Last year, in May 2023, my local Skoda dealer finally caved in to my demands about replacing my car´s 12 Volt battery with a new one under the warranty.

After having experienced several incidents with a car that did not react to the electronic key and thus barred the access to the car, I demanded that Skoda should fit a new 12 Volt battery in my car.

Of course I was able to get access to my car using my mechanical key. Opening the bonnet and measuring the voltage of the battery to below 6 Volts made me realise that this battery was damaged beyond repair.

 

At that time the car was less than two years old.

 

My first car in 1966 was a Triumph Herald. In spite of its beauty it was an industrial heap of junk but the battery lasted all of its lifetime (8 years).

Now, 58 years later, I must accept a battery lifetime of two years unless I regularly connect a charger to the terminals in the engine compartment. I have to, because I mostly drive short distances only in e-mode. This was why I purchased a PHEV.

And now I would like to know if anybody could tell me where to find the 12 Volts battery in my car because sooner or later I will have to replace it again and I would hate to pay Skoda for doing it.

Your 12V battery is charged every time HV battery is charged and every time car recuperates energy while braking. So there's no need to charge it separately. The problem lies in parasitic drains and infotainment issues Octavia is known for, and before changing battery you'd need to check these first. There were service campaigns addressing battery drain issues, as well as infotainments and screens are being replaced under warranty for starting up in the middle of the night and draining battery.

Edited 21 August, 20241 yr by Edela

1 minute ago, Edela said:

Your 12V battery is charged every time HV battery is charged and every time car recuperates energy while braking. So there's no need to charge it separately. The problem lies and parasitic drains and infotainment issues Octavia is known for, and before changing battery you'd need to check these first. There were service campaigns addressing battery drain issues, as well as infotainments and screens are being replaced under warranty for starting up in the middle of the night and draining battery.

Thanks for your answer.

I realise that the 12 volt battery is charged while charging the HV battery but that does not suffice. After charging the HV battery I can measure 13.5 volts on my 12 Volt battery but it only lasts a few hours. The tension then slowly drops to 12,1 volts after 10 hours. and keeps on dropping. Somebody at the Skoda dealer tried to convince me that it would stop at 11.5 Volts and that a tension of about 11.5 volts would be fully acceptable. A statement  that I cannot accept, having dealt with 12 volt acid/lead batteries for many years. But it still leaves me without knowledge about where to locate the 12 Volt battery in my car. I could of course start removing several covers in the back of the car, but I hoped it would be easier to ask here.

43 minutes ago, Edela said:

The problem lies in parasitic drains and infotainment issues Octavia is known for

 

24 minutes ago, Keld said:

After charging the HV battery I can measure 13.5 volts on my 12 Volt battery but it only lasts a few hours. The tension then slowly drops to 12,1 volts after 10 hours. and keeps on dropping.

I think you've just confirmed that your car has a parasitic drain problem, which Skoda need to solve under warranty.

I fully agree with both of you. But this question of mine is not a about a flawed software, allowing this condition to exist, but a question about how to locate my 12 Volt battery.

I would  look in the boot in one of the cubby holes left or right

From the manual:
 

Quote

 

Disconnecting, connecting and replacing

The 12 volt vehicle battery is located in the luggage compartment and is not accessible. The 12 volt vehicle battery may only be disconnected and connected by a specialist company.

 

Changing
The new 12 volt vehicle battery must have the same parameters as the original battery. Have the replacement carried out by a specialist garage.

 

 

 

2 hours ago, Keld said:

I realise that the 12 volt battery is charged while charging the HV battery but that does not suffice.

 

It would suffice if you did no have a parasitic drain.

 

Do you really want to spend whatever small fortune the so called "specialist" will rush you for to end up with another irreversibly damaged battery?

 

I despair of modern vehicles

1 hour ago, Keld said:

but a question about how to locate my 12 Volt battery.

