2011 W221 Aux Battery Diagram

[the director]

Does anyone have a schematic diagram to show the location of the aux battery?

My car has lit up the battery malfunction warning on the dash (having been fine for the 18mths of ownership). When I check where I think the location should be (behind the steering wheel/lower dash) I can access what looks like the perfect bracket to hold the battery, but there is no battery in sight! I also can’t locate any wires that would connect to said battery even if it was there!

This is a complete mystery as everything worked fine for 18mths.

Thanks

Ian

 

[Phil woods]

That’s the location of mine I’ve seen it,how you get it out I’m not certain maybe remove the fuse box that’s behind the end panel of the dash.

 

[the director]

It’s relatively easy to get to.......if it was actually there!

 

[the director]

Anyone got a schematic diagram?

 

[AMGeed]

Is the main battery in the boot or in the engine compartment?

If its in the boot, the 2nd diagram below shows that is also the location of the Aux battery (Item#600).

If it's in the engine compartment, the Aux battery is shown in the first pic as Item#120

https://mercedes.7zap.com/en/eu/fg/car/s-klasse/s+350/63w/221056/fg/0/0/54/0/030/0/0/

 

[alexanderfoti]

If yours is pre facelift, then AMGeed is correct, its the battery behind the back seats. If you have a BATTERY warning that you cannot dismiss then that normally refers to the battery in the dahs.

 

[the director]

Is the main battery in the boot or in the engine compartment?

If its in the boot, the 2nd diagram below shows that is also the location of the Aux battery (Item#600).

If it's in the engine compartment, the Aux battery is shown in the first pic as Item#120

https://mercedes.7zap.com/en/eu/fg/car/s-klasse/s+350/63w/221056/fg/0/0/54/0/030/0/0/

Thanks AMG - my main battery is in the engine compartment. I’ll have a look to see if the aux battery is also located there as well.......everything else I’ve seen seems to indicate it would be behind the dashboard.......it’s not, but the bracket to hold a battery is.

 

[the director]

Nope, it’s not!

 

[AMGeed]

This thread from MB World may help

https://mbworld.org/forums/s-class-w221/629195-changing-auxiliary-battery-2011-s550.html

 

[the director]

This thread from MB World may help

https://mbworld.org/forums/s-class-w221/629195-changing-auxiliary-battery-2011-s550.html

Yes, seen that one before. It’s weird, the bracket is there under the dash to take the battery, but there is no sign of the old one or indeed wires to connect a battery to.

 

[AMGeed]

Yes, seen that one before. It’s weird, the bracket is there under the dash to take the battery, but there is no sign of the old one or indeed wires to connect a battery to.

How strange.

Perhaps worth taking into your local dealership and ask them to change the Aux battery for you.

Let them find it

 

[Oldspanners]

Yes, seen that one before. It’s weird, the bracket is there under the dash to take the battery, but there is no sign of the old one or indeed wires to connect a battery to.

Is this any help?
https://mbwis.net/en/doc/18013570

 

[the director]

Is this any help?
https://mbwis.net/en/doc/18013570

Thanks, I’ll look around the various documents on that site.

 

[Botus]

Does anyone have a schematic diagram to show the location of the aux battery?

My car has lit up the battery malfunction warning on the dash (having been fine for the 18mths of ownership). When I check where I think the location should be (behind the steering wheel/lower dash) I can access what looks like the perfect bracket to hold the battery, but there is no battery in sight! I also can’t locate any wires that would connect to said battery even if it was there!

This is a complete mystery as everything worked fine for 18mths.

Thanks

Ian

I was at an indie a year back - a car they had been fighting the same issue just came back in - they had replaced both batteries with brand new merc replacement and each time a few days later the light came back on.... after more merc diagnostics and head scratching the gist was the control module had gone pop - it was the same age - and they aren't cheap

 

[Tony Dyson]

I was at an indie a year back - a car they had been fighting the same issue just came back in - they had replaced both batteries with brand new merc replacement and each time a few days later the light came back on.... after more merc diagnostics and head scratching the gist was the control module had gone pop - it was the same age - and they aren't cheap

do you recall exactly which Control Module Botus?

 

[Botus]

battery control module..... I think its the same one that puts the light on

you could ask Wayne gates how they got on ….

 

[the director]

AMGeed is correct. I found the fecker behind the back seats (accessed via removing the panel in the boot). I think that the story might be that this is where the late Diesel engines cars have them, and the petrol or earlier versions having them behind the dash........something like that anyway.

 

[alexanderfoti]

Petrol versions also have them there. Its stop/start vs non vs face-lift that changes the setup.

 

[ajlsl600]

a related Q i believe the small batt in the d/s rear of boot (ml250 2012) is my stop start job and the other under driver seat is main batt there aint another under the dash somewhere ? i hope...

 

[Botus]

the small battery in the boot is 25kg !!!