Hi everyone.

Back in June, we bought an approved used 20 plate Karoq 2.0tsi 4x4 from our local Skoda dealership. About a month after the battery went flat. Skoda took the car back, charged the battery and tested everything, and said they couldn't find an issue. It's been fine since. Last week we went on holiday in my car and the Karoq stayed at home. Upon our return, the car started but struggled. We noticed the cruise control, even though it was on, had no symbols in the dashboard. I charged the battery overnight, and the next day the cruise control worked. The battery was showing 12.6v when sitting turned off, and when starting dropped to 10.6v. However, when sitting at idle, the battery initially shows 13.3v and then drops and shows 12.1v, which is where it stays, which to me does not seem right. I tested my car, a Skoda Superb, and at idle, mine sits at just over 14v. So it's almost like the alternator isn't working correctly, but the car does start.

Does anyone know if an alternator can do this? I just assumed it either worked or it didn't.

Thanks.

Adrian.

I admit to not fully understanding it, but modern charging doesn't seem to be constant any more. So seeing the battery level drop on idling isn't unusual. I saw this on a Polo with similar battery issues & thought the same as you. But it was just a dying battery.

I guess it's difficult to claim under warranty if it works under regular use conditions.

Dropping to 10.6v whilst cranking is not necessarily a sign of a bad battery,but it's getting close .

The bounce back to 13.3v then dropping to 12.1v could be a sign that everything is working as normal because initially after the cranking the alternator responds to put it back. Once idling it then depends upon what you have switched on in the car Lights/heater etc. Once thee engine is running the BMS starts it's process off running the car and slowly replenishing the battery

How it works from our good friends at AI

In essence a car that does mainly short trips, especially in colder weather could require maintenance charging each week.

A plug-in digital voltmeter in the 12 volt socket will allow you to monitor the alternator output, it should register something over 14 volts on braking overrun or when battery is loaded (lights, fan, steering etc)

Ok thanks for the input. I kinda just wanted to get some idea before I take it to Skoda and they tell me it's all ok. It's already left my wife stranded once when it went flat before so I'd be less than pleased if it did it a second time after Skoda telling us it's all ok. We have bought one of those jump start packs so hopefully get us out of a hole if the worst happens. But we will see what they say when it goes in on 25th November.

Has your battery actually been load tested?

I'm not totally sure. When it went in last time they just said they charged the battery and tested it and were happy with it. But what they tested im not too sure.

I'd suggest getting it properly tested - preferably by somewhere not primarily focused on selling you a new battery.

An accurate test really requires the battery to be charged to 100% first, which may not necessarily be the case with these smart alternators.

Managed to get my appointment moved to the 18th November. Bloody car wouldn't start yesterday so put the jump pack on it and got it going. The rest of the day after a drive to work and back it was ok and we charged it over night and it fired up ok this morning.

Very likely that your battery is failing.

Agreed ^^^^^. Sounds like time for a new battery. Not worth the hassle of putting up with a dying battery for £80 or so.

If you do get the battery replaced, ensure the fitter is able to adapt (code) it to the BCM.

I spoke with Skoda again yesterday evening as yesterday morning my wife took the car to go to work and it started ok. The stop start kicked in at a junction when she stopped (she forgot to disable it) then the car couldn't restart so she had to use the jump pack on it to get it going. I spoke with Skoda and asked how that was possible and they couldn't tell me. I asked if I were to go and have a new battery fitted elsewhere would they reimburse the cost and they said no. So, I'm still having to wait until next Tuesday for it to go to the garage. In the meantime time my wife is now driving mine as I don't seem this safe now. Yesterday evening when my wife bought it home she left it running on the drive and the battery with the car running showed 14.5v which to me shows the alternator was working. When I shut it off it rapidly dropped to 12.3v and then upon starting it again it fell to under 9v briefly before recovering again.

So it's got to need a new battery l, but I'm still.notnconvinced the alternator is doing its job correctly either.

8.8v on start up

Bit odd that stop/start would work if the battery is iffy - mostly people complain it hardly ever works.

Bit of a faff if you're both working so probably not worth it now, but if it fails again you could call Skoda Assist - if it needs to go into a dealer they can jump the queue.

Sounds like maybe a poor connection. I'd disconnect the battery, check both posts & clamps are clean & then reconnect, making sure everything's nice & tight.

Reading back through the thread the car is five years old so if it is the original battery that is the most likely problem.

So effectively we are discussing who is responsible for paying for it.

Strictly speaking within 5 months of car purchase it's the Dealer.

It's automatically their responsibility to fix it.

But they have the right to check it's faulty and not just happening because of the way the car is used. This takes time.

If it was me for the sake of a Battery and my Wife's safety and convenience I would have replaced the battery.

Hopefully they will replace it next Tuesday but I would have put my time above the price of sorting this out a fortnight ago.

6 minutes ago, Stonekeeper said:

Reading back through the thread the car is five years old so if it is the original battery that is the most likely problem.

