2015 G550 Auxiliary Battery
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Joined: Jun 2025
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2015 G550
2015 G550 Auxiliary Battery
The vehicle is a 2015 G550, completely stock. I need to replace the auxiliary battery. Question is, where is it and what part?
There are many posts everywhere about the auxiliary battery. They all say it is a fairly large battery, and show it located directly below the main battery under the rear seat floor.
The problem is, there is no battery below the main battery, just the bottom of the battery box. What I do see is a small battery, mounted to the left side of the main battery, with quick-connect terminals. It seems to be an original part. I presume that is the auxiliary battery but cannot find anything to confirm this or to assure me that I will be buying the correct replacement.
I wold be very grateful for information to confirm this and advise on the correct replacement.
There are many posts everywhere about the auxiliary battery. They all say it is a fairly large battery, and show it located directly below the main battery under the rear seat floor.
The problem is, there is no battery below the main battery, just the bottom of the battery box. What I do see is a small battery, mounted to the left side of the main battery, with quick-connect terminals. It seems to be an original part. I presume that is the auxiliary battery but cannot find anything to confirm this or to assure me that I will be buying the correct replacement.
I wold be very grateful for information to confirm this and advise on the correct replacement.
Junior Member
Joined: Apr 2005
Posts: 64
Likes: 1
From: Los Angeles, CA
2021 GLC43, 2014 G550, 2000 C280 Sport EX: 2019 C300 Convertible, 2010 GLK350, 2006 C55 AMG
Not sure if you got the answer already, but it's on the left-side of the main battery compartment. You need to take out the main battery completely to get to the auxiliary battery. There is a bracket holding it down you need to remove to replace the battery. Opposite of that on the right side of the compartment is the multi-contour seat pump.
Super Member
Joined: Jun 2025
Posts: 784
Likes: 248
From: USA
The vehicle is a 2015 G550, completely stock. I need to replace the auxiliary battery. Question is, where is it and what part?
There are many posts everywhere about the auxiliary battery. They all say it is a fairly large battery, and show it located directly below the main battery under the rear seat floor.
The problem is, there is no battery below the main battery, just the bottom of the battery box. What I do see is a small battery, mounted to the left side of the main battery, with quick-connect terminals. It seems to be an original part. I presume that is the auxiliary battery but cannot find anything to confirm this or to assure me that I will be buying the correct replacement.
I wold be very grateful for information to confirm this and advise on the correct replacement.
There are many posts everywhere about the auxiliary battery. They all say it is a fairly large battery, and show it located directly below the main battery under the rear seat floor.
The problem is, there is no battery below the main battery, just the bottom of the battery box. What I do see is a small battery, mounted to the left side of the main battery, with quick-connect terminals. It seems to be an original part. I presume that is the auxiliary battery but cannot find anything to confirm this or to assure me that I will be buying the correct replacement.
I wold be very grateful for information to confirm this and advise on the correct replacement.
