The replaced under warranty (in 2019) battery is showing signs of lower voltage in local use. Car 1.4TSI still starts ok. The Stop/Start system only works after a run of 20 miles or so.

If I need to replace the battery, is the correct specification EFB or AGM? Sorry for not posting recently, my car has been wonderfully boring and reliable. Now on a fresh set of Vredestein Quatrac.

Either type will do, EFB is cheaper, AGM is supposed to be superior and last longer - but is considerably more expensive.

Be aware that you will need to adapt a new battery into the BCM, particularly if you change from one type to the other.

Do you know if this was done correctly when the battery was replaced under warranty? That AGM really should have lasted longer than that.

What do you mean by voltage is showing low in local use?

Mine was efb from factory, I had mine replaced a year ago by a trusted Independent, charged me £150 all in, inc a 2 year guarantee and they coded it in. 

I checked mine prior to a cold start and during tick over with my multi meter, then had it load tested. They confirmed it was getting down. It was 4 years old when I had it replaced. 

Edited 12 December, 20232 yr by Phoenixboy

Thanks for your explanation. I'll keep an eye on the voltage. Makes it a lot cheaper if it's an EFB type. Halfords seem to be competitive on price, if they code it in. Otherwise it'll be be my local independent garage. 

The replacement battery, under warranty,  was EFB btw.

2 hours ago, gregoir said:

Thanks for your explanation. I'll keep an eye on the voltage. Makes it a lot cheaper if it's an EFB type. Halfords seem to be competitive on price, if they code it in. Otherwise it'll be be my local independent garage. 

Be aware that some Halfrauds branches are apparently unable - or unaware of the necessity to do a battery adaptation when fitting a new battery. 

18 hours ago, ApertureS said:

What do you mean by voltage is showing low in local use?

The voltage, on idle, is not getting as high as I'd hope when doing short runs.

2 hours ago, Warrior193 said:

Be aware that some Halfrauds branches are apparently unable - or unaware of the necessity to do a battery adaptation when fitting a new battery. 

I'd check that out with them first. My local branch has always been excellent fitting batteries, wiper blades and light bulbs.

4 hours ago, gregoir said:

The replacement battery, under warranty,  was EFB btw.

Good news it was replaced under warranty, efb's were probably originally fitted because they're cheaper. 

33 minutes ago, gregoir said:

The voltage, on idle, is not getting as high as I'd hope when doing short runs.

That is very likely correct operation of the smart alternator - the only real way to check alternator output on these micro-hybrids is live data on a run - in particular, checking the output while in energy recuperation mode.

Another way could be to temporarily disconnect the battery monitoring module on the battery negative clamp. 

Edited 13 December, 20232 yr by Warrior193
grammar

Thanks for mentioning the micro hybrid system. I've no wish to try DIY diagnostics due to lack of skill and deteriorating health. I'll just have  to wait for the car to not start. A jump start pack is on hand.

Assuming (from your model year) that you do not have the SOC function in your Maxi dot display, a reasonable indication of falling battery state is the stop/start frequently not shutting the engine down when stopped in neutral - IIRC, message displayed in 'vehicle status' will be 'load too high' or something similar. 

Thanks. Stop/start has recently only worked after a long run. Not many of those recently .I experienced it not working at all before I got a new battery fitted under warranty, about 4.5 years ago. If starting gets dodgy, then a new battery will be needed.

3 hours ago, gregoir said:

The voltage, on idle, is not getting as high as I'd hope when doing short runs.

As high as you’d hope isnt a specification? 
Voltage on idle and doing short journies aren’t a correlation?

 

Im still a bit confused what the technical reason is you think the battery is faulty

6 hours ago, gregoir said:

Thanks for mentioning the micro hybrid system. I've no wish to try DIY diagnostics due to lack of skill and deteriorating health. I'll just have  to wait for the car to not start. A jump start pack is on hand.

You can get cheap voltmeters that plug into the cigarette lighter socket, which should give you an indication of what the alternator is doing under various conditions.

Depending on what the BMS thinks the battery state of charge is the voltage at idle or when driving can be anywhere between about 12V and 14.5V

16 hours ago, Rodge said:

You can get cheap voltmeters that plug into the cigarette lighter socket, which should give you an indication of what the alternator is doing under various conditions.

Yes, I already have one incorporating a USB outlet. That's how I know about the low voltage.

5 hours ago, PetrolDave said:

Depending on what the BMS thinks the battery state of charge is the voltage at idle or when driving can be anywhere between about 12V and 14.5V

It's more than simply that surely?  The Stop Start system failed to work with my previous EFB even when the voltages were normal for the system.

