2006 W211 E320 Cdi 7G- What's the auxiliary battery's function?

[jon_viola]

As it says. Wondering what systems rely on the auxiliary battery.

Thanks

Jon

 

[Diesel Benz]

I assume the question is about the SBC/AUX battery on a pre-facelift W211?

You will have very different answers to this question (at least has happened previously to the same question) which is why it might be better to build your own opinion:
http://www.mercedestechstore.com/pdfs/W211_advisor/219 HO Dual Battery (ACB - ICC) 11-29-02.pdf

Essentially anyway the battery is there to guarantee power for the SBC brakes because the car would have very limited braking power if battery power was lost. The facelift with traditional (but enhanced) brakes does not need this battery, meaning there are no other electronics in a 211 that really need the AUX battery.

You can conclude differently too because the AUX battery is connected with a relay in parallel with the main battery and thus (when closed) powers up all electronics that has not been switched off previously (at low battery voltage all MBs switch off less important features in different stages). Most of the time the AUX battery is disconnected from the rest of the car (excluding a voltage sense wire and ground of course). At times the battery is charged (along with the main battery) but otherwise the relay closes only if SBC brakes are in danger to loose supply power.

 

[whitenemesis]

Perhaps these two threads should be merged?

http://www.mbclub.co.uk/forums/gene...-cdi-7g-what-auxiliary-batterys-function.html