Octavia iV Estate - flat 12v battery

[Sir_Ron_Norris]

• On March 2 this year I took delivery of a new Octavia iV Estate, my fourth Octavia since 2002.
• One month ago the 12v battery failed and the car had to be transported to the dealer. They had it for three weeks but were unable to find the reason for the fault.
• My driving style is mainly local trips, <30mls, with occasional journeys of c.200mls. Making many small journeys I considered a mild hybrid a good choice.
• The high voltage battery is charged regularly to full (at least twice a week). 
• The manual states explicitly "The 12-volt vehicle battery is automatically charged when the high-voltage battery is charged". Worryingly, this seemed to be a surprise to the dealer.
• My question is this - can anyone confirm that statement in the manual is correct? If so, why did the 12v battery should go flat?

 

I raised this question with Honest John https://www.honestjohn.co.uk/ and one of their correspondents replied that they had always understood that the two batteries were entirely independent of each other - which contradicts the information in the manual.

[PetrolDave]

Since the 12V battery is required for things like door locks, vehicle lighting, etc. then if it isn't charged when the high voltage battery is charged that makes a mild hybrid totally useless for shorter journeys where the ICE never starts IMHO. I can't believe that VAG would make a silly design error like that? Surely....

[Sir_Ron_Norris]

Hmmm ... I was afraid of that. But thanks for the rapid response.

[MarkyG82]

Someone on speak ev had to change the 12v battery on their passat.  Found the system performed better with a cheaper basic battery rather than a modern stop start battery.  Do you know what is installed now?  It's in the boot under the left cubby In the passat so very likely to be the same position in the superb.

[cheezemonkhai]

I've heard of the same "oversight" on other brands of hybrid and EV, which lead me to help my mate out with a cigarette lighter socket to get the 12V up enough to work.

I too was amazed they didn't charge the 12v when plugged in.

 

I imagine there are third party options to do it, but it's a daft one for sure if it's the same here.

[Jim2015]

The 12 volt battery definitely charges at the same time as the 400 volt battery. I have a voltmeter plugged into the 12 volt boot socket and occasionally monitor the resting voltage, which varies between 12.4 and 12.9 volts, but as soon as I plug in the main charger, the battery voltage increases to above 13 volts. If the 12 volt battery does need charging, then the handbook clearly explains where the charger should be connected. I assume that using a C-Tek  trickle charger plugged into the boot socket to charge the battery (as I did with our Karoq during lockdown) is not suitable. However, as I charge the main battery at least three time a week, I should never need to recharge the 12-volt battery.

Edited 20 July, 2021 by Jim2015

[Sir_Ron_Norris]

On 20/07/2021 at 14:10, Jim2015 said:

The 12 volt battery definitely charges at the same time as the 400 volt battery.... However, as I charge the main battery at least three time a week, I should never need to recharge the 12-volt battery.

That is reassuring, thank you. Like you, I charge the HV battery several times a week, and that is why I was surprised and highly disappointed when the 12v battery died. What I didn't know was that the car, when started, defaults on Emode - and that was how I was driving it. Apparently the battery doesn't last long like this. But in Hybrid mode the IC engine and alternator have a chance to re-charge the battery. I guess that makes sense - it's a hybrid so drive it in Hybrid mode. The supplying dealer had my car for 3 weeks and there was no conclusive answer as to why the battery went flat. But a 15-minute conversation with an alternative dealer explained (what now seems obvious) about Emode and Hybrid mode.

[Jim2015]

I know of another case where the sales manager at our dealership lent his Octy iV to a colleague to try it out and was surprised the next day to find that that the 400-volt battery charge was low. It turned out that his colleague did not realise that e-mode is the default setting.  I'm aware of the default being the electric-only setting, so I press the 'mode' button to chose hybrid if needed, but I think that hybrid should be the default. If the battery level is getting low, then hybrid kicks in if you are in e-mode, so it's not a major issue.

[MickyD44]

I am guessing here, but with my limited knowledge, it could be a hangover from being purely ICE. 

 

With a full EV like the Enyaq, the big 400v battery will have an inverter that will supply charge to the 12v battery, which is required for the stereo, aircon,  other ancillaries and will possibly allow a charge to the 12v when plugged in.

