C300h w205 2016 Electrical fire in boot

NacNac

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Hello,

I would like to share what I have just experienced and to find out if others had similar issues.
Yesterday morning I went in the boot to take the plastic crate and I was horrified by what I have found.
after I discovered this and try to figure out if the process was still ongoing or not. Everything was cold not smoke etc..., I put everything in place to film this video to contact Mercedes. The car is with them right now but I do not trust them and therefore I am doing research on the internet to find out if similar issues occurred.
I drove the car the night before for about 15min and did not smell anything or noticed. I have no idea if this has been a very slow process or quick. The only thing I know is that the last time I lifted the board was about 5 weeks ago and I had not noticed anything. It does not mean that the process had not started from underneath but did not make it through the flexible cover and therefore was not noticeable by just lifting the board.
Here is the video (no audio)

Also, no one else has used the car.

Thank you very much for any info.
 

alexanderfoti

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Wow that is bad! I will be interested to see MB's outcome.
 

alexanderfoti

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Looks to be just the ground line from the battery?
 

Tony Dyson

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Looks to be just the ground line from the battery?
As above but the source looks to be a high resistance joint at either the crimp connection between the cable and the crimped lug connected to the chassis or the termination between the crimped lug and the chassis termination itself, it has definitely started at the chassis termination end and slowly worked it's way down the negative cable towards the battery.
I would be looking for a high resistance termination at the chassis end, and that the cable is solid copper and not a copper coated aluminium alternative, these have a history of oxidising and developing high resistance joints over time when not treated correctly before termination.
 

LostKiwi

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Looking at that I would say you were lucky it didn't burst into flame. It will be very interesting to see what MB have to say.
 

M80

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By the looks Tony Dyson is right.
So a high resistance causing a slow progress heating of the cable. I would assume due to the battery being under heavy recharge as the alternator would feed the cars load when running.

Is it possible the grounding lug was pushed causing the bolt to loosen some?

That makes me think it's worth checking the integrity of high current grounding lugs, especially if prone to trauma. Rust could cause the same.

Very lucky that there wasn't something with a low flashpoint near.
 
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NacNac

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Hello
Thank you everyone for your comments and suggestions.

I now have the investigation reports which reads:

“The technician found that the non Mercedes-Benz battery was 4cm too short for the housing. The battery was not fully secured with the holding bolt causing the battery to move, causing the live feed to rub through the insulation and causing the earth to overheat and melt.”

This was indeed an electrical fault.

And no, I have not had this battery replaced since I got the car so the story continues...
 

Tony Dyson

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"causing the live feed to rub through the insulation and causing the earth to overheat and melt.”

It's unclear from the video where the 'Live feed' is that the investigator has blamed for the cause. Additionally, I would suspect such a fault to have catastrophic outcomes of fire and total battery destruction as what he is describing is a dead short across the battery terminals with no fuse protection in line but all the evidence in the video is as described in my earlier post #5.
The initial statement of the OEM battery is the most relevant, unusual that a battery was changed so early on a 2016 car but the wrong spec and not fixed down properly is clearly where the mistakes were made.
 

alexanderfoti

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From the video, it does look like a non-genuine battery (banner maybe?) 1619008377432.png
 

V6Matty

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Think you need to find out who changed the battery to a non standard one and have them discuss things with a lawyer
 

M80

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So we've to assume that the technician refers to positive as live and negative (ground) as earth. That doesn't instil much confidence.
I'm struggling to see the 'live' positive that was shorting.

Maybe the video doesn't show the cause very well??
 
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NacNac

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Thanks for your comment
The video was to show what I have seen when I lifted the board that morning and how I have found things. It does not show the cause as I did not know what the root cause was at the time of filming.
The cable seeing in the video is the Earth.

I do not know the brand of the non genuine battery. I'll try to find out.
 

Rotorhead500

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Ah, ok. If it was new or Approved, you'd have a very clear channel to pursue.

I'd suggest a discrete, non-leading enquiry (in writing) to supplying dealer asking if they replaced the battery prior to handover.
 


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