nikk777

2004 SL500. I've already replaced the battery control module once before. It was electronically fried when I pulled it out. Caused a distinct chemical (catlike) smell in the car. Electronic consumers were obviously off and red battery light (visit workshop) was on. Now it appears to have happened again. What could be frying the BCM?

Back story: Both times the car sat for an extended time period. Car would start but trunk battery was dead. Replaced trunk battery both times. Before replacing, I placed a battery tender on the trunk battery. Can that burn up the BCM? How else do you trickle charge the battery since it dies over time regardless?

Tonight I will test the voltage from the alternator and at both batteries before pulling it apart to get the BCM out. How does such an expensive car, originally, have such a horrible battery/charging system? Trunk battery is dead if you don't drive it for a few weeks! My 98 dodge ram sat for 2 years and fired right up with no issues when I decided to jump in it...

Any help or ideas is greatly appreciated. I searched but nothing sounded like what I'm dealing with exactly. Possibly the voltage regulator is bad and frying the bcm but that would have happened while I drive it. This seems to only happen if I let it sit and/or put a battery tender on it.

cadbob

What type of Trickle Charger are you using?

Are you absolutely sure Positive to Positive when you have it hooked up?

I know that sounds stupid but I never ever reversed Poles on any vehicle but I did it once on my SL and fried mine. Not even sure how I could make the mistake to this day.

carguyshu

use a CTEK charger on the rear battery and you should have no problems. The trunk battery has lots of things slowly draining it like an alarm system, keyless go, etc. That is why there is also the front battery that has the lone purpose of starting the car and the rear battery does everything else. The reason your 98 dodge ram can sit and then start up is b/c there is no battery drain on it b/c it has few if any electronics slowly bleeding power. Checking the voltage off the alternator and at each battery wont tell you much. The alternator directly charges the rear battery and then the BCM determines through a DC/DC converter if and when the front one gets any charge. In the event the back battery is dead the BCM opens a couple relays that tie the 2 batteries together temporarily. This is when you get the 'consumer electronics offline' message.

colouredfrog

That was a very informative expaination of what the BCM does. Can you add further, and state what parameters the red battery visit workshop message occurs in relationship to the BCM switching or coupling the batteries, and how this relates to the consumer of line message.


Is there anyway for testing the Battery Control Module and its relays, I think no.57 and no.75

colouredfrog

Sorry furthermore, can a issue like this show a fault too, a red warning ABC message.


I have just replaced my consumer battery on my 04 SL55, because the old battery would not charge, even with a ctek charger overnight.


However the red battery visit workshop light is still on, coupled with red ABC message. I don't know if the two are linked.


Thats why posted my previous question. Just want to know how I can carry out a test to establish what is at fault. Funny enough my suspension has not sagged, just rufuses to go up or down from the button, which does not light up.

bobterry99

The attached PDF is a training document for M-B technicians that explains the dual-battery system in detail.

A Star Diagnosis computer is needed to evaluate the error messages you see. I would take the car to an independent shop that has one, or better still, purchase one of your own from Alibaba for $240.

Lee Wireless

Bob-Would you post the correct supplier/link that you trust on Alibaba for the SDS? I find lots there but don't know which one to pick. Thanks

bobterry99

This $240 system was recommended by a member of another website who purchased the kit back in September.

colouredfrog

Thanks for that PDF - explains in detail.


Also thanks for the link for the star system from Alibi, its a good price.


I already have a star system, which I bought back a while.


Thing I find annoying is I have a red Visit Workshop message. Does this message switch off automatically, if not where on the Star system do I go and how do I do it.


Accoding to the PDF file the relay K57 is activated when the consumer battery is below 10.8 v, and a consumer off line message is sent.


I do not have a off line message, after I changed the battery, but still have this Red Battery Visit workshop message.


Any advice guys.

DavidCA

See page 18 on the PDF file.
The module is called BNS in Star (Xentry / DAS)

bobterry99

According to the PDF you must erase the fault codes to clear the message. To do that, once Star Diagnosis is connected to your vehicle from the main menus choose:A list of all current and stored codes will appear. Press the F9 key to erase them all.

mikefamig

Bob

I looked at a bunch of these Star diagnostic systems on Alibaba and noticed that they have versions of C3, C4 etc. What is the significance of this? The one that you linked to is C3 and claims to have the latest Xtend software. What is the "C3"?

TIA, Mike..

dsmall7777

2008 R230: Does the "red battery" icon indicate that the BCM is bad? Or can the BCM need replacing whether or not the red battery icon appeared? My repair shop says I need the BCM replaced but I never saw the red battery icon. This was recommended after I couldn't start the car. They claim it had a dead battery because of a bad BCM. Typically, my experience with a weak battery has been a slow start warning. This time I had no warning, just a "single" click sound when I tried to start it. Any ideas?



