kinglenario

thats interesting. What options differ between the two?

2012 merc amg

The Wagon does come STD with the rear Air suspension although not up front, I hardly ever hear the pump run. With my 2018 AMG wagon I use to hear it running a lot. The Cabriolet does have a few extra options over the wagon, the mulitcontour seats/ventilated. The heads up display, leather int. other than that not much of a difference. The Cabrio has no Air suspension. It does seem like with the cabriolet after it's turned off I do hear the int. fan coming on and off a lot whereas I don't really notice it with the wagon, maybe thats the difference and accounts for the battery drain. Both cars have the same V6 Twin turbo motor with the 9 speed auto.

2012 merc amg

I was thinking about it, I guess the main reason I have issues with the Cabriolet going Critical low charge is it sits around a lot more than my wagon. The Cabriolet only has 8800 miles on it after a year and 2 months. The Wagon same age has 22K miles on it. I have the Cabriolet on the Maintainer right now as it went low again after sitting 4 days or so and it does not get the long trips the wagon gets.

b0rderman

Just an FYI, the cigarette lighters in my 2020 wagon are on a different circuit so my CTEK tender needed to be connected under the hood.

Anyone have an elegant in-cabin solution for a tender lead?

2012 merc amg

I suppose it would be possible to take the quick connector with the maintainer and connect it to the terminals under the hood and extend the cord and then zip tie it somewhere under the grill and keep the cap on it when not in use and connect to it when parked in the garage. Just don't forget to disconnect it when you go and drive away in the morning. Connecting to a maintainer every night would probably greatly extend battery life.

amgliturbo

I used to keep my Porsche Turbo on a battery tender and did exactly that--ran the cable from the battery thru the grill--and yes on more than one occasion I pulled out of the garage forgetting that it was connected. Luckily most times the sae connector simply unconnected. Twice the battery tender was pulled off the shelf it was on but it didn't break--my garage is carpeted with old carpet from one of my rooms in the house that was replaced with new carpet--sounds crazy but carpeting your garage with carpet you do not care about is great especially in the winter when going into the garage without shoes. That said, now when I hook up my E63s to my NOCO charger/tender I lift the hood so the same thing re forgetting that the tender is hooked up won't happen again

2012 merc amg

Ya probably the safest idea just leaving the hood open although to do that on a regular basis gets old after a while. I’m thinking just fully charging the battery in my Cabriolet like once a month or so should be adequate. During other times not going to let the battery critical message bother me too much. I would estimate critical comes up at about a 40 or 50 percent charge. Being that the battery is only being fully charged to 80 percent even after an hour of highway driving that is only a 30 percent margin or so. I really think the mb critical terminology is too strong. It should say 50 percent charge and then say critical at like 20 percent or so. Just my opinion.

Ed99

Was curious if we get any warning messages if our battery is running low? Its winter and its a common time for batteries to die out. I had a few start up where it didn't start on the first try. But no warning message?

6G Schnell

yes, me connect will send you a message “battery is at critical level”…
one can monitor battery using this app, there are three levels:
fully charged, partially charged and critical
example below

bobblehead

signs of electronics malfunctioning messages. Lit up like a X'mas tree. LOL.
I had:
- electronic rear axle diff lock inoperative
- Active Brake Assist functions limited
- Blind spot Assist inoperative
- No ESP assistance
- Adaptive Highbeam Assist inoperative

You also get the battery icon every time you start up the car.
On the accessory mode (without the engine being started), car will turn itself off after about 4-5 minutes time.

My battery was 4 yrs old and it has just been replaced after having the dealer checked over (all those above issues) and confirmed the battery has fault and in need of replacement.