Van won't start; software fault or battery issue?

[benfarley]

Hi,

I'm new to this forum, having come across it whilst searching for help with an issue with my T6. I wonder if anyone has had similar issues. I'll try to be brief...

I own a 2021 T6.1 converted into a camper, with a split charger to enable the leisure battery to be charged when running. The vehicle has refused to start several times, each time immediately after a long journey (>80 miles). On the first occasion I was outside the house so left it overnight and it started no issues the next morning. The second and third times, I called VW Roadside Assistance (its still under warranty) and on both occasions the technician identified that the battery was low and it was started with a jump pack.

VW say that the vehicle has a known software fault and that there currently is no fix, rendering the vehicle unusable as it has broken down each time we have tried to use it in the past few months. The AA guy who attended last time it broke down, found no software errors, just the low battery (11.8v) and said that he thought something odd was happening with the battery. Our local independent garage has checked the battery and it appears that something is draining it when running, but did not manage to isolate the cause of this (they only briefly looked at it). On each time it has refused to start, it had been running just fine up until a few minutes before (stop start working etc.).

Any thoughts? VW are knocking us back saying its a software fault but it just feels like it's related to the battery charge/drain. Has anyone had similar experiences? Could it be linked to the split charger (I have no disconnected that and will see if that affects the charge when running)?

Many thanks in advance.

 

[Pete C]

When you say it doesn't start, do you mean it turns over but won't start, or it won't even turn over ?

Pete

 

[jimc91]

Post a picture of your starter battery, sometimes converters add stuff to the negative terminal which confuses the battery monitor

 

[Pauly]

How can the battery drain while running. That sounds weird and could only be an issue with the charging system, in particular the alternator I would think ?

Smart alternators regulate the charge by adjusting the output voltage so could be something going on there with either the sensing or adjusting of the voltage ?
Do you have any means of testing or reading fault codes ?

 

[benfarley]

I turn the key and it seems to try to turn over, but stops with a thump. Is that what you mean? Sorry for my ignorance.

 

[benfarley]

How can the battery drain while running. That sounds weird and could only be an issue with the charging system, in particular the alternator I would think ?

Smart alternators regulate the charge by adjusting the output voltage so could be something going on there with either the sensing or adjusting of the voltage ?
Do you have any means of testing or reading fault codes ?

Yeah, got an obd scanner. No error codes visible

 

[benfarley]

Post a picture of your starter battery, sometimes converters add stuff to the negative terminal which confuses the battery monitor

I'm wondering this too. I have removed the shunt from the charger but not yet used the vehicle to see if this helps.

I'm thinking I should use the vehicle and monitor the battery charge (using Carista app) to see what happens.

 

[Sim60]

What do you mean ‘removed the shunt’ ?
The VW shunt connected to the battery negative?

 

[benfarley]

What do you mean ‘removed the shunt’ ?
The VW shunt connected to the battery negative?

Sorry, the fuse in the leisure battery charger on top of the vehicle battery. Just to isolate the habitation/leisure battery side of things from the vehicle side.

 

[Sim60]

Show us a photo of your starter battery terminals.

You say ‘leisure battery charger’. Do you have a DC-DC converter to charge the leisure battery ( rather than a split charge system)? how is it controlled? What state is the leisure battery in? Can you measure it’s voltage?

 

[benfarley]

Show us a photo of your starter battery terminals.

You say ‘leisure battery charger’. Do you have a DC-DC converter to charge the leisure battery ( rather than a split charge system)? how is it controlled? What state is the leisure battery in? Can you measure it’s voltage?

I'm currently away so won't see the van for a few days. But I'll post a photo when I get home.
The leisure battery is in good health with good charge (topped up by solar panels).

From what you helpful people are saying, the issue seems very likely to be related to charging or drain (perhaps into leisure battery) and not a software fault. Am I right in presuming this? I only say this because VW keep saying its software and I want know where to focus.

Thanks everyone, this is helpful.

 

[Sim60]

It’s too early to say where the problem is . I’m just trying to split the problem in 2.
Is it the van? Or is it what’s been added to the van?
The second of these is probably easier to deal with.

How long do you leave the van without starting it.?

The starter batteries do drain while not used. It may be the starter battery is on its way out through over discharge - either through some extraneous current draw or just the standard ‘off’ current draw for repeated long periods ( repeated 2 weeks without starting it)

Simon

 

[benfarley]

It’s too early to say where the problem is . I’m just trying to split the problem in 2.
Is it the van? Or is it what’s been added to the van?
The second of these is probably easier to deal with.

How long do you leave the van without starting it.?

The starter batteries do drain while not used. It may be the starter battery is on its way out through over discharge - either through some extraneous current draw or just the standard ‘off’ current draw for repeated long periods ( repeated 2 weeks without starting it)

Simon

Thanks Simon. I get you. I'm not at the point of knowing the answers to your questions I'm afraid. Haven't had a chance to try using the van with the habitation side isolated, but will do next weekend.
I never have issues starting the van after being left unused for long periods, although tbh it gets used regularly and is rarely left unused for more than say a week or so. Its only ever failed to start minutes after a long drive. This could be coincidence but it does seem a bit odd. Surely the starter battery should be fully charged after a two hour motorway drive?
Thanks for your repeated replies.

 

[jimc91]

I think the thing to focus on is if the starter battery has not charged after a 2 hour drive there’s a couple of possibilities; the starter battery has something connected to its negative terminal drawing current that the battery shunt on the starter battery is not seeing so not replacing or the alternator is not working properly to replace the current being used as you drive. A multi meter on the starter battery after a long drive and a photo of your starter battery is the first thing to report.

It maybe starts after sitting for a while because the solar panel is somehow topping up the starter battery once the leisure battery is full (the CTEK units do this)

Some photos of your whole set up will help folks get a better idea. Not convinced it’s a software issue

 

[benfarley]

Thank you Jim. I'll be back with more info and a photo when back at home.
I do have a CTEK that does top up the starter battery. Good point.

I really appreciate the responses from everyone, hope you have a nice sunday. I'm not very knowledgable so realise that I'm not always clear or get the wrong end of the stick sometimes.

 

[benfarley]

An update. VW have reassessed the van and diagnosed a faulty alternator. Replaced under warranty.
I'm going to keep the leisure charger/habitation side isolated and use the van for a while, hopefully wont see a reoccurance then reintroduce the split charger to the mix.
Thanks again for the time and input last week.