It was an over the air update from about 2 weeks ago.

They have not done any updates this week whilst they had the car 

Does phev use HV battery or 12v battery to start the petrol engine? Im quite sure it doesnt have regular starter motor.

The ICE is started by the electric motor (that can be used as a motor, generator or starter), so it uses the HV battery.

7 hours ago, SkOmk4 said:

The ICE is started by the electric motor (that can be used as a motor, generator or starter), so it uses the HV battery.

So is the 12V just for the systems in the cabin? Can it be supplemented/charged by the HV battery?

1 hour ago, mccririck said:

So is the 12V just for the systems in the cabin? Can it be supplemented/charged by the HV battery?

There is no 12V alternator so logically electric motor or plug charges HV battery -> HV battery charges 12V battery. Pls someone correct if im wrong.

3 hours ago, mccririck said:

So is the 12V just for the systems in the cabin?

No, not only for the systems in the cabin; there are plenty of relays and low-voltage components powered by the 12V battery. 
 

3 hours ago, mccririck said:

Can it be supplemented/charged by the HV battery?

Unfortunately there's no scenario which allows the HV battery to directly charge the 12 V battery. 
AFAIK the 12 V battery on our cars can be charged while:
- driving in EV-mode;
- driving on ICE;
- charging the HV battery.
I remember seeing such a diagram on some technical documentation posted on this Forum if I remember correctly.

The normal Car Battery is there needed for the door locks, lights, the ECU,s controlling everything. 

20 hours ago, SkOmk4 said:

Unfortunately there's no scenario which allows the HV battery to directly charge the 12 V battery. 

I'm not sure that's exactly the case. When car is parked but ignition is on, all 12V consumers are drawing power from HV somehow. I mean, switch on music, fans, etc and you see consumption in the range of 0.5-0.9kWh/h on the VC. Does it bypass 12V battery or does it go through the battery, I don't know. But myself I often sit in the car for long time and as long as ignition is on, it drains HV battery and 12V stays charged.

Yep, with ignition on, I don't know how the 12V systems take/drane power from the HV battery - if it goes through the 12V battery or not. 
My previous statement was related to the "car parked and turned off" (e.g. overnight) - when most of the reported 12V battery drain occurred.

3 hours ago, SkOmk4 said:

Yep, with ignition on, I don't know how the 12V systems take/drane power from the HV battery - if it goes through the 12V battery or not. 

The car includes a HV to 12V down converter so, in theory, the 12V battery is charged whenever the HV battery is being charged. I say in theory as there have been several owners complaining of the 12V battery going flat, but it appears that a software update to this system supposedly fixes the problem.

14 hours ago, PetrolDave said:

so, in theory, the 12V battery is charged whenever the HV battery is being charged

Yep, I mentioned that in the enumeration a few posts above...

Battery flat again

2 hours ago, mccririck said:

Battery flat again

Had flat battery Tuesday. Today it gave yellow warning. Low battery. No clue what’s happening as well

4 hours ago, SkodAlex4RS said:

Had flat battery Tuesday. Today it gave yellow warning. Low battery. No clue what’s happening as well

Mine goes in for a service tomorrow. I'm sure they'll just charge the battery up and say it's ok...

2 minutes ago, mccririck said:

Mine goes in for a service tomorrow. I'm sure they'll just charge the battery up and say it's ok...

Could be the alternator? 

45 minutes ago, SkodAlex4RS said:

Could be the alternator? 

They don't have an alternator.

1 hour ago, SkodAlex4RS said:

Could be the alternator? 

I stand correct. It would be the DC-DC converter. 

Edited 7 February, 20251 yr by SkodAlex4RS

18 minutes ago, SkodAlex4RS said:

I stand correct. It would be the DC-DC converter. 

I think it's more likely the control software for the charging circuitry is poorly designed.

Having had the car in at the garage last week to be told the 12v battery issue was fixed by an over the air update, they were wrong.

 

even though I have had the car 14 months I am back to telling  Skoda I am rejecting the car.

 

2 hours ago, wantaskoda said:

Having had the car in at the garage last week to be told the 12v battery issue was fixed by an over the air update, they were wrong.

 

even though I have had the car 14 months I am back to telling  Skoda I am rejecting the car.

 

Pfff this is the future. OTA updates for battery’s. 

9 hours ago, SkodAlex4RS said:

Pfff this is the future. OTA updates for battery’s. 

It's possible they could improve the charging software like that but clearly it was either a lie or they don't understand the problem properly. It's not good enough really being in the situation where you don't have full confidence in your car's reliability.

Car was at the dealer yesterday to look at the 12V battery issue. They say they identified a problem with some modules drawing too much current, and xdid a software update. We shall see if that fixes the problem...

And the battery is flat again...

2 hours ago, mccririck said:

And the battery is flat again...

How old is your battery?

15 hours ago, SkodAlex4RS said:

How old is your battery?

Same age as the car. 1 year and 5 months. 33k miles.