KYBRIGGS82

2012 GL350... I just had the main battery replaced under the passenger seat and I wanted to replace the 2nd auxiliary battery. Where is the auxiliary battery located on this vehicle. I’ve checked for videos and even opened up the owners manual without success.
Photos or video or location please. I really don’t want to start taking parts apart unnecessarily!
Thank you..

DennisG01

Ummm... it's right there next to the main battery

See if this link helps: https://lmgtfy.com/?q=mercedes+gl+aux+battery+location Or, do the same thing directly in Google.

I think that the car will tell you when it needs replacing, though.

KYBRIGGS82

Damn it.. I wish I would have known and had the installer replace the auxiliary battery at the same time.
i thought the auxiliary battery was in the rear of the GL so I wasn’t worried about it.
What is the importance of the auxiliary battery other than being a back up battery?

Max Blast

It powers some vital keep alive systems while the main battery is disconnected or depleted, that is about it.

KYBRIGGS82

Thank you! I guess I’ll need to have the installer remove the new battery and put a new auxiliary battery next to it. I thought the auxiliary battery on a 2012 GL was located in the rear of the vehicle and the 2011 GL and older vehicles were located next to the main battery under the front seat.

DennisG01

Is 2012 when the GL changed to the X166 chassis? I didn't realize that. I guess I just assumed it was an X164 since we're in the X164 forum here. Or maybe MB changed locations BEFORE switching to the X166 platform. Seems like an odd thing to do, though?

A quick google search provided this thread here on mbworld: https://mbworld.org/forums/gl-class-...x-battery.html which says it's in the right, rear.

But I wouldn't replace it until the car tells you it's time. If it's working, it's working.

chassis

The "additional battery" (Mercedes' name for it) is under the passenger seat, adjacent to the main starting battery. Per WIS AR54.10-P-0005GZ with your VIN.

lkchris

The purpose of the auxiliary battery is to run the solenoid that shifts the transmission into gear. Otherwise, with a dead main battery the car would be locked in park.