Really useful video for post August 2008 S And CL owners regarding Einbatteriebordnetz code A57

[Submariner1]

Interesting anti parasitic drain feature. Turns off Terminal 30G :-
1. If the car is off , after 6 hours
Or
2. Main voltage drops under 11.8V
Or
3. There is a drain of over 75mA after 75 minutes

Technically prevents your battery being flattened by consumers, to the point You cant start the car !

Also it shows we have a secret backup battery in the dashboard, behind the light switch sure as hell there is one on EPC its a 1.2AH
Oddly WIS ignores it apart from explaining how to get at it.
I.e. WIS goes into great detail about
- how to check, and charge, PDI check, and jumpstart both the Main Systems Battery and the Start stop battery in the boot ( if you have that code) BUT no mention of this little battery.
- it also instructs you how to remove and replace the 2 big batteries, but the removal process of the little backup battery does not state if the big battery should be disconnected first or even if the key should be turned off, thats a bit wierd.

One could only assume you leave the big battery connected when you remove this?
I woukd assume its key left and removed before you mess with this little monster.

Apparently the function of this little battery is to maintain gearbox shift by wire comms in the event if low voltage.

Assuming its an AGM battery like my house alarm, Chubb insist these 7AH batteries are changed after 5 years.
Just a thought is this on the Service schedule? I.e. to check them!
Some could be nearly 10 years old in August.
Wow its £67.15 for a 1.2AH , whereas a Yuasa AGM 7AH is £16


I guess if your main battery is good ... you would never know you have lost this one?

The more you learn the more complicated this car gets ... no wonder they have issues ... God help us when they overlay this star wars stuff, with driverless technology.

The thought of untrained, back street garages fiddling with these when they get older makes you shudder!
Thank God I will be protected by a tank like S Class built car. :-0

 

[Westheath]

Holy Sh*t

 

[alexanderfoti]

My dual battery system has been fine for 2 years.

Part of the reason current flow is measured is for ECO functionality, I.e managed alternator charging under overrun.

 

[Botus]

my 335d had this rubbish

along side overly big rear brakes, when really pressing on they both tried to kill you. It made the rear of the car exceptionally unstable under big braking manoeuvres. I guess its still not as dangerous as the suspension, which liked to lock up the rear dampers. Once picking the rear of the car 1 metre off the ground and trying very hard to throw it at the shrubbery when I was busy going 85mph round some interesting bends...

funny enough I got rid of that car quite quickly