Low battery warning

[El-Cap]

Keep getting a low battery warning on the Passat estate - it’s a 2016 model. Taken it for a drive and it goes away but not before long it comes back. It’s now saying battery almost flat.

Thinking of just fitting a new battery but wondering if it need to go into a dealer rather then just kwikfit?

[philipharmes]

If it has Stop/ Start it will need an AGM replacement battery.

Then after fitting, coding with VCDS so the electronics knows there is a new battery fitted & charges accordingly.

[El-Cap]

Thanks wasn’t aware of the coding requirement. I assume any reputable garage can do that now.

[philipharmes]

"
I assume any reputable garage can do that now. "

I don't think so.

They would need specific VW software like VCDS to get into the battery module.

[jc41]

I have a similar 2015 model GT Bi-Turbo 4-Motion Passat Estate and noticed last year that cold starting the engine was beginning to sound as though the battery was approaching the end of its useful life - no battery warnings though.

I bought a replacement battery with a five year warranty from Halfords. They fitted it, then plugged in a box and pressed its buttons for a while and that was that. It seemed that the button pressing also turned off some features in the Driver Assistance Pack, but when I drove it the next day everything was working normally.

In November 2019 the battery cost £157 fitted. I see that today's price has advanced to £184.

[vince47]

You were lucky! For the first time in my long life I discovered that I should not change the battery unless I have VCDS/diagnostics to 'register it'.
So in these difficult times I decided to spend £25 for Halfords to come to my house and do it for me. The advert clearly stated they would register it with the ECU. Good. I then got confirmation of payment emails from a mobile tyre firm! (Halfords have bought them it seems). I emailed them asking them to confirm they will register the new battery with the ECU and they confirmed this by email. Bang on time the chap arrived to change the battery and I asked if he had the diagnostic gear before he started the job. He had no idea what I was talking about and 'I've done loads' he said. He then rang his manager who 'confirmed' they had a 'new way' of registering the battery. Steering wheel 3 turns left then 3 turns right. I said thats for the power steering so he decided to leave it and I got a refund. So there's a lot of B8's out there that don't have the battery registered to the ECU. The worst thing is that after a month of chasing I have not had one single call/email to apologise.
That was pretty poor but is now history, What I cant get my mind around is why this car needs a lengthy serial number copied from the battery BEM label so it knows how the charge it appropriately. Isnt the cars charging system clever enough the charge at the correct level? Modern chargers manage it. If it really needs to know its a new battery why not just tick the VCDS box to say 'New'.

[32110]

I believe that if the battery is not coded in at the time of fitting that the system will slowly adjust to a revised charging regime.

[vince47]

I believe that if the battery is not coded in at the time of fitting that the system will slowly adjust to a revised charging regime.

Hi, I would like to think that was correct but my email back from VW says a replacement battery needs to be coded and the Halfords advert says they do it. If it slowly adjusts then why go to the trouble of typing into VCDS a string of numbers copied from the new battery. All so annoying really

[MikeBz]

Different batteries have different optimum settings for bulk, absorption and float charging stages. A lot of very fancy battery chargers are programmable for each stage. Less fancy ones can at least be configured for the battery type (wet cell, gel, AGM etc.). I'm sceptical that a charger could correctly and safely auto-configure itself.

There may be safety issues with trying to charge a conventional lead acid battery as though it were an AGM battery, in the eventuality that someone put the wrong battery type in.

[32110]

In my post above I was referring to the vehicle charging system rather than external battery charger.

[MikeBz]

Yes I know, but the vehicle charging system is still a battery charger... so where I've said "sceptical that a charger could..." replace with "sceptcal that a charging system, whether internal or external, could...".

[32110]

I believe the charging system in the latest models is fairly intelligent thus the need to recode a new battery but I could be wrong:confused:

[MikeBz]

I may well be wrong, I'm just sceptical that it's possible to build in intelligence that means the system doesn't need some battery parameters in order to charge it both optimally and safely. Specifically it's post #7 (http://www.vwaudiforum.co.uk/forum/usertag.php?do=list&action=hash&hash=7) that I'm commenting on. AGM and conventional lead-acid have quite different optimal charging voltages, charging a conventional lead acid battery as though it were AGM could lead to gassing (which with a sealed battery could lead to it exploding). Anyway all I've done is thrown in some doubt so I'll leave it there.

