W220 Positive Battery Lead Gauge/Amperage

lordgaz

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Hi All

Does any one know what level of current rating the very thick positive battery cable is supposed to handle? I cannot get a measurement of the conductor diameter without stripping off the insulation - but I am estimating the insulation to be about 1.5mm thickness, and coupled with the overall diameter of 15mm meaning a conductor outside diameter of 12mm -
There are 2 cables available

240A 11.8mm Outside diameter &
300A 12.7mm Outside diameter

There is also a 345A 13.5mm Outside dia cable if I have overestimated the insulation thickness.

So I am not 100% which size I need - It would be better to know what the cable needs to be rated at.

(I am fitting a remote controlled battery cut off solenoid as I am fed up with parasitic drain, and need a stop gap solution until I can hand over the car for investigation, and need to buy a short length of same type of cable in case you were wondering ;) )
 

Paul Goff

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Hello,
The simple answer to your question is, IF you can terminate & accommodate the largest one, then that is the one to get.

But forgive me if I answer you with a question! Can you source, connect, accommodate and supply the coil current of a solenoid that can handle the starter motor load? It is fairly unlikely that the starter gear forms any part of your parasitic drain, it might be a great deal easier to break into the circuit further "downstream" of the big fat positive main cable.
 
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lordgaz

lordgaz

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a2aee6a833374926ad74560d18f705ef.jpg


Thank you for the reply.. I may be able to isolate the supply in the engine compartment if there’s room.. I’ll need to investigate, though I would prefer to isolate at source as there is a smaller +ve feed taken off the battery which goes to a point in the boot which could relate to the drain.
You will see above the unit I will be using. Rated up to 1000A max for short bursts


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Craiglxviii

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If you install a battery cutoff then you will get a lot, and I mean a LOT of systemic module failures due to no power.
 
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lordgaz

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Yeah, noted. I need my car every day, and have been trying to find a window to get the drain sorted.. I have been disconnecting the battery manually each time with a cut off switch for a fair while and shudder each time I have to do it... does anyone know of a good electrical specialist in the West Midlands? (Birmingham to Cheltenham/ Herefordshire/Worcestershire)


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Craiglxviii

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Mercman in Nuneaton or MSL in Brummagem...
 
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lordgaz

lordgaz

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Oddly enough, the car has never ran better as the time I have been disconnecting the battery... I had a problem before (documented on this forum) where cylinders were cutting out/misfiring on random occasions... not had a single occurrence of that issue since I have been chopping the battery power. Seems something (adaptions?) are being reset and preventing the misfire issue....


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lordgaz

lordgaz

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Mercman in Nuneaton or MSL in Brummagem...

Hi Craig,
I can only see a Mercman in Cornwall (and Mercland in Nuneaton) do you know any other details?


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lordgaz

lordgaz

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Mercman in Nuneaton or MSL in Brummagem...

Sorry, and MSL, is it MSL centre Ltd, or MSL performance in Brum?


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Craiglxviii

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Hi Craig,
I can only see a Mercman in Cornwall (and Mercland in Nuneaton) do you know any other details?


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Mercland. My mistake!!!
 

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Sorry, and MSL, is it MSL centre Ltd, or MSL performance in Brum?


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Its MSL Performance located in Armoury Rd, Small Heath trading Estate Birmingham.
 

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Thanks Ken - Do you know if MBB have particular expertise in the electrics of Mercs?

Never used them but, from your profile location, and your listed locations, I'm presuming you either work/or have work commitments, in Cheltenham. If you go to the Home page of the Forum you will find a link to a Specialist Finder. It asks for a postcode but, also accepts a Town location.

I would prefer to isolate at source as there is a smaller +ve feed taken off the battery which goes to a point in the boot which could relate to the drain.

If you think that could be the cause, then I would get a multimeter, set to Amps, and connect such between the battery and the connecting lead. My limited knowledge of any Merc is that they may take several minutes [after key extraction] 'to go to sleep'. If you are registering a 'drain' after, say, 20 minutes, then removing fuses, one by one, could assist in identifying the source of the problem.
 
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lordgaz

lordgaz

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Never used them but, from your profile location, and your listed locations, I'm presuming you either work/or have work commitments, in Cheltenham. If you go to the Home page of the Forum you will find a link to a Specialist Finder. It asks for a postcode but, also accepts a Town location.



If you think that could be the cause, then I would get a multimeter, set to Amps, and connect such between the battery and the connecting lead. My limited knowledge of any Merc is that they may take several minutes [after key extraction] 'to go to sleep'. If you are registering a 'drain' after, say, 20 minutes, then removing fuses, one by one, could assist in identifying the source of the problem.

Thanks Ken. I’ll check out the specialists page... I’ve yet to find a local Indy who is anywhere near as good as Alex Crow, but he’s in Lowestoft which is a good 4hrs from me! Hence looking for qualified recommendations. Had too many Star read outs around here which are not backed up with some experienced diagnosis / fix solutions for various problems I’ve not been able to sort out on this forum.

I know I have about 3 to 4A current drain (a hell of a lot) when car is supposed to be sleeping (and I have taken each fuse out, but found it may be more than one fuse circuit causing the issue, so gave up for now.. probably need to remove all fuses and then add them back one by one)


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