Thanks

David

Fort Lauderdale, FL USA

Tomcat SL

I am joining this discussion...What can cause a burned up module?
https://mbworld.org/forums/sl55-amg-...or-module.html

cdk4219

My guess is jump starting these cars is detrimental to the electronics. Possibly jump starting or charging with a battery charger that puts out too much voltage. I would guess this damages things.

BenzNinja

iTrader: (4)

jvakos

Been following this thread as my 2004 SL55 AMG just started giving me red battery warning light after pulling it out of storage and the trickle charger for the past month where it sat. I installed a new voltage regulator earlier this year and since then the trunk battery was charging fine and always 14V or higher.

I left the car on a Noko Genius 3500 trickle charger for about 6 weeks now as the Chicago weather went from 60 to 30F and now the trunk battery only shows 12.5V at start up and declines to about 11.0 after about 20 mins of driving and I have to get the car back in the garage on the trickle charger.

Could the trickle charger have damaged my alternator or BCM? Should that throw a code on my Foxwell scanner if so?

Or could my battery just be bad and no longer retaining charge? The battery is a AGM H6 that I purchased from Advance Auto and was a direct replacement for the MB OEM one.... I'm gonna return the battery to see if a new one fixes this but am worried that the BCM is bad.

As of right now I dont see any codes from my Foxwell scanner everything shows OK which is hard to believe.... would be grateful for any input on what this issue is and how to fix.

Tomcat SL

I am following too...

jvakos

@Tomcat SL hey are you also having a similar issue with Red Battery / not charging via alternator issue?

I’m stumped as I don’t have any codes showing on my Foxwell scanner and also have a new voltage regulator installed earlier this year and the car had been driving perfect.

I had been driving the car a lot this summer until early October when I put her into my garage storage on my Noco Genius trickle charger and after about 5 weeks when I tried to drive her again the battery stopped charging from the alternator. Maybe the alternator needs replacing which is better than replacing the BCM from what I understand.

Tomcat SL

I attributed my BCM issue to NOT disconnecting the trunk battery while jump starting the car (due to a dead/old starter battery). I used two battery maintainers (one on each battery) for 5 years of ownership before the incident and (knock on wood) have continued to use trickle/maintainer since.

Tom Manning

I’m stumped as I don’t have any codes showing on my Foxwell scanner and also have a new voltage regulator installed earlier this year and the car had been driving perfectly.

Have you checked that both batteries are charging? Rear gets charged directly from the alternator. Front gets charged via the BCM. If the BCM isn't giving the right voltage level then it may throw a red code, but I'd expect a stored code too.

Unlikely to be the alternator - there's nothing in them, just windings. Regulators can give trouble.

Have you disconnected both battery negatives then reconnected? That's been known to clear the red code.

Start by testing the charge on both batteries - should come up to about 13.8 pretty quickly.

jvakos

thanks @Tomcat SL same here had good success keeping both batteries on the trickle but as I think about the last month I only had the trickle on the rear…..wonder if that causes an issue with the car recognizing the rear battery is fully charged while the front might be weaker?

Have never needed to jump start the car so should be ok on that…

jvakos

@Tom Manning thanks very much Tom I just put my trickle charger on the front starter battery and it does show extremely low. I had the rear battery tested and they said it’s in perfect working condition being a year old and no issues.

just before this all happened, I was moving around the spare tire since I had to use it a couple months ago and was a pain to deflate and get back in to the spare tire space. I doubt I could’ve damage something bite stuff and get back in there as I was for the most part pretty careful. When I checked after pulling the battery out to get it tested I did find this one strange connector that I can’t figure out what it plugs into. It must’ve been lodged loose when I pulled the spare tire. Any idea what the connectors for where it goes?

I’ll get the battery reinstalled and test it once the front battery is fully charged and see what readings both of them give me. I’ll rescan it and see if there’s any codes as I’m still shocked that the Foxville scanner doesn’t show any codes.



SL 55 rear trunk battery mysteey connector that was found loose

Tom Manning

Someone will know about that plug. Get in there with a bright torch and poke around and see if you can find the female.

To check the charging system you need a voltmeter across the battery, then start the car and watch the voltage rise to about 13.8 on each battery.

The front battery can be not charging and still have plenty of oomph to start the car; all it does is turn the starter so it could take a while to discharge. I'd be checking that it's getting charge.

Tommyboy928

front batteri dies often after 6 years, hot Florida probaly even before that . Front batteri is only for start , should not be BCM issue that one. change K57 batteri relay and clean terminals, My 2007 low miles/ km was corroded terminals K57. All need change this important part, is like 20 dollars for this relay or around that. But then again, Florida and close to humid sea air , then is idea clean terminals and check contacts batteri and other contacts on the car, use electro spray and spray contacts .