MX-5

I replaced all my interior bulbs with cheapie LEDS from AliExpress and they work fine - including dimming correctly when they go off.

I'm not quite sure how to parse that particular line, or whether your interpretation is the correct one. They also quote Škoda themselves as saying "Without configuration or by installing a replacement battery from the free aftermarket, this may cause restrictions in the functionality and increased battery wear due to incorrectly functioning shut-off stages." Again, the language isn't exactly crystal clear.

That's a somewhat confusing web page - they seem to mix up what they refer to as "Open" and "Closed" systems, and the paragraph you quote is under a heading of "Self Learning Systems", which (from everything else that I have read around the topic) the Škoda system isn't. (Basically there are 3 types of systems - (1) Self Learning, (2) Coding (which Škoda uses) and (3) "chipped" batteries which report to the car that they are new). Further down the same web page, under the marque specific section, they say for Škoda: For models with a start-stop system (GreenLine), the control unit that monitors the battery must be reset using a diagnostic unit. Installing an original battery or original replacement battery and BEM coding. Without configuration or by installing a replacement battery from the free aftermarket, this may cause restrictions in the functionality and increased battery wear due to incorrectly functioning shut-off stages. Banner conclusion: Registration recommended, BEM code required, comfort features may not work immediately and unrestricted without registration.

That's a bit like saying that using the correct grade of oil in the engine, or using the correct air pressure in the tyres, is only a "nice to have"! The - robustly designed - charging system is dependent on being told (through coding) when a new[*] battery is fitted. Not doing so will potentially impact the life expectancy of the battery, and the correct operations of various sub-systems such as stop/start and emissions control. [*] to be precise, when a new battery is fitted with a different State_Of_Health to the battery being replaced, such as when an old defective battery is replace by a new, good, one.

If it's any help, when I ordered parts from skoda-parts.com, they arrived 7 days later.

You asked for evidence about how a particular system (the battery management system) worked. I provided a link to a page from a very large, reputable battery manufacturer explaining how it was implemented. I even spoon fed you with the appropriate paragraph, to save you having to read the whole page. No, I didn't drill down to the next level, for reasons that I explained. It would be impossible to live life by investigating everything from first principles. I trust the Škoda engineers who designed my car to have done the job properly, just like I trust the Shell engineers who designed the petrol that I put into it, and the food scientists at Tesco who have created the lasagne that I'm having for dinner tonight. And yet that wasn't enough for you - you criticised me for "just parroting stuff I'd read" (as if any of us have ever said anything completely original) and got on your high horse about "try to have a shred" of evidence. I'm out of this discussion now. Anybody who puts a new battery in their (battery management system-equipped) Yeti should by now fully understand the advantages of coding it. Anybody who chooses not to should at least understand some of the risks they take.

That was a management decision, not a technical or engineering one. Again, you show up your total ignorance of how things work in the real world.

What a ludicrous and patronising view of the world you have. I assume that every single aspect of your life is based on having performed (or at least exhaustively read) the primary research involved, and that you never, ever try to help or educate people without having the full panoply of supporting evidence available. You very obviously have zero knowledge of how engineering, or science, works.

The charging voltage will probably vary over time (I know that Ctek trickle chargers vary their charging voltage at different phases of charge), but really your question doesn't make sense without also considering Current and Time. The overall charging envelope (Voltage, Current, Time, End Point) will definitely vary depending on the State Of Health of the battery. Charging Voltage is only one part of the equation. Yes, but you're trying to ask a "scientific" question about an engineering issue. I've no doubt that the engineering decisions made by VAG - and all other manufacturers - will be based on sound scientific research, but I don't have the time or the inclination to try to find that original research, and nor is it my area of expertise so I probably wouldn't understand much of it. But I also haven't read up on the first-principles research about all the other parts of my cars, or my TV, or my computer, or ... and I still can understand and use them.

LOL. Would you like the moon on a stick as well? If Varta (who are one of the world's largest battery manufacturers) are not a sufficiently authoritative source for you, then I suggest that you perform the research yourself and report back to us. Not the voltage, but the capacity - expressed in Ah - of the battery, will differ depending on the SoH (State of Health) of the battery. This in turn will affect the charging rate, the point at which charging will cease and, of course, the ability of the car to draw power from the battery.

