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What is the SAM? If I want to keep my auxiliary battery fully charged should I use a maintainer attached directly to the auxiliary battery?
That would sure do the job. The only thing that gives me pause about doing so is that I've seen a few threads here where people were having trouble with their start/stop modules... and sometimes after "I even charged the battery". I have to wonder if it's possible to harm that module in the process of externally charging the battery. I take it that you've been charging your battery to no ill effect regarding the module, so it's possible my fear may be unfounded.
I believe I've been getting by without charging it myself because of my usage cycle. My car may sit as long as some others here, but when I do drive it, it's for several hours on the highways and mountain roads in northern Georgia...so, very little, if any, start/stop action. I think that's plenty long enough for the car's system to top it up, if it's needed.
You've made it almost seven years on your original battery. That sure seems like reasonable life on the battery. I know your car had the pigtails on it already when you got it, but do you have any idea whether or how often they were used by the previous owner?
And, I don't know what the "SAM" is either...
Last edited by Dr. Manhattan; Jan 17, 2022 at 06:29 PM.
I don't know if and how often the previous owner used the pigtail on the auxiliary battery. In fact, I didn't even know it was there until I removed the trim panels and discovered it. It is now left out so I can connect one of my CTEKs whenever the car is unused for several days.
I'm still not convinced that using the underhood charging posts is maintaining a full of charge on the auxiliary battery.
One of the first things I do after starting my SL is to turn OFF the start-stop function. I despise it and have coded it OFF on my BMW X5.
Last edited by rmorin49; Jan 17, 2022 at 06:53 PM.
What the MB Shop Foreman told me is to hook up the batt maintainer only to the main battery in the trunk and that is what I did.
He said that the connection in the engine comet is for jumbo start only as it is not connected into the battery mgmt system (the SAM) and the B95 cat that monitors the system is connected to the trunk battery as well.....He told me that connecting to the + and - terms at the battery in the trunk would allow the SAM to monitor and adjust charge as needed to the Aux Battery.
I have been doing this "C-Tek" to batt terms at trunk battery since purchasing the car in late 2017 and use infrequently in winter (sometimes don't use for 2 months) and have had no battery issues.
What the MB Shop Foreman told me is to hook up the batt maintainer only to the main battery in the trunk and that is what I did.
He said that the connection in the engine comet is for jumbo start only as it is not connected into the battery mgmt system (the SAM) and the B95 cat that monitors the system is connected to the trunk battery as well.....He told me that connecting to the + and - terms at the battery in the trunk would allow the SAM to monitor and adjust charge as needed to the Aux Battery.
I have been doing this "C-Tek" to batt terms at trunk battery since purchasing the car in late 2017 and use infrequently in winter (sometimes don't use for 2 months) and have had no battery issues.
Best I can advise.
Steve
Better change your workshop.........It makes no sense to pull everything out of the “trunk” to charge the battery when MB say to use the jump start points. I’ve been doing it for 5 years with no issues. If the AUX needed to be charged in a different way, why is it not mentioned?
Just completed installation of a CTEK pigtail on the main battery in the trunk. I'll try using it and will see if it keeps both batteries fully charged.
Btw Randy, if you bump your CTek up to "winter" mode, it raises the voltage to just about where your AGM battery likes it. AGMs need a slightly higher charging voltage than conventional batteries do. If you were already aware of this, please forgive...
I'm also wondering how the SAM and the "smarts" in the CTek are going to interact. Will the SAM allow the CTek to go through its normal regimen of steps during charging, or will they get in each other's way?
Last edited by Dr. Manhattan; Jan 20, 2022 at 04:49 PM.
Is the main battery an AGM? I was aware that the AGM batteries do like the "winter" mode but didn't know if the main battery is an AGM. It is a Mercedes branded battery manufactured by VARTA.
Btw Randy, if you bump your CTek up to "winter" mode, it raises the voltage to just about where your AGM battery likes it. AGMs need a slightly higher charging voltage than conventional batteries do. If you were already aware of this, please forgive...
I'm also wondering how the SAM and the "smarts" in the CTek are going to interact. Will the SAM allow the CTek to go through its normal regimen of steps during charging, or will they get in each other's way?
How could the “car smarts" affect the charger programme? Connecting directly to the battery in the trunk will bypasses any “car smarts”
When charging from the manufacturer recommended points ( I’m pretty sure that the positive is a direct connection to the main battery (via the starter) anyway, as it is a jump starting point) the CTEK goes through all the phases as normal.
I do not understand the logic of wanting to connect directly to the cranking battery (except for some sort of convenience ........) when the manufacturer has provided charging points. However each to his own.
Last edited by rorywquin; Jan 21, 2022 at 05:38 AM.
How could the “car smarts" affect the charger programme? Connecting directly to the battery in the trunk will bypasses any “car smarts”
When charging from the manufacturer recommended points ( I’m pretty sure that the positive is a direct connection to the main battery (via the starter) anyway, as it is a jump starting point) the CTEK goes through all the phases as normal.
I do not understand the logic of wanting to connect directly to the cranking battery (except for some sort of convenience ........) when the manufacturer has provided charging points. However each to his own.
Are these "charging" points or "jump starting" points? Do we have any certified MB technicians on this forum?
Are these "charging" points or "jump starting" points? Do we have any certified MB technicians on this forum?
Take a look at the extract from the owners manual that I posted above. It clearly states to use the jump start points for charging. Don’t need a “certified MB technician”. In any event a jump start point would be directly connected to the starter motor with a thick cable and so would the cranking battery in your trunk be connected to the same point on your starter motor with that thick cable that you see. Nett result it that the jump start point (+) is directly connected to your cranking battery with a big thick cable ...........
Last edited by rorywquin; Jan 21, 2022 at 08:33 AM.
Yes, it is connected directly to the battery via the pigtails you installed. Was there a reason that you expected anything different?
I did not but I am still curious to confirm that the auxiliary battery will be "maintained" by the CTEK connected directly to the main battery vs connected to the underhood points vs connecting a second CTEK directly to the auxiliary battery as I have been doing for the last 3 years.
I'm using a CTEK charger connected to the battery in the trunk for years during the winter time and it keeps the battery fully charged, never had a problem.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I just have a set of winter tires and don't worry about the car sitting unused. I drive it daily as long as we don't have an ice storm. It's my daily addiction fix.
I'm using a CTEK charger connected to the battery in the trunk for years during the winter time and it keeps the battery fully charged, never had a problem.
What about the auxiliary battery? Also kept charged?
I did not but I am still curious to confirm that the auxiliary battery will be "maintained" by the CTEK connected directly to the main battery vs connected to the underhood points vs connecting a second CTEK directly to the auxiliary battery as I have been doing for the last 3 years.
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