I put my battery on charge around every 3-4 weeks (C-tek) my milage is lower than usual due to operation complications

1 hour ago, gumdrop said:

I put my battery on charge around every 3-4 weeks (C-tek) my milage is lower than usual due to operation complications

Even if your battery is fully charged, assuming its a VAG car, then it will still only be at 85% SOC and assuming ~ 75AH battery, it will still take around 24 hrs to bring it up to 100% assuming your smart charger is probably only charging at about 0.8A after its initial 3/5A or whatever, i wonder would my 6.5 year old battery now achieve this, I might, for the first time in 62 years give that a go but just wonder would it confuse the cars BMS which always charges at 14.8V on car overrun, my car too does very short runs but daily runs and I did see the SOC down to 73% (previous post) at one stage but it never affected the stop/start when I occasionally use it as circumstances dictate

@Johngerard these VW stop/start cars will first not operate the stop/start system when the battery is too low for the computer system then if the battery isn't charged enough, by driving the car enough with enough net input to the battery, or using an appropriate battery charger maintainer following the instructions in the 'Owner's Manual' and for charger maintainer, then unexpected various issues, warnings and unseen error codes can follow. There are lots of threads and posts on Briskoda about this for the various models.

It confuses some owners as they think the battery is fine because the headlights seem bright enough and the engine starts easily on key turn / button press, but this is the last thing to go and by then obviously the battery is very low (but possibly can still be recovered for more reliable use but that depends on how much and how long it's been flogged).

Modern cars are not like the older cars as the engine still starts even when the battery is far to low for the liking of the computer systems.

Until 3 years ago, and for the previous 16 years, my one and only everyday (and all else) car was a 1973 MG Midget which was a basic car even when new had it been a few months older it would have had a dynamo rather than an alternator, four fuses in the box plus a factory inline. Previous to the MG Midget going back 15-20+ years from it I had various British 60s and 70s cars as everyday, commute, work, holidays and club events use so I've always known the importance of having a good battery in good condition as generally if the engine starts you could at least get home in the car.

I was bought a battery charger by my neighbour in the 90s but only once had to use it in our old, or new, cars and that was totally my fault for flattening the battery trying to start it when I'd messed something up on the car - then my wife bought a VW stop/start product . . .

Well done on getting 6.5 years out of the battery so far, VW want you to change the battery at 4(?) or 5 years (have a look in your 'Owner's Manual' and many owners don't get that far. Also one person's definition of a short journey is a reasonable length journey to another, I'm use to neighbours' car doing less than 1,000 miles or less a year some hardly into hundreds, two at the moment have been months without being driven.

Edited 24 August, 202524 Aug by nta16

Please ignore me. I deleted what i posted.

I had not seen several of the posts before i posted.

..........

One thing that people need to be aware of is using the term Charged to 100%.

There are batteries and systems and the space left in batteries is for regeneration.

Edited 24 August, 202524 Aug by Ootohere

49 minutes ago, nta16 said:

@Johngerard these VW stop/start cars will first not operate the stop/start system when the battery is too low for the computer system then if the battery isn't charged enough, by driving the car enough with enough net input to the battery, or using an appropriate battery charger maintainer following the instructions in the 'Owner's Manual' and for charger maintainer, then unexpected various issues, warnings and unseen error codes can follow. There are lots of threads and posts on Briskoda about this for the various models.

It confuses some owners as they think the battery is fine because the headlights seem bright enough and the engine starts easily on key turn / button press, but this is the last thing to go and by then obviously the battery is very low (but possibly can still be recovered for more reliable use but that depends on how much and how long it's been flogged).

Modern cars are not like the older cars as the engine still starts even when the battery is far to low for the liking of the computer systems.

Until 3 years ago, and for the previous 16 years, my one and only everyday (and all else) car was a 1973 MG Midget which was a basic car even when new had it been a few months older it would have had a dynamo rather than an alternator, four fuses in the box plus a factory inline. Previous to the MG Midget going back 15-20+ years from it I had various British 60s and 70s cars as everyday, commute, work, holidays and club events use so I've always known the importance of having a good battery in good condition as generally if the engine starts you could at least get home in the car.

I was bought a battery charger by my neighbour in the 90s but only once had to use it in our old, or new, cars and that was totally my fault for flattening the battery trying to start it when I'd messed something up on the car - then my wife bought a VW stop/start product . . .

