Heyloft wrote:

Yep got that it’s battery related

The main battery is 98% charged and 13.8v so I’m happy with that.

The Aux battery after 2 hrs of charge is 10% charged and 10.2v. That’s just not right.

I don’t want to fix it, it’s under warranty, I just want to tell the dealer that they’re talking sh*te and it’s the aux battery not the main one, rather than them blaming the main starting battery again. I’m evidence gathering, I guess.

Charge your aux battery overnight, if it’s not now well over 12 volts it’s useless and the stop start will not work.

Tell the dealer your results, also for info the aux battery is used to keep the system stable on a restart, IE it does not start the engine, the main battery does, it just stops other systems dropping below a voltage threshold to stop unwanted fault codes.
Once either battery fails the stop start will be disabled. The dealer will need to fit a new aux battery then tell the system it has been fitted via a quick plug in of their diagnostic equipment. Even basic equipment can do this so there should be no excuse. Hope you get sorted

Good evening everyone,

I would like to take up this topic again with the annoying start-stop device: the 4.4 SDV8 always has an additional battery installed, even in the 2017 model, if you disconnect it the seat heating doesn't work either. I found a young programmer here near Düsseldorf who permanently programmed the start-stop function for me for 100 euros. It gets into the entire software of the car, far deeper than GAP Tool and other OBD devices. The start-stop disadvantage is clearly the oil pump problem and the associated lack of engine oil lubrication, as a BMW engine designer explained it to me. It was no problem to disconnect the secondary battery on my 2014 Range Rover SDV6 because it had no side effects.

Best rgs, Uli L405 SDV8 2017 + Lancia Flavia Coupe 1964 + RRS L494 3.0 SDV6 + C220CDI Convertible 2021