Hi Folks, thought I'd share a very recent experience for future reference as there doesn't appear to be any similar case of it mentioned elsewhere on this forum.

 

I have full KESSY on my Octavia (ignition, door locks and mirrors) which has managed to bug me several times over the years.  However, this evening it's managed to exasperate me beyond belief trying to work out what was wrong.  I've previously had at least two occasions where the KESSY fob has suddenly, with zero notice, decided to not work.  In each case I've thankfully been parked up on my drive, rather than several thousand feet up a mountain on a dark, rainy night, as one individual I was just reading about, had been.  The fact the fob has failed so suddenly has been a bit of an annoyance each time, but I've replaced the battery and everything has been peachy, for another 12+ months anyway.

 

Having been caught with the same problem more than once, I have a reminder in the diary on my phone to therefore make sure I replace the fob battery every 12 months.  The reminder went off last month and I've been putting off doing the replacement until finally getting around to it last night.  Having bought several packs of CR2025's last year, each with a stated shelf life until 07/2026, I fished one of these out, popped the cover, made the swap and swiftly put things back together again.  I then went outside and confirmed that the car recognised the fob, opening and re-locking the doors several times.

 

However, this evening when I came to leave, the doors unlocked with KESSY the once and the fob then totally failed to do anything else at all.  From my previous experiences, I'm already familiar with the manual unlocking process with the key and syncing the fob if need be, but all to no avail.  In fact the display in the centre binnacle was even kind enough to say that no key could be found and I should refer to my manual.  After this things took a downward spiral, with the manual key in the lock successfully being able to engage and disengage the central locking, but as soon as any door was opened the alarm went off, long and loud.  After 30+ minutes of messing around trying all the resets and syncs I could think of, and with various neighbours' curtains starting to twitch, I beat a retreat back inside.  The new battery shows as having a full charge, one of the first things I checked when I noticed the red LED on the fob wasn't working, so I was starting to think there was either something wrong with the fob, or worse yet the car's KESSY had screwed up completely.

 

After searching Google for another hour or so I came across one thread on a VW group saying how not all CR2025 batteries are created equal.  Several people reported that they'd changed their batteries and had similar problems to myself.  I then dug around in our battery waste pot, where all our batteries go before going to the local recycling point, and fished out the old CR2025.  Looking at it alongside the new one there is literally no difference whatsoever.  The old one came out of one of the packs I bought last year, and the new was from its sibling which has been in the cupboard the past year.  Putting the old battery in, I noticed the red LED worked again straight away, so I went back out and low and behold everything worked as it should do.

 

Not one to let this lie without understanding why the new (fully charged) battery wouldn't work, I've tried swapping over to the new one again.  Bizarrely, the fob is good for either a single flash of the LED, if you press any of the buttons, or can unlock the driver's door just once.  After that it's as dead as a dodo, whether you're near the car or not.  I've also tried the same defective battery in the spare KESSY fob and it exhibits exactly the same traits, so the fault is clearly something to do with the battery rather than either of the fobs.

 

I've then tried fishing out the second new battery from the same blister pack the rogue one came in, and it's working perfectly when in either KESSY fob.  It seems the comments posted on the other forum's thread are correct - some batteries really aren't made equal.    Looking at them, they're identical genuine Energizer CR2025's.  Each has been removed and reinserted circa ten times, just to rule out if there is some subtle variance in the contacts when I'm inserting them, but in each case, in each fob, the results are 100% consistent. Both of the new batteries show as having a full charge when I put them in my tester, so my suspicion is that there may possibly be some slight voltage variance between them which influences the fobs.  Either way, the fact they both work / will flash the LED at least once before conking out shows the fobs do at least work, albeit very briefly with the rogue battery.

 

As I'm now completely out of CR2025's I'll be ordering some more very shortly, but for peace of mind think I'll be going with Duracell rather than Energizer in future.

 

Just wondering, has anyone else encountered a similar issue?

17 hours ago, TechyDonkey said:

Both of the new batteries show as having a full charge when I put them in my tester, so my suspicion is that there may possibly be some slight voltage variance between them which influences the fobs.

I've seen similar problems with CR2025 batteries, my theory is battery internal resistance differences (causing voltage drop under load) as they measured the same voltage down to the 1mV level on my 3 1/2 digit DMM on no load.

 

I always uses CR2032 batteries now (a bit of a tight fit) and have had no repeat problems.

Edited 2 November, 20232 yr by PetrolDave

I’ve had the same issue last week with cr2025 on my normal (non kessy) keys. Car put the “replace key battery” message on but key was still working ok. I changed it for a new cr2025 which I had that, like yours, was still within lifespan date on the packet. It locked the doors once then didn’t work, I put the old battery back in and that didn’t work even though it had been working perfectly….

Looked on here and read about fitting cr3032  instead.

I put a new cr3032 in and it worked but I couldn’t get the case to clip shut, so I bought a new Duracell cr2025 and it worked straight away no issues.

Edited 2 November, 20232 yr by classic

+1 with this issue!

 

No low battery warning prior, key didn’t want to start the car and gave me an indication saying it could not detect a key etc. Took the battery out and put it back in then I worked.

 

Ordered some decent Energiser CR2025 ones to replace what’s currently in there.

It's Energiser CR2025s, or more specifically just the one Energiser, I've had the problem with.  Bought some more batteries for 'in stock' but have gone with Duracell for now.  We now have three Skoda's across the family with KESSY, as well as on one with a regular remote fob, so I'm sure we'll get around to needing more batteries soon.

 

I have seen posts a while ago of people putting (squeezing) a CR2032 in, instead of the CR2025.  We've got lots of the larger size kicking around as just about everything from the doorbell, to the Samsung SmartTags, to some bits of PC kit I have seem to take them.  If I get the problem again I may well switch battery type just to sort things out.

 

In general for me, the key failing of the KESSY system is the lack of notice when the fob/battery is about to pack up.  Our oldest car with KESSY is now 8+ years old, but I've only ever once had a message warning of an imminent failure crop up on the car's display.  The garage actually was pre-emptive and changed the battery once without my asking, but on all other occasions the first I know about it is when the car simply refuses to open.  As I mentioned on my earlier post, thankfully this has (so far!) only ever happened when on the drive at home, but I've heard of others who've not been so lucky.  Besides setting a yearly reminder in my phone, the one only other possible indication things are close to packing up is possibly when opening the tailgate.  I've noticed on a couple of occasions now the tailgate refuses to open/unlock - I have an estate - so I have to first go to the driver's door, trigger the unlock, and the tailgate then opens fine.  The only explanation I can think of is that for the tailgate the remote is the length of an estate away from the receiver inside the car, which is possibly just a fraction too far and out of range when the battery is weakening.  The driver's door is closer and hence still works.