[kern417]

mine is not comfort access, so like I said i think the ignition switch i installed a few months ago is faulty. for some reason it's not charging when I drive around.

[Soravia]

I cut opened my NON Comfort access key using a carpet cutter knife, down and away from hand (wearing mechanic gloves), many times and got it cut opened. I pried it using flat head once one side was cut open.
I replaced using Amazon battery and cover that snaps on and off. Battery solders on and off easily. Just got to make sure they sit as low as possible.
It worked first few times but now it doesn't. I'm trying to charge it in the car right now. If that doesn't work, I'll try my tooth brush charger. The car is on Duralast trickle charger so the battery shouldn't have issue.

[kern417]

Originally Posted by Soravia

I cut opened my NON Comfort access key using a carpet cutter knife, down and away from hand (wearing mechanic gloves), many times and got it cut opened. I pried it using flat head once one side was cut open.
I replaced using Amazon battery and cover that snaps on and off. Battery solders on and off easily. Just got to make sure they sit as low as possible.
It worked first few times but now it doesn't. I'm trying to charge it in the car right now. If that doesn't work, I'll try my tooth brush charger. The car is on Duralast trickle charger so the battery shouldn't have issue.

I'm hoping this works for me. I switched to my backup key. If in 3-4 months I don't get the error, then I know the ignition switch is charging properly and it's just my 10year old key not holding a charge anymore.

[Soravia]

Originally Posted by kern417

I'm hoping this works for me. I switched to my backup key. If in 3-4 months I don't get the error, then I know the ignition switch is charging properly and it's just my 10year old key not holding a charge anymore.

One of the key works and not works. I had double checked the solders.
The other only unlocks but won't lock the car.

So it's hit or miss? LoL Both keys went into washer and dryer before the battery swap.

[kern417]

Originally Posted by Soravia

One of the key works and not works. I had double checked the solders.
The other only unlocks but won't lock the car.

So it's hit or miss? LoL Both keys went into washer and dryer before the battery swap.

Both keys work, i just get the error with my old key. Bought the car with one key, so bought a backup from the dealer at the same time. Now that my normal key appears to be dying, I switched to my backup key and no errors are showing.

I was assuming that the replacement ignition switch I installed 3 months ago wasn't charging it. So to eliminate it as a potential concern, I'm going to use the new key and see if it starts throwing the error after a few months. If so, then I know the ignition switch isn't charging it. If no error, then it's charging fine and my old battery just can't hold a charge anymore.

If someone has an idea on how long it would take for a non comfort access key to completely drain it's battery without charging, that would help too. otherwise I can only go off of my experience.

[Soravia]

Is it possible to switch to comfort access forb? I'd rather swap battery every two years

[kern417]

Originally Posted by Soravia

Is it possible to switch to comfort access forb? I'd rather swap battery every two years

Honestly not sure, but I assumed it would also be more expensive. But I agree that's much easier.

[liquidsmoke]

So can I use any inductive charging pad for iPhone etc; and it will charge my e92 fob ok?

[BlackNight28]

I did like Soravia did but instead of soldering a replacement battery in I left the leads for the old battery in-place and removed the flat top and bottom tabs from the old battery (took a bit of prying). Remember which tab went to the top or +. Bought LIR2032 recharable batteries from Amazon and along with a new case, laid the new battery (bottom) - in the new case and placed the + tab on the top and snapped the case together. Thought I'd screwed up but accidently pressed the lock button and heard the locks engage in the garage. So far, it charges and does what a good fob should. Did I get lucky? Probably. But it works and I'm happy.

[liquidsmoke]

I did get a wireless charger to try to resurrect my fob that’s not working for remote locking; but i don’t think it’s gonna work, cos it seems like the charger pad doesn’t stay online when I only have the key fob placed on it…ie when I put my phone on it, it stays online with led indicator to show its charging it up, but if there’s only the key on it, it doesn’t stay online…
This is the one I’m trying:
yootech Wireless Charger,10W Max Fast Wireless Phone Charging Pad Compatible with iPhone 14/14 Plus/14 Pro/14 Pro Max/13 Pro Max/13/13 Mini/SE 2022,Samsung Galaxy S22/S21,AirPods Pro(No AC Adapter) https://amzn.eu/d/9qY9hqx

Does anyone know if there’s a different charger that will stay online even if there’s only a key placed on it?

