Hey guys,
I have a 2016 W212R E550 Sedan. A couple of months ago I had gone on a work trip and gave the car to a friend to use. He had left the inside lights on and the battery died. He then attempted to boost it but it didn’t work and he even blew the fuse for the ignition. After changing both the primary battery in the hood and the auxiliary battery under the driver side as well as the fuse, the car seemed to be perfectly fine but the car’s battery dies every other day since then. Alternator is perfect as well, no faults in the system either. Does anyone know what the problem could be or have experienced this before?
Also, when boosting the car now, you need to let it sit to a proper connection or jumper for 5-10 minutes in order to start it or else it won’t start. Lights and other functions turn on but the car doesn’t have enough power to turn on.

 

Don't make the assumption the new battery can't be defective. Have the new battery checked first. Sometimes we assume new items are good when they are defective.

 

The car computer should not allow for interior lights to discharge the battery. It turns the lights off after few minutes.
So looks to me that the car had a problem before you lend it to a friend.
Observe when the car goes to sleep after closing doors. Should take about 10 seconds for all lights and displays to go off.
DID YOU CHECK CODES ???

 

What is a 2016 W212R E550? Are you in Europe?
The last E550 sedan was produced in 2015 for the Canadian market. Then the model ended.

 

Tested both the batteries and they’re good.

 

The last year they were produced was 2016.

 

Thats what I had figured too, lights would’ve automatically turned off. No codes.

 

I think the boost/jump by your friend created the problem. If your friend blew the fuse, that means it was not done correctly and resulted in an overload on a circuit. You now may have a short that drains the battery. Start with the circuit(s) on the blown fuse.

Good luck!

 

Sweet, I’ll look into that. The fuse blew when he attempted to start it multiple times. Eventually, the ignition or the cracking noise stopped and that’s when they realized the fuse needed to be replaced. Once replaced, the car turned on and was working perfectly. No errors on the dash or any codes.

 

01. Every other day is 48 hours, approx.
Assuming your new battery is equal to MB spec, the parasitic drain need to be quite heavy at 1 amp hour or more.....to not able to crank-to-start in 48 hours.
You need to open up the hood, and then lock all doors, wait for minimum 1 hour for the computer to REALLY sleep and any auto-drying of the HVAC evaporator core to end,
and then read how much amps is being pulled from the battery as parasitic load. You amperage clamp meter need to be able to read accurately down to 1 amp.

I am a Fluke lover but I bought UNI-T UT201E for approx US$60 early last year, which has a 2AMP selection and it is good to 50 milliamps or 0.05 amp.... so that I do not need to remove any battery cable.
Don't use too big a clamp rating like 600AMPS, its <1 amp resolution is not good, even Fluke if 600 amps rated.
Becareful when using sensitive DC clamp meter at under 1 amp of load, nearby ferrous metal can give you variable readings depending on clamp positioning and metal proximity, in AC current no issue...DC is VERY finicky.


02. Your definition of alternator is "good", how did you test it and how long did you maintain the test ?


Below is a test using 2 methods.
One is the *UT210E clamp meter and one is a regular Fluke 179 digital multi-meter.
I removed the NEGATIVE battery cable and connect small extension wire for me to easily adjust various clamping arrangement to try to make the small extension cable as center
as possible on the clamp inner diameter.
*UT210E , must have the E to get the under 2 amps reading both in AC & DC.
The Fluke 179 DMM uses its milliamps setting via hardwire, so it is less prone to magnetic field when load is under 10 milliamps.
Notice how UT201E clamp meter can actually produce similar accurate 6 milliamps reading as Fluke 179 ( 5.59 milliamps ), but I really need to place the wire properly mid center of the clamp and its a nightmare,
or else I get up to 21 milliamps. I also raised the small cable away from the car engine bay, for less magnetic interference. Basically clamp meter reads magnetic field produce by cable carrying amperage.




Direct clamping of UT201E clamp meter to battery negative or positive cable, due to magnetic interference, would read as high as 250 ish milliamps for a <10 milliamps load.
Since your parasitic load is close to 1 amp or more ( I suspect ), you can clamp the battery cables if you so wish, for easier work.

This is direct clamping of POSITIVE battery cable, where for my car, that is the easiet to clamp position. See, 255 milliamps for a 6 milliamps actual load. 249 milliamps error from magnetic field.
Cyan Circle = Ignore the fact that there is another POSITIVE cable with the pyro fuse which I did not read/clamp together... I done the test separately on that particular pyro-fused wire.



Good luck troubleshooting....

 

Assuming your new battery is healthy, 2 highly possible scenarios caused your current problem.

01. Alternator not charging enough/properly.
02. The mishap which cause your ignition fuse to blow, has caused some other issue somewhere....which in return cause parasitic load.

Can you explain the action/method or equipment you called BOOST: "Also, when BOOSTing the car now, you need to let it sit to a proper connection or jumper for 5-10 minutes"

 

Where?

 

S-Prihadi is spot-on regarding troubleshooting. I use cheaper equipment than he does but that's neither here nor there.
What he is describing is a methodical approach to finding parasitic drain. Note especially that the car must sit undisturbed with hood up for a period of time to allow systems to go to "sleep" mode.
If you find an electrical draw with the clamp or a meter, you can pull a fuse at a time to see what fuse (circuit) stops it. Tedious but will find the circuit. Remember also that there is a rear SAM with fuses so trunk should be left open as well. Car should shut down all lighting even before it goes to sleep mode.

 

One way to find a parasitic draw is to check total draw while the electrical system 'sleeps'. Your may have a clamp on meter to tell you that, or your DVM may be able to measure this if the draw is not too large for the fuse in the meter, about 5 amps IIRC. Another way to check draw is to use your DVOM in voltage mode and check each fuse in place, one probe of your DVOM on one side of the fuse, the other probe on the other side of the fuse. Note that neither test probe is grounded. If current is flowing thru a fuse, there will be voltage - no amp flow, no voltage. With this method, you run through all your fuses in just a few minutes and your electrical system does not wake up. Also, when you find a fuse with voltage, you know which circuit has the draw and most likely the specific device to check for problems, i.e. radio, heated seats, etc.

 

I have same exact issue like OP had previously. Did anyone able to figure what could be the issue!

I installed nee battery a week ago and after 2 days car sitting, car is completely drained. Alternator is working in great condition. I did check for parasitic drain after 1 hour of locking the car, amp was showing below 0.02 A

I would appreciate any help

 

What is your battery voltage now?

 

Currently it is at 10V now. I am trying to figure out what is draining the battery in 2 days. I checked for any parasitic drain using meter but I am not seeing something unusual.

Is there some unit that wakes up at middle of night that runs something then goes back to sleep?

 

I hear a noise coming from the front of the car but that's a typical Mercedes-Benz Unique sound .It looks like fans running but it should not cause any battery problem .
I just realized you must have an AIRMATIC , I doubt its compressor could drain the battery but I thought I have to say it anyway

 

No I don't have airmatic system.

Any other feedbacks on what could be the issue?

 

welcome to the real joy of ownership. What wakes up other modules is the F-SAM. It keeps poling security from door modules over a slow CAN-B bus bugged down by any other chassis modules.

Use a good scanner ($100 LAUNCH ELITE CREADER) to get a comprehensive fault survey of your WHOLE chassis.
This will help you identify active troubles.

In the mean time use a CTEK float charger. I used to get low battery in 4 days when new, now I can go over 3 weeks, perhaps more. Just like a good car.

Low voltage is bad news... this engine itself is voltage sensitive.