 

With the Octavia and Superb iV being hybrid, I would guess they still have an alternator to provide power to the 12v, and if you run the car in E Mode without the ICE running, it will never charge the 12v as it doesn't have the inverter like a full EV.

 

Maybe the trick is to at least once a week, drive it like you stole it to make sure the ICE kicks in and the alternator spins up to charge the battery.

 

Interesting to know for when my vRS iV arrives in a few months.

[Jim2015]

Correct but as the 400volt battery has a range of about 36 miles, it will need charging regularly if this is a typical mileage, so that the 12 volt battery will also charge. The problem of a discharged 12 volt battery may occur if the car is only used in e-mode for short journeys without charging. In that case I'd recommend a voltmeter plugged into the boot 12 volt socket to check the resting voltage ocassionally. I'll be doing this in the winter, when it will only be used for short journeys.

[cheezemonkhai]

IIRC the 12v battery would require 14V to charge, not just over 12.

Are you sure it is actually charged when it's plugged in. It would be good to get confirmation of this.

[Jim2015]

2 hours ago, cheezemonkhai said:

IIRC the 12v battery would require 14V to charge, not just over 12.

Are you sure it is actually charged when it's plugged in. It would be good to get confirmation of this.

From my post on this thread dated 20th July: 'The 12 volt battery definitely charges at the same time as the 400 volt battery. I have a voltmeter plugged into the 12 volt boot socket and occasionally monitor the resting voltage, (which varies between 12.4 and 12.9 volts) but as soon as I plug in the main charger, the battery voltage increases to above 13 volts.' Checked again: it rises to 13.1 volts as soon as the main battery charger is switched on and drops again as soon as it is switched off. I'll check the resting voltage tonight and tomorrow after an overnight charge of the main battery. Note: when on charge I can only monitor the battery, not the voltage produced by the charger supplying the 12v battery.

[Breezy_Pete]

13.1V is a very low charging voltage for a 12V lead acid battery, 13.8 or more is usually applied, for even trickle-charging, I think? In other words, it will only recharge very slowly at that voltage.  

[cheezemonkhai]

4 hours ago, Jim2015 said:

From my post on this thread dated 20th July: 'The 12 volt battery definitely charges at the same time as the 400 volt battery. I have a voltmeter plugged into the 12 volt boot socket and occasionally monitor the resting voltage, (which varies between 12.4 and 12.9 volts) but as soon as I plug in the main charger, the battery voltage increases to above 13 volts.' Checked again: it rises to 13.1 volts as soon as the main battery charger is switched on and drops again as soon as it is switched off. I'll check the resting voltage tonight and tomorrow after an overnight charge of the main battery. Note: when on charge I can only monitor the battery, not the voltage produced by the charger supplying the 12v battery.

I think that was my point. You say you read 13V at the battery, but 13V isn’t enough to charge a 12v lead acid battery 

 

It’ll be interesting to see what happens, but I was just saying I wouldn’t take it as conclusive.

[VAGProf]

Hello all, I've read all the posts in this topic and found some wrong information.

 

I'll try to explain how the system works in short, if anyone has some questions, I will kindly answer them.

 

To start with, the 12V battery is charged ONLY with the high voltage system, by the power electronics that also drives the motor (the big metal block with the 6 orange wires connected to it next to the ICE) to be more precise.

There is no alternator on the ICE, so if you drive in E-mode or hybrid, it doesn't make a difference in charging the 12V battery. 

 

This means the high voltage system must be active to charge the 12V battery, so only when driving or charging the HV battery.

 

The reason why there is only 13.1 or .2V  is because the 12V battery is monitored by the gateway, it knows the charging state, so if it is above 80%, ther is no need to charge it, purely wasted energy to keep the system at 14V all the time. This is why the converter only supplies 13.2V to the system to just prevent the battery from discharging. 

 

When driving and using the regen while braking, the system will be at 14V, all the modern cars do this, not only the hybrids. Actually most of them only have 12 - 12,5V while accelerating, when coasting or braking the alternator will start to charge the battery. 

