Something is draining the battery on 2019 E220D

[fatboydel]

My E220D is currently in the workshop for an issue with the battery going flat. They have it on an oscilloscope and can see that after the car is locked for a while something wakes up and is pulling around 11 amps from the battery, but they are not sure what.

Does anyone have an idea what would cause this?

 

[Trev1964]

That's a hell of a current draw.
Not going to be some minor component.

 

[fatboydel]

Something around 120 watts, not sure what it might be?

 

[V6Matty]

At that sort of rate it’ll likely be the audio system, either the command unit or the amp

 

[alexanderfoti]

If the car is waking up, then 11amps is probably the normal amount of current the car will draw with all the BUS'es awake.

They need to isolate what is waking up the BUS as the 11amp is draw is only becuase the whole system is being woken up by one module, akin to opening the door etc.

 

[brandwooddixon]

Start pulling fuses and putting them back in I guess. It's going to be a long process as you'll need to leave the vehicle standing and locked for a good while before you'll find the module that is waking the system up (typically it may take up to 20 minutes for a car to fully go to sleep).
Had a similar issue on my last car, at one point it sat at the garage for over a month. Interaction with the car wasn't much, check battery voltage remove or plug in a fuse, lock the car up and wait overnight.
A number of parts were replaced as the issue was sporadic, the car would sit for a week with no issues, I'd use it one day and the battery may be flat the following morning, or I'd use it several days in a week without issue before the battery drained again. In total it took several months to fully cure it - I took to driving around with a big battery pack in the boot.
My CL500 would draw just over 10A when sat fully awake - just unlock, open the door and close it.

 

[RedCar24]

I had an issue with one of my pervious cars it's battery was constantly being drained and I never got to the bottom of it in the end i ended up getting rid

 

[Timeandleisure]

Try replacing relay N… or look for faulty wiring to ECM

 

[fatboydel]

Thanks for the input guys, the garage had it for a few days and it didn’t re-appear. I have created a new thread regarding not fully charging when in Eco mode, which may be the issue here.