[Mittens247]

Had this issue a few times over lockdown. Car is only driven once a week on average and twice after cold spells it wouldn't start. After recharging it was all OK. Checked with VW and batteries are guaranteed for 5 years (mine is 3.5 years old). They kept the car plugged overnight, did a battery test and it came back "battery good". I think I will bite the bullet and get a new battery sooner rather than later. Can the battery be recoded using OBDeleven?

[user name]

ok, so this is what you need to know, covid has affected a few batteries due to cars not being used. if you have a modern charger that charges an AGM battery properly put it on for 24 hours and it should be fine and pick up. If you decide you need one,
A: you dont need a radio code,
B: you only need worry about reconfiguring a new battery if it a different spec.
C: even if it is a different spec - if its a bigger spec it wont hurt the new battery, it just wont charge it up to full capacity. If its a smaller spec - you need to or it will over charge very quickly and kill your new battery.
D: you can configure it with VAG COM OR OBDELEVEN.

[MikeBz]

That's useful. Just a minor quibble, " if its a bigger spec it wont hurt the new battery (https://www.vwaudiforum.co.uk/forum/#), it just wont charge it up to full capacity" - the best way to damage a lead acid battery is to regularly fail to fully charge it. In this instance I suspect that all will happen is its capacity will gradually reduce to the meet what the charger is expecting so no real harm done.

I have suspicions about the state of the battery in my Dec '19 Passat. A couple of weeks a ago I had a week of lots of driving (a couple of 200+ mile runs, and 20-40 most other days), then a week later the car refused to start because the battery was too low. Jump started it and went for a drive, 10 mins later tried to restart it - refused. Jump started it again to get it home (battery was at 11.8V, not good) and then put the battery charger on for 24 hours after which it started. I've always had suspicions because unlike the previous 2 Passats, where the stop-start system stopped the engine almost every time you came to a stop, on this one it hardly ever stops it - even after a 4 hour daylight drive with no air-con etc. you can come to a stop and the A symbol on the dash has the line through it meaning that it doesn't want to do it for some reason (e.g. battery too low). On the very rare occasion that it does stop the engine it generally restarts it after anywhere between 5 and 15 seconds. Maybe the battery has always been slightly dodgy.

Car is still under warranty so it's booked in to a VW dealer for a battery test next week.

[user name]

Mike, an AGM isn't a lead acid battery.....
The other thing is it charges differently, even when fully charged it will only show about 12.6. Question. When did it start normally? After it was trickle charged? You may have an alternator/charging problem rather than a battery problem

[32110]

AGM IS a lead acid battery but with major improvements over the older batteries. As with many advances in technology they were developed by the military in the 1980s.

[MikeBz]

Mike, an AGM isn't a lead acid battery.....

Oh yes it is :o ... it's not a 'wet' cell lead acid battery, but it is lead acid. The acid is Absorbed in a Glass Mat, the plates are lead. AGM batteries have a lower internal resistance and hence will charge a lot faster (draw a higher charge current for a given applied voltage). I use AGM batteries as leisure batteries on a boat for that very reason (though they stay at around 13V for a long time after a full charge, and only decay to around 12.8V after the surface charge has dissipated).

Useful info here on different types of batteries and absorption/float charge voltages: 5 Battery Types Explained - Sealed, AGM, Gel | BatteryStuff (https://www.batterystuff.com/kb/articles/5-battery-types-explained-sealed-agm-gel.html)


Question. When did it start normally? After it was trickle charged? You may have an alternator/charging problem rather than a battery problem

Yes after a day on the charger it started OK. I had the same thought as you about a charging problem. When the battery was down at 11.8V I monitored the voltage with the engine running after a jump start (jump battery now disconnected), it was showing around 12.5-12.6V (more revs made no difference) which is nowhere near enough to properly charge the battery - so that point I did suspect the alternator/charging system. However after charging the battery and starting the engine from it unassisted the voltage with the engine running was showing 14.8. I wonder whether the charging system has some intelligence built in such that if the battery is really low it does some sort of soft-start on the charging, and I just didn't monitor it for long enough when it was showing 12.6V.

