15 minutes ago, Cairus said:

I can hardly imagine...

No it's true - the 12V battery charges from the drivetrain, rather than an alternator. It's interesting as it means having the engine running would have no impact on jump starting another car, for example.

I think it's a bit stupid (I also think they could have designed a system to draw charge from the 48V battery) but there we go.

I placed a voltmeter to the battery and it reads 4.2V. The battery may be RIP after all. But still, this seems like a common issue on the Skoda PHEVs and the EVs as they are equipped with far too many electronic gadgets draining the battery constantly and short trips aren't good enough to recharge the 12V battery.

I guess we just need to carry a small jump starter pack with me as well as all the other cables etc.

Post deleted.

52 minutes ago, OccyVRS said:

Nein, es stimmt – die 12-V-Batterie wird über den Antriebsstrang und nicht über eine Lichtmaschine aufgeladen. Das ist interessant, denn so hat beispielsweise ein laufender Motor keinen Einfluss auf die Starthilfe für ein anderes Auto.

Ich finde es ein bisschen dumm (ich denke auch, sie hätten ein System entwickeln können, um Ladung aus der 48-V-Batterie zu ziehen), aber so ist es nun einmal.

No DC/DC charger?

3 minutes ago, Cairus said:

No DC/DC charger?

If I read correctly, the DC/DC charger only supplies minimal current to the 12V battery, when the vehicle is moving, but not when it's idling.

PS. When we jump started it, the brain went crazy started giving messages about not recognizing the keyfob and parking brake related error messages. Had to disconnect the jumper and wait another 5 minutes before it all came online. Now it's in the tow truck heading to the Skoda Service.

The positive side is, as the car was inspected merely 2 weeks ago, the repair cost + parts will be covered by the Service. Hopefully they have some kind of a permanent fix.

Edited 7 August, 20257 Aug by Octawia

4 minutes ago, Octawia said:

If I read correctly, the DC/DC charger only supplies minimal current to the 12V battery, when the vehicle is moving, but not when it's idling.

PS. When we jump started it, the brain went crazy started giving messages about not recognizing the keyfob and parking brake related error messages. Had to disconnect the jumper and wait another 5 minutes before it all came online. Now it's in the tow truck heading to the Skoda Service.

The positive side is, as the car was inspected merely 2 weeks ago, the repair cost + parts will be covered by the Service. Hopefully they have some kind of a fix.

Pretty standard. I remember mine was like a Christmas tree when the battery went - everything from ACC to the reverse lights. When the module voltage drops below what it likes, the module will panic and log a code. Skoda will sort it all out.

19 minutes ago, Cairus said:

No DC/DC charger?

For the 48V yes, however AFAIK for the 12V no - the only way is to either manually charge it or drive around. I suspect it's because in their head, when driving on EV mode the battery still gets to charge - otherwise the alternator wouldn't be doing anything.

1 hour ago, Octawia said:

I also found out that the only way to recharge the 12V battery is by recuperation as these cars don't have the traditional alternators anymore.

It is charged while HV battery is charged.

1 hour ago, Octawia said:

I placed a voltmeter to the battery and it reads 4.2V. The battery may be RIP after all. But still, this seems like a common issue on the Skoda PHEVs and the EVs as they are equipped with far too many electronic gadgets draining the battery constantly and short trips aren't good enough to recharge the 12V battery.

For sure battery is defected, as many were.

Many of us here went through this. It comes to a multiple fw updates for ECUs and battery replacement. For most of us, that was the final solution. So no, PHEVs as they are not a problem as long as all fw problems are sorted and as long as you don't get that covid battery, which were sitting on a factory lot for a year. Still, some folks were saying it did not help them, which made me think their workshops did not update everything they had to.

4 minutes ago, OccyVRS said:

For the 48V yes

You keep repeating 48V, but I think you are confusing PHEV and mHEV. The battery is 350V here.

1 hour ago, Edela said:

You keep repeating 48V, but I think you are confusing PHEV and mHEV. The battery is 350V here.