 

Why Sir_Ron_Norris' battery died, I haven't got a clue, but it isn't related to driving in E-mode or hybrid. Could be an driver error (leaving a light on, something plugged into the 12V socket,...), bad ground connection or just a faulty battery. 

 

I hope with the new battery the problem has been solved.

[Jim2015]

Thank you VAGProf. That is an excellent answer. I used to monitor the battery voltage in our previous car, a Karoq. When coasting, the voltage was around 14 volts and when accelerating it dropped just as you described. I've noticed that in Hybrid mode on a long journey in our Octavia iV which results in the 400 volt battery dropping to 1%, it then remains there but the car seems to begin moving in e-mode until the IC engine kicks in. If the car is taken on a very long journey, with no recharging facilities and you say that the IC engine doesn't have an alternator, is there a chance that the 12-volt battery could have a reduced capacity such that the IC engine wouldn't run?

[VAGProf]

2 minutes ago, Jim2015 said:

Thank you VAGProf. That is an excellent answer. I used to monitor the battery voltage in our previous car, a Karoq. When coasting, the voltage was around 14 volts and when accelerating it dropped just as you described. I've noticed that in Hybrid mode on a long journey in our Octavia iV which results in the 400 volt battery dropping to 1%, it then remains there but the car seems to begin moving in e-mode until the IC engine kicks in. If the car is taken on a very long journey, with no recharging facilities and you say that the IC engine doesn't have an alternator, is there a chance that the 12-volt battery could have a reduced capacity such that the IC engine wouldn't run?

 

Hey Jim,

 

The ICE is always starts with the HV motor, there is no ordinairy 12V startermotor. That is why the car always takes off on the electric motor. Even if the battery is at 0 or 1%, it may indicate a range of 0 miles, but in fact isn't completely empty.

 

When the HV battery is at 0% and you are driving for days or weeks on the ICE without charging, the 12V system is still being charged from the HV system. When the ICE is running, the HV motor is also spinning, as there is only one clutch to engage the ICE.

This means the ICE is making the car move, but at the same time spinning the HV motor, so it can charge the HV system (and 12V system).

The A/C compressor is also a small 400V motor, so with 0% battery, the compressor also gets some power from the spinning HV motor.

 

The unit responsible for the 12V battery always tries to keep the battery around 80%, so there is some free space to save some energy that would otherwise be lost. ( for example starting on the top of a mountain with 100% HV battery, when coasting downhill the car can't save the energy in the HV battery, so it has to find some other way to save it, this is mostly done with the 20% reserve in the 12V battery and cooling/heating the coolant for the HV motor and battery)

[Jim2015]

Thanks VAGProf. You are good! Whereabouts in Belgium are you? I used to do some work for the Commonwealth War Graves Commission and always stayed at the Ariane Hotel in Ypres/Ieper. My wife and I liked that part of Belgium so much that we used to stay on for a few days holiday. Great food and my favourite beer - Leffe Blonde. I've seen the Last Post at the Menin Gate a few times and it always moved me. My apologies for going off-thread moderators.

[BigEjit]

11 hours ago, VAGProf said:

Hello all, I've read all the posts in this topic and found some wrong information.

 

I'll try to explain how the system works in short, if anyone has some questions, I will kindly answer them.

 

To start with, the 12V battery is charged ONLY with the high voltage system, by the power electronics that also drives the motor (the big metal block with the 6 orange wires connected to it next to the ICE) to be more precise.

There is no alternator on the ICE, so if you drive in E-mode or hybrid, it doesn't make a difference in charging the 12V battery. 

 

This means the high voltage system must be active to charge the 12V battery, so only when driving or charging the HV battery.

 

The reason why there is only 13.1 or .2V  is because the 12V battery is monitored by the gateway, it knows the charging state, so if it is above 80%, ther is no need to charge it, purely wasted energy to keep the system at 14V all the time. This is why the converter only supplies 13.2V to the system to just prevent the battery from discharging. 

 

When driving and using the regen while braking, the system will be at 14V, all the modern cars do this, not only the hybrids. Actually most of them only have 12 - 12,5V while accelerating, when coasting or braking the alternator will start to charge the battery. 