[BlackNight28]

I tried a couple of the batteries with solder-in connectors for the existing fob. The idea is sound but the replacement batteries were crap and didn't work well. Looked like the connectors were resistance welded to the batteries (can't help wonder that did to the battery itself). Those replacement batteries were 3.4v and had no charge present in the battery either. The battery I used was a 3.6v and probably had a bit of a charge present. It still works too with no low battery showing during starting or shut-down. Just sayin'.

[liquidsmoke]

Originally Posted by BlackNight28

I tried a couple of the batteries with solder-in connectors for the existing fob. The idea is sound but the replacement batteries were crap and didn't work well. Looked like the connectors were resistance welded to the batteries (can't help wonder that did to the battery itself). Those replacement batteries were 3.4v and had no charge present in the battery either. The battery I used was a 3.6v and probably had a bit of a charge present. It still works too with no low battery showing during starting or shut-down. Just sayin'.

What do you mean when you day "low battery showing during starting or shut-down"; is there supposed to be some warning in the car for the fob battery health?

[BlackNight28]

Originally Posted by liquidsmoke

What do you mean when you day "low battery showing during starting or shut-down"; is there supposed to be some warning in the car for the fob battery health?

If the battery needs charging this symb shows. see previous posts as some show this in pic.

[dr.ashoka]

Originally Posted by Soravia

Is it possible to switch to comfort access forb? I'd rather swap battery every two years

Yes, it is possible to switch to comfort access key fob. I got a comfort access key fob on eBay with the same frequency as my original key fob, got it programmed and voila my new comfort access key fob works perfectly. Now I have to just change the battery when it runs out.

[M-technik-3]

My Samsung inductive pad does not illuminate to say it's charging. How would i know if the battery in e90 with comfort access is working to charge it?

[tinkerman]

I dug around in ISTA and found the frequency (125kHz) along with the fact that pins(1&2) of the 14pin cable are associated with the coil(s) (not sure if there's one each for charging and data transfer, or if it's just one coil used for both charging and data transfer simultaneously) in the socket, but not yet any info on the voltage applied. Hopefully someone can use this info to test with a multimeter to find out the voltage(for charging) and share their findings.

ISTA Notes:
[Remote key]
"A 125 kHz interface within the ignition lock executes the recharging. The rechargeable battery voltage is monitored independently by the remote key and is transmitted to the central gateway module via the data bus K-CAN PERIPHERY."


[CAS control unit: E60, E61, E63, E64, E70, E81, E87, E90, E91, E92, E93]
"The slot is connected to the CAS control unit via a 14-pin connection."

A = Output
E = Input
M = Earth
V = Supply
* = Connected to slot and START/STOP button
** = Only connected to slot
("aerial" = coil)

Pin Type Description
1 A Transponder aerial 2**
2 A Transponder aerial 1**
3 A LED* earth connection
4 A START/STOP button illumination*
5 A Power supply for Hall sensors 1 and 2*
6 E Hall 1 input (START/STOP button)*
7 E Hall 2 input (remote control unlocked)*
8 E Hall 3 input (START/STOP button)*
9 E Hall 4 input (remote control locked)*
10 A Power supply for Hall sensors 3 and 4*
11 A Terminal 31 (earth connection for Hall sensors 3 and 4*)
12 A Terminal 31 (earth connection for Hall sensors 1 and 2*)
13 A Negative-side (driver) for bistable magnet**
14 A Positive-side (driver) for bistable magnet**


[Electronic immobiliser]
"Remote key with integrated transponder chip
A transponder chip is integrated in each remote key, which can both transmit and receive. Data transfer takes place like in a transformer between the ring aerial in the insertion slot or ignition lock (only E83) and the transponder chip. The remote key transmits data to the EWS or CAS control unit and receives data from this.

The authorisation of the remote key for the respective vehicle is also encoded in the transponder chip.

The EWS or CAS control unit can manage max. 10 remote keys matching the control unit, i.e. max. 6 remote keys can be obtained as replacements. The EWS or CAS control unit can identify the individual remote keys. It is thus possible to block or enable individual remote keys. If faults occur during communication between the electronic immobiliser or CAS control unit and the individual remote keys, these are stored in the fault memory separately for each individual remote key.

Ring aerial
There is a ring aerial (coil) for querying the transponder chip in the insertion slot for the remote key, or around the ignition lock (only E83). The transponder chip and EWS or CAS control unit communicate via the ring aerial."

[tinkerman]

I found a nice TI(Texas Instruments) article from 2011 which demystifies how wireless charging transmitter & receivers work, and attached below.

