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Michael, as far as I understand,
1.-The BCM monitors the charge level of the rear battery and if it is under a voltage threshold, turn off the consumers while the alternator charges the battery, and turns them on once the battery is charged.
2.-The BCM monitors the charge level on the starter battery and establish a connection through K57 to charge the starter battery. and opens it when it is fully charge.
Now I quite do not understand the function of the DC-DC built in the BCM board since the charging is supposedly to be done through K-57..unless it is just a trickle charger!
The function of the DC-DC standalone charger, it determines voltage differential between the input and output to charge the second battery, then goes in trickle mode when it is fully charged. When the ignition is off completely disconnects the starter battery doing as the K57 relay..!
Your wonder "micro controller" fools the BCM and creates the CAN messages to enable the consumers, but cannot indicate when the rear battery is low or defective, which could be easily determine using a voltmeter in the dashboard! So, the trick to completely emulate the BCM would be a "device" that measures the rear battery voltage and turns the power off to the "wonder microcontroller" and perhaps send a message to the dashboard saying, "CONSUMERS OFF." ! Seems pretty achievable for a guy like you!
BTW, I am enjoying being able to roll that hardtop into my trunk and let the stars shine over my head..! No radio yet but sooner or later I get an android to replace it!
Right. I wouldn't use this same circuit as the emulator. I would need one with a couple ADCs to sense voltages and some MOSFETs to control the relays and perhaps the DC-DC converter (if it's externally controllable). I think the bulk of the work would be gathering all of the "acceptance criteria" then writing the software to meet it.
Luckily we have the PDF which describes the various BCM functional modes (normal, emergency, etc)
This new controller could even use the signal from the EIS (N72) to wake up, just like the OEM BCM.
And if it could simply plug-in to the BCM harness for ease-of-install, even better.
After a bit of investigation, I'm envisioning a module to sit beside and interface with this DC-DC converter. The module would monitor both voltages and do all the things the BCM does with relays and throwing codes.
The DC-DC would be wired much like this, but reversed in that the Aux battery receives the alternator charge and the starter battery is connected to the output of the DC-DC.
It's really cool that you can use your smart phone to also monitor and adjust the charge settings. This would have so much more functionality than the BCM, would be more reliable and less expensive.
I think this could easily cost less than $500 for everything. Whereas used and unknown condition BCMs are going for $1000 - $3000 on eBay the last time I checked.
I have six more BCM emulators ready. Search for "Mercedes Benz R230 BNS/BCM CAN Emulator - Fix Dash Warning" on eBay.
These are the same kind elMacko has installed in his BCM case. (Small green with an LED)
I have six more BCM emulators ready. Search for "Mercedes Benz R230 BNS/BCM CAN Emulator - Fix Dash Warning" on eBay.
These are the same kind elMacko has installed in his BCM case. (Small green with an LED)
Great work Michael. Solves the BCM problem that many of us have lurking at the back of our minds when we're out and about in our SL's. Do you know if the emulator and DC-DC charger solution would work on a 2006 UK/Euro SL 350 3.7? I can't think that Merc in their infinite wisdom designed a completely different electrical charging system and regime for the 350 version to be honest. Also, I lost the thread when it came to connecting the DC-DC charger. How do you connect it to the old BCM connections? Looks simple but can't see enough detail. A combination of emulator and DC-DC charger would go down a storm here in the UK too. No need to make it too interactive as most people would just 'fit and forget' rather than wanting to develop a meaningful relationship with their charging systems. Also keeps the price down. Do you think the problem with making the radio system work will be sorted in future versions of the emulator? Keep up the good work - a big thumbs up from this side of the world!
Great work Michael. Solves the BCM problem that many of us have lurking at the back of our minds when we're out and about in our SL's. Do you know if the emulator and DC-DC charger solution would work on a 2006 UK/Euro SL 350 3.7? I can't think that Merc in their infinite wisdom designed a completely different electrical charging system and regime for the 350 version to be honest. Also, I lost the thread when it came to connecting the DC-DC charger. How do you connect it to the old BCM connections? Looks simple but can't see enough detail. A combination of emulator and DC-DC charger would go down a storm here in the UK too. No need to make it too interactive as most people would just 'fit and forget' rather than wanting to develop a meaningful relationship with their charging systems. Also keeps the price down. Do you think the problem with making the radio system work will be sorted in future versions of the emulator? Keep up the good work - a big thumbs up from this side of the world!
What do you mean by: make the radio system work? Does a faulty BCM knock out the radio?
This will eliminate the fire risk provided the original BCM is removed. I highly recommend changing the electrolytic caps and MOSFETs in the original BCM if it’s still working!
The radio issue mentioned earlier turned out to be a blown fuse. But apparently a missing BCM will block operation of the roof.
