W166 Auxiliary Battery Location
However, it doesn't tell me where this thing is located. Anyone know?
Its a 2012 ML350. Thanks


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.
Last edited by another_geek; Jul 22, 2014 at 07:03 PM.


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?
Last edited by another_geek; Jul 22, 2014 at 11:03 PM.
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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
cheers




Right now, you sound like a fool who doesn't know what car you have.
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.
Last edited by bob58d; Aug 10, 2020 at 09:14 PM.
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. https://www.amazon.com/dp/B07Y2FDD14...EmFb42X0HY3%5D
I used the short cut method is this video to replace it. I would do it again. https://m.youtube.com/watch?v=ATjTFgx2Yzs
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.



