SL/R230: electrical service battery
Thread Starter
Newbie
Joined: Aug 2019
Posts: 4
Likes: 0
From: Springfield, Mo
2000 sl500
electrical service battery
2003 SL500. New battery in trunk goes down when car is not driven for weeks. Is there a source of battery drain when everything is off ? No problem with starting battery. Thinking I made need a battery maintainer for this battery.
MBWorld Fanatic!
Joined: Mar 2008
Posts: 1,232
Likes: 168
From: Glasgow, Scotland, UK
SL 350 R230 (3.7L with AMG Speedshift autobox)
The car should be able to work after a few weeks of not being used. You may get the message convenience functions off line on dash, but it will clear once the battery charges a little after 10 mins. I would recommend using a genuine Mercedes dealer battery, they are the best I have experienced. Good luck
Junior Member
Joined: Nov 2014
Posts: 18
Likes: 0
From: Oregon
2004 Mercedes SL500
Rear battery loosing charge
Above 2 answers are right. It's a common problem. If I am going to leave my SL500 for more than 3 days, I hook it up to a battery slow charger (Mercedes charger). No big deal so long as I don't drive off with it still attached to the battery. 
(me)
Before you get a new battery, have the existing one checked. You can always drive off and it will charge up within minutes (Just can't hear radio or lower top, etc.)
You might google battery failure or similar term. I recall seeing a YouTube on this exact problem and some ways to stop it or at least reduce it.
Good Luck. It's a great car.
(me)Before you get a new battery, have the existing one checked. You can always drive off and it will charge up within minutes (Just can't hear radio or lower top, etc.)
You might google battery failure or similar term. I recall seeing a YouTube on this exact problem and some ways to stop it or at least reduce it.
Good Luck. It's a great car.
Senior Member
Joined: Nov 2021
Posts: 469
Likes: 119
From: North West England
SL500
Thats because he can sell twice as many "battery tenders" 
Only need one on rear battery, though I would chase down as many parasitic drains before using one.
If you have more than about 200mA parasitic drain, you have a problem that needs sorting before relying on a battery tender!!
Car should start after at least 3 weeks of non use without consumer offline warnings.
Only need one on rear battery, though I would chase down as many parasitic drains before using one.
If you have more than about 200mA parasitic drain, you have a problem that needs sorting before relying on a battery tender!!
Car should start after at least 3 weeks of non use without consumer offline warnings.
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MBWorld Fanatic!
Joined: Sep 2007
Posts: 1,481
Likes: 310
95 SL600
You can do the same thing with the multimeter in the picture. I dont see any advantage to this at all. Plus this just tests the drain at the battery, doesn’t help find the culprit at all. Unless I am missing something with the lisle contraption.
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