Gents, adding to the dc-dc charger Michael's solution returned my car to the condition as it was before the burned BCM... excepting the white battery warning and suppression of consumers when the accessory battery is low in charge.
I have added a couple of low drain LED voltage monitoring gauges to the front and rear batteries. This tells me at any time the condition of the batteries and charging system...better than the BCM..!
I am a happy camper with the present solution...perhaps in the future Michael or someone else may create a more advanced system....but, the good news is you do not have to be thousands of $$ for a used BCM that can burn again at any time, and secondly, the fear of fire is completely gone since DC-DC converters are a very safe and self-contained unit having minimal value fuses at the positive connections just in case....and the microprocessor is very low amp and it is fully enclosed inside the old BCM container....! When my BCM burned, while looking for the cause of the issue I removed several fuses and accidentally the 7.5 amp fuse for the radio got broke, so, went back to checking and all was fine after replacing that 77 fuse! I also have noticed that the normal drainage of the accessory battery has somewhat diminished! And as for the front battery, it becomes completely isolated with the car off and no or very little drainage is present. So...it is a better car now...!
This will eliminate the fire risk provided the original BCM is removed. I highly recommend changing the electrolytic caps and MOSFETs in the original BCM if it’s still working!
The radio issue mentioned earlier turned out to be a blown fuse. But apparently a missing BCM will block operation of the roof.
I sent out my BCM for repair. I lost connection to all CAN BUS B modules, also my Radio would not turn on. I am hoping the refreshed BCM will alleviate all those problems.
I sent out my BCM for repair. I lost connection to all CAN BUS B modules, also my Radio would not turn on. I am hoping the refreshed BCM will alleviate all those problems.
Gents, adding to the dc-dc charger Michael's solution returned my car to the condition as it was before the burned BCM... excepting the white battery warning and suppression of consumers when the accessory battery is low in charge.
I have added a couple of low drain LED voltage monitoring gauges to the front and rear batteries. This tells me at any time the condition of the batteries and charging system...better than the BCM..!
I am a happy camper with the present solution...perhaps in the future Michael or someone else may create a more advanced system....but, the good news is you do not have to be thousands of $$ for a used BCM that can burn again at any time, and secondly, the fear of fire is completely gone since DC-DC converters are a very safe and self-contained unit having minimal value fuses at the positive connections just in case....and the microprocessor is very low amp and it is fully enclosed inside the old BCM container....! When my BCM burned, while looking for the cause of the issue I removed several fuses and accidentally the 7.5 amp fuse for the radio got broke, so, went back to checking and all was fine after replacing that 77 fuse! I also have noticed that the normal drainage of the accessory battery has somewhat diminished! And as for the front battery, it becomes completely isolated with the car off and no or very little drainage is present. So...it is a better car now...!
I’m a new member here and a very excited one after reading and rereading this thread. I was only vaguely aware of the BCM fires until my 65k mile ‘03 SL500 almost got burnt completely with the house two weeks ago- very lucky there.
My question is, as you can see from the attached pictures the BCM is completely toast, will I therefore need to get another one (even if reconditioned) plus the new wire harnesses before this new magic board works? Great work guys. Many thanks.
I can tell you got lucky since the burning was just limited inside the trunk.....Good luck finding a "new" BCM since it does not exist anymore and if you are willing to shell over $1000 for a used one, which may not work or may burn again without warning.
Regarding the connector, a junkyard is your only option. I had the same situation, but my burn was limited to the board itself.
You could also consider using the system described in previous responses to this thread. With that, the risk of fire is "zero" and will be easier to wire since you only will be using 4 cables from that burnt connector and no connector at all..! And the cost will be around $300.
I have six more BCM emulators ready. Search for "Mercedes Benz R230 BNS/BCM CAN Emulator - Fix Dash Warning" on eBay.
These are the same kind elMacko has installed in his BCM case. (Small green with an LED)
Hello Mike, any chance you will have more emulators for sale soon? Thanks
In the FB BNS/BCM Fires group, there is a solution that will become available for purchase soon. It's almost plug n play, just need to tap a signal wire to turn it on.
Details can be found here:
facebook.com/groups/2166105433538146/
josh, I saw that and I wonder how he managed to replace the DC-DC charging system which other than using a VRS (Voltage Sensitive Relay) circuit to latch the K57 relay, it would need a little more than that to fully replace the original BCM functions. The original BCM senses when the front battery needs charging and when it is fully charged. In the fully charged case, it disconnects K57 and the system only charges the accessory battery. The VSR only senses a voltage and connects to the secondary battery while the engine is running. A smart DC-DC charger senses when the front battery is charged and trickle charge it. Summing up, I would like to see if indeed is a DC-DC charging circuitry inside along the necessary logic to make sure it is a plugged-in complete replacement! So far my smart DC-DC charger is doing the job in keeping the starter battery charged and the MP microprocessor is keeping the consumers active. All that at a fraction of the cost of that potential plug-in. But, as you know, some owners like uncomplicated solutions no matter the cost!