2 minutes ago, gregoir said:

It's more than simply that surely?  The Stop Start system failed to work with my previous EFB even when the voltages were normal for the system.

The car maintains the battery at different levels depending on the driving state in the moment as well as other factors.

 

You keep using very non specific terms like ‘voltage were normal for the system’ , how do you know what is and isn’t normal for the system and what the car wants? It could be perfectly within the cars tolerances.

 

alternators have came a long way from being used to simply pump out as much current as possible and a good alternator will vary its output from 12v-15v in some cases all to support better emissions, more power, regenerative braking, better battery life, micro hybrid systems and more.

 

if the start stop isn’t working there can be a variety of reasons and these need looking into using a diagnostic computer to see any faults or live data.

 

im still none the wiser as to what’s actually wrong with your battery other than you think something is wrong based on what?

Using the (supposedly) failure of the SS as a guide to the health of the battery is a non starter. As @ApertureS says there are many reasons for it not to work,

 

Mine can work after a few minutes driving, then a few miles later into the journey it may stop working. It usually works consistently after about an hour. I don't give myself even more grey hairs worrying about it.

 

This is with an almost 11 yr old AGM battery and SS has always been activated.

 

2 hours ago, gregoir said:

It's more than simply that surely?  The Stop Start system failed to work with my previous EFB even when the voltages were normal for the system.

The only really reliable way to test the condition of the battery is -

1 - Give it a full charge with suitable charger, ideally, a 'smart' charger.

2 - After full charge achieved, remove surface charge by allowing battery to stand for around 12 hours - or by using a load such as headlights, etc, for a short period. If the test is done while battery is connected in vehicle, you need to ensure that all control modules have been allowed sufficient time to enter sleep mode.

3 - Test battery condition with specialist battery condition tester (not expensive) - or an 'old school' high-rate discharge tester. 

Edited 14 December, 20232 yr by Warrior193
correction

@gregoir as you don't use your car in the average way you could just fully recharge the battery and extend its useful life just by using a a battery charger and maintainer.  Plenty around for £25 or less (Lidl usually have them for about £15 this time of year).   Jump start is for when things have gone too far whereas charger/maintainer can be for rescue before that or better still prevention.  You want to recharge your before you get the start/stop not being available or at least when it first starts to become available then you'll get more years out the expensive EFB (and much more expensive AGM) battery.

 

To recharge the battery just follow the instructions with the charger and in the Owner's Manual of the car.

 

For slow discharge from lack of car use and short journeys, unless you're also use lots of the electrical items in and on the car during these short journeys, best is a slow recharge, so a 3-amp or 4-amp charger and maintainer is best, it will charge the battery from shorter and heavier discharge easily too but just take longer than a 6-amp (or 8 amp) charger and maintainer.

 

My wife's car (2016 Fabia) does lots of very short journeys so I recently put the battery on charge just as a preventative measure as the time before I unexpectedly put the battery charger and maintainer on when for the first (and only time) the start/stop was unavailable from the expensive AGM battery (fitted a couple of years ago).

 

If you can cancel the jump pack and get a battery charger and maintainer as needing to jump start the car doesn't always happen at a convenient time whereas you can do preventative chargers at convenient times.

 

ETA: Using a battery charger and maintainer is a very easy and clean-hands job, it does the work whilst you're inside warm and dry doing anything a lot more interesting than farting about to keep the VW computer programs happy.

 

Photo of my wife's Fabia being charged overnight when it was around freezing (above and below) this January.

 

(Other makes, models suppliers and prices are available) - Ring RSC804 "4a Smart Battery Charger & Maintainer" (up to 90 Ah)  (they do a 6 amp version too RSC 806, up to 110 Ah))  - https://www.ringautomotive.com/en/product/RSC804

 

£23.49 - a bit less from some other places - https://www.ebay.co.uk/itm/334438759247

 

Edited 14 December, 20232 yr by nta16
ETA:

I already have the jump start pack. I bought a smart? charger a few years ago but using it on my wife's Kia just sets off the alarm. I used my Optimate battery maintainer on the Skoda via the power socket, but I note it's only intended for batteries up to 50Ah.

1 hour ago, gregoir said:

I already have the jump start pack. I bought a smart? charger a few years ago but using it on my wife's Kia just sets off the alarm. I used my Optimate battery maintainer on the Skoda via the power socket, but I note it's only intended for batteries up to 50Ah.

While not ideal, the lower capacity battery maintainer (charger?) will still keep the battery in better condition than without - it would only affect the length of time it takes to attain a full charge - and possibly any test function your Optimate maintainer has.

Re. why your using a smart charger was setting off your wife's Kia - could it have been because the alarm was sensing the hood was open while charging?