Well done on getting 6.5 years out of the battery so far, VW want you to change the battery at 4(?) or 5 years (have a look in your 'Owner's Manual' and many owners don't get that far. Also one person's definition of a short journey is a reasonable length journey to another, I'm use to neighbours' car doing less than 1,000 miles or less a year some hardly into hundreds, two at the moment have been months without being driven.

The parasitic loss in this car must be very very low because we often go abroad for 10 days or so, on return, as soon as the car has travelled its mandatory 500 meters to arm the stop/start, the engine will immediately shut down if I re enable it, I can't remember but I think the low voltage inhibit is set at something like 12/12.5V, however even though its never lower than 13.2/13.5V with all auxiliaries on the stop/start is disabled at fairly high electrical loads. It clearly states in the manual that one of the conditions for enabling the stop/start is that "a minimum engine temperature has been reached" This certainly does't apply to this car, as long as the ambient temperature is > -2C then the stop/start is enabled once you drive 500 meters even after been parked up all night, however I don't get neurotic about it as I do find it useful at times.

1 hour ago, Ootohere said:

Please ignore me. I deleted what i posted.

I had not seen several of the posts before i posted.

..........

One thing that people need to be aware of is using the term Charged to 100%.

There are batteries and systems and the space left in batteries is for regeneration.

I'm not sure but I think I did see the voltage drop from its usual 14.8V on overrun to 13.6 ish on a 4 hour trip one time, so probably will do likewise if "100%" charged?

Sounds like your short trips are longer then many other owners trips and you use less electric than some other owners (and probably less wasteful about the use). A 2019 Polo would (probably) have less comfort features and possibly less driver "aids" and "assists" than later years (thank gawd in my tastes) with perhaps the computers going into rest sooner after you park and lock up and you probably have less gadgets running with the car in use or parked up.

In the VWŠkoda 'Owner's manuals' (well the ones I've looked at) it has to disconnect the battery if the car isn't used for 4-weeks and later 3-weeks (IiRC) this will be over cautious for some and perhaps good advice for others but they will generally be the ones to ignore it and the car will generally open and engine will generally start so reinforcing that things like this can be dismissed, which often they can - but of course the number one reason for breakdown call-outs is . . .

Very few owners read the 'Owner's manual' (for anything if it's a Billy-big-*******s macho man, or many engineers or tradesmen) other than perhaps very rare occasional glances and of course now many they consult the internet for everything where they may well find the correct info, or near enough (or not).

Some take great exception to me charging my wife's 2015 car 12v battery to 100%, seem to take it as a personal assault on them, and rightly point out the car's system will soon have it back to it's ay 80% charge but total missing or ignoring why I charge the battery to 100%.

An occasional preventative recharge using my Ring 4-amp charger maintainer has taken up to 15 hours (IIRC) which also seems to upset some but my attendance in this is about 5-minutes including getting the charger out of the shed and hooking it up an, putting away again and very occasional glances from inside a warm, dry building. It's clean-hands, very easy, quick and comfortable 'work' which is very unusual when farting about with cars and I can be away from the car doing something more interesting than farting about with cars which for me is most things.

This thread has, sadly, descended into a lot of whataboutery.

There is some hugely uniformed opinion based on what folks did 20 plus years ago. I'm old enough to remember back 50 years to what we did to keep simple lead / acid batteries in good nick. But I'm also wise enough to understand that technology has moved on.

Geez would love to get 8 years out of any battery. My 4 VW's got about 4 1/2 years out of each battery and that seems to be about average.

Shortest time I ever got was 3 months when I left the heated rear window on in my Falcon taxi and fried a tractor battery. LOL

3 hours ago, Aldfort said:

This thread has, sadly, descended into a lot of whataboutery.

There is some hugely uniformed opinion based on what folks did 20 plus years ago. I'm old enough to remember back 50 years to what we did to keep simple lead / acid batteries in good nick. But I'm also wise enough to understand that technology has moved on.

😄 You wanna get yourself a marketing job with VW or Ctek and at least get some money.

I've been charging a 4-year old AGM battery with a 2023 (so-called) "smart" charger so the furthest my uniformed opinion goes back for practical and actual charging of a VW(Škoda) is to 2023.

When the battery fails because of my uniformed opinion I'll let you know. 😉 VWŠkoda would have my wife change the battery on her 2015 model next year at 5 years old - if I've not killed it before then. 😄

39 minutes ago, Exkiwi said:

Geez would love to get 8 years out of any battery. My 4 VW's got about 4 1/2 years out of each battery and that seems to be about average.

For you.