I'm going to monitor the battery voltage over the next couple of days and see if it drops significantly when the car is sitting unused.

[user name]

If you want to picky you will find it was developed FOR the military it will be a cold day in hell when the military starts inventing batteries. I was trying to point out they are different that's all. Alternator charging should be around 14.4 so if your car Alternator is only charging at 12.6 you have your culprit.

[MikeBz]

If you want to picky you will find it was developed FOR the military it will be a cold day in hell when the military starts inventing batteries. I was trying to point out they are different that's all.

***? You said "Mike, AGM is not lead acid", so I said "Oh yes it is" (which it is) with a smiley, and pointed out why. I haven't claimed credit for anything. No I'm not a yank and I made no comments about who invented it or why.


Alternator charging should be around 14.4 so if your car Alternator is only charging at 12.6 you have your culprit.

I had the same thought as you about a charging problem. When the battery (https://www.vwaudiforum.co.uk/forum/#) was down at 11.8V I monitored the voltage with the engine running after a jump start (jump battery now disconnected), it was showing around 12.5-12.6V (more revs made no difference) which is nowhere near enough to properly charge the battery - so that point I did suspect the alternator/charging system. However after charging the battery (https://www.vwaudiforum.co.uk/forum/#) and starting the engine from it unassisted the voltage with the engine running was showing 14.8. I wonder whether the charging system has some intelligence built in such that if the battery (https://www.vwaudiforum.co.uk/forum/#) is really low it does some sort of soft-start on the charging, and I just didn't monitor it for long enough when it was showing 12.6V.

[Mittens247]

That's useful. Just a minor quibble, " if its a bigger spec it wont hurt the new battery (https://www.vwaudiforum.co.uk/forum/#), it just wont charge it up to full capacity" - the best way to damage a lead acid battery is to regularly fail to fully charge it. In this instance I suspect that all will happen is its capacity will gradually reduce to the meet what the charger is expecting so no real harm done.

I have suspicions about the state of the battery in my Dec '19 Passat. A couple of weeks a ago I had a week of lots of driving (a couple of 200+ mile runs, and 20-40 most other days), then a week later the car refused to start because the battery was too low. Jump started it and went for a drive, 10 mins later tried to restart it - refused. Jump started it again to get it home (battery was at 11.8V, not good) and then put the battery charger on for 24 hours after which it started. I've always had suspicions because unlike the previous 2 Passats, where the stop-start system stopped the engine almost every time you came to a stop, on this one it hardly ever stops it - even after a 4 hour daylight drive with no air-con etc. you can come to a stop and the A symbol on the dash has the line through it meaning that it doesn't want to do it for some reason (e.g. battery too low). On the very rare occasion that it does stop the engine it generally restarts it after anywhere between 5 and 15 seconds. Maybe the battery has always been slightly dodgy.

Car is still under warranty so it's booked in to a VW dealer for a battery test next week.
I had the same issues and car went into VW for a battery test. This is a binary test (only shows pass or fail) and they needed the car overnight. The problem persisted and I checked the alternator which as Ok, so I began to think it might be a parasitic drain. Long story short, replaced EFB with an AGM battery and it all seems Ok so far.

VW batteries have a 5 year warranty. If VW say battery is good, then suggest they carry out a parasitic drain test and check alternator.

[MikeBz]

VW service centre had the car for 90 minutes and say they checked everything out - all OK except the battery which has been replaced under warranty. Drove for about an hour afterwards and put the meter on the battery - just under 12.6V with and without the engine running. So that leaves me still suspicious of the charging system, but I note many threads on other forums which talk about the charging system aiming to keep the battery SoC between 50 and 80% charged to save fuel (by not charging it to 100%). It might save a few drops of fuel but it will shorten the battery life - this isn't progress... Lots of reports of premature EFB battery failures in VAG cars on other forums.

[Mittens247]

VW service centre had the car for 90 minutes and say they checked everything out - all OK except the battery which has been replaced under warranty. Drove for about an hour afterwards and put the meter on the battery - just under 12.6V with and without the engine running. So that leaves me still suspicious of the charging system, but I note many threads on other forums which talk about the charging system aiming to keep the battery SoC between 50 and 80% charged to save fuel (by not charging it to 100%). It might save a few drops of fuel but it will shorten the battery life - this isn't progress... Lots of reports of premature EFB battery failures in VAG cars on other forums.
Was the replacement AGM for AGM or EFB for EFB?

