Scoop7

I occasionally put a battery maintainer on the provided positive and negative posts under the hood, thank you MB, in my 2017 GLE 350 4M. The question is: will this charge both the primary battery AND the auxiliary battery, if that's the correct term? Secondly, does the alternator charge the auxiliary battery directly, or does it somehow pass through the primary battery first ensuring the primary battery gets priority in the event of a weak charge from the alternator? Thank you, Larry.

BACnMercedes

I thought there was only one large battery for both under the passengers front seat.


I could be wrong though and I have been told before by my wife.
Good luck.

chassis

W166 has a main (starting) battery and an auxiliary battery. For the W166 SUV without air suspension, the aux battery is in the rear right lower cargo area behind trim panels. For other variants it is mounted under the carpet under the rear seat.

Scoop7

OK, Egg on my face. I am the author of this post. I did research this subject "BEFORE" I generated my first post as we all should. I did not find what I was looking for so I made the post. It got little response. So I figured it must be because the subject matter has already be answered too many times before, and the regulars just didn't want to go there again (experience from other forums). So back to Google I went. After three days I finally got some answers, but they are a little contradictory. Research says:

One can not charge the auxiliary battery through the main battery but they also stated that the auxiliary battery gets a trickle charge from the alternator once the main battery gets a full charge. Isn't a battery maintainer doing the same thing? Research also stated that the auxiliary can only be charged via a running engine.

I guess I can sleep at nights with that information, but don't be shy about adding a few additional comments to my findings. Thanks, Larry

Isawelvis

Thanks Scoop7- I have always had questions on the auxiliary battery. I have a 2015 ML with 70,000 plus miles with factory battery which I keep trickle charge. I ve been waiting for the dreaded warning light that the aux battery needs replacing. But I can relax a little now.

Scoop7

There is one large battery under the front passenger seat and a smaller one at the rear cargo area on the right floor, visible via the small side cover, but not fully accessible from there. As a reminder, it's a 2017 GLE 350 4matic.