putter

That's the message on the screen after the cruise control would not turn on. This happened twice in three days.
Anyone experience this?

Is this a "fix" or "replace" situation?

Where is this battery on a 2013 SL?

Rockinrob

Putter:
Previous posts show photos of the aux battery behind the passenger seat, under a cover. Getting it out is a pain in the butt, but do-able.
The previous post I'm referring to was very explicit , with good photos. see "Battery Location in my '13 MB SL550 post on 11/29/17".
No sure if he was getting a warning like yours...our aux batteries are getting on 5 years old now.
I charge both of my AGM batteries from the 2 posts under the hood.
It is a Battery Minder 2 amp AGM desulfator charger that extends the life of the batteries..

The main battery is where the spare tire used to be, under the trunk floorboard. It is a large AGM style type. That one is easy to get to..
Hope this helps...
rockinrob .

putter

Thanks. This helps a lot. When I did a search I got nothing helpful.

putter

Here's an update on my situation.

New one installed at MB Dealer for $278. Given its location, I was expecting a higher price. Everything works again.

Rockinrob

Putter- Thanks for the update! I would have expected a higher charge for the battery & labor .
An AGM battery's worst enemy is heat... so it would not last long under the hood.
That's why both are now in the cooler temp areas..inside the cab and in the trunk..The R230's had one under the hood...
I'm sure I'm running on borrowed time for mine as well since it is 5 years old.

Box5232

Thank you Rockinrob for your post. I use to own a 2008 Cadillac XLR and the owners manual stated that when the windows start to malfunction that is an indication that the battery needs to be replaced. Traded up to my 2015 SL550 and the windows were not going down together when retracting the roof. Been looking on-line for a couple of weeks unable to find auxiliary battery location. "Auxiliary battery malfunction" message came up on Thursday, found this post that evening, replaced the battery yesterday. Note to others removal takes about 10 minutes. New battery terminals are closer to the edge of the battery, and I had to cut a little off the battery hold down. I used my dremel, and it was very easy to do. Total time, not including going to MB dealership for battery, about 45 very easy minutes. Cost $145.

rorywquin

I ran an AGM (Exide Orbital) for Auxillary power under the hood (along with the two main cranking batteries) in my Landcruiser 200 series for 4 years - never a minute of trouble. I used it in some pretty extreme conditions including a drive from South Australia via Alice Springs, Uluru and many other detours to Brisbane (6000km) temps were in the high 40s most days. Also did the Simpson desert, and many other trips in South Australia (very hot place, 40+ in summer is normal) ---- It was also my daily drive and the battery was still taking a proper charge when I sold the car.

I believe the battery in the rear is two fold. Improves weight distribution and is protected from impact damage, reducing fire risk etc.