11.9 Volts
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Joined: Feb 2019
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From: indiana
2008 s550
11.9 Volts
Last year on my 08 s550 I had a parasitic draw that drained the battery down to 5 V in one day I solved it by removing the tele aid module. I have replaced the consumer battery but it still drains down to 11.8-12 volts after a couple days any ideas?
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
What do you expect your battery voltage to be when car is not running? Mine is 11.7V - 11.8V. Just checked yesterday, it was 11.7V.
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From: indiana
2008 s550
You need to be under 50mA. The S Class is (as are all Mercedes as well as other computer-controlled vehicles these days) highly complex with their electronics. If it were me, I would want access to a Xentry scanner. It will show you where your drains are. If that's not possible, the next step for me would be an official of all circuits, which, in the case of the S Class, can be a lengthy process. These after using common sense first, of course. Was any work done to the car recently/what is the car's history/etc. In healthcare (I'm an ER nurse), it's always in the history. If you can target specific areas you think or know to have recent issues or a change in condition, start there. Xentry can give you graphs over time of different module activity. You can also get your hands on a logging DMM and leave it connected over night then read for power draw spikes. Might help narrow it down. Without any more info, there's not much else I can say without simply speculating.
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'11 E350, '11 E550, '98 M3, '95 E320
Xentry, as Senecan points out could certainly make things easier.
Instead of pulling fuses, measure the mV drop across them. The one with the highest reading would be on interest. SMA and PHAD on YouTube have videos describing the process...
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Joined: Oct 2017
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From: Silicon Valley, 94070
2009 W221
Pulling fuses won’t work, because as you pull them you wake up modules in the process. Unless you pulled the exact fuse the first time.
Xentry, as Senecan points out could certainly make things easier.
Instead of pulling fuses, measure the mV drop across them. The one with the highest reading would be on interest. SMA and PHAD on YouTube have videos describing the process...
Xentry, as Senecan points out could certainly make things easier.
Instead of pulling fuses, measure the mV drop across them. The one with the highest reading would be on interest. SMA and PHAD on YouTube have videos describing the process...
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'11 E350, '11 E550, '98 M3, '95 E320
Yup, I'm in CT. I know there are cheaper options off Aliexpress, eBay and the sort... but good luck with support. For me it was worth the little extra, good reviews from members and future help with coding and access to files for updates.
Last edited by doni01; Apr 5, 2021 at 11:25 AM.
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W222, W221, W218, W211
2009 W221 S63 here - same "issue" - At some point last year I just replaced my battery to OE after I could not start the car leaving it for 2 weeks on my driveway (Mercedes OE, not OE-type).
The car is usually parked for 2-3 days in-between short rides - battery indicator on dashboard or xentry is usually showing below 12V (11.7-11.8), while measured on the battery terminal - 12.2-12.3, so there is some voltage drop in-between. After starting it holds 14.7V strong, so no charging issue there... I did not have a problem starting in almost a year now, so I blame low voltage in my usage habits - I did <10k last year...
ah... and I am running single battery type car (no aux battery in the trunk).
The car is usually parked for 2-3 days in-between short rides - battery indicator on dashboard or xentry is usually showing below 12V (11.7-11.8), while measured on the battery terminal - 12.2-12.3, so there is some voltage drop in-between. After starting it holds 14.7V strong, so no charging issue there... I did not have a problem starting in almost a year now, so I blame low voltage in my usage habits - I did <10k last year...
ah... and I am running single battery type car (no aux battery in the trunk).
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From: Silicon Valley, 94070
2009 W221
Last edited by Hatzenbach; Apr 9, 2021 at 12:12 PM.
Thread Starter
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Joined: Feb 2019
Posts: 96
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From: indiana
2008 s550
@Will Hunt , when you write "removing the tele aid module" did you simply pull the fuses (F73 & F138) or is there a more sophisticated method?
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Joined: Jun 2013
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From: Staten Island, NY
2010 MB S550, 2017 MB SLC 300
here is a good explanation on how to find battery drains
https://youtu.be/UEYGmSn01Bw
https://youtu.be/UEYGmSn01Bw