Hello All,
Just today while taking my 2004 sl500 out of storage I noticed smoke coming out of the trunk! I quickly disconnected the battery and prevented a disaster. I have 2 questions, 1 is it possible to start the car with bcm removed? 2 is the bcm emulator for sale anywhere?
Thank You
Yes you can start the car with the BCM removed....but.....the auxiliary battery cable must be connected to the conductor to which it is attached on the BCM..!
I have been struggling with this BCM problem for months I have an 05sl500 it started with the charging fuses under the dash. Fixed that and the BCM for sure is the problem like all of you 3000 dollars for a BCM used at that is ridiculous. Please help me could you post a detailed plan how to wire your findings from front to back I also want to eliminate BCM but really don't know how could you list what I need and how to do it I would greatly appreciate it. I love my ride but this from fuses under dash to the rear is a nightmare. Thank you and I look forward to hearing from you all you that have experienced my same nightmare issue.
After a bit of investigation, I'm envisioning a module to sit beside and interface with this DC-DC converter. The module would monitor both voltages and do all the things the BCM does with relays and throwing codes.
The DC-DC would be wired much like this, but reversed in that the Aux battery receives the alternator charge and the starter battery is connected to the output of the DC-DC.
It's really cool that you can use your smart phone to also monitor and adjust the charge settings. This would have so much more functionality than the BCM, would be more reliable and less expensive.
I think this could easily cost less than $500 for everything. Whereas used and unknown condition BCMs are going for $1000 - $3000 on eBay the last time I checked.
Originally Posted by elMacko
Tom, no need to get so complicated..! If you join 30a and 30 you will have a system of two batteries in parallel, and the alternator will be charging both at the same time..as you stated, but do not know what secondary consequences it may bring...!
I see clear the alternator will be fully working charging the two batteries. Another solution would be using a single battery, buy you would have to use a heavy gauge cable from the rear towards the front...and when the battery is drained, no starter!!!...
To simplify these issues I just connected a 25 a/h dc-to dc which will trickle charge the starter battery when fully charge, giving a break to the alternator..! When the vehicle is off, the two batteries are completely isolated.. This is a simple proven technology....! There are chargers with higher a/h, but more than 25 a/h is unnecessary since you could restore the charge loss for starting in less than 5 miles of driving! My system works like a charm and it is safe and reliable.!
Originally Posted by elMacko
Thank you my friend....! This work is mainly attributed to my colleague the "software developer genius" who was able to get that little computer to do what the CAN B bus wanted to hear. So far, with the system previously described all the functions in the car are active excepting the radio, which I am trying to find where is the "link" to get it to speak. I am considering replacing that old system with a 7" touch screen unit anyway. The only thing you won't get with this system is the "charged condition" on the rear battery, which could be replaced by simply using a digital voltmeter with very low current draw permanently connected to the rear battery, so in that way you know that if your voltage is under 11.5 volts, you should wait to charge it before opening/closing the Vario roof.! Another potentially missing function is the detection of a malfunctioning alternator, which could be detected with the above-described voltmeter or a LED with a gate that allows power to the LED when voltage drops under 12.7 volts...! This is part of a development journey which for sure will end with all corners covered..!
As once upon a time a great philosopher said: The need is the mother of all inventions...!
Below is how my trunk looks. I temporarily have the liner off while I get all my connections completed and have access to the BCM box. The charger connector with the blue cable is for attaching a solar panel if necessary! That charger will trickle charge the starter battery once it is fully charged.
When finished, the only thing visible will be the DC-DC charger.
@elMacko@Michael Pitts thank you both so much for figuring this out. My new-to-me SL55 became a massive paperweight the day I bought it, (saw the previous owner jumping the car from the rear battery).
I just purchased the emulator from @Michael Pitts - thank you again!!
I am trying to understand what is required of me to get this to replace my BCM. @elMacko would you mind making a video explaining to a very lay man like me, how you did this?
I don’t fully understand everything that needs to be done, i.e. where all of the wires you have plugged into your DC-DC charger came from?
Please correct me where I am wrong:
Steps:
Purchase emulator and DC-DC charger
Remove 🔥 BCM
Tap emulator into the original output wires of the BCM
Tap DC-DC charger into the wires that were originally going into the BCM from the rear and front batteries
Connect the DC-DC charger into the emulator
Toss BCM into the sea, preferably while driving the SL top down over a bridge (that way it will never catch on fire in the ocean, right 🤣 )
Last edited by thesheikh; Nov 9, 2024 at 04:56 AM.
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