How to Trickle Charge Primary and Auxiliary Battery - S-Class 550 2014
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Junior Member
Joined: Mar 2011
Posts: 25
Likes: 3
From: Naples, FL
2014 S-Class S550 2023 Audi Q8
How to Trickle Charge Primary and Auxiliary Battery - S-Class 550 2014
I have a couple questions regarding trickle charging my MB S-Class 550 2014. We need to leave our car dormant for a few months during the winter while we’re away. First, how long can we expect the battery to last before it goes dead? Is there a specific timeframe, in weeks or months, when the car should be started to maintain the battery’s health? Secondly, the car has two batteries: the primary one in the front and an auxiliary in the trunk. We’re considering using trickle chargers for both. The primary battery in the front seems straightforward, but accessing the auxiliary battery in the trunk looks more complicated. Do you have any suggestions or advice on how to set up the trickle charge for both batteries?
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Joined: Oct 2011
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From: Illinois
S560/SL550/LS460/Q70L 5.6 AWD
Simply use the red and black posts in the engine compartment and you should be ok, my car mostly sits in one or our garages and this is what I'm always doing, no problems whatsoever !
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 25
Likes: 3
From: Naples, FL
2014 S-Class S550 2023 Audi Q8
just follow up question - What about the second auxiliary battery in the trunk ? Do you trickle charge it separately?. In your opinion, how long before the batteries go dead if they are not hooked up to a trickle charger?, for both batteries?.
Super Member
Joined: Oct 2011
Posts: 697
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From: Illinois
S560/SL550/LS460/Q70L 5.6 AWD
As mentioned in my previous answer I only charge using the engine bay terminals, I assume ( I may be wrong ) that using these the main battery get maintained, I left may car one time w/o the charger for a couple of weeks and I got the "battery low" message on the dash, charged the battery using a charger, back in business.
From my experience of many years using the trickle charger, as long as the charging is completed (green light on my CTEK) then the battery is full and the charger will kick in only when it sees a low voltage, bottom line, using the CTEK will keep your battery always full, I hope this answer you question.
From my experience of many years using the trickle charger, as long as the charging is completed (green light on my CTEK) then the battery is full and the charger will kick in only when it sees a low voltage, bottom line, using the CTEK will keep your battery always full, I hope this answer you question.
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Joined: Oct 2011
Posts: 697
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From: Illinois
S560/SL550/LS460/Q70L 5.6 AWD
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2014 S63 2010 ML350 Bluetec 2009 SL550
I think you are supposed to do the opposite - trickle charge the aux battery and let the cars electronics sort out how it gets that up to the main battery. That's what I was advised to do on our R230 and it's been fine over the last 3 winters doing it this way.
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From: DFW
SL63
That trickle charger link was a good beginner primmer. But it was generalized. The battery has to be paired with an appropriate trickle charger. AGM batteries, for instance, do not maintain peak performance if overcharged. So a trickle charger for that battery should have an auto shutoff circuit after it detects a full charge. If the same battery is connected to parasite loads, then the trickle charger should have enough capacity to power all the parasite loads, and have charge over and above that capacity to fully charge the battery. Then, the charger should step down output to feed only the parasite load.
There is a lot more to this trickle charger topic than may first meet the eye.
There is a lot more to this trickle charger topic than may first meet the eye.
Super Member
Joined: Jul 2007
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From: Santa Barbara, CA
S550C4, Porsche Cayenne
That is how my R230 is set up using a MBZ-branded CTEC trickle charger attached to the aux battery. Surprisingly the MBZ price was almost the same as I as able to find for the CTEC. I had it installed during routine service for very low cost. Since then no more battery warnings after periods of inactivity. Good luck.
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2014 S550 AMG, 2017 XT5
That trickle charger link was a good beginner primmer. But it was generalized. The battery has to be paired with an appropriate trickle charger. AGM batteries, for instance, do not maintain peak performance if overcharged. So a trickle charger for that battery should have an auto shutoff circuit after it detects a full charge. If the same battery is connected to parasite loads, then the trickle charger should have enough capacity to power all the parasite loads, and have charge over and above that capacity to fully charge the battery. Then, the charger should step down output to feed only the parasite load.
There is a lot more to this trickle charger topic than may first meet the eye.
There is a lot more to this trickle charger topic than may first meet the eye.
