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Cable size


Sanddancer

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  • 2 weeks later...
On 02/06/2019 at 12:16, Alan de Enfield said:

Whatever size is suitable for the current output of the charger - we cannot answer directly as we don't know if you have a 4 amp charger or a 120 amp charger.

 

A properly crafted question will result in informative answers.

IMG_20190615_121051631.jpg

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11 minutes ago, Sanddancer said:

IMG_20190615_121051631.jpg

 

OK - and the distance from the charger to the batteries s ?

(quote either the simple distance, or allow for 2x the distance as the leccy has to go in a circuit) 

 

'Normally' something like 3 to 4% volt drop is considered acceptable.

 

If your batteries are 3mts away from the charger, then you will need to use 10mm squared (not 10mm diameter) cable.

This will give you a volt drop of 0.46 volts and a 3.83% volt drop.

 

For comparison using 4mm squared cable would give a volt drop of 1.16 volts and a 9.7% volt drop.

Edited by Alan de Enfield
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54 minutes ago, Sanddancer said:

IMG_20190615_121051631.jpg

 

On 02/06/2019 at 12:16, Alan de Enfield said:

Whatever size is suitable for the current output of the charger - we cannot answer directly as we don't know if you have a 4 amp charger or a 120 amp charger.

 

A properly crafted question will result in informative answers.

It's about 4 feet

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6 minutes ago, Sanddancer said:

 

It's about 4 feet

Ok taking it as 2 metres (to allow for routing and a bit of slack) you need 8mm squared (not 8mm diameter) 

 

That gives you 0.36 volt drop (or 3%)

 

This one would be ideal.

 

https://www.12voltplanet.co.uk/63-amp-single-core-thin-wall-auto-cable.html

Edited by Alan de Enfield
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pedant alert -  '4mm squared' is actually 16 square mm.   If you want to be unambiguous it would be helpful to get the 'dimensions' right, in this case I assume you mean 4sq.mm. 

as you imply - many vendors are lazy and describe 4sq.mm. cable as 4mm. 

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on the subject of confusing arithmetic, it really bugs me when advertisers claim something is '2 times more' when they mean 'twice as much'.........    2 times more means 3 times as much;   if they want to claim it is twice as much they should say '1 time more', or more easily understood 100% more.

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1 hour ago, Murflynn said:

pedant alert -  '4mm squared' is actually 16 square mm.   If you want to be unambiguous it would be helpful to get the 'dimensions' right, in this case I assume you mean 4sq.mm. 

as you imply - many vendors are lazy and describe 4sq.mm. cable as 4mm. 

You are of course correct.

As I spent 9 years designing cables for one of the UKs major cable makers I should have known better.

 

(goes out into the yard, head down and quietly kicking small stones around)

 

Edit to add - my excuse being I could not find the superscript button - and the 'squared' comes after the mm's in the notation anyway.

 

Done it in word and copied / pasted

4mm2

Or - is the correct notation 42mm

 

Edited by Alan de Enfield
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34 minutes ago, Alan de Enfield said:

You are of course correct.

As I spent 9 years designing cables for one of the UKs major cable makers I should have known better.

 

(goes out into the yard, head down and quietly kicking small stones around)

 

Edit to add - my excuse being I could not find the superscript button - and the 'squared' comes after the mm's in the notation anyway.

 

Done it in word and copied / pasted

4mm2

 

Or - is the correct notation 42mm

 

yes, I can see where you're coming from.  in dimensional analysis we would only use the notation: 4mm2  but in longhand and spoken it has to be 4 sq.mm. 

 

I am always bamboozled when someone says their living room is '16metres squared' - that makes it a ballroom. 

 

The worst offenders when using dimensions (that in their case they don't understand in the slightest) is journalists and documentary film makers when they refer to, for example, 'the wind farm that can supply 5,000 houses with electricity per year', or 'the power station that generates 5 megawatts per day'. 

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1 hour ago, Alan de Enfield said:

Before the OP gets hung-up on 4mm cable he actually needs 8mm2 for his cable length and current.

 

(I gave a link to the correct cable)

Seems an unnecessarily harsh punishment for asking a reasonable question!

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18 hours ago, Murflynn said:

yes, I can see where you're coming from.  in dimensional analysis we would only use the notation4mm2  but in longhand and spoken it has to be 4 sq.mm. 

Well, to be fair, when spoken that size cable is normally referred to as "4 Mil".

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30 minutes ago, Sea Dog said:

Well, to be fair, when spoken that size cable is normally referred to as "4 Mil".

we know that, but therein lies the problem. .............  '4 mil' might mean summat to an electrician buying his stuff at the local wholesale outlet, but for the layman it is far better to use the correct description to avoid any misunderstandings.   the guy at the counter isn't going to think any the less of you if you do, and even if he does who gives a XXXX ?

if you are buying off ebay you may only see the shorthand version, which leaves some doubt, and it is likely that the vendor hasn't got a clue what he is selling.  If you buy from a professional outlet like this, there is absolutely no doubt what you are getting: 

https://www.tlc-direct.co.uk/Main_Index/Cable_Index/index.html?ad_position=1t1&source=adwords&ad_id=109759653317&placement=&kw=electrical cable supplier&network=g&matchtype=b&ad_type=&product_id=&product_partition_id=&version=finalurl_v3&gclid=EAIaIQobChMIiZTi1OHt4gIVaLHtCh120AXpEAAYASAAEgIDH_D_BwE

Edited by Murflynn
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to go off-topic for a moment, isn't it absolutely daft that the conventions for describing the sizes of plumbing pipes is so inconsistent?  There are websites that exist just to guide you how to specify pipe sizes, and in some cases, for example PVC waste pipe, even those websites don't help much when you go to screwfix or whatever to identify what you need.

Edited by Murflynn
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44 minutes ago, Murflynn said:

but therein lies the problem. .............  '4 mil' might mean summat to an electrician buying his stuff at the local wholesale outlet, but for the layman it is far better to use the correct description to avoid any misunderstandings

It is even worse than that. To an American, 4mili might mean 0.004"! Most Americans firmly believe that if they go metric, then the terrorists have won.

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I was watching a documentary about Mary Schweitzer from Montana who says she found organic tissue in a T Rex fossil 68million years old.  The Creationists loved it - they reckon she has proved that the world was created 7000 years ago because everyone knows that organic tissue cannot exist for much more than a few thousand years. 

 

 

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3 minutes ago, Murflynn said:

I was watching a documentary about Mary Schweitzer from Montana who says she found organic tissue in a T Rex fossil 68million years old.  The Creationists loved it - they reckon she has proved that the world was created 7000 years ago because everyone knows that organic tissue cannot exist for much more than a few thousand years. 

 

 

I wonder how the OP is getting on with wiring his dinosaur battery charger ?

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