I think your priority should be to get the cause of the battery draining solved, then you wouldn't need to know where the 12V battery is as you wouldn't need to keep replacing another damaged battery!

Is there a permanent 12v power socket in the octavia?

 

Anything plugged in that?

29 minutes ago, Stonekeeper said:

Is there a permanent 12v power socket in the octavia?

 

Anything plugged in that?

There is a 12 Volt cigarette lighter socket in the bagage compartment and no, there is nothing plugged into this socket.

Modern computer controlled cars will have some draining of the battery while parked, but a well written software would prevent the battery from being drained beyond the point where the car would be unable to start let alone be able to open the doors with the electronic keys.

If some specialist can change the battery then so can I. I just needed to know where to look for the 12 Volt battery, so thanks to all for their contributions to this thread

The very systems that you believe this well written software should protect are ones (amongst others) that are depleting the battery.

 

 

Horse, water, drink.

13 hours ago, J.R. said:

The very systems that you believe this well written software should protect are ones (amongst others) that are depleting the battery.

 

 

Horse, water, drink.

A well written software would put the system into sleep mode when the battery tension drops below 12.5 Volts.

If the system drains the battery in sleep mode then somebody at Skoda needs to go back to the drawing board.

According to what I have heard and read about PHEVs then the 12 Volt batteries have had problems in several PHEV car brands incl. Ford.

It seems as though some of the car owner´s drive patterns difer from what the car builders expected.

If you, like I, drive many short trips in e-mode then you will regularly have to put a charger to your 12 Volt battery.

The charging of the High Voltage battery alone doesn't seem to suffice.  Choosing the hybrid drive mode seems to keep the 12 Volt battery happy.

Then you could ask yourself why the Skoda PHEV defaults to e-mode when starting the car. I still haven't tried long time parking at an airport. (I don't dare)

 

4 minutes ago, Keld said:

A well written software would put the system into sleep mode when the battery tension drops below 12.5 Volts.

Very true, but given the number of owners having problems with the 12V batteries dying on VAG PHEVs we have to assume that the early versions of the hardware & software do NOT have well written software!

 

Why are you so reticent to tackle the root cause (modules not turning off) and so insistent on only tackling the symptom (a knackered 12V battery)?

 

When fault finding the only sensible method is to identify, and then solve, the root cause. Repeatedly tacking symptoms is just expensive, frustrating and ultimately pointless.

2 minutes ago, PetrolDave said:

Very true, but given the number of owners having problems with the 12V batteries dying on VAG PHEVs we have to assume that the early versions of the hardware & software do NOT have well written software!

 

Why are you so reticent to tackle the root cause (modules not turning off) and so insistent on only tackling the symptom (a knackered 12V battery)?

 

When fault finding the only sensible method is to identify, and then solve, the root cause. Repeatedly tacking symptoms is just expensive, frustrating and ultimately pointless.

I don't think that I am reticent. I am obviously unable to solve the problem by myself so I have a running discussion with my Skoda dealer who doesn't seem to realise that there is a problem.

His only advice to me is to connect a charger to my 12 Volt battery with regular intervals, apparently not realising that the repetitive drainings of the battery will kill it eventually and much too soon.

Anyway I'll ask him to do the latest software updates to my car. Do any of the updates like the 1941 or the 1969 solve the problem with the draining of the battery?

35 minutes ago, Keld said:

Do any of the updates like the 1941 or the 1969 solve the problem with the draining of the battery?

Those are updates to only the infotainment system of the car, so I very much doubt they will solve this problem.

 

There have been several posts/threads in this forum about this 12V battery problem on PHEV versions, so your best plan is to search/surf this forum to find those posts and ask the owners what fixed it for them. Then armed with that information go back to your dealer and tell them what they should know (but either don't or can't be bothered) about what needs updating.

