Mercedes-Benz SL55 AMG Battery Drain

Has anyone else encountered a problem with their battery losing a charge when the car is sitting? Richard asks:

A problem has plagued my SL55 AMG for the last 2 years. I have since brought the MB AMG to service twice for the same problem. This last time the service mechanic replaced my second battery found in the trunk and gave me a battery conditioner that needs to be connected to the battery when the MB AMG is sitting. The manager notified me there is a drain on the battery that they cannot find. Is this a problem all ’03 SL55 AMG’s have and if not does anyone have an idea why there would be a constant drain on the second battery, and is there a fix? – Richard

Leave your comments and we’ll see if we can help him out – thanks!

Subscribe to AMG Market and receive
updates via email; no SPAM [click here]


  1. konstantine said,

    Wrote on July 16, 2009 @ 8:29 am

    i had same promlem with my 03 cl55 had to replace altenator generator bettery cause there was a recal beck in 05 look into it richard good luck

  2. Lisa said,

    Wrote on July 16, 2009 @ 4:24 pm


    I was doing research online and came across your blog. The dealership here has been unable to fix or diagnose the problem. It has been in the shop 4 times in the past 18 months. We are having the same issues with his 2003 SL55 AMG and would love to know if anyone else has been able to resolve the problem.

  3. Gary Anderson said,

    Wrote on July 17, 2009 @ 5:44 am

    Funny you should have that problem. After I came in with the second battery having lost its charge, my tech did some research and came up with the fact that the voltage regulator on many of the 05 models, including the C Class (my C55) and SL Class cars with the 5.5 engine was some sort of non-Bosch brand, and that there had actually been a recall memo on them for the SLs. Apparently, the regulator would get confused and stop charging at 11.5 volts. Not good/ He replaced mine on my C class under warranty (which had three weeks left to run), and everything seems to be copacetic, now.
    Certainly have them check your voltage regulator output. Bet it’s not uniform and may be constantly too low.
    I only have his word on the recall info, so don’t know how much of that is factual, or the service memo number or whatever, but that could be your problem.
    Gary Anderson

  4. Faisal said,

    Wrote on July 17, 2009 @ 9:49 am

    Actually, I have been working with Mercedes-Benz for the past 4 years; it is correct that there was a problem with the alternator regulator and it was a recall. Replacing the regulator with correct MB part no.; (Bosh) will solve the problem.

    Thanks and Regards,

  5. Greg Magnus said,

    Wrote on July 17, 2009 @ 9:55 am

    Thanks for the feedback – looks like this is a common problem. Is your MB dealer on top of this issue (Lisa & Richard)?

  6. Lisa said,

    Wrote on July 17, 2009 @ 10:07 am

    They have been unable to diagnose any fixes for the problem. I have left her a message and will provide her with the information that I am getting here. I will update when I get a response from her.


  7. Ken said,

    Wrote on November 8, 2009 @ 1:04 am

    I have an 07 SL55 that sits for long periods, (30 days), at a time. I have not experiened any problems like you described. If the problem has been identified by MB and there was a recall such as mentioned by Faisal, shouldn’t your MB service department know about it?

  8. Lisa said,

    Wrote on November 9, 2009 @ 11:15 am


    In a word, NO. They have exhausted all their resources and can not figure it out. We are still having issues. It has been back to MB twice between July and October.


    I am sure that your 07 will not have the problems we have had with the 03. MB has most definetly taken care of this issue in the newer vehicles, which may be the problem with the technicians not knowing how to correct ours. Everything that they could have done, they apparently have done and we still have the issues. We are thinking about bringing it to another mechanic who works on the high end foreign cars to see if they can figure it out. Other than that we are very puzzled by these issues and MB’s inability to pin point the issue.


  9. Greg Magnus said,

    Wrote on November 9, 2009 @ 11:51 am

    Call MBUSA and ask for a “regional rep” for your area. Call your local MBCA (Mercedes-Benz Club of America) section and see if they have the name of the regional rep also. If you are a MBCA member, you can ask for assistance through the ombudsman program as well. I hope this helps.

  10. eugene said,

    Wrote on July 15, 2010 @ 12:58 pm

    my 2004 sl 55 amg’s flasher lights keep on coming on which could be as a result of coltage drop or the backup battery in the alarm module going off to below its reserve level. ill have the car checked and enquire as to the recall. regards eugene

  11. Shaneeta said,

    Wrote on November 29, 2010 @ 3:53 pm

    I have a 1997 MB E320 and have the same issue of the Battery not holding it’s charge. New Battery and all. What’s up? Alternator or electronic issue? someone please help, one with little money.!!

  12. Steve said,

    Wrote on December 20, 2012 @ 8:19 am

    My sl55 2003 when you turn of the ignition, there’s a sound coming from behind the speedo dash area and the 6cd changer keeps making sounds like its still working, I’m sure that’s what’s flattening my battery…

  13. Joe Falconi said,

    Wrote on January 21, 2013 @ 2:31 pm

    Just replaced the trunk battery with MB battery. Fully charged…lasted about one week.
    The prior battery gradually got worse until it wouldn’t hold a charge for more than a day.
    No issue with the battery for almost ten years…until the gradual reduction of holding the charge started Fall of 2012. Sl a 2003 SL55 AMG…
    Getting ready to bring in to dealer who I hope has had other experience with the same issue. First guess of battery was probably correct due to the fact the battery was ten years old.
    Hopefully will correct issue soon and report back.


  14. Rene said,

    Wrote on January 12, 2014 @ 7:24 pm

    Good A have a 06 sl55 same thing and replace the alt and solve the problem Thanks. Rene

Comment RSS