Hi all. 3 weeks ago we bought a 20 plate Karoq from our local Skoda dealer and it's been running fine. My wife went to start it to come home from work and it wouldn't start. She said it said something like unable to start due to insufficient 12v charge. Luckily another lady had one of those jump pack things and it fired straight up. Cruise control is not working currently. So I assume we have a poorly battery. I checked it when she got home and it read 12.8v and it's currently on charge. I put my obd reader on it and it has 22 fault codes. It's booked into Skoda for next Friday.

Hello, depending on how (and with what) you tested the battery voltage, a reading of 12.8 volts should be ok - however, a more significant test is what the terminal voltage drops to when a load is applied to the battery - when the starter motor is operated, for instance.

It is common for numerous and seemingly random faults to be reported when the battery is failing.

Edited 3 July, 20253 Jul by Warrior193
added information

Very common to have lots of unexpected warning messages and (unseen) error codes when the battery gets too low for the car's computer systems and this is when the headlights seem bright enough and well, well before the engine won't start. The battery has to be very low before you get any difficulty starting the engine let alone before it can't start the engine.

Usually the first sign the battery is too low for the car's computers is when the stop/start doesn't work when it should, at that point the battery needs charging and sometimes just driving the car isn't enough and fully recharging with an appropriate battery charger maintainer, following the instructions in the car's 'Owner's Manual' and for the charger. A long low (amps) recharge is best.

The 12.8v can be when the battery has just been charged and drops given a little time and as has been put drops, possibly a lot, given load.

If you only got the car three weeks ago there are three possibilities I can think of -

1. the battery was/is old and worn and should have been replaced (but car 12v batteries are the most oversold car part and very often prematurely replaced rather than properly fully recharged

2. the battery was low and not recharged by the seller before you took the car (possibly car not used whilst on sale)

3. your use of the car and electrical systems in the car has taken the battery to a low state of charge

4. there is a constant drain the battery from a fault or perhaps(?) something you have added to the car(?).

The car battery likes 20c weather temperature and self-discharges at twice the rate at 30c and twice again at 40c - and of course during hot weather you use the air-con a lot more and the air-con (and steering) use a lot of electric.

If it wasn't for the fact you have booked the car I would have suggested deleting all error codes straight away, though they should resolve themselves if the battery is in a good state of charge and/or with use of the car.

You have learnt how important it is to keep the car's 12v battery in a reasonable state of charge to avoid upsetting the car's computer systems, many/most/(?)all of these error codes may have been present well before the engine wouldn't start so bear that in mind if the stop/start doesn't work when it should or you get low battery or other warnings.

HTH. Let us know how you get on.

Edited 4 July, 20254 Jul by nta16
missing word

Just to add to this - after almost killing my battery by leaving my windows open all night (I was exhausted, alright) I was met with a list of fault codes as long as my arm. When the battery voltage drops too low, lots of stuff becomes unhappy and logs a code - from the ACC and collision avoidance to power windows and gateway signal codes.

I had a heart attack as I thought it could be to do with water damage. The battery was replaced, along with the window switches as a precaution - it's just coming up to a year and all is well.

I would leave it as is, until Skoda look at it. I would also plug it into a trickle charger - I did the same on my Octavia and it lasted the week or so until I replaced the battery.

Once the battery is replaced, look up 'reset one touch windows'.

I've not reset any of the codes and I've been putting a charger on it each night. So yes, will wait to see what the dealership says next Friday.

1 hour ago, Itsrelfy said:

I've been putting a charger on it each night

If the recharging isn't left on long enough then it may take two or more sessions to get the battery back to "full", low amps for long and slow charging is generally better than high amps for quicker recharging on a truly flat battery. After this you shouldn't need to charge it every night that unless the battery is weak and/or you're using a lot of electricity when the car is driven and/or parked up. Do follow the instructions for battery charging in the 'Owner's Manual' to ensure the car's computer knows what's going on.

If you are using your charger maintainer every night as a maintainer until you are sure of the car and the battery to reassure your wife and yourself that's a different matter and understandable.

Have you added anything electrical to the car since you bought it, a camera say or 12v socket extended with anything plugged into it?

6 hours ago, Itsrelfy said:

I've not reset any of the codes and I've been putting a charger on it each night. So yes, will wait to see what the dealership says next Friday.

What instrument was used to get the 12.8 volt battery reading - and under what conditions?

12 hours ago, nta16 said:

If the recharging isn't left on long enough then it may take two or more sessions to get the battery back to "full", low amps for long and slow charging is generally better than high amps for quicker recharging on a truly flat battery. After this you shouldn't need to charge it every night that unless the battery is weak and/or you're using a lot of electricity when the car is driven and/or parked up. Do follow the instructions for battery charging in the 'Owner's Manual' to ensure the car's computer knows what's going on.

If you are using your charger maintainer every night as a maintainer until you are sure of the car and the battery to reassure your wife and yourself that's a different matter and understandable.

Have you added anything electrical to the car since you bought it, a camera say or 12v socket extended with anything plugged into it?

