Cable size

[mikewroe]

If you're going to use 16mm cable on the output then closer than 1.5M between the two will give you that 0.1v drop or less.
If you've not purchased your cable yet then this may interest you

20mm² Flexible Battery Cable 135 Amp Black & Red - Automotive & Marine | eBay

Conductor Cross Section : 20mm². Not sure what you need?. Give one of our trained sales advisors a call and they'll be glad to help you out. Product Information. ALM Electrical Solutions is the UK's premier supplier of auto electrical parts and products.

www.ebay.co.uk

I used some recently and it's nice stuff. 20mm so slightly heavier/better but cheaper than 16mm probably because of it's slightly oddball size.

Thanks for that excellent link. The 16mm cable I found was £19.79 per 5 m, now I shall use the 20mm @ £16.49/ 5m
Will check that the Sterling unit can accept that size cable when the units delivered in the next day or so.

 

[gasgas]

Can I chip in that the conductivity of the cable will depend on the material it's made of. I suspect that some cable manufacturers are copper coating steel wires to make what looks like copper cable. That is just a random throw-in of information, I'm not saying the suggested wire is like that. Also of course there are various purities of copper. It can be mixed with some other metal and still look coppery.
As an aside - I presume that my 1999 Ford Transit AutoSleeper won't have an intelligent alternator, will it. So I wouldn't need a B to B would I? Just the usual relay activated by the D+ from the alternator. Though I would use two 30A relays in parallel to minimise contact resistance. And there again, these relays will vary in quality. Some with steel contacts will work - for a while, sparking - while proper ones like Hella presumably will be using properly rated contacts.

 

[wildebus]

Can I chip in that the conductivity of the cable will depend on the material it's made of. I suspect that some cable manufacturers are copper coating steel wires to make what looks like copper cable. That is just a random throw-in of information, I'm not saying the suggested wire is like that. Also of course there are various purities of copper. It can be mixed with some other metal and still look coppery.

Cable supplied with Inverters tend to be aluminium - sometimes made to look like copper. I always use those cables as bin-ballast.
I find the best initial test of heavy cable is the floppiness check. The floppier the cable, the better the quality (and the cable linked to by Merl is very nice and floppy! I used 10 metres of it last week).

As an aside - I presume that my 1999 Ford Transit AutoSleeper won't have an intelligent alternator, will it. So I wouldn't need a B to B would I? Just the usual relay activated by the D+ from the alternator. Though I would use two 30A relays in parallel to minimise contact resistance. And there again, these relays will vary in quality. Some with steel contacts will work - for a while, sparking - while proper ones like Hella presumably will be using properly rated contacts.

 

[gasgas]

Next time I am in a copper wire shop I'll ask if it meets BS/EN69382 for floppiness.
Good tip, that. But of course the floppiness quotient must be a function of the number of conductors. The more conductors the floppier it will be.

 

[wildebus]

Next time I am in a copper wire shop I'll ask if it meets BS/EN69382 for floppiness.
Good tip, that. But of course the floppiness quotient must be a function of the number of conductors. The more conductors the floppier it will be.

As you get to heavier cable, the floppiness test must be done over a greater length however, as the thickness of the outer sheath insulation starts to impact the internal FQ.
Fitting some 70mm2 cable last couple of days and the shorter lengths would have probably not passed the FQ for that reason. I think it is the formula FQ=(G x L)/sqRt(Ins) ?

 

[gasgas]

...............I think it is the formula FQ=(G x L)/sqRt(Ins) ?

I could have told you that.


If I knew what I was talking about
The square root of the insulation quotient will of course affect the FQ. Silicone insulation is of course the best for the FQ factor, however it does cut easily if it encounters sharp edges. It has one great advantage - that it will not catch fire but instead emit highly toxic fumes.
There is also the factor that if the insulation has a very low coefficient of friction, the conductors within the cable will slide inside the outer. This will greatly enhance the FQ.

However we have not yet discussed the advantages of Litz wire, or braided copper which is usually used for connecting the engine to the chassis and the battery negative to chassis. Braided copper usually has a very high FQ. Thus it is also used to connect the base plate of the points in a distributor to the chassis thereof. Also it is excellent for not transmitting or being susceptible to RFI.

On the other hand I have got better things to be getting on with just now. The kettle has just boiled and I have some 25 yr old wheels that are rusty and need removing from Polly the Camper and repainting black, before fitting new tyres.

 

[wildebus]

I could have told you that.


If I knew what I was talking about
The square root of the insulation quotient will of course affect the FQ. Silicone insulation is of course the best for the FQ factor, however it does cut easily if it encounters sharp edges. It has one great advantage - that it will not catch fire but instead emit highly toxic fumes.

I have switched to silcone-insulated tinned-copper for a couple of products I sell/install.
I quite like it but one annoyance I have found ... when stripping the ends, the insulation doesn't cut so easily but tends to stretch, which makes the end slightly messy (need strippers which sharper blades basically, so overall tool expense bit more).

There is also the factor that if the insulation has a very low coefficient of friction, the conductors within the cable will slide inside the outer. This will greatly enhance the FQ.

However we have not yet discussed the advantages of Litz wire, or braided copper which is usually used for connecting the engine to the chassis and the battery negative to chassis. Braided copper usually has a very high FQ. Thus it is also used to connect the base plate of the points in a distributor to the chassis thereof. Also it is excellent for not transmitting or being susceptible to RFI.

On the other hand I have got better things to be getting on with just now. The kettle has just boiled and I have some 25 yr old wheels that are rusty and need removing from Polly the Camper and repainting black, before fitting new tyres.

As an overall .... I have found best to get cable that is physically MADE in the UK or the EU (the Italians are for some reason very adept at making top quality cable - I guess they have that experience of floppy spaghetti?) - the Chinese-sourced cable is almost always poor

 

[gasgas]

I used to be employed as Salesman / Project Manager / specifier for projects involving wiring up factories and large office blocks for computer networks. On one job I needed so much IBM Type 1 cable that I bought three month's production from the Pirelli factory. I think the Pirelli salesman made a few bob out of that deal, I seem to remember it costing a bit over £1million.

A serious factor with silicone wire is that a manufacturer can specify thinner conductors for cheapness, so the wire can run warm / hot. Contrarily, In the Days Of Yore Ