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Discussion Starter #1
Hi folks, I was wondering about the process with the Touareg V10 (dual battery arrangement) if one has to do any work that would normally require disconnecting the battery, like say changing the starter or alternator. On a ‘conventional’ car it would be easy to just lift the battery terminals (+ and -) off the single battery and the car is dead.

My question is, for the Touareg dual battery arrangement, is it necessary to disconnect both batteries - or does it depend upon the job that is being performed?

The safe way for sure is to lift both batteries off but maybe there is a smarter way.

Just curious if any V10 people out there know about this.

Pete.
 

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Hmmm. The seats are sort of easy to tilt to get you access to the main battery - is the one in back isolated by a relay? I know I've read it's not involved in starting ....
 

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The rear battery starts the car with the assistance of the front consumer battery.

The front consumer battery can start the car if the rear starter battery isn't up to its job.
 

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Wait until the correct procedure is posted. VW recommended that one specific battery always be disconnected first. Then unhook the second battery.

VW warned that doing it wrong way around could mess up the system. I don't remember which battery was supposed to be unhooked first.
 

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Do a search for VW Self Study Program 298 - Touareg electrical system. The instructions might be in there.
 

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The rear battery doesn’t start the car. Fake news


There are several ways the batteries are used to start the systems depending on battery condition.


procedure for disconnect is disconnect front first then rear


reconnection is rear first then front.
 
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Discussion Starter #7
Thanks for that folks, will read the SSP on this as well to be fully briefed.

Pete
 

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Discussion Starter #9
Thanks for that Steve, will review this and report its content in the context of my enquiry.

Pete
 

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Under seat must be disconnected first. Nothing else special to do. Rear can stay connected.
It is not connected to anything electrical unless told to do so during starting, or while being charged on a drive cycle.

Very easy to tilt the seat backward. Just make sure you've got the plastic trims off from the rear of the seat first.
 

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Someone needs to amp-clamp the cables. I have heard also to get the rear battery (maybe front?) to boost you turn the key left first then right......so amp-clamp the rear, and start it - should be clear if the amps are flowing or not - if not, do that left-turn key thingy... and recheck. If the rear turns out to be the starter battery..... then check the front, confirm "not high amps" when starting, then again try that left-key turn trick. I have a fluke I use at work, they would let me borrow it. I just need the time and space (and running V10 :D ).
 

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Even simpler than an amp clamp would be to check voltage drop when cranking.
Fact is, rear battery is for starting in V10s.
 

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The four different start procedure circuits in that document show the two batteries are always connected together to power the starter motor.
The only change is where power comes from to supply the consumers.

Also,
The circuit shows a direct link from the starter batt to the glow plugs, with no way to disconnect the starter batt.
Yet the wording at the beginning of that section suggests the glow plugs are supplied from the onboard batt, and can be connected to the starter if needed.

So can that document really be trusted?
 

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Those of us who have experience getting these things to start know... the rear battery is not needed to start a V10tdi. But this is the internet so everyone is free to post what they believe. Eventually people that have experience will stop posting.

235431
 

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VW (and my own experience) disagrees with you. :p
please share your experience... mine is posted above in a stand alone V10tdi using only the main battery...
 

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please share your experience... mine is posted above in a stand alone V10tdi using only the main battery...
The rear battery isn't abolsutely required to start, it will start with the front battery if needed.

My experience is with my own 2004 V10. I had a weak rear battery and it either cranked very slowly, or not at all and I had to do the emergency start which then uses the front battery (or bridges, depending on conditions). I replaced the rear battery and it cranked fine thereafter. The front battery had been changed perhaps a month prior.
 

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The rear battery isn't abolsutely required to start, it will start with the front battery if needed.

My experience is with my own 2004 V10. I had a weak rear battery and it either cranked very slowly, or not at all and I had to do the emergency start which then uses the front battery (or bridges, depending on conditions). I replaced the rear battery and it cranked fine thereafter. The front battery had been changed perhaps a month prior.
So what I posted was correct, thank you... Over the past 15 years of V10tdi ownership and 5 Touaregs I have been through more quirks than I can recall.
 

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Discussion Starter #19
The rear battery isn't abolsutely required to start, it will start with the front battery if needed.

My experience is with my own 2004 V10. I had a weak rear battery and it either cranked very slowly, or not at all and I had to do the emergency start which then uses the front battery (or bridges, depending on conditions). I replaced the rear battery and it cranked fine thereafter. The front battery had been changed perhaps a month prior.
It looks clear to me from SS+298 and the circuit diagrams in it that the rear battery is dedicated for starting purposes (but it depends on some prior tests by the car). If voltage is <11.5V - then the starter battery is deemed discharged and then the Onboard Power supply battery becomes the battery providing power to start (as well as everything else - glow pugs, radio, whatever is on).

The three images below show the 3 possible scenarios when an engine start is required.

235432


235433

235434


Pete
 

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When you have the entire harness laid out on the floor and tracing it, let us know your thoughts.
 
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