those HF batteries you’re using. I use Energizer lithium ion batteries and they last at least a year.
Geez, even the cheap coin cells I buy last a couple of years inside my key fobs (for the non-MB cars). Like Cerberus asks, are they close to the car? 6 weeks is not right.
Yeah, the first time I saw that on the invoice I was upset because I had just replaced it a week earlier. If I had known, I would have dug out the other key fob.
I don’t mind the battery replacement on the proximity keys, but I do mind it when super soft plastic is used in the notch designed for separating the fob. I hate prying them open only to have the plastic all deformed on the exterior edge of the fob.
We’d purchased a new car a few years back, I didn’t have a choice on key style as they’re all proximity keys these days (despite the fact that I’m not a fan of them) – with the number of times that the keys have been forgotten in the car when we first got it: I’m surprised ‘easy’ car thefts aren’t far more common.
I think the 2nd Gen Prius also had you insert the fob into the dash, it was kind of nice.
Some of the early Nissan/Infiniti pushbutton start systems had a dash spot too, if just as a spot to turn it on when the fob battery was dead.
My favorite feature that I never use due to proximity keys is the all windows up/down by holding the lock/unlock buttons. My car will roll them all up and close the sunroof if you lock the car by touching the door handle and continue touching it till they’re all closed, but I can’t make them all roll down without finding my fob.
My wife uses the roll down feature in the summer regularly and loves it. She just uses my proximity key which is always stored in its little cubby in the house instead of fishing her key out of her purse. It turns out having me around is good for something.