Others get a lot longer - but there are many variables, including the person with the car and battery. Plus you might be somewhere very hot in Australia, the UK is only at the start(-ish) of that.

Batteries are a bit of a mystery to me, you frequently read posts re over and under charging or whatever, I knew several people who's batteries lasted for 8+ years, even though constant charging at 14.2/14.4V while driving for well over 4 hrs every day, my own cars, with bog standard lead acid (original) batteries all lasted for 10+ years, also charging at this constant 14.2/14.4V, some cars doing aroud 15K miles/year, others ~ 3k miles/year, but very rarely if ever requiring topping up with a drop of distilled water. Fast forward to modern times where batteries are now only charged to ~ 85% SOC so I wonder does this give reduced or increased battery life vs 100% SOC assuming same operating conditions. I would also be a bit doubtful about the longevity of battery life where the car is only used say once every few weeks but kept fully charged with a smart battery charger, but perhaps they do/will last for years.

My only experience of "shelf like" charging is the 12V 7.2AH battery in my house alarm cabinet which only ever operates in anger during the very very seldom times when we get a elec mains blackout of generally a few hous only, I replaced it after 7 years purely as a routine. This battery is charged continuously while installed in the alarm cabinet.

Edited 25 August, 202525 Aug by Johngerard

Well Im not into voltages and stuffing around. My 4 VW's in last 12 years have all done the same thing. S/S gives up for lack of battery grunt. In the Passat I hooked the Ctek up and persisted for about 6 months and got P'd off and put a new battery in and no more trouble. We have 2 cars and most of the time neither get used much and so the battery doesnt get charged enough. First indication of a failed battery is a dash full of lights when trying to start and then S/S not working. Is not worth stuffing around with so just stuff a new one in and code it and forget about it.. If you have starting problems there is 2 ways to check. Go to a battery place and get them to load test it or as someone posted put your meter across terminals and try to start it. if arse falls out of the reading you have the answer.

1 hour ago, Johngerard said:

Fast forward to modern times where batteries are now only charged to ~ 85% SOC so I wonder does this give reduced or increased battery life vs 100% SOC assuming same operating conditions.

'They say' the stop/start batteries are for such use. Based on the evidence of the many threads and posts here and my 'logic' the batteries don't last as long as they could but as I put different people use different amounts of electric and the modern the car the more 'blessed' they are with gadgetry. With the newer models some owners have posted here about getting only 3 or 4 years out of the (expensive replacement) batteries.

Most car batteries now I think are properly sealed, not like the former pretend ones where you could peel back the labels and take the cell caps off. Some have that floating ball 'magic eye' thing which I used to find unreliable but it get extra battery sales. The old and current battery testers could also be used to get extra sales, sometimes a bit like saying there's not much fuel left in the tank so the car will stop soon so you need to buy a new car. 😄 "Yeah, I've tested your battery and it's no good but we can fit you a new one" some RAC recovery men seem to do that, they must be on commission for their very expensive battery fitting service.

The 12v batteries that VW fit to the VWŠkodas, I've seen mentioned here anyway, aren't that different at all to 50 years ago, bigger and heavier certainly but VW like that in their wide overweight cars. There seems to be all sorts of things 'they say' about what you can't do with these batteries or er, I don't know, you'll kill 'em, the car will be destroyed, you're taking the souls of others to hell, I've no idea. a long time back I put I always charge check and battery charger(maintainer) charge a new 12v battery to 100% full before I fit it to the car and some treated that as if I'd insulted their wives so I got a quote from the supplier of the battery (a well known supplier here) who put that was fine, but still that wasn't good enough so I gave up on that then.

You can honestly get away with murdering the 12v battery on a modern car, keeping it below or well below a reasonable state of charge for the computers and other systems for months on end - then the battery fails so it must be a duff battery. 😄 A few times on here I've seen Dealerships (and garages) get a s/h car in and it's battery might be low, the car may sit unsold for a while then is sold and the buyer finds problems with the battery and the seller argues the battery is fine. They usually have far too much standing stock to worry about charging batteries.

You'll be fine with your battery, as Ootofhere put you know the scores on the doors from your decades of experience and you seem to have read up about these "new" battery types. As I put before 3k-miles a year is high mileage to some of my neighbours, one has a 9 year old car with just turned past 9k-miles recently and the majority of the mileage was on the car when they bought it a number of years ago, they had a new large expensive battery fitted last year or year before, not part of the monthly paid servicing contract, no stop/start or VW product but (old-style) automatic.

