hi I need your advice my car is E220 cdi 2005 ,my problem is from a week there is rained a lot and water is inside my trunk and a red warning battery visit workshop and I went to three different workshops
first one replaced the front battery and cost me $$$
second one replaced the Battery control unit (N82) and cost me $$$
third one replaced Additional battery relay (K57/2) and cost me $$$

and all it will go back after 30 minties from a drive the car and espicaily when I steer left and right

today I measured the voltage of the batterys after the warining

When car is on (both are 13.5V)
when car is off (the front 12.7 & the rear 12.2)

the electical told me that the water in the trunk make the thing worse and I am confused to buy a new rear battery
or i I change all the wires in the car and cost me $$$$

what is your advice?did anyone have this problem

have you tried to recharged aft bat ?

I am currently having the same problem but over the last 2 days i am not getting the alarm. When trying to activate the SBC (as a braking system when stationary with break pedal depressed) the instrument panel alem indicated "SBC not available" during the period when i had the problem. But over the last 2 days i am not having the alems comming on and the SBC is also normal. I am working with my mechanic to troubleshoot this problem. One item we want to check is the Alternator activity. Will keep informed on outcome. Best Regards

thank you both
today I went to a electronical and check the rear battery voltage is 14V when car is on and 12.3V when off

But the problem is from the front battery it isn't charging when car is on (it is new for 5 days) it is 12V on or off

and in star diagnos the status that it is "stored" in the K57/2
he asume that the wires isn't stable

and I went to other one and check the wires and told me it is good

any advices

As per Mercedes, the front battery only comes into play when the main battery voltage is low. I have checked the back battery and the voltage is 12.5 which I believe is sufficient. I have also checked the front battery voltage which actually is low at 10.5 Volt. Although the front battery voltage is low it may not be the source of the problem as it acts as a spare. However I have to have this replaced soon. I still believe that the problem may be the Alternator which may be operating intermittently. The control units (switching from main to spare battery) could be faulty (intermittently) intend to check all this over the next few days. Currently I am not having any problem...front battery voltage still low. Meanwhile any other input from members will be of great help. Regards

yes he told me that he upgrades and download a new software to it and then test it with xentry and do not mark any problem

until now i did not solve it because no one did know how to fix it

thank you for your reply
no it just did not mark that it have a problem for 1 hour then it shows that the other k57 have the problem with the wires between it and the device

For the past 2 days everything seems to be normal including the SBC. Checked my back battery voltage (without engine running) the voltage was 12.5 volt (expected). Started the engine (to get alternator running) the voltage was 14.3 ( at the back battery). Checked the front battery and the voltage was 14.2. The front battery voltage during the problem time was 10.5 volt. From all the checking I did I have arrived at the conclusion that the problem (intermittent though) is confined to the Alternator and other control system on the charging circuit . Keeping my fingers crossed and hope the problem doesn't recur.

drive around with the voltage screen on. If you ever see it drop off below 13.5V, it means that is when it stops charging and is running on the battery alone. If you can start to notice a cycle of when it starts to drain, it may help you come to the final solution.

Hi I hace a Mercedes E550 and i change the alternator and is just showing just 12.6 12.7 or .9 if i put it on reverse show 13.6 only and before Was showing up to 15 volt is this modele have a power relay plegase if some one can throu some light please

What year is your E550? Also, what type (name) and where did you purchase your alternator? If the alternators regulator is not bosch, this may be your trouble.
Mike T.

Hi
Is a E550 2010 and yes it have a Bosh voltage regulator this morning when I turned on the car was charging up to 14.8 but when I whent back home start and was 12.8, 12.7, 12,6is this norma or not if some one can tel me somthing please. Thanks the alternator is the original rebuild but it have a bosh regulator

Has anyone solved this problem yet? I'm having the same issues with my car i went ahead and check out the main components of the w211 and the last thing I haven't check was the K52/2 "auxiliary battery relay".

I changed out the rear SAM, checked the BCM- ok, check the battery fuses under the passenger side floor-ok. I have new aux batter and rear trunk battery and the alternator i have on is an Reman autozone.

I just want to see if this was solved before I buy a new auxiliary relay.

This is going to sound crazy, but instead of guessing, and throwing sub standard parts at it, why not have it properly diagnosed, by either a qualified independent shop, or the dealer.

Before it finally stopped running I took it to an ASE automotive electrician who traced it back to a "bad passenger seat module" but that's not the case. I don't think a seat mod would cause my car to randomly shut off or stall out or go into limp mode.

The car is completely DEAD to where my dash cluster didn't even come on when I open the door. New aux battery + trunk battery, still no juice.

I do work on my own cars.

When I said take it to a qualified independent shop, I meant a German/Mercedes specialized shop. That ASE patch doesn't make him a high tech master. It's just a test. So you replaced the batteries, and alternator. Why? What testing methods did you use? Load test? Batterie conductance test? Did you check the alternator control signals, and output? What brand of scanner are you using, and how many hundreds of hours do you have using one? I'm not trying to beat you up, but unless it's a pattern failure of certain parts, or circuits, YouTube, and forums won't help much. Like we say in the trade, "bad information, is worse than no, information" Watch a few of this Guy's video's, and see the equipment, and process a real experienced pro uses.

Bro, im not here to go back and forth with you about what I should do and how i should spend my time and money. Im here on this forums to discuss about this specific topic to get some leads.

You aren't giving enough info. Right now, we don't know if you've been driving this car for 10 years, or if you bought it off Craigslist 2 days ago not running. Start with the year and model of your car, then maybe give us a little history and how/when your specific problem started. I'd suggest starting your own thread.

I didn't want to hijack the OPs thread I just wanted to get an idea if the OP ever solved his issue.

I think benz superceded the relay.

Pretty common to replace it if its original and get the updated one.

M

The K57/2?

​​​​​​​Did anyone ever get this figured out?