So effectively we are discussing who is responsible for paying for it.

Strictly speaking within 5 months of car purchase it's the Dealer.

It's automatically their responsibility to fix it.

But they have the right to check it's faulty and not just happening because of the way the car is used. This takes time.

If it was me for the sake of a Battery and my Wife's safety and convenience I would have replaced the battery.

Hopefully they will replace it next Tuesday but I would have put my time above the price of sorting this out a fortnight ago.

But what if the issue isn't the battery alone? It's ok saying go and buy a new battery, but if the alternator is also faulty or there is an issue somewhere else, a new battery isn't going to fix my problem. I'd happily go and find someone if Skoda paid for the cost. I don't see why I should have to pay to fix a fault in a car that we've owned less then 6 months. But because they won't do the right thing I have no choice but to wait.

My frustration is, we bought this to Skoda's attention in July and we were told nothing wrong, your wife must have left something open or on. Which clearly isn't the case. But quite clearly there is something wrong.

In my view Skoda should have said bring it in and we will find time to look at it.

I'm not a mechanic so I can't say either a new battery will sort the issue,

1 hour ago, Itsrelfy said:

I spoke with Skoda again yesterday evening as yesterday morning my wife took the car to go to work and it started ok. The stop start kicked in at a junction when she stopped (she forgot to disable it) then the car couldn't restart so she had to use the jump pack on it to get it going. I spoke with Skoda and asked how that was possible and they couldn't tell me. I asked if I were to go and have a new battery fitted elsewhere would they reimburse the cost and they said no. So, I'm still having to wait until next Tuesday for it to go to the garage. In the meantime time my wife is now driving mine as I don't seem this safe now. Yesterday evening when my wife bought it home she left it running on the drive and the battery with the car running showed 14.5v which to me shows the alternator was working. When I shut it off it rapidly dropped to 12.3v and then upon starting it again it fell to under 9v briefly before recovering again.

So it's got to need a new battery l, but I'm still.notnconvinced the alternator is doing its job correctly either.

That is atypical for stop/start - the function should be automatically inhibited if the battery SOC is too low to allow a restart.

1 hour ago, Itsrelfy said:

8.8v on start up

That is an immediate fail - what is the reading with the engine running?

1 minute ago, Warrior193 said:

That is an immediate fail - what is the reading with the engine running?

I've had different readings the few times I've checked it. Last week when I checked it it said 12.1v whilst sitting on the drive running. So I thought maybe the alternator was faulty. Yesterday doing the same check 14.5v which would suggest the alternator was working.

Which is why I said in a post above I'm not sure that it's just the battery. Especially if you factor in the car yesterday allowed the engine to stop but then it didn't have the guts to restart. That to me points to something else.

1 minute ago, Itsrelfy said:

That to me points to something else.

As I said, possibly a bad connection. It'll take a few minutes to disconnect, clean posts & terminals & reconnect. A light going over of both with a low grit sandpaper would be good idea. If it doesn't help, at least you've ruled it out.

Edited 11 November, 202511 Nov by Rbz5416

What could possibly be happening is one (or more) cell has developed a high internal resistance, which will display a fairly reasonable voltage under no load conditions - but will severely restrict current when load is applied.

The only way to diagnose this is a proper battery load test - although your cranking voltage test does indicate the battery is either discharged or faulty.

9 minutes ago, Itsrelfy said:

My frustration is, we bought this to Skoda's attention in July and we were told nothing wrong, your wife must have left something open or on. Which clearly isn't the case. But quite clearly there is something wrong.

I understand and that is actually my point. If a fix is relatively cheap it's best to just do it because at least it eliminates the simple stuff and leaves the expensive time consuming thing to the dealers.

You had trouble in July and Skoda did what Dealers do, they can only be sure what needs to be done to confirm if they do it themselves. Charge it up and see what happens i.e "Do you come back?"

If you had come on here in July it would have been "Change the Battery"

You then came on here on 31st October and immediately were pointed towards the "battery"

Main dealers have waiting lists for scheduled work so they are doing it "As soon as they can"

I have Fords mainly and they were the same I had a dsg fail and it was a fortnight to get in, "change oil and filter" a month later it failed again another week to get in "new gearbox unit"

With Skoda i was contacted recently to book an "Inspection" when i rang "two weeks away" so I thought to also book it in for the MOT in January now in case they say "too busy" when it's due.

On the what if it isn't the battery, if in July you had just bought a Battery and the problem could have been sorted but had it continued you would now be having whatever the problem was sorted next Tuesday under the warranty. If on Tuesday they change the Battery will you "feel" any different than you do now. Because you will still have the wonder of what if it isn't.

My peace of mind is worth more than the price of a battery four or five months ago.

When they do change the battery next Tuesday and it fixes it. Start looking around for your next nearest Dealer to go to in future because the one you are using is incompetent.

Edited 11 November, 202511 Nov by Stonekeeper