Does the Mains Charger Charge the Engine Battery?

[WelshGas]

A question often asked. VW categorically say NO, it does not.
However there is a body of Forum members that believe it does “ Trickle Charge “ the Engine Battery once the Leisure Batteries are Full.
Proof.
On site and I plugged in my 2 Voltmeters. Cheap and cheerful but they both under read by 0.1v, which might be due to the fact that they have dual usb connectors rated at 3.1v combined.
Anyway, both plugged in, top one into Dashboard Leisure Socket and lower one into Cupholder 12v Socket powered by the Engine Battery.
Fridge and Heater running.
Leisure Batteries shoved 12.6v and Engine Battery also 12.6v and this was 45mins after switching off Engine.
Mains Charger plugged in.
Leisure Batteries voltmeter showed 14.6 v within 5 minutes and Engine Battery voltmeter still showed 12.6v.
However, 1 hour later, Leisure Batteries voltmeter showed 14.5v AND Engine Battery voltmeter now showing 13.2v and has since climbed to 13.3v.
Whether this is a fault or not, or if it happens on All Vehicles I do not know, but it definitely happens on mine.

 

[VW Guru]

Hi having looked at the wiring diagrams for years on these vehicles the ehu does not directly charge the engine battery the split charge relay decouples the main battery from the leisure battery’s, however there is an anomaly in the wiring which involves a fused connection between the charger and the main vehicle fuse box this is where the main battery gains a very small trickle charge from I’m sure @Loz can tell you which fuse as I don’t have the wiring diagrams to hand. This connection is not intentionally designed to charge the vehicle battery but it does. The small trickle the battery gets from this connection is enough to add a little charge but would not be capable of maintaining a heavy consumer such as the radio. Hope that all makes sense

 

[WelshGas]

Hi having looked at the wiring diagrams for years on these vehicles the ehu does not directly charge the engine battery the split charge relay decouples the main battery from the leisure battery’s, however there is an anomaly in the wiring which involves a fused connection between the charger and the main vehicle fuse box this is where the main battery gains a very small trickle charge from I’m sure @Loz can tell you which fuse as I don’t have the wiring diagrams to hand. This connection is not intentionally designed to charge the vehicle battery but it does. The small trickle the battery gets from this connection is enough to add a little charge but would not be capable of maintaining a heavy consumer such as the radio. Hope that all makes sense

I accept that. We tend to just use the vehicle radio in the morning for the news and switch on when in bed knowing it will switch off automatically. But at least I know that it seems to cope with 40mins a day Radio use and cab lights if I forget to switch them off.

 

[EddieEagle]

What is the necessity for EHU once a month ?
I am blundering around in the dark on this, does the Bluemotion add or subtract from the equation somehow?
Which of the batteries only gets 80% and needs EHU to fully charge.
I am desperately trying not to be too stupid (read unsafe! ) here yet the OP and VW Guru on tap is too good an opportunity to miss...

 

[CYCLOPATH]

Hi having looked at the wiring diagrams for years on these vehicles the ehu does not directly charge the engine battery the split charge relay decouples the main battery from the leisure battery’s, however there is an anomaly in the wiring which involves a fused connection between the charger and the main vehicle fuse box this is where the main battery gains a very small trickle charge from I’m sure @Loz can tell you which fuse as I don’t have the wiring diagrams to hand. This connection is not intentionally designed to charge the vehicle battery but it does. The small trickle the battery gets from this connection is enough to add a little charge but would not be capable of maintaining a heavy consumer such as the radio. Hope that all makes sense

If you keep coming out with post like this,,,showing a dealer knows what they are talking about, And seems to care, I think you might find yourself getting a lot more trade,,I would gladly travel to Poole !

 

[VW Guru]

What is the necessity for EHU once a month ?
I am blundering around in the dark on this, does the Bluemotion add or subtract from the equation somehow?
Which of the batteries only gets 80% and needs EHU to fully charge.
I am desperately trying not to be too stupid (read unsafe! ) here yet the OP and VW Guru on tap is too good an opportunity to miss...