 

Why Sir_Ron_Norris' battery died, I haven't got a clue, but it isn't related to driving in E-mode or hybrid. Could be an driver error (leaving a light on, something plugged into the 12V socket,...), bad ground connection or just a faulty battery. 

 

I hope with the new battery the problem has been solved.

 

A 12v battery is used to maintain the electrical systems so it is at risk of deep discharge if the vehicle is parked up for a few weeks or months (also includes the transport network from factory to dealership in the history of the vehicle and more so if its an early vehicle and part of the launch stock built and stored). If its discharged and left for a few days, it can lose enough capacity to never recover or shorten its life in service. A big indicator for this is looking at the vehicle build date vs the sale date/when you took delivery.

[MickyD44]

Brilliant information VAG Prof, thank you for sharing that.

[Sir_Ron_Norris]

Going back to my original post at the top of this thread, I charged the HV battery today in the garage. Went back into the garage an hour or so later and the brake lights were on. I suspect now that this is what happened when the 12v battery went dead in July and caused me to be 3 weeks without the car. I have a larger-than-average single garage but, nevertheless, it is a tight fit amongst the bikes and shelving. So when the garage door is closed it almost touches the rear of the car. I suspect now that rear sensors (auto braking or parking, or both) were triggered by the very close proximity of the garage door, even though engine was off and the car locked. What do you think..?

[BigEjit]

The condition the vehicle was parked up in shouldn't cause the brake lights to illuminate.

 

So long as something daft, like a set of aftermarket car mats are interfering with the brake pedal or switch up in the pedal box, brake lights shouldn't be on. Its likely a software issue triggered by a bunch of random events coming together. Unless you can recreate the issue on demand, its going to be very difficult to diagnose at the dealership without a data logger present.

 

 

[Skoolboyerror]

On 06/09/2021 at 12:56, BigEjit said:

The condition the vehicle was parked up in shouldn't cause the brake lights to illuminate.

 

So long as something daft, like a set of aftermarket car mats are interfering with the brake pedal or switch up in the pedal box, brake lights shouldn't be on. Its likely a software issue triggered by a bunch of random events coming together. Unless you can recreate the issue on demand, its going to be very difficult to diagnose at the dealership without a data logger present.

 

 

So ongoing issue with my vehicle is sometimes having warning that 12V battery low.

My security camera has been picking up the octy brake lights coming on throughout the night sporadically with no rhyme or reason (and no aftermarket gubbins). VRS Phev Mar 21 delivery date.

Been in twice, had software fixes and most recently swapped a light switch module or something with a newer vehicle and monitoring it to see if now fixed or not. 

Possibly original poster getting same problem ive had of brake lights draining battery

[brelmondo]

On 09/09/2021 at 22:22, Skoolboyerror said:

So ongoing issue with my vehicle is sometimes having warning that 12V battery low.

My security camera has been picking up the octy brake lights coming on throughout the night sporadically with no rhyme or reason (and no aftermarket gubbins). VRS Phev Mar 21 delivery date.

Been in twice, had software fixes and most recently swapped a light switch module or something with a newer vehicle and monitoring it to see if now fixed or not. 

Possibly original poster getting same problem ive had of brake lights draining battery

 

Having very similar issues with my Octavia VRS IV, which I took ownership of from Trust Skoda Stourbridge at the end of July.

 

Had an amber warning light on the dash due to 'Vehicle Lighting' and 'Adaptive Frontlight System' at the beginning of September. Which meant I was driving with the head and tail lights on permanently for almost three weeks. When I was finally able to get the car in at the dealer (due to lack of curtesy car availability at Trust Stourbridge) they swapped out lighting control switch with a doner vehicle, the warning lights cleared. Swapped back with my original switch, still no warning lights. 👍 A software update was also completed during the same visit. Dealer has ordered a new light control switch in any case, currently awaiting delivery.

 

This past Friday the car was connected to the 3pin HV charging cable after getting back from work, HV charge at roughly 30%. I use the 'Departure Planner' within the MySkoda app to schedule overnight charging. Leaving the car at home, I went out for the evening. On my return, at roughly 23:45, I could hear that the radiator cooling fan was spinning! The car was locked, the HV charging indicator was not illuminated, nothing displayed on the dashboard. Unlocked the car, fan still audibly spinning. Turned on the ignition, turned off the ignition, fan audibly spinning. Switched power off at the socket supplying HV charging cable, fan stopped a few seconds later?!?

