SL/R230: Can I put a trickle charger on both batteries in my 2009 SL550
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Newbie
Joined: Jan 2018
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SL 550
Can I put a trickle charger on both batteries in my 2009 SL550
I only use my SL550 every other 4 months and come back to dead batteries. Can I put trickle chargers on the batteries if I disconnect Them?
Super Member
Joined: Feb 2007
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From: Dallas, TX
2008 E63 wagon (1 of 62)
yes you can. Just disconnect the ground cables at the batteries and hook up the battery tenders. Its cheaper and easier than replacing $450 worth in batteries 2-3 times a year
Member
Joined: Apr 2014
Posts: 127
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SL550
I have read many posts that say only hook up rear battery. If front battery is low then that will charge it. Not sure if any issue hooking up both. I periodically use CTEK maintainer but hook only to rear. Have never had a low/dead battery issue but may not have let them sit long enough to get there. Mark
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Newbie
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SL 550
Member
Joined: Apr 2014
Posts: 127
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SL550
I missed the point about disconnecting them even though clearly stated. That's what I get for scanning. I agree, if they are completely separated, no issues. Like two batteries sitting on a bench. Charge away. But I may be missing the point of your question since, as you suggest, they are disconnected, so of course they can be charged/maintained as individual batteries. I believe though you are taking unnecessary steps since I believe leaving all connected and connecting one maintainer to the rear battery accomplishes what you are after...keeping both batteries fully charged. Mark
Thread Starter
Newbie
Joined: Jan 2018
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SL 550
Trickle charge
Ok I thought I HAD to disconnect any battery to charge or do anything with it otherwise I would ruin the electronics in the car? So I can put the trickle charger on it and just the rear battery? What needs to be disconnecting?
Thank you so much for your replies by the way. You are so helpful
Thank you so much for your replies by the way. You are so helpful
I missed the point about disconnecting them even though clearly stated. That's what I get for scanning. I agree, if they are completely separated, no issues. Like two batteries sitting on a bench. Charge away. But I may be missing the point of your question since, as you suggest, they are disconnected, so of course they can be charged/maintained as individual batteries. I believe though you are taking unnecessary steps since I believe leaving all connected and connecting one maintainer to the rear battery accomplishes what you are after...keeping both batteries fully charged. Mark
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Member
Joined: Apr 2014
Posts: 127
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SL550
I do not believe that is the case. It may depend on the type of charger you are using. I do not believe disconnecting the battery is required. I will say I have never disconnected the battery when using CTEK maintainers in any of my vehicles. And the SL is probably the one most likely to have an electronics issue. Some people even design elaborate connections so they don't even need to open the trunk to connect the maintainers. I just open the trunk, remove the floor to get access to the battery and connect the clips. Never an issue with electronics.
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Banned
Joined: Jan 2006
Posts: 1,982
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
The Starter battery powers nothing more than the armature of the starter motor. A good battery should not go flat after 4 months; but since yours is, you could simply put a charger on the Starter battery and disconnect the Systems (trunk) battery.
Putting a charger on one battery will have no effect on the other battery.
According to M-B disconnecting the Starter battery while the Systems battery is connected will set a fault causing a message to display in the cluster, but this has not been my experience.
Disconnecting the Systems battery will reset all OBD-II monitors.
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Joined: Oct 2014
Posts: 168
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2005 SL65
I successfully used two battery tenders without disconnecting the battery. I also have used just one battery tender on just the rear with no problems with the car sitting for six months.
Some insurance companies require the battery to be disconnect while is storage. I think they are worried about an electrical fire.
Some insurance companies require the battery to be disconnect while is storage. I think they are worried about an electrical fire.