[MikeBz]

Was the replacement AGM for AGM or EFB for EFB?

EFB for EFB - Moll, same as the faulty one. I see from other forums that there was a bad batch of Moll batteries a few years ago - it seemed to pre-date my car although I guess its possible it was from the batch. I didn't have to mention 'warranty', they just told me what they'd found and handed me the key.

[mike6265]

This is an old thread but I have a similar problem.

1997 Passat Estate B8. So coming towards 5 years. Not used too much in the last couple of years but battery warning after a week of no use every so often.

With years of experience I think the easiest solution is get a new battery (it is 4 1/2 years old)

My question is. Do I get VW to replace it or is Halfords (possibly easiest) just as good?

I know it seems a simple question - not too worried about cost (sorry but looking for easiest solution) but concerned about getting it correct first time.

[vince47]

If you are thinking of Halfords, beware and read my experience near the start of this thread (5th Feb). Cant say every area is that bad but I will never use Halfords again

[MikeBz]

This is an old thread but I have a similar problem.

1997 Passat Estate B8. So coming towards 5 years. Not used too much in the last couple of years but battery warning after a week of no use every so often.

With years of experience I think the easiest solution is get a new battery (it is 4 1/2 years old)

My question is. Do I get VW to replace it or is Halfords (possibly easiest) just as good?

I know it seems a simple question - not too worried about cost (sorry but looking for easiest solution) but concerned about getting it correct first time.

I guess you mean 2017? I would first try giving the battery a proper full charge, but it may be that long periods of only being partially charged (or more likely rarely fully charged) have reduced its capacity. If it needs to be replaced then TBH if I were paying I would just source the battery from an online battery retailer and fit it myself - with the caveat that I don't know whether completely disconnecting the battery would require anything in the car to be reset/programmed etc, but I could fashion a way of keeping 12V power to the car whilst I swapped the battery over.

[jc41]

My battery gave signs that it was coming towards the end of its useful life after 4 1/2 years. Starting the engine from cold as Winter approached just didn't sound right. There was no dashboard warning light to say there was a battery problem and it always started alright, but I was concerned it wouldn't for much longer. When a battery does fail, it always seems to be at the most inconvenient time and place and everywhere is closed.

Halfords fitted a replacement AGM battery, for which they charged £25 extra.

Removing and replacing the battery is somewhat awkward, because of poor access to the compartment where it is installed. You may want to keep an eye on its fitting; I had to show the young man, who did the work, where the battery was and how to gain access to it and refit the panel etc. After the new battery was fitted, an older man with a gizmo appeared. He plugged it into the Service socket and pressed buttons and that was about it.

So no problem getting it done outside the VW garage network, but the choice of battery manufacturer may be limited.

VW Passat GT 4-Motion 2.0 BiTdi Estate, 2015 model

[jc41]

My battery gave signs that it was coming towards the end of its useful life after 4 1/2 years. Starting the engine from cold as Winter approached just didn't sound right. There was no dashboard warning light to say there was a battery problem and it always started alright, but I was concerned it wouldn't for much longer. When a battery does fail, it always seems to be at the most inconvenient time and place and everywhere is closed.

Halfords fitted a replacement AGM battery, for which they charged £25 extra.

Removing and replacing the battery is somewhat awkward, because of poor access to the compartment where it is installed. You may want to keep an eye on its fitting; I had to show the young man, who did the work, where the battery was and how to gain access to it and refit the panel etc. After the new battery was fitted, an older man with a gizmo appeared. He plugged it into the Service socket and pressed buttons and that was about it.

So no problem getting it done outside the VW garage network, but the choice of battery manufacturer may be limited.

VW Passat GT 4-Motion 2.0 BiTdi Estate, 2015 model

[Mittens247]

I would recommend sourcing an 096 AGM battery from Tayna batteries and then find a local garage to fit and code it for you (assuming you have not got access to VCDS, obd11 or carista type devices). Last time I looked Varta and Bosch batteries were about £125 and maybe another £25 to fit and code. The coding takes 2 mins and only involves updating the battery type and altering the serial number.