Yes - I am confusing them. My girlfriend's dad has just bought a Passat MHEV with the 1.5 and 48V battery, and I seem to be thinking about that.

None of the Covid cars did very well - most sat for months, while those built during it were missing options due to the chip shortages.

After 3 days waiting, the Skoda authorized service gave the diagnosis. Apparently one of the BCM (battery control module) module firmware was out of date and it caused the 12V battery drain itself even when the car is in off mode!

As I had service insurace, the towing (twice in a day), jump starting etc. was covered, but for some reason upgrading of the BCM firmware was not. As car had only been inspected by the same service only 2 weeks ago, they accepted the diagnosis cost, so I only had to pay 120 eur for the upgrade. That's a number I guess I can give with.

Though I admit, I lost confidence in the car. I mean only a month ago, I drove this car 7500 km across Europe, believing that it's trustworthy. But a simple bug could have made my trip horribly wrong. I am fortunate that I drove around 750 km/day so the percupiration saved me.

By the way, the service also confirmed that the only way to recharge the 12V battery is by percupiration process.

As a back up solution I've decided to buy a small jump starter pack, which is the size of a VHS tape (youngsters won't know what that is !) generally a small box packed with batteries, capable of supporting 800A/1000A, just good enough to start the car up. It's quite nifty and handy. It's good to keep one charged all times in the boot. It costs around 30-50 eur for a decent one from Amazon.

Anyway, I'm grateful for all of your help.

Summary:

Reason: BCM Fault

Solution: BCM firmware upgrade and recupirate until the battery is recharged.

Risk: It can happen to anyone with a PHEV or EV. Carry a small jumpstarter pack.

Such updates, where there is a bug in the firmware, are free of charge by us

Edited 14 August, 202514 Aug by Cairus

22 minutes ago, Cairus said:

Such updates, where there is a bug in the firmware, are free of charge by us

It may differ from country to country perhaps. Thanks for letting me know, I will ask Skoda about it.

On 14/08/2025 at 19:10, Octawia said:

Though I admit, I lost confidence in the car. I mean only a month ago, I drove this car 7500 km across Europe, believing that it's trustworthy. But a simple bug could have made my trip horribly wrong. I am fortunate that I drove around 750 km/day so the percupiration saved me.

I feel you. I do trips of anywhere between 7k and 9.5k every year and just came back from another one two days ago. This car is the least reliable car I ever had, but surprisingly, it never failed during long trips. Some bugs and glitches yes, but nothing that simple reboot wouldn't solve. On the other hand, just commuting daily within my town I had all the possible problems. So really mixed feelings about this car. But for sure, won't keep it a single day after warranty is over.

Hi, I have a 2024 Octavia 1.5 TSI E-Tec and have had occasional 'Low 12v' warnings even though the car had been driven for an hour or so the day before.

I eventually worked out that it was related to the 'KESSY' system - The car is parked on our driveway only a few yards from where I sit in the house. Whilst carrying a set of keys in my pocket and moving around the house, the car kept on 'Energising' the doorhandles etc. Thus it never really 'Went to sleep'. I found that even after a full charge the 12v warning could appear after only a week of normal driving.

The solution was to put the keys in 'Faraday Pouches' when not needed! A shame this is not mentioned in the Manual!

I hope this helps, kind regards, Alan

I found the solution of carrying a small backup battery with me that I go from Amazon for €40. Although it didn't occur again, after reading the forums I found out that the backup battery may run out eventually if you are only driving short distances as the only way to recharge the backup battery was by braking.

As I live in very cold climate, I am expecting it to happen again sometime.

How to start with a backup battery: connect the backup battery to the positive terminal in the fuse box under the hood, negative terminal anywhere else on the chassis. Press down the accelerator pedal, then power on the car. As soon as the engine starts, let go of the accelerator pedal. Then all you have to do is just drive around for an hour or so for it to recharge. I know it's a dumb solution but it works apparently.