No nothing has been added to the car since we bought it. Car has started fine every time since that one occasion on Tuesday. It was 34c temperature on Tuesday. Just very odd. I'm hoping it's a duff battery that just needs replacing. The only other thing I can think of is maybe my wife didn't close a door fully or something like that. But she does not recall.

7 hours ago, Warrior193 said:

What instrument was used to get the 12.8 volt battery reading - and under what conditions?

I have a multi meter. The reading was taken after she got home. But I understand it should really be left half an HR or so to get a true resting voltage.

12 hours ago, nta16 said:

If the recharging isn't left on long enough then it may take two or more sessions to get the battery back to "full", low amps for long and slow charging is generally better than high amps for quicker recharging on a truly flat battery. After this you shouldn't need to charge it every night that unless the battery is weak and/or you're using a lot of electricity when the car is driven and/or parked up. Do follow the instructions for battery charging in the 'Owner's Manual' to ensure the car's computer knows what's going on.

If you are using your charger maintainer every night as a maintainer until you are sure of the car and the battery to reassure your wife and yourself that's a different matter and understandable.

Have you added anything electrical to the car since you bought it, a camera say or 12v socket extended with anything plugged into it?

I haven't been able to leave it on long enough to get it full. It needs to be used pretty much everyday.

I checked the battery with my meter last night after it had been sitting for a couple of hours, and it read as 12.7V, which was 10pm. I've just been out and read it again, and it's dropped to 12.54V. So it either is capable of holding a full charge or something is drawing power out of it. Its a stock car no dash cams or anything. all doors closed, lights off windows closed.

A voltage drop is normal, due to surface charge dissipation, once charging is stopped. 12.54 is about 85% fully charged for AGM/EFB.

If you unlocked the car to get the 12.54 volt reading, there will be modules awake and drawing power.

There will always be a very small discharge, even with everything switched off and modules in sleep mode.

15 hours ago, Itsrelfy said:

I have a multi meter. The reading was taken after she got home. But I understand it should really be left half an HR or so to get a true resting voltage.

A lot more than half an hour, that might only be enough to get some of the computer systems asleep anyway. You are best to take a reading as many hours later as possible, then perhaps allow a 0.2v or 0.3v drop if the car's systems are running and not asleep.

15 hours ago, Itsrelfy said:

I haven't been able to leave it on long enough to get it full. It needs to be used pretty much everyday.

Yeah it will take more than one session to get to full with the battery so low it won't start the car (24+ hours with 4-amps) so just keep topping up as much as you can each day until full.

It's as Warrior has put above. If it drops quickly from say the 12.54v then the battery might have been bu**ered up or you have a drain from something.

The car's battery system doesn't want the battery at 100% - but that doesn't mean it can stop you fully recharging the battery with an appropriate charger maintainer which is a good idea occasionally (particularly as an occasional preventative measure).

The main thing is if the battery can hold a good charge after a good load has been put on it.

Let us know how you get on, you really want a printed battery health report from the seller, or a new battery 'coded in' for added reassurance and the chance to keep the new battery in good condition for a long reliable life.

4 hours ago, nta16 said:

A lot more than half an hour, that might only be enough to get some of the computer systems asleep anyway. You are best to take a reading as many hours later as possible, then perhaps allow a 0.2v or 0.3v drop if the car's systems are running and not asleep.

Yeah it will take more than one session to get to full with the battery so low it won't start the car (24+ hours with 4-amps) so just keep topping up as much as you can each day until full.

It's as Warrior has put above. If it drops quickly from say the 12.54v then the battery might have been bu**ered up or you have a drain from something.

The car's battery system doesn't want the battery at 100% - but that doesn't mean it can stop you fully recharging the battery with an appropriate charger maintainer which is a good idea occasionally (particularly as an occasional preventative measure).

The main thing is if the battery can hold a good charge after a good load has been put on it.

Let us know how you get on, you really want a printed battery health report from the seller, or a new battery 'coded in' for added reassurance and the chance to keep the new battery in good condition for a long reliable life.

When I get it to the dealership next Friday I'll see what they say and update.

Is it possible that something was left drawing power to cause the original failure to start?

Have you tested the battery terminal voltage with the engine running?

Got the car back from Skoda. They had it over the weekend. Tested the battery and checked it's health and they say everything is ok. They charged it fully over the weekend and we're happy with it. They saw all the codes and reset them, none returned. Said to keep an eye on it. So we will see how we go I guess. It has been fine since the issue occured.

Fully charging the battery is a good idea and clearing the error codes as computers are extremely dumb and easily confused by their own messages (an error codes). It would probably pay to keep on the on the battery state of charge as the battery really has to be hammered to get to a state where it can't start the engine on modern cars. As you have seen well before that there should be warnings and lots of (unseen error codes). The battery has been weakened by this experience and if it's an original factory fitted battery it might have had its useful life shortened.

You really need to know what caused the battery to be so low, was there a drain, a mistake made with leaving something on when the engine wasn't running, or is there a VWŠkoda fault with the car. See my first post here to possibly help avoid the same situation reoccurring too soon. Also consider preventative charging using a charger, best to get the battery to full even if it takes more than one session and going lower and slower will get more of the Henikein effect.

Good luck, let us know if this returns.