12 minutes ago, Exkiwi said:

First indication of a failed battery is a dash full of lights when trying to start and then S/S not working.

Other way round.

13 minutes ago, Exkiwi said:

Is not worth stuffing around with so just stuff a new one in and code it and forget about it.

For you and perhaps others maybe.

18 minutes ago, Exkiwi said:

In the Passat I hooked the Ctek up and persisted for about 6 months and got P'd off and put a new battery in and no more trouble.

You're shutting the gate after the horse has bolted and blaming the horse. You can obviously afford the costs and not worried about a bit of waste, you do what you want to do no-one is stopping you, but why not let others offer alternatives, these can easily be ignored or taken up.

19 minutes ago, Exkiwi said:

If you have starting problems

By the time a modern car has engine starting problems the battery is very low indeed, one of the last things to go, either the battery has been well drained in which case it might be easily recharged with the very simple method mentioned countless times or if the battery has been flogged far too often and far too long the chance of reviving the battery by recharging get significantly less and if the user is the type to keep repeating this behaviour then yes probably best to replace the battery - or if someone would just sooner replace the battery that's their choice but you'd hope they'd not moan about it.

27 minutes ago, Exkiwi said:

put your meter across terminals and try to start it. if arse falls out of the reading you have the answer.

Loas test, as with any other test, should be repeated, first test might show reasonable, but if first test is very bad then the rare thing 'common sense' could be introduced.

When are we getting off this roundabout, don't you ever get dizzy . . .

On 24/08/2025 at 11:28, Johngerard said:

Even if your battery is fully charged, assuming its a VAG car, then it will still only be at 85% SOC and assuming ~ 75AH battery, it will still take around 24 hrs to bring it up to 100% assuming your smart charger is probably only charging at about 0.8A after its initial 3/5A or whatever, i wonder would my 6.5 year old battery now achieve this, I might, for the first time in 62 years give that a go but just wonder would it confuse the cars BMS which always charges at 14.8V on car overrun, my car too does very short runs but daily runs and I did see the SOC down to 73% (previous post) at one stage but it never affected the stop/start when I occasionally use it as circumstances dictate

This is the reason for attaching the charger negative lead to the tag on the firewall bulkhead - rather than the negative terminal of the battery.

I'm out of this thread, Just for info you can, for about £45, buy a battery tester that tests every aspect of all types of battery.

It'll detect cranking voltage, starter issues form excess current draw, will also determine charging voltage and ripple current as well as giving overall state of health reports.

Nothing surprises me anymore, re what you can buy these days. I suppose it's just knowing what is good and what is not so good ill say.

I've booked the car into Skoda for Thursday, so see what they say. Deep down I hope it's just battery replacement and the faults all go away.

The one thing I don't like with a dealer, you don't get the opportunity to talk to the person who carried out the investigation and repair.

On 24/08/2025 at 14:24, Johngerard said:

The parasitic loss in this car must be very very low because we often go abroad for 10 days or so, on return, as soon as the car has travelled its mandatory 500 meters to arm the stop/start, the engine will immediately shut down if I re enable it, I can't remember but I think the low voltage inhibit is set at something like 12/12.5V, however even though its never lower than 13.2/13.5V with all auxiliaries on the stop/start is disabled at fairly high electrical loads. It clearly states in the manual that one of the conditions for enabling the stop/start is that "a minimum engine temperature has been reached" This certainly does't apply to this car, as long as the ambient temperature is > -2C then the stop/start is enabled once you drive 500 meters even after been parked up all night, however I don't get neurotic about it as I do find it useful at times.

500 metres might just be enough to get the primary coolant circuit hot enough for SS to be activated

1 hour ago, Warrior193 said:

500 metres might just be enough to get the primary coolant circuit hot enough for SS to be activated

It most certainly wouldn't be IMO, I monitored it with the VCDS one time and coolant temp was something like 25C with a ambient of 5C after 500/600 meters, apart from being frozen almost to death if you left the stop/start enabled and just doing very short trips then you would probably need to get the engine replaced every 4 years or so as well, of course you could fit it in when they are renewing that pesky battery at the same time!.

Also, I noticed one time that after driving around 50 miles (stop/start working because the ambient was ~ 0C) when the engine etc would be well warmed up that the ambient temperature dropped below -2C and the stop/start was again disabled, logic at its very best.

The parameters in computer programs aren't always the best and VW certainly have an up and down history with their computer programs, one member posted that a professional auto-electrician put 7ah instead of 70ah when 'coding' in a new battery and the VW computer system allowed this, irony was the member could have 'coded' the battery himself but was too busy and left it to a professional.