Hi @EddieEagle

So to answer your questions, the necessity for charging the leisure battery’s once a month is to gently trickle charge the batteries up to full capacity. The problem is with modern battery’s is that they cannot cope with fast and hard charging from an alternator the output from an alternator will only charge battery’s to 75-80% of capacity the idea behind modern charging systems is to run the vehicle and the battery is used to store excess voltage and start the vehicle. The problem with the leisure battery’s is that they get discharged while camping then the vehicle is driven and the alternator throws huge current at the battery’s so they will only ever part change. Your display will show a 100% charge but that’s just surface charge normally after a-few hours and the battery’s have stabilized they show 75-80% on the camping display. So charging say once a month on the ehu will charge your battery’s to full capacity and lengthen the lifespan of them.

The display shows the charge of the rear two battery’s as a whole due to the way in which electrons flow both the leisure battery’s will balance out, if one becomes less charged than the other the battery’s will naturally equalize themselves.

As for blue motion technology that only effects the main vehicle battery and not the leisure battery’s.

Hope all that makes sense

 

[EddieEagle]

Thank you!
Will continue to hook up once a month....

 

[VW Guru]

If you keep coming out with post like this,,,showing a dealer knows what they are talking about, And seems to care, I think you might find yourself getting a lot more trade,,I would gladly travel to Poole !

I thank you for your kind comments, we/I as a dealer group do care and strive to look after our customers, we don’t get it right 100% of the time but no one company or person can say they do but we have a wealth of experience working on calis and we take what we do seriously with the upmost respect for the vehicle and the customer. Sometime our hands are tied and backs are against the wall with the rules and regulations we have to work under as a vw dealer and every dealer is the same however we try to be clear with everything we do and why we have to do it. We are a family run company all be it a big company and those family values are at our core. If you don’t believe me you should see the posters in our break room

 

[Volkywagen]

I thank you for your kind comments, we/I as a dealer group do care and strive to look after our customers, we don’t get it right 100% of the time but no one company or person can say they do but we have a wealth of experience working on calis and we take what we do seriously with the upmost respect for the vehicle and the customer. Sometime our hands are tied and backs are against the wall with the rules and regulations we have to work under as a vw dealer and every dealer is the same however we try to be clear with everything we do and why we have to do it. We are a family run company all be it a big company and those family values are at our core. If you don’t believe me you should see the posters in our break room

Good to have you on board

 

[Hotel California]

i've been putting mine on 220v regulary since day one i got the Cali as my dealer told me it was best to ....
And he also me it did do good for the starterbat. also , and i've been saying this over and over again on the forum .
Never had any issue with my battery's in 7y , knowing my Cali sometimes stays unused sevral weeks as it is not my daily driver (with is my electric bike)
Even my other cars i put on a charger for a weekend once or twice a year .

 

[IanE]

Just a note of reassurance - I only replaced our batteries a couple of months ago. They were the original batteries and were nine years old and were still functioning to a degree ( percentage dropped rapidly from a mains charge down to 50%). Because the van lives on the street and I had no means of regularly plugging in for the first c five years (I have now so do plug in monthly) it was rare for us to hook up - only when we were on a campsite in fact.

Damn good batteries!

 

[WelshGas]

The voltmeter on the Starter Battery has now climbed to 13.7v overnight.

 

[johnyboy]

Great to hear the full explanation
Ours is nearly 8 years old and I have not followed the regiment, batteries still performing well over a long weekend; not saying this to be boastful but to stop any new owners from panicking if, like Ian you are not able to follow the advice - I had always figured they would probably need replacing after ten years (and I was hoping there would be a way of replacing with lithium or dry batteries or something that I would never have to think about again )

 

[18hunts]

I like to read threads like this, not that I'm going to dive into the inner workings but I do like to know how they work. Or supposed to!
However, isn't there always, having just checked both my dashboard socket and cup holder socket are live when no ignition key is present!

 

[ArunAlec]

I like to read threads like this, not that I'm going to dive into the inner workings but I do like to know how they work. Or supposed to!
However, isn't there always, having just checked both my dashboard socket and cup holder socket are live when no ignition key is present!

