Xentry is telling me I have about 0.6V coming from the aux battery which should be at least 7.5V.

However, it doesn't tell me where this thing is located. Anyone know?

Its a 2012 ML350. Thanks

 

I believe both batteries (primary and aux) are located under the right front seat - front passenger if in the US, driver's seat if in the UK

 

Spoke with a tech who said its behind the right side panel in the back cargo area...I know its not under the seat nor in front of it because I was in there today.

 

The right side panel in the cargo area contains the air tank for those of us with airmatic suspension. Its empty if you don't have airmatic. I just double-checked my car and there's no battery in there. Left side compartment holds the subwoofer if you have the HK audio system.

I've never opened up the battery compartment on my W166 but I'm told its similar to the W164. In the W164, you had to remove the main battery to gain access to the aux battery. The aux battery on the w164 was smaller - same size as used in home computer UPS and garage door openers.

If the tech is correct and it *is* in the back, then the only place I can think of where it might be is if you remove the entire panel in the cargo area because it isnt visible through the access panel.

 

The air tank for my 13 ML550/Airmatic is by the spare tire in the center compartment of the rear cargo area.

 

Yes. Sorry I wasn't more specific in my post. My car has 2 tanks for the airmatic. One behind the right side panel and one under the spare tire. I'm guessing one for each side. There might be even more tanks hidden somewhere but I haven't found them (1 for each corner?)

I believe if you have the multi-contour seats, there is a tank hidden on the left side of the rear cargo area where most of us have a recessed storage bin.

Does yours have a 2nd tank on the right?

 

Auxiliary battery is right hand rear. Not easy to see down there. It is positioned across the rear of the vehicle on the right hand side below the base of the cargo area.

 

Just had mine replaced under warranty, was told its under the spare wheel.

 

Behind the spare wheel compartment, between that and the rear bumper.

 

Here is a pix of were it is. For 2012 w166. It's on the R. Rear below as stated before.

 

Hi,

Can anyone help?
Today I followed another thread and removed the cover over the main battery in search of the auxiliary battery.
I did not find the aux battery there.
Looked in the boot and removed the small panel on the right hand side. Inside you can see the positive terminal of a battery.

Can someone confirm that this is the auxiliary battery and how do you change it?

Jim

 

mine is located on the back. Remove the right rear trunk panel. Look below. Is there. Then just remove the arm of the bracket that holds the battery in place.

 

how do you remove the panel?

 

Remove 2 of these. And pull the panel. It's held by inside clips.

 

already removed those clips, then I used a flat screwdriver to pop all the white push in plugs that hold the top of the panel. How do you release the bottom of the panel?

 

This is what my auxiliary battery looks like!

 

Mine is right side rear right at back behind side panel ,,,ML63 and soon needs to be replaced...if you run it down your vehicle will NOT shift into gear

 

 

 

 

 

please is it the same with gle 400 amg I want to change my auxiliary battery but I can't locate where it is on my car

 

There is no such car as a GLE 400 amg. Why not try starting with the problem, and describing what is wrong with your vehicle, and why you want to change the aux battery.

Right now, you sound like a fool who doesn't know what car you have.

 

I have a 2014 ML350 4MATIC and just replaced both my starter battery and my auxiliary battery.

There are plenty of video resources to help replace the starter battery that is located under the passenger seat but finding a good video to replace the aux battery is harder.

This is the replacement auxiliary battery that I ordered from Amazon.
I used the short cut method is this video to replace it. I would do it again.

 

Well done, thanks for posting.

That is quite the shortcut. Imagine if the Mercedes engineers designed the existing removable panel with four more inches of length onto the floor of the niche.