SL/R231: CTEK Maintainer Question
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From: Hagerstown MD
2015 SL400; 2019 X5M40i
CTEK Maintainer Question
I am using a CTEK on my SL when it isn't used on a regular basis. My garage is not heated so it does get well below freezing during the winter months when I am not driving the SL at least once a month.
What is the correct mode to use for maintaining the batteries in the SL? I think I remember reading that the "snowflake" mode should be used. Is this correct? I thought it was the mode used in cold environments and also for AGM batteries.
Isn't the main battery a traditional lead acid battery? What about the small auxiliary battery? I replaced my auxiliary battery last year and it also looked like a lead acid battery.
What is the correct mode to use for maintaining the batteries in the SL? I think I remember reading that the "snowflake" mode should be used. Is this correct? I thought it was the mode used in cold environments and also for AGM batteries.
Isn't the main battery a traditional lead acid battery? What about the small auxiliary battery? I replaced my auxiliary battery last year and it also looked like a lead acid battery.
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
I am using a CTEK on my SL when it isn't used on a regular basis. My garage is not heated so it does get well below freezing during the winter months when I am not driving the SL at least once a month.
What is the correct mode to use for maintaining the batteries in the SL? I think I remember reading that the "snowflake" mode should be used. Is this correct? I thought it was the mode used in cold environments and also for AGM batteries.
Isn't the main battery a traditional lead acid battery? What about the small auxiliary battery? I replaced my auxiliary battery last year and it also looked like a lead acid battery.
What is the correct mode to use for maintaining the batteries in the SL? I think I remember reading that the "snowflake" mode should be used. Is this correct? I thought it was the mode used in cold environments and also for AGM batteries.
Isn't the main battery a traditional lead acid battery? What about the small auxiliary battery? I replaced my auxiliary battery last year and it also looked like a lead acid battery.
The main and small (eco start/stop battery) are AGM lead acid batteries.
Here’s the part numbers for a 2019 SL450:
Eco start/stop battery: A211-541-00-01; and
Main battery: A 001 982 82 08 26.
Joined: Nov 2016
Posts: 7,847
Likes: 3,498
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I don't think it has gotten below freezing in our area this year. I know I have water in containers in the garage and they haven't frozen. That aside, I don't think there is any harm leaving the CTEK connected to the main battery if you are not driving your car often. I drive mine daily, so I don't have this concern. Now, my 2004 SL500 is another story. I used to connected that whenever I wasn't using the car. But, it stayed outside.
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Joined: Feb 2014
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From: Central Florida
'13 SL550 Mars Red, Designo White interior, B and O sound
Slightly off topic but the discussion of batteries (and their part numbers: thank you!) raises a query I've been mulling for a while. After I start off and drive a while I might come to a stop at a light: the 'ECO' display is yellow but often will then change to green and the engine will appropriately cut out. In other words, the 'ECO' display doesn't often actually show in green even after a good (say) 20 mile cruise with the only 'consumable' being the head unit. I am wondering if that's indicative of the battery losing its health meaning a replacement will soon be required?
And, if so, which battery - the one in the trunk or the one in the cabin? 🤔
Edit: I found a really informative thread here (https://mbworld.org/forums/sl-class-...ry-type-2.html) and am now assured its the ECO start battery that's going south. I'll have them both checked. Thanks to all who contributed to that thread a couple of years back ...
And, if so, which battery - the one in the trunk or the one in the cabin? 🤔
Edit: I found a really informative thread here (https://mbworld.org/forums/sl-class-...ry-type-2.html) and am now assured its the ECO start battery that's going south. I'll have them both checked. Thanks to all who contributed to that thread a couple of years back ...
Last edited by Bitbytr; Mar 9, 2023 at 10:47 AM. Reason: Found the answer in another thread.
Thread Starter
MBWorld Fanatic!
Joined: Dec 2015
Posts: 1,636
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From: Hagerstown MD
2015 SL400; 2019 X5M40i
I don't think it has gotten below freezing in our area this year. I know I have water in containers in the garage and they haven't frozen. That aside, I don't think there is any harm leaving the CTEK connected to the main battery if you are not driving your car often. I drive mine daily, so I don't have this concern. Now, my 2004 SL500 is another story. I used to connected that whenever I wasn't using the car. But, it stayed outside.
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
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Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Jetta, you must have taken a long winter's nap. We had a very cold spell earlier this year when the temps were in the single digits for a couple nights at least in Hagerstown.
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
The normal and the cold weather modes are suitable for AGM charging.
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Joined: Nov 2016
Posts: 7,847
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From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Jetta, you must have taken a long winter's nap. We had a very cold spell earlier this year when the temps were in the single digits for a couple nights at least in Hagerstown.
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
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Joined: Nov 2016
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From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
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From: God's County (Yorkshire)
Shanks’s Pony
The “snowflake” mode provides higher charging current for cold weather applications.
The main and small (eco start/stop battery) are AGM lead acid batteries.
Here’s the part numbers for a 2019 SL450:
Eco start/stop battery: A211-541-00-01; and
Main battery: A 001 982 82 08 26.
The main and small (eco start/stop battery) are AGM lead acid batteries.
Here’s the part numbers for a 2019 SL450:
Eco start/stop battery: A211-541-00-01; and
Main battery: A 001 982 82 08 26.
MBWorld Fanatic!
Joined: Jan 2017
Posts: 1,040
Likes: 234
From: God's County (Yorkshire)
Shanks’s Pony
Jetta, you must have taken a long winter's nap. We had a very cold spell earlier this year when the temps were in the single digits for a couple nights at least in Hagerstown.
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
Is the "snowflake" mode the correct one to use since the batteries are AGM even if ambient temperatures are well above freezing?
Last edited by rorywquin; Mar 11, 2023 at 11:23 AM.
