- Mercedes-Benz E-Class: Warning Lights
Important information to help you understand your Mercedes-Benz
Red battery message ( Visit workshop)
From what I understand you have a NEW Gel Cell OEM battery from the dealer. Consider taking the car to autozone and let them do a load test in the car on the main battery. If it states needs recharging and your low bat message is off when you drive in this would still steer me to the main battery not having the reserve capacity necessary for the car.
Remember "new battery" doesn't necessarily mean "Good Battery" every company makes a few defects.

I guess the front SAM can be faulty, I've heard of several cases where the rear SAM has failed from a wrong jump-start.
I guess the front SAM can be faulty, I've heard of several cases where the rear SAM has failed from a wrong jump-start.
I looked at my auxiliary battery it was manufactured 48 week of 2002. Rear battery is also old (original), however I decided to only change the auxiliary battery.
Best place I found was Walmart. Got the Everstart ES 14-BS AGM for $68.99 (plus $9.00 core charge) (Same size)
Changing out the battery took less than 10 minutes. What took longer is prepping the new battery.
The ES 14-BS AGM need to have electrolyte added (comes with the battery)
Once added, it needs to "rest" for about 1 hour. After 1 hour, the battery can be sealed with the provided plugs.
Then it needs to be slow charged (at 2A) for 3-5 hours.
After that, remove the air conditioning filter cover
Remove the negative connector
Remove the positive connector (make sure to isolate the plug, i did not unplug the main battery, did not want to run the risk in getting any type of error message)
Install the battery by plugging in the positive connector first, then the negative, put the filter cover back in, et voila.
The red warning is gone, no error message popping up and no reprogramming of anything.
Hope this helps others
The Best of Mercedes & AMG
I've got a few questions questions before I proceed with the replacement:
- Where can I find instructions on replacing the Battery Control Module? I'm pretty sure it's quick and easy, but I would want to make sure I don't short/fry anything in the process. I ordered the Model 211 Star Service Manual Library on DVD (P-2700-211-07), will that have instructions?
- The BCM part number has gone through several replacements: 211-540-27-45 (currently in my car) has been replaced by
211-540-42-45, which was then replaced by
211-540-69-45, then by
211-540-38-45, and finally by
211-540-86-45.
I'm guessing that all of these are pretty much the same, except for minor tweaks, and ideally I should go for the latest part number (211-540-86-45). I've found new ones for around $370 and used ones for $250. Does anyone have any recommendations on installing used BCM's vs. new? - Will I have to pay a visit to the stealership to have them reset the electrical system and such? i.e. Does anything beyond the typical reset procedures in the Owner's Manual (clock, windows & sliding roof resynch, turning wheel all the way left & right) need resetting?
I tell you, this is the first time I spent any money on a stealership coz my wife was pestering me to do it asap and I am a shop owner hahahahahaLMAO. Never again.
The stealership then quoted $5,000 plus for additional recommended service needed. Yeah right(*&%!>M<?:{#@#@# 's
Thank you so much for sharing. I am going to get an AUX battery now to swap the bad one with. My fix was to yank out the AUX from my CLS and swapped it with my wifes 4matic wagn.hehehe.. I will deal with mine later.
Now my wife is a happy camper.
Thanks for the instructions. I own a R230 SL500, and I checked that the AUX battery is 12v 35aH. Best battery down in my country is only made by Varta. Could anyone recommend me which is the exact fitment for my car ?
Thanks.

The point is that this is a W211 thread and the R230 dual battery system is a bit different from the W211. The R230 has a starter battery at the front while the W211 does not use the front battery at all when the car is started. The front battery still serves as a reserve power source for SBC brakes.
Thank you for replying and I apologize for the short post. I just changed the rear battery about 2 months ago and now I am having the red battery alert, visit workshop. I thought that it would just be a simillar case.
I will have the tech re-check the front and rear battery, I dont mind paying $200+ for a front battery, but down here for an OEM from battery they want $600+.
Should I assume that voltage wise they should be around 12.6v as per this thread for the R230 ?
Thank you.

Thank you for replying and I apologize for the short post. I just changed the rear battery about 2 months ago and now I am having the red battery alert, visit workshop. I thought that it would just be a simillar case.
I will have the tech re-check the front and rear battery, I dont mind paying $200+ for a front battery, but down here for an OEM from battery they want $600+.
Should I assume that voltage wise they should be around 12.6v as per this thread for the R230 ?
Thank you.
I did not check if the R230 front battery is charged similarly as the pre-facelift W211 or if it is similar to the W211 which is using a simple relay, it could be this relay too but I assume the car is more like the W221.
I opened up the bonnet, on the front battery it actually says "starter battery" on one of the plastic cover. The Varta tech will be back tomorrow with the meter to check on both batteries before replacing or doing any work.
Any insights ?
Cheers.


Greatly appreciated

Thank you.
Car would work normally before, just give me the msg...so it must have been getting low enough to throw an error, but not enough to affect anything else.
I was a little confused at first, but the mechanic said he checked everything and it seemed that was the problem.
Hope that helps a little