"If a battery now needs to be replaced, it needs to be reprogrammed into the vehicles energy management system. Why is this important? An aged worn out battery shows a different behaviour with regards to available capacity, energy output and charge acceptance then a new unused one. The Battery Management System (BMS) together with the Electronic Battery Sensor (EBS) monitors the battery over its lifetime. It detects e.g. the number of starts and the energy flow (Ah throughput), monitors the state of charge, controls the charging and adapts the energy management of the battery over the time dependent of its state of health." (my emphasis) From https://www.varta-partner-portal.com/en-GB/local/batteryworld-professional/coding-of-battery-energy-management-system

I'm afraid that this is incorrect. Leaving aside the cost of coding, even if the replacement battery is the same type and capacity as the original, the car still needs to be told that the old (reduced capacity, especially if at/close to end of life) battery has been replaced by a new one. Otherwise the battery management system will only charge it at the rate and to the maximum capacity of the (reduced capacity) one that it has leaned about. It will also continue to report to the car's other sub-systems based on this reduced capacity. There is significant complexity involved in battery management on modern cars - the old simplified model of "the alternator puts charge into the battery and various items then consume that charge" no longer really applies.

As long as you appreciate that this is completely irrelevant. Once again, it what the car does with those readings which matters - and if it doesn't know what battery is fitted, it can use them to do "bad" things rather than "good" ones.

As I said before, it's not a case of "belief". It's a case of simple engineering facts. There's nothing "supposed" about the J367 or J533 modules - they are referred to within Škoda's engineering documentation. Are you doubting that they exist??? Yes, of course the module can measure the current/voltage/temperature - but it's what the car does with those values which matters. And the state of the battery (capacity, level of degradation, technology, etc) will determine that course of action (which might be whether to activate the Stop/Start system, or manage the rate at which the battery is charged). Hence why the car need to be told (by coding) when a new battery is fitted. (Also, my user name is MX-5, not MX5, but I'll assume that's just a typo on your part).

The Škoda Stop/Start system monitors (I think) 31 different parameters on the vehicle when deciding whether to operate or not. State of Battery Charge is just one of those parameters, so your Stop/Start working might be related to your new battery, or it might be entirely co-incidental. But the Battery Monitoring unit will have no way of "magically" knowing that one day you have replaced your knackered old battery with a brand new one (and especially if you have replaced it with one of a different capacity or technology) - hence why you have to tell it by coding it. It would be technically possible to put some technology in the battery which would communicate with the car (in the same way that some printer cartridges are chipped so that you can only use the originals) - but then people would complain that they can only use Škoda-branded batteries in their cars, and couldn't use a third-party one. Have a look at the attached, which explains how Stop/Start works. S0020028620-Nr__86__System_START-STOP_in_ŠKODA_cars.pdf

The parameters (temperature, voltage, charging current) have to be analysed in the context of the capacity and state of degradation of the battery. It's not a matter of whether I "believe" it or not; it's a simple engineering fact.

That's not what I said. It needs to know the state of degradation (and the capacity and type) of the battery in order to contextualise those parameters.

Sadly many "old school" mechanics, who may be extremely good with mechanical systems, don't always have the knowledge, expertise or understanding of how complex modern electronic systems work. On the Yeti with Stop/Start, the Battery Monitoring Control Unit (J367) talks to the databus diagnostic interface (J533), and relays information including the current temperature, voltage and charging current. These can vary depending on the level of degradation of the battery, and coding in a new battery is a necessary step to ensure that the J367 is providing the correct information back to the J533 and onwards to other sub-systems. I would suggest that you ask your indy (1) why he thinks that Škoda (and most other manufacturers) go to the expense and complexity of fitting such systems, and (2) whether he has the capability of coding in a new battery (I suspect that the answer is "no"). You might then want to look for a new indy who actually knows what he is talking about.

Have to disagree. If you have Stop/Start on your car, you'll see the electronics for monitoring the battery attached to the -ve terminal (along with a sticker warning you that chargers have to be attached to the chassis and not directly to the battery -ver terminal, where they would bypass the monitor). Modern cars have very complex battery requirements (especially if they have Stop/Start, keyless entry, always-on infotainment, etc), and the charging requirements for EFB and AGM batteries are different to classic Lead-Acid batteries. Hence the need to code in new batteries to ensure that both the charging regime and the information provided by the monitoring sub-system are accurate.

Isn't the problem that the Intelligent Battery Sub-System will now be charging the battery at the rate appropriate to an "old" (deteriorated) battery rather than the "new " one which you have fitted, which could reduce the life of your replacement battery. Also, it may not be reporting correctly back to the Stop/Start (and other electronic sub-systems) so they may not be operating optimally. So it may appear to be fine, but actually you could be storing up problems for yourself.

I've been reading through the links that @e-Roottoot posted, and I see that one of the things the dealer said was "The inner face of the discs tends to deteriorate more than the outer face you can see". Assuming that this is true (is it?), can anybody explain to me why this might be?

That sounds like a possibility. If the siren has a back-up battery and that battery is end-of-life, then turning on the ignition might be powering it up, and giving it enough charge that it can carry on for a short while after turning the ignition off?

And it's still sitting there unsold...

If there's one thing that I would want top quality (and not "mid-range") on any of my cars, it would be brake pads and disks, closely followed by tyres!

Hi - would appreciate link to update, if one exists. Many thanks in advance.