So before purchasing any type of watch chargers or electric toothbrushes, I attached some wire leads to the VL2020 battery soldered on the fob PCB, and took the fob with a multimeter and a USB powerbank to the local electronics shop to test various chargers and got some interesting results.

1. None of the chargers resulted in the charging voltage at the battery's leads to "jump" to say 3.4V +/- 0.15V as I'd expected, instead the multimeter showed a very slow increase in voltage from 2.987V up to 2.991 over several minutes of charging with 3 types of chargers (generic Samsung Galaxy Watch charger, Oral-B/Braun electric toothbrush charger, Apple Watch display stand/charger).

2. The multimeter's numeric voltage seemed to not change at short term glances, but the graphic display of voltage showed a steady ripple suggesting that the transponder's voltage regulation either pulses very small voltage changes for the charging, or the ripple is just a result of the rectification at the transponder's side.

Therefore, unlike how a car battery is charged(say at 14.6V for a 12V battery), the fob battery seems to be charged at relatively very small voltage difference from the present voltage of the VL2020 battery increasing gradually in mV increments. As the receiver(in this case the fob/transponder) controls the charging not the transmitter(fob socket/other chargers), it seems that the fob would behave similarly in the car's socket, unless the transponder chip includes BMW's proprietary programming with various communication messages for charging like the Qi chargers.

Of course, despite my observations above, if anyone has more insightful info, I'd be grateful to be enlightened.
Attached Images
File Type: pdf Wireless Charging one-way communication via loading modulation-backscatter (slyt401).pdf (114.8 KB, 0 views)

[Captain Buumer]

So there is Panasonic VL2020 battery inside keyfob.

Panasonic recommends to charge with:
Constant charging voltage 3.4V with 1.5mA which is very small current and takes about 20 hours to fully charge by our car induction charger (this was written somewhere in the manual).

I suppose you could attach multimeter in series (milliAmper mode) with keyfob VL2020 battery to confirm if it is charging with some wireless one.

But any basic wireless charger should work because they generate magnetic field that is then accepted by keyfob tiny coil which has circuitry inside to accept 3.4V and slowly charge.

I would trust the Panasonic provided information because the keyfob circuitry is built around the battery that is 3V rated and the car keyfob insertion area is just providing magnetic field.

I have spare key that i don't use and could try this experiment at some point.

[tinkerman]

Originally Posted by Captain Buumer

...
But any basic wireless charger should work because they generate magnetic field that is then accepted by keyfob tiny coil which has circuitry inside to accept 3.4V and slowly charge.

I would trust the Panasonic provided information because the keyfob circuitry is built around the battery that is 3V rated and the car keyfob insertion area is just providing magnetic field.

I have spare key that i don't use and could try this experiment at some point.

Despite online comments elsewhere that common Qi phone chargers don't work with the fob, I tried myself with my Qi type phone charger, and indeed the LED that indicates the Qi charger is powered ON, stays OFF or in standby mode(i.e. placing the fob/transponder on the Qi charger, even without the casing for closer contact does not trigger the Qi charger ON). My understanding is that in this standby mode(charger is not in charging mode), the Qi charger only checks for a compatible receiver by transmitting a particular type of pulse at certain intervals, which a Qi compatible receiver would recognize and respond to by sending back to the transmitter a certain signal representing the receiver's presence / coil alignment etc.. Since the fob/transponder is not a Qi device, the Qi charger doesn't respond to the fob's presence at all, and just stays in the standby mode only sending out brief pulse(s) to check for a compatible(Qi compliant) device within the charger's range.

I suspect that the fob/transponders and watch & toothbrush chargers don't have this relatively complex and strict communication protocol between the charger & device as with Qi specification devices, and this allows some charging(albeit inefficiently) of the fob.

I too noted Panasonic's datasheet for the VL2020 battery and expected the transponder to regulate charging at around 3.4V, but my simple multimeter test proved otherwise. Perhaps a multimeter is inappropriate for checking this charging voltage, and an oscilloscope is necessary to clearly understand what is actually going on?

'Look forward to those with more experience chiming in on this matter for clarification. Cheers~

[codeterrorist]

This whole complexity is intentional. And it becomes worse when you don't have a replaceable battery keyfob.

My E90 sits in the garage for winter, and our winter stretches for about 7-8 months. The other day I wanted something from the car and it gave me the low battery icon for the key. And I don't have comfort access.

There should be a class action against BMW for doing such a horrible thing. At least make the comfort access keys and non-comfort access keys the same with replaceable battery.