You won't change the battery yourself, it must be coded.
You need to ask your servicemen to install all necessary firmware updates to tackle drain, there were service campaigns for early Octavias. Software was bad, but it was fixed 3 years ago, so I don't understand why rant if it can be just updated and all be well. Particularly, 90V7 may solve your issue, but there may be others for your VIN. If they bull**** you saying you have to charge your battery, raise a complaint to importer and go to another service. After all updates are done, they must change battery on their expense, otherwise you'll get many new faults soon.

Also, at least in Spain, when car is immobilized and has to be towed to a workshop, things are resolved way better and faster. So might be useful to let it discharge once again and make your car towed.

1 hour ago, Keld said:

A well written software would put the system into sleep mode when the battery tension drops below 12.5 Volts.

If the system drains the battery in sleep mode then somebody at Skoda needs to go back to the drawing board.

According to what I have heard and read about PHEVs then the 12 Volt batteries have had problems in several PHEV car brands incl. Ford.

It seems as though some of the car owner´s drive patterns difer from what the car builders expected.

If you, like I, drive many short trips in e-mode then you will regularly have to put a charger to your 12 Volt battery.

The charging of the High Voltage battery alone doesn't seem to suffice.  Choosing the hybrid drive mode seems to keep the 12 Volt battery happy.

Then you could ask yourself why the Skoda PHEV defaults to e-mode when starting the car. I still haven't tried long time parking at an airport. (I don't dare)

 

It is not all PHEVs.  I have had a 2021 PHEV for 6 months and practically all my driving is in e mode (I have used half a tank of petrol), the car is charged on the 10A charger and I have had no (touch wood) problems with the 12V battery.  That time included 3 weeks when I was away on holiday and the charger was not plugged in.  My software is version 1941.

Do VAG really not have anyone in design that worked for Toyota ?

2 hours ago, Keld said:

A well written software would put the system into sleep mode when the battery tension drops below 12.5 Volts.

 

The volt drop from the modules active during the first 30 minutes after locking alone are sufficient to put the battery below 12.5v especially if you have done a short journey and the battery has not heated internally through charging.

 

You want the battery to go into sleep mode yet still be able to open the doors with the electronic keys, that is precisely what it would do if it were functioning correctly, shut down all of the controllers aside from the alarm and central locking after no more than 20-30 minutes, it will not do so if any of them are still communicating so that is the root of your problem.

 

As myself and others have pointed out multiple times replacing the battery would be as big a waste of money as would filling  a car with fuel which has a hole in the bottom of the tank.

1 hour ago, RobL50 said:

My software is version 1941.

As previously said that is only the software of the infotainment system - it says nothing about the software level in the other 30+ modules in the car!

 

Stating the infotainment software level as though it applies to the whole car is such a common misunderstanding, and one that's been commented on here more times than I can remember.

3 hours ago, PetrolDave said:

As previously said that is only the software of the infotainment system - it says nothing about the software level in the other 30+ modules in the car!

 

Stating the infotainment software level as though it applies to the whole car is such a common misunderstanding, and one that's been commented on here more times than I can remember.

I agree with you.  I quoted the infotainment version because there are references above to the known infotainment issues.  In terms of other software all versions are 'no update required' according to the dealer.

Thanks to all for the many responses to my question. However, the responses quickly turned into a discussion about software and firmware. I realise that the software level of the infotainment system probably has nothing to do with the draning of the battery. And yet, an infotainment system that doesn't shut down properly when the car is turned off may still drain the battery. The bottom line is that I have no overall knowlegde about how the various systems and computer units in my car interact with each other.

Anyway, I just wanted to know how to locate my 12 Volt battery. My intention was to replace the battery myself when the time comes. And it will come, sooner or later, because no acid lead battery can endure repeatedly being discharged below 12 Volt. But now I have learned that a replacement of the battery can only be done by someone who knows about the coding of the battery. I assume that this coding is some kind of chip built into the battery in order to prevent us mortals from interfering with the servicing of our own cars.

I'm afraid that the same level of ignorance as mine exists among a large percentage of the service persons at the dealers. People who are supposed to help me instead of telling me fairy tales.