E55Killa

For some reason when my car sits for more than 2 days the battery is dead.
Everything in the car is shut off but the battery keeps dying. Any thoughts?
Oh yea both batteries are less than 4 months old.

Max.H

Did you check your charging system?

E55Killa

how would i do that?

altenator?

Max.H

Easiest way is right through the gauge cluster. Yes, perhaps your alternator is not giving the battery a sufficient charge. Pure speculation at this point. But, It's a good place to start.

You can do this by turning the key to the 1st position and pressing the reset button quickly 3 times. The battery voltage should display. Mine reads about 12.2 volts off and 13.9 volts when the car is on.

E55Killa

i have the same voltage.
there has to be something draining the battery when it sits.

MJ50

check door control module...

E55Killa

how would i go about doing that?
i know the interior lights arent staying on.

Busta Riles

There is also such thing as a bad battery.

We have replaced a few under warranty.

E55Killa

this would be the second bad 1 in a yr

Busta Riles

Maybe something is constantly drawing from the battery. It should throw a code, though, if that's the case. I've seen cars that have been boosted improperly come in & need multiple modules replaced cuz they keep killing batteries.

raymond g-

unfortunately it is not uncommon for recent model MBs (heavily electronic
reliant) to suffer from occasional parasitic power drain when the ignition is
off.

if you've already discounted the easy checks (voltage regulator, alternator,
battery health/condition), then the next thing are the appliances such as
door and seat control modules.

check amperage draw with ignition off. then, unplug devices systematically
(while still observing amp reading) to attempt to isolate failed part.

if this isn't making any sense, find a buddy who has electrical/electronic
knowledge and buy him/her lunch and let tackle this

Busta Riles

The overhead control module is another common one...the one that has interior light/sunroof buttons.

RickyN F355

i had the same issue...took it to the dealer and they traced it to some part of the electronic system...

E55Killa

Thanks for all the input guys.
I might take it to the stealership and see if they can diagnose the problem..

how can i check on the overhead control module?
its only when the car is sitting for a while i checked the voltage after 1 day and it seems fine.

RonnieRenaldi

I just had the same problem, replacing the altenator this week!

TopGun32

I guess since our cars get to sit longer period of time due to the holidays.. battery issues are springing up.

My E is at the dealer for same issue. Battery drain problem.

RonnieRenaldi

Do you guys know how much the dealer cost for a new alternator?

Yacht Master

If you do go to the dealer, get the information "TSBs", from the stickies, regarding all the software updates for the model year of your car, here are a few. Ask the dealer if all of them are up to date. If they are up to date and your batteries are new your car is not going to sleep, the dealer will be able to diagnose this in less than a hour, most common cause bad module. If every thing checks out OK but you still have a drain on the battery, this condition could take many hours to find.

TSB Number & Issue Date TSB Title
P-54_21-137 MAR 05 Electrical - Battery Control Module Reprogramming

P-54_21-113 SEP 04 Battery - No Start Condition Due To Quiescent Drain

E55Killa

thanks so much

LanceA

Have the same problem with my E55 AMG 2005. Quite frustrating!

Kelvin07

Did you install an aftermarket head unit or amp or both?

LanceA

No....nothing out of the ordinary. Got up on Wednesday and the battery was dead. So I replaced it. Its dead this morning.

moosejaw

Have the same problem.
I've replaced the voltage regulator and replaced both batteries.
Ive pulled each and every fuse from the trunk, the front driverside dash panel, and the front underhood. I couldnt find the one in the underfloor of the passenger side
If i drive it everyday its not bad. But after three days or more its charging at 6v. Obviously the car is not starting

I could throw money at the BCM in the trunk but that's no guarantee either
it could be the polyswitch fuse under the dash?
I have a tech friend at the dealer who updated all the software for me free of charge.
Still didn't fix it

Going to bring it back to him to do a trace, thats the only way
Unless you want to locate all four or five fuse boxes and do a amp draw test?

stockC43

It may sound stupid but some people still have the old v60 phones still plugged in and they can cause a draw. Easy fix, take it out of the cradle. Had one come in a few weeks ago.

LanceA

Moose....I went out and bought a volt / amp meter this afternoon. Charging the battery on my S500 and I think its almost at full charge. I will do a fuse / amp test in the morning with my Wife's help and hopefully locate the draw.

Failing which, I guess I will have no option, and will take it into MB and hold my breath as to how much that is going to cost.

Let me know how it works out with your car. I will post an update when I have anything to add.