Jun 10, 2020
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Hello everyone!

I seek help and advice installing a leisure battery on my new VW Caddy Maxi!
It's a 2015 model with blue motion technology, therefore smart alternator and break-regen and all of that!

I searched for battery chargers and recently bought a " Schaudt WA 121525" booster because it seemed well priced, had good reviews and was on a German website where I had already a full shopping cart (and therefore free shipping :sneaky:).

NOW, I'm pretty confident about the wiring, but I'm confused about the D+ connection : is it really necessary? And where can I source a wire to it? Diagrams suggest a connection to the alternator, but it looks really tricky to access.. I've seen a few tricks on the internet, like sourcing the D+ from a fuse box or glove box light.. Could this work?
Is the D+ just an "ignition signal" and any 12v signal when the engine is running would do the job?

Or.. Should I just ship back the unit and buy a Sterling or Votronic that seem a little more straight forward to install and apparently don't need a D+ signal?

Thank you all for your help, and enjoy the camping summer!!
Oct 8, 2006
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I would suggest you get the 12V+fridge wiring loom from VW or one of the towbar companies such as Westfalia and use the fridge circuit as a charge cable. It means it will only be live when the engine is running and will disconnect during BMT action <and> when the smart alternator stops charging. You may however need to have the ECU updated to let it know the cable is present.
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