The 12v sockets are independent of the ignition so will be live.

 

[18hunts]

OK, thank you.
Does that means it is part of the Canbus system and switches off after 30 mins or can I connect something into and drain/flatten my battery?

 

[ArunAlec]

OK, thank you.
Does that means it is part of the Canbus system and switches off after 30 mins or can I connect something into and drain/flatten my battery?

No 30 min cut off, so you could flatten either Starter or Leisure battery depending which socket you are plugged into ( there seems to be some variation in the wiring) but my 12v sockets are all fed from the leisure batteries apart from the one in the front cup holder which is off the starter battery.

 

[18hunts]

So short answer is I don't know wether the plugs are leisure or main battery. I wonder if VW know?

 

[ArunAlec]

So short answer is I don't know wether the plugs are leisure or main battery. I wonder if VW know?

The one that seems to vary is the cup holder. if you get a plug in voltmeter ( couple of quid on eBay ) you can easily check. EG when on hook up my dash socket is at 13.4V and the cup holder at 12.7V.
You can check all of the sockets and you should find they will all be near enough the same, with the exception of the cup holder, which could/should be the odd one out.

 

[18hunts]

Again thank you ArunAlec, will check to see what I am.

 

[Romke]

my 12v sockets are all fed from the leisure batteries apart from the one in the front cup holder which is off the starter battery.

Are you sure about that? The 12V socket under the rear bench (next to the sliding door) is not Cali-specific; afaik it is also available in other models, such as the Caravelle which does not have leisure batteries. Would VW wire this socket differently for different Transporter models?

 

[WelshGas]

Are you sure about that? The 12V socket under the rear bench (next to the sliding door) is not Cali-specific; afaik it is also available in other models, such as the Caravelle which does not have leisure batteries. Would VW wire this socket differently for different Transporter models?

The Socket you are referring to definitely runs off the Leisure Batteries on mine.
The Socket, part of the trim panel, as you say is found in other variants, such as the Caravelle, but I think you might find that the wiring loom used might be California specific.

 

[ArunAlec]

A question often asked. VW categorically say NO, it does not.
However there is a body of Forum members that believe it does “ Trickle Charge “ the Engine Battery once the Leisure Batteries are Full.
Proof.
On site and I plugged in my 2 Voltmeters. Cheap and cheerful but they both under read by 0.1v, which might be due to the fact that they have dual usb connectors rated at 3.1v combined.
Anyway, both plugged in, top one into Dashboard Leisure Socket and lower one into Cupholder 12v Socket powered by the Engine Battery.
Fridge and Heater running.
Leisure Batteries shoved 12.6v and Engine Battery also 12.6v and this was 45mins after switching off Engine.
Mains Charger plugged in.
Leisure Batteries voltmeter showed 14.6 v within 5 minutes and Engine Battery voltmeter still showed 12.6v.
However, 1 hour later, Leisure Batteries voltmeter showed 14.5v AND Engine Battery voltmeter now showing 13.2v and has since climbed to 13.3v.
Whether this is a fault or not, or if it happens on All Vehicles I do not know, but it definitely happens on mine.
View attachment 44929

I’ve run a similar test and reckon you are right, the clincher was when I took the van off hookup... when connected the cup holder was showing 13.2v but when disconnected 12.8v.

 

[Geesvw]

The one that seems to vary is the cup holder. if you get a plug in voltmeter ( couple of quid on eBay ) you can easily check. EG when on hook up my dash socket is at 13.4V and the cup holder at 12.7V.
You can check all of the sockets and you should find they will all be near enough the same, with the exception of the cup holder, which could/should be the odd one out.

I recently replaced one leisure battery that had failed. When doing so I fitted tails to allow the ability to connect a “smart charger” to check the battery condition with a “maintenance” charge. I do this every six months or so as a maintenance procedure. If you use this method, remember to disconnect one leisure from the other as they’re linked in parallel, and make sure that the disconnected live terminal isn’t touching any chassis parts as the other battery will fry your leisure wiring loom!