 

The car remained parked up at home during Saturday whist I went out. On my return I had a visit from the neighbor to let me know my car alarm had gone off a number of times during the afternoon.  Unlocked the car, switched on ignition. The dashboard displayed numerous error messages and warning lights. Exited the car, pressed 'lock' on the drivers door handle, nothing happened. Pressed the lock button on the key fob, nothing happened. Back in the car, ignition button pressed, nothing happened. The 12 volt battery was completely dead. 

 

Visit from Skoda assist on Sunday morning, connected a 12 volt charger and shortly after the car was back to life. Hooked up to diagnostics and the results displayed a number of warnings and errors. I was told that the errors pointed to an issue with charging of the HV battery. But the engineer was not HV certified and therefore nothing further he could do, other than pass on diagnostics outcome to a dealer and recommend I get the car booked in ASAP.

 

The car is now with Trust Skoda Wolverhampton. I'm told a replacement vehicle control module will be fitted later this week. 🤞

[Skoolboyerror]

2 hours ago, brelmondo said:

 

Having very similar issues with my Octavia VRS IV, which I took ownership of from Trust Skoda Stourbridge at the end of July.

 

Had an amber warning light on the dash due to 'Vehicle Lighting' and 'Adaptive Frontlight System' at the beginning of September. Which meant I was driving with the head and tail lights on permanently for almost three weeks. When I was finally able to get the car in at the dealer (due to lack of curtesy car availability at Trust Stourbridge) they swapped out lighting control switch with a doner vehicle, the warning lights cleared. Swapped back with my original switch, still no warning lights. 👍 A software update was also completed during the same visit. Dealer has ordered a new light control switch in any case, currently awaiting delivery.

 

This past Friday the car was connected to the 3pin HV charging cable after getting back from work, HV charge at roughly 30%. I use the 'Departure Planner' within the MySkoda app to schedule overnight charging. Leaving the car at home, I went out for the evening. On my return, at roughly 23:45, I could hear that the radiator cooling fan was spinning! The car was locked, the HV charging indicator was not illuminated, nothing displayed on the dashboard. Unlocked the car, fan still audibly spinning. Turned on the ignition, turned off the ignition, fan audibly spinning. Switched power off at the socket supplying HV charging cable, fan stopped a few seconds later?!?

 

The car remained parked up at home during Saturday whist I went out. On my return I had a visit from the neighbor to let me know my car alarm had gone off a number of times during the afternoon.  Unlocked the car, switched on ignition. The dashboard displayed numerous error messages and warning lights. Exited the car, pressed 'lock' on the drivers door handle, nothing happened. Pressed the lock button on the key fob, nothing happened. Back in the car, ignition button pressed, nothing happened. The 12 volt battery was completely dead. 

 

Visit from Skoda assist on Sunday morning, connected a 12 volt charger and shortly after the car was back to life. Hooked up to diagnostics and the results displayed a number of warnings and errors. I was told that the errors pointed to an issue with charging of the HV battery. But the engineer was not HV certified and therefore nothing further he could do, other than pass on diagnostics outcome to a dealer and recommend I get the car booked in ASAP.

 

The car is now with Trust Skoda Wolverhampton. I'm told a replacement vehicle control module will be fitted later this week. 🤞

Wow a lot going on but like you said very similar. You are mentioning things and I am thinking ah yes ive had that too!

 

With regards to the fan, mine still does this and I always assumed that it was to do with keeping the battery cool, I may be wrong though.

 

Since the replacement module/part from a new donor vehicle, touch wood I have not had any 12v battery issues that I am aware of.

 

I am keeping a close eye on it still however. Im interested in what you say about the hv battery charging so would love to hear when you get an update. Maybe the fan is not supposed to come on so be keen to hear what the garage say to you. I have noticed that full charging now will not display more than about 23 miles of electric regardless of weather etc. To be fair it seems to be a more accurate mileage prediction than when it would on a  rare occasion say 30 to 40 odd miles and get nowhere near it.