C63 two battery's?

[AL3X]

Does my c63 have a secondary battery? I've been told it does but I'm unsure where it will be?

 

[AL3X]

Anybody?

Battery keeps dying but I've replaced it for a new one, still the same so wondering if there's a convenience battery?

 

[Dec]

Below is some useful info for a W211, much the same for your car I should think.
http://www.mercedestechstore.com/pdfs/W211_technician/319 HO Dual Battery (ACB - ICC) 11-29-02.pdf

What year is the car?
How often does it die, do you do a lot of short, infrequent journeys?

Dec

 

[Dieselman]

No there isn't. Check the alternator output and any battery drain when the car is off.

 

[AL3X]

The car is an 08 c63 mate, it has been fine since I bought it a few months ago, then one day I came to unlock it and it was dead, so got it started, then it worked fine all day, left it overnight it started ok in the morning, took the van to work, when I came home the merc was dead again

So I replaced the battery yesterday, worked fine, this morning it was dead again

How do I do those tests dieselman, i do have a multimeter if that helps?

 

[AL3X]

I have noticed a faint buzz from the sunroof switch/ map light area even with the engine off and keys out if that could be it?

 

[Dec]

Complicated business trying to find a battery drain, needs a bit of knowledge and experience or a lot of luck.

Test you’re alarm to see if it is in working order, post 8 here… http://www.mbclub.co.uk/forums/electronics/160849-battery-drain-w215-cl55-2001-a.html

The buzz might be a small fan that draws cabin air in over a thermostat so as to monitor and regulate cabin air temperature, you could lock yourself in the car and listen… and stay completely still so as not to trigger the alarm motion sensors… see how long the buzz lasts.

Dec

 

[V12]

Anyone with a multimeter and a brain can find battery drain.

Oh, you do need to be able to remove fuses as well...

 

[Dec]

https://www.youtube.com/watch?v=KF1gijj03_0
https://www.youtube.com/watch?v=P-wxG6U5TuY

Dec

 

[AL3X]

Right, just had a quick check, I turned the car off, opened the boot, popped the latch in so it didn't sense the boot as open, I then locked the car with the fob, connected my meter with the black in com port, the red In the adc one, and set it to 10a

From this I got a reading of 5.8! This to me seems huge? Should I be leaving the car unlocked and waiting a period of time for the systems to shut down or what?

 

[Dieselman]

Leave it for 30 minutes and check again. 5A drain is huge, that has to be something big like seat heaters or window winders. Time to start pulling fuses out.

 

[AL3X]

Should I leave it unlocked, with the multimeter in series for half an hour? But pop the boot latch so the light is off? That way everything should shut down?

I did pop the fuse 26 for comand which dropped it down to 3.8 amps or so, unless I'm doing the test wrong I really am worried!

Thanks fellas

 

[Dieselman]

Comand will stay alive for a while, most other things should shut down pretty quickly.

Lock the car and try again.

 

[AL3X]

Ah I see, that might be part of it then, I shall try tomorrow

I did the initial test with the car locked, bonnet and boot open but the latches clicked shut so the car didn't recognise these were open, is my best bet to lock it all but with boot and bonnet open, leave for half an hour and then connect the multimeter and try removing fuses to find the issue?

Cheers

 

[Dieselman]

It will probably sleep after about 5 minutes with it locked.

You do have the meter connected in series, don't you? Or is it a clamp type meter. Connect it and then lock up and watch the current draw from then on.

 

[AL3X]

Ah will it?

Yeah I've connected one leg to the battery, and one to the negative terminal

I did think of that but that YouTube video mentioned any triggers of electrical components may raise the amps and blow the meter?

 

[Dieselman]

There will be a 10A fuse in the meter, but the door locks shouldn't draw 10A.

Alternatively pull the door lock fuse and manually lock them.

 

[AL3X]

Ah yeah good point, how about the alarm system?

Well, I suppose the alarm shouldn't draw much as it's active all the time

I'll see how I get on in the morning and report back, thanks for your help so far!

Out of interest, what's the next stage after finding the source of the drain? Hopefully not a costly replacement of the whole seat setup for instance if it is that

 

[Dieselman]

Let's see what it is first.

If it's seats look at the heater control or wiring loom.

At ~4A, something will be getting hot.

 

[AL3X]

Good point.

As in when the cars off the module/item causing it will be getting hot temperature wise?

Let's hope I don't have a fire then!