23 hours ago, EMike said:

The one thing I don't like with a dealer, you don't get the opportunity to talk to the person who carried out the investigation and repair.

Could you not take it to a good (VW) independent where that should be easily possible if they've not already detailed the work or told you about it at collection, Dealerships are more interested in tick(lie)sheets and the staff looking for more chargeable work on your car to increase their revenue and profits.

Investigation might just be plugging in the scan tool, if available, then firing off the parts cannon rather than proper diagnostics which the staff may not be allowed to do for various reasons even if they want to and able. I see some good Dealerships might exist from what other members write but generally that's not my experience, then independent garages are often a let down. I've finally found an honest garage fairly local to us, they close for lunch and full weekends, that was a good sign to me, look after the staff to look after the customers, also recommended by reliable people we know.

Good luck to you, let us know how you get on.

There are many differences among VW Group Stop / Starts.

I could reverse the 2016 Seat Alhambra 2.0 TDI SCR DSG from the front of my house and across the pavement when weather below freezing first start of the day, select D and move 20 yards to the main road & it would stop the engine. 'Autohold enabled' Stop / Start enabled. Heated rear screen, mirrors & fan on.

Restart with a wiggle of the steering wheel or touch the accelerator or brake pedal.

It was that way from new and until it was handed back 3 years later. A decent sized battery fitted.

Same with hot weather and AC on. Stop / Start always there ready to do it,s stuff.

The heated rear screen doesn't activate until the engine is running even if switched on I think, and has been that way for years.

For the first time in over 62 years of driving I put my battery on charge for 2 x 12 periods, the smart chargedr is a 5A, Ultimate Speed ULGD 5.0 C1, it charged at a continuos ~ 13.1V after briefly hitting 14.4V for a few minutes and should have been charging at ~ 0.7/0.8A which is "verified" by the charge level increasing from 66%(24AH) to 74%(32AH) in the first 12 hrs charge period, this charge level stayed the same for the next 12 hr charge period which suggests to me that this my new now max charging level, the Alternator is fine because at idling, with the fan speed on its max of 4, the HRS ON and the headlights on, it still slightly charges at ~ 0.2A, the battery at idling at 13.3V and charges at slightly over 1.0A at idling or driving normally with no auxiliaries on. It doesn't run continuously at 14.8V even with the now 74% charge level which suggests that the battery is, as expected, deterioriting, after 6.5 years, so we'll see what happens.

From what I am seeing, the Stop/Start will operate (on this cart ) until the battery is on its last legs, at 65% charge level it stopped and started 6 times in less than a mile and after a hour or so the stop/start gain worked perfectly after its customery 500/600 meters.

11:12:41 30/8 engine idling

  IDE01834   Battery voltage 13.325 V

  IDE01836   Battery current 0.153 A   Fan Speed 4, HRS ON, Headlights ON.

  IDE01839   Battery charge level 74 %

  IDE01843   Battery voltage at rest 12.4 V

 

11:11:40 30/8 engine idling

  IDE01834   Battery voltage 13.500 V

  IDE01836  Batterycurren1.223V                                                                                                                                                                        

IDE01839   Battery charge level 74 %

  IDE01843   Battery voltage at rest 12.4 V

 

11:13:32 30/8

  IDE01834   Battery voltage 13.509 V

  IDE01836   Battery current 1.086 A

  IDE01839   Battery charge level 74 %

  IDE01843   Battery voltage at rest 12.4 V

 

23:34:13 28/8 After another 12 hr Smart Charging, 24 hr in all

  IDE01834   Battery voltage 12.311 V

  IDE01836   Battery current -4.305 A

  IDE01839   Battery charge level 74 %

  IDE01842   Usable battery charge 32 Ah

  IDE01843   Battery voltage at rest 12.4 V

 

23:34:13  After 12 hr Smart Charging

  IDE01834   Battery voltage 12.311 V

  IDE01836   Battery current -4.305 A

  IDE01839   Battery charge level 74 %

  IDE01842   Usable battery charge 32 Ah

  IDE01843   Battery voltage at rest 12.4 V

 

07:48:16  Before(12 hhr Smart Charging)

  IDE01836   Battery current -4.414 A

  IDE01839   Battery charge level 65 %

  IDE01842   Usable battery charge 24 Ah

  IDE01843   Battery voltage at rest 12.3 V

Edited 30 August, 202530 Aug by Johngerard