Mercedes engine battery problems

[Casper46]

Good morning everyone and a belated Happy New Year.

Our 18 month old Carthago has had a problem with the engine battery not holding charge unless run each day or on hook up, I have posted about it previously.
6 weeks ago the dealer put a b2b on it which was faulty and the battery went down very quickly. The took it away 5 weeks ago and have been testing it. Prior to the Christmas holidays they put a new battery on it and kept it over Christmas for a test. Monday this week I had a warning from Mercedes to say that the battery was getting low. New Year’s Day another message to say it was critical.
The dealers were back at work yesterday and sent me the attached message, can anyone interpret it for me please, prior to the dealers “sorting”it.


Thanks.

 

[Googlebot]

There is an option to have systems shut down quickly with less voltage drain, usually for when they are shipped so the batteries don’t go flat. May exclude things like door opening sensors and only puts everything on when the key is turned.

It’s usually enabled via a computer plugged into the ECU. Should be taken off when the vehicle is sold.

The garage need to find the voltage drain, not solve it by enabling a work around that means you won’t get all the systems active all the time.

 

[Eddie H]

My van is in storage, I’m getting an alert once a week to say the cab battery is critical ( 2023 sprinter )

The van starts when I go to it, and I normally go for a 30min drive.

I have seen the stand by mode in the vehicle settings, which apparently puts the MBUX unit properly to sleep, apparently this is a drain on the battery. Once asleep no updates from the vehicle to the app, and no Mercedes alarm.

I don’t know if any additional alarms or trackers are affected.

 

[Pausim]

Strange that the problems started with the B2B installation. Presumably they replaced the faulty one but have they got it wired correctly?

One of my B2B installations ended up with a dealer installed D+ activated isolating relay between the engine battery and the B2B. Totally unnecessary, the dealer misunderstood my instructions but I left it in place because it was doing no harm. It also ruled out any possible quiescent drain from the B2B. I am not convinced all dealers really understand these devices.

 

[Eddie H]

Here’s an image of where the standby mode is within my menus.

It does state system inoperative due to me already having low charge when the image was taken.

Also below is a video I found fairly interesting on cab batteries for Sprinters, although not exclusive to Sprinters but quite interesting.

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[Derbyshire wanderer]

Good morning everyone and a belated Happy New Year.

Our 18 month old Carthago has had a problem with the engine battery not holding charge unless run each day or on hook up, I have posted about it previously.
6 weeks ago the dealer put a b2b on it which was faulty and the battery went down very quickly. The took it away 5 weeks ago and have been testing it. Prior to the Christmas holidays they put a new battery on it and kept it over Christmas for a test. Monday this week I had a warning from Mercedes to say that the battery was getting low. New Year’s Day another message to say it was critical.
The dealers were back at work yesterday and sent me the attached message, can anyone interpret it for me please, prior to the dealers “sorting”it.


Thanks.View attachment 996045

The Body Control Module should disconnect all non critical loads and put other various ecu’s into sleep mode to ensure the battery is able to start the engine.
On modern systems there are usually at least two voltage thresholds for first dropping less important loads like interior lighting and then everything else apart from the security and starting systems.
It is possible that the B2B has effectively bypassed this protection and being triggered to discharge the battery.
Have you got any solar fitted as this could be a reason to cause this depending upon the B2B trigger wiring

 

[Casper46]

Strange that the problems started with the B2B installation. Presumably they replaced the faulty one but have they got it wired correctly?

One of my B2B installations ended up with a dealer installed D+ activated isolating relay between the engine battery and the B2B. Totally unnecessary, the dealer misunderstood my instructions but I left it in place because it was doing no harm. It also ruled out any possible quiescent drain from the B2B. I am not convinced all dealers really understand these devices.

The problem did not start with the B2B, we have struggled with the engine battery charge since new. It went back for them to try to solve the problem again, at that point they connected a B2B, it was not visible so I couldn’t tell what they had done. We drove 70 miles home and within 2 days the battery was reported a critical again.
They sent someone to collect the Motorhome and we have not seen it since. They took the B2B off and wired the charge from the solar via a Sterling unit which then works through the CBE as recommended by CBE and Carthago. ( so they say).
After all of this the engine battery is still losing charge.

I threatened to reject the vehicle months ago, I wish that I had followed it through, but as the dealer would insist that there were no problems, and found an answer to every query, along with witnesses to conversations —that I dispute.
If I was 20 years younger I would have parked up across the dealers door and left it there. I have done that once before, but 30 years ago. I really do not have the enthusiasm for a court battle but I wish that we had not bought the vehicle and stuck to our E Line.

 

[Casper46]

Here’s an image of where the standby mode is within my menus.

It does state system inoperative due to me already having low charge when the image was taken.

View attachment 996061


Also below is a video I found fairly interesting on cab batteries for Sprinters, although not exclusive to Sprinters but quite interesting.

Eddie H,
That is very interesting and could be very useful. Thank you.