PetrolDave

But it does, the more current the external voltage tries to draw the lower the battery voltage will be due to the battery internal resistance. Simple (very exaggerated) example: battry no-load voltage=12V, battery internal resistance=1 ohm, load resistance=2 ohms. Total resistance=3 ohms therefore current=4A (NOT the 6A which would be expected from 12V and 2ohms load) AND the battery terminal voltage won't be 12V it will be 8V due to the voltage drop of the internal resistance.

Halfords guy was speaking out of ignorance, your car can easily handle a 75Ah battery. I fitted a 75Ah 096 AGM battery to my previous 1.4 Octavia with no problems, and have done even larger battery changes on a previous Citroen C1 (almost double the Ah battery from a petrol spec to a cold climate diesel spec).

Since headlamps are only on the front of a vehicle that cannot be true???

Correct it, so the BMS knows what new battery the muppets at Halfrauds have fitted.

That means the radio isn't seeing the CAN bus message that the ignition is on, so that's where the problem lies.

Given that OP is in Denmark, I reckon that's a good assumption.

The fusebox is hidden behind the glovebox.

The higher profile will increase the diameter of the wheel. Since the speedo actually counts wheel revolutions your speedo will under-read as you'll be travelling further for each wheel revolution. According to this tyre size calculator the speedo reading will be 6.8% lower, the recommended change is no more than 2%.

You have to ask the dealer or go online to e.g. erWin.

As proved by the great work done by member DV52 on the Ross-Tech forum, he produced a chart showing the (often very large) differences between different MQB platform models - and even between cars of the same model with different equipment.

VAG stopped fitting car stickers a few years ago.

Both are MQB platform, but that doesn't mean they're the same! As requested post an Auto-Scan and an adaptation map from 09 and what you changed - without that we are just guessing...

That's normal behaviour, the Battery Management System tries to charge to battery to 80% SOC so when it reaches that the voltage will drop - until you get onto the brakes when it will go into micro-regenerative braking mode and increase the battery voltage. In normal driving I see the battery voltage go to 14.x after starting then drop to around 12.x for most of the time when driving, but increase again to top up the battery and when braking.

What do you see when you scan module #19? Anything showing under the Battery Monitoring Control Module J367 that is a subset of #19?

Does any reason for start-stop not working show up on the infotainment screen? There's an option to see the reason, I think it's under CAR?

The first mobile I designed was an analogue TACS phone, which predates any of the digital GSM/CDMA ones.

Blah blah waffle - typical dealer nonsense!

They're right that 2015 was a transition year, early 2015 builds had a MIB1 which cannot have Smart Link, later builds (like your it appears) have a MIB2 which can have Smart Link enabled. The key fact that Marshalls seems to have missed is that you have a MIB2, which means there is no doubt about being able to enable Smart Link and all they have to fdo is order the VIN specific key for your car.

Which surely makes the ULEZ zone and expansion fairly pointless as it won't be tackling the biggest source of pollution from vehicles?

This has been known and posted on here since at least 2016 when I purchased my first Octavia - it didn't have memory seats so I had the same lack of success when I tried to setup mirror dip on reverse. My current L&K Octavia has a memory drivers seat so mirror dip on reverse works perfectly. IIRC @SashaGrace discussed this issue at length as one her many retrofits.

I wouldn't agree that loose covers/trim isn't the problem, because what you describe sounds like a loose piece of trim or cover to me - that's fairly tight so it only vibrates when the vehicle speed is high enough for the airflow to make it vibrate.

I would suggest that 20-30 minutes would be a time many (most?) people would find acceptable.

Is a 2015 A5 Haldex or Torsen? A4/A5 quattros were originally Torsen but changed to Haldex to reduce emissions, but I can't remember what model year the change was made.

That's not true of all new cars, the Toyota I ordered new in 2020 came with a space saver spare and I quickly discovered that there WAS room for a full size spare which I duly purchased.