SL/R231: Second Battery?
Newbie
Joined: Jul 2012
Posts: 14
Likes: 1
2013 SL550, '06 Corvette Convertible
Question for MBtech: In addition to my new SL550, I have an '06 Corvette. I rarely drive eiher in the winter due to all the "gravel" on our Colorado roads. I have used a trickle charge battery maintainer for years on the Vette, as sometimes it's months sitting under cover in the garage. I'm doing the same thing for the SL, attachig the battery maintainer to the positive and negative posts in the engine compartment. I was assuming that both batteries would be maintained using this proceedure, but maybe not. Any thoughts?
Super Member
Joined: Dec 2009
Posts: 541
Likes: 22
From: USA
10 speed bicycle
Question for MBtech: In addition to my new SL550, I have an '06 Corvette. I rarely drive eiher in the winter due to all the "gravel" on our Colorado roads. I have used a trickle charge battery maintainer for years on the Vette, as sometimes it's months sitting under cover in the garage. I'm doing the same thing for the SL, attachig the battery maintainer to the positive and negative posts in the engine compartment. I was assuming that both batteries would be maintained using this proceedure, but maybe not. Any thoughts?
Newbie
Joined: Jan 2018
Posts: 3
Likes: 0
From: Liberty, MO
SL550
Junior Member
Joined: Aug 2009
Posts: 26
Likes: 0
sl500, bentley GT, 911 cab, 1947 lincoln continental cabriolet
Close but not exactly. The ECO start/stop battery G1/13 actually only supports active electrical loads during the brief starting sequence when ECO start/stop is active. During this time the main battery, G1, is isolated from the rest of the vehicle to allow full power to the starter armature only. The starter solenoid power still comes from G1/13 in this case. Of course with ECO start/stop the starter is not the only thing used to start the engine.
The 230 dual battery system is quite different. The trunk battery aka systems battery aka G1 provides power to all electrical loads of the vehicle under normal conditions with the exception of the starter armature. The front battery aka starter battery aka G1/4, only provides power to the starter armature, the solenoid for the starter is still powered by G1 under normal circumstances.
Normally these two batteries are completely isolated, only for charging or undervoltage are they linked in parallel by battery cutoff relay K57.
Once again see previous quote, under normal circumstances the starter battery powers ONLY the starter armature.
The 230 dual battery system is quite different. The trunk battery aka systems battery aka G1 provides power to all electrical loads of the vehicle under normal conditions with the exception of the starter armature. The front battery aka starter battery aka G1/4, only provides power to the starter armature, the solenoid for the starter is still powered by G1 under normal circumstances.
Normally these two batteries are completely isolated, only for charging or undervoltage are they linked in parallel by battery cutoff relay K57.
Once again see previous quote, under normal circumstances the starter battery powers ONLY the starter armature.
MBWorld Fanatic!
Joined: Jan 2016
Posts: 2,336
Likes: 936
From: Brookshire, Texas & Cat Spring, Texas
2019 SL550/2023 EQS 580 SUV
I'm finding it difficult to follow all the battery opinions. I have an R231 2013 sl550 and battery cranks starter rather slowly. It starts but will not shift from PARK into R or D. If I leave it running for a while a battery must be charging and it will then shift. What battery is controlling that? Both batteries are almost 6 years old
MB World Stories
The Best of Mercedes & AMG
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Mercedes Teases Updated EQS With Steer-By-Wire and a Yoke
Verdad Gallardo
8 Mercedes Models With Poor Reliability Records
Verdad Gallardo
Senior Member
Joined: Oct 2018
Posts: 380
Likes: 99
From: Orlando, FL
2017 550SL - 2018 560S
If you received a response to this question, I could not find it. I also would like to put a tender on my 2017 550SL. If I attach a maintainer to the main battery (one to the positive terminal and one to the body frame), in the trunk, will it maintain BOTH batteries or only the trunk battery?
Junior Member
Joined: May 2017
Posts: 61
Likes: 11
From: Phoenix
2015 SL400, BMW Z3, Datsun 280Z, a couple of jeep Grand Cherokee's - And a Commander Airplane
Battery tender
If you received a response to this question, I could not find it. I also would like to put a tender on my 2017 550SL. If I attach a maintainer to the main battery (one to the positive terminal and one to the body frame), in the trunk, will it maintain BOTH batteries or only the trunk battery?
Senior Member
Joined: Oct 2018
Posts: 380
Likes: 99
From: Orlando, FL
2017 550SL - 2018 560S
Junior Member
Joined: May 2017
Posts: 61
Likes: 11
From: Phoenix
2015 SL400, BMW Z3, Datsun 280Z, a couple of jeep Grand Cherokee's - And a Commander Airplane
Tenders
I have been using the attached for some time now on a car that I keep at my other house, and it works great.
