My E300 BlueTech hybrid (2015) has a consistent parasitic drain of about 480mA. The drains seem to come from an Eletronic load since the power (i.e. volt * current) seems to remain constant despite lowering battery voltage. I have done an XEntry scan and it does not show any faults other than teh ageing health state of teh hybrid battery (however the hybrid system works without any problems).

Other than teh drain (which makes teh 12V battery to go flat after about 5 days on non-use), teh car is performing fine. Teh auxiliary battery retains its charge. Teh 12V battery is also new (1.5 months old)

I did a "current draw test" on the front and rear SAM fuses and none of the fuses show any current drain.

Any suggestions on where the drain could be? Anyone else has experienced a similar issue?

Your suggestions and comments are highly appreciated.

 

Okay, sorry Mercedes got you in hell with this drain. If that can comfort you 3 day drains are worse!

What's draining is likely....
the F-SAM/CGW itself doing busy work polling for security.

Now that you're done pulling fuses for troubleshooting purpose, REBOOT THE CHASSIS and scan all modules faults.
Pulling fuses makes things worse. The chassis network is not plug-n-play, at all. When the doors are missing SAM goes nuts.

Thanks to Bosch, there's no real good way to pin point vampires or poor performers.
It's the process of elimination over CAN-B.
You can see that chassis has entered sleep low-power and still get drain.
Of course you can double check for evidence of the standard water intrusion at SAM + Footwells.

I find it particular your chassis has no faults. That in itself is a problem of modules missing.
Even factory new chassis have a handful of faults...

I would be more comfortable starting with a sanitized chassis to then concentrate on CAN-B.

How many miles on this vehicle?

 

Dear CaliBenzDriver

Thank you for the response.

The vehicle has 42,000 km clocked.

Infact, I did not pull any fuses but instead used a DMM (in milli-volt range) to check the voltage drop across each fuse in the SAM. None of them indicated any drop and hence no current flow (I checked the DMM on a different vehicle and it was sensitive to detect about 50mA drain through a 10A fuse).

I think CAN-B goes into sleep since, after about 30 minutes from locking the vehicle, the seat controls from the door panel (i.e. memory seats) becomes non-operative.

I am yet to check the fuses on teh Hybrid relay module. I wonder there are any additional fuses inside the cabin (e.g. under dashbaord etc.).

If that fails I am thinking of checking the current flow through each wire spanning out from the F32 (pre-fuse box), using a DC clamp meter. I believe 480mA should show some indication on the clamp meter (my clamp meter has a 400A range with 6000 counts - hence it is not that sensitive). I am not sure whether there is any other connection between the battery and the F-32, which may draining power.

I will keep the forum posted on teh progress.

Thanks again for the response.

 

Instead of measuring voltage drop across fuses you may want to visualize activities with an oscilloscope. This should help improve your research of cyclical electronic loads.

Some ppl have good success using thermal camera to identify hardworking modules.
Your 500mA drain put out 6W which can be easily picked out.

Not all Modules don't mature into vampires randomly.
Suspects are CAN-B :
Signal Acquisition Modules (SAM's)
seat modules
door modules
KeylessG

Other module power is cutoff during low power modes.

I would not poke at all fuses blindly but do poke at all CAN-B fuses.

 

Dear CaliBenzDriver

Thanks a ot for the advice. I will do the same over the weekend and provide an update.

 

Silva,

Give us your VIN.
I am curious as to how the wiring is for this engine + hybrid.

ASK :
01. Is your Lithium Ion Battery at the location of our 12V normal battery in engine bay ?
02. Is your regular big size (nromal ) starter 12V battery at the trunk ?
03. Does your car also have the baby sized start-stop or AUX battery at the trunk ?

Later.....

.

 

Thanks a lot for the reply

This is an Edition-E vehicle, I believe some facelift features like memory seats etc.

01: It has the 0.8Kw hybrid battery in the engine-bay (on passenger side for the RHD vehicle)
02.: It has a 100A main 12V battery in the trunk
03: It also has a small axillary battery in the trunk

 

I ask for the VIN so that I can find the correct wiring diagram for you.
I want to help you find the parasitic drain as I am very familiar with non hybrid DC power distribution lay out.

With the hybrid 120V system, it is new to me. So must read its relevant wiring diagram.
Your engine does not have starter anymore, it has starter-alternator-generator combo inside the tranny.
It has the typical DC to DC converter ( hybrid power module ) which often burnt out.

The starter-alternator-generator combo inside the tranny, red arrow







The video above is from Malaysia and he is speaking broken Malay, he is a Chinese Malaysian.
If you are curious of what he is saying :
He said the start stop starter always break, the one he is holding with his finger. Since this hybrid does not use regular starter motor using flywheel outer teeths, it uses middle of flywheel, its a spline hole.




This Hybrid Electronic Power Module is what I am curious about. Does it use the normal 12V battery for its management ?





If in older W211, electric power seat often is the source of parasitic drain, but usually bigger than 500 mA you are seeing.

NOTE : If your current clamp does not have the 2 AMPS setting, it is likely anything under 1 AMP is not accurate.

Typical W212 normal drain is here , based on my car option level : https://mbworld.org/forums/e-class-w...-your-car.html

 

Thanks again for the information and help offer.

I do not have the vehicle at sight now (it is at my hometown) and therefore I could not get the VIN plate. However, according to the registration the chassis no is WDD2120982B276632. I am not sure it is same with the VIN. (I will be able to get the VIN over the weekend). IF you can get me teh wiring diagrams it woudl be of a invaluable help.

I am sure that the 500mA (480mA to be exactly) as I used a bench power supply to provide a parallel feed (i.e. connected it parallel to the main battery and then removed the main battery terminal after the car has shutdown, without disrupting the power supply). I got a constant accurate drain from the power supply, which did not change over a 6 hr period. Also when I increase or decrease the voltage slightly (between 11.8V and 12.6 V) the current changed inversely, suggesting that the drain is from an active-load (Eletronic load), that consumed a constant energy.

Despite this drain, rest of teh car seems to have no issues at all. Teh hybrid system also works fine and provide electrical drive, charging etc. without any apparent issues. Teh XEntry scan too did not show any faults other than stored code for "system low voltage < 7.5 V" on multiple modules. This could probably be to the first instance where the battery got flat when the car was not used during a week time.

As a next step, I am thinking of tracing alone the 12V battery +ve cable (i.e. a top-down approach) with a clamp meter to see if I can isolate the branch which causes the drain. I think the first distribution point to the +12V will be from the F-32 pre-fuse box (not sure whether this assumption is correct, and the wiring diagram will help in that.

Apparently, this car seems to have the electric drive start, a starter motor and an alternator (according to information I found on the Internet). The Strater motor is used to crank the engine when the vehicle is moving (as part of start-stop / hybrid drive). Teh alternator is also used to charge the battery )12V and HV through the tow-way DC-DC converter) under certain conditions. Teh DC-DC converter is used as teh primary means of providing 12V power and charging the +12V battery.

On the vehicle at present, these systems seem working fine and the battery gets charged quickly within a couple of KM drive.

 

This is the VIN WDD2120982B276632
When I am done with my wheel work, I will find the wiring diagram for you yah.

 

Take note of these information :

01. Your hybrid system is called ME04

02. A79/1 Electric Machine is below. WIS does not show its physical appearance, only mentioned it. WIS = Workshop Information System

The German engineers have no better name for this device ??? Hello ???



...


03. Take note of Circuit 30 and Circuit 30g

.




.

04. Use your car DataCard ( based on ur car VIN ) of your car when reading Wiring Diagram. It is in Hybrid zip, it is from Vin Decoder service.
Wiring diagram supports many models and options, hence you refer to data card what is for your car and what is NOT for your car.


05. Use this to convert XPS file to PDF : https://online2pdf.com/convert-xps-to-pdf
I have attached 3 Zip file set. Study them if you want to troubleshoot electrical matters on your car.


Have fun and some migraine ..............

 

With the help of information provided by S-Prihadi and a lot of checking and tracing, the drain was isolated to the hybrid inverter. The drain occurs through the +12 high amperage connection (that is also connected to the alternator via the F-32 pre-fuse box).

The drain stops when the control socket (i.e. the one that carry CAN, power through hybrid SAM (circuits 30, 15), and other signals) is removed. When it is plugged again the drain settles to 480mA after about 5-6 minutes. There is no drain through the control socket itself.

We did another x-entry scan and the Inverter shows absolutely no-fault codes. Other than the drain, it also seems working fine when the car is started and running (i.e. charging the +12 battery, powering the hybrid system, etc.)

 

480 mA drain is too much. Within 5-6 days your 80Ah battery will be DEAD.
This could be a sign of worse things to come as the inverter is known to go bad, mainly from overheating, if seeing the burnt marks on most of them.

If you are based in Sri Lanka, its just as hot as my country and the inverter is at the engine bay ? If so, can't be any worse place to be

N129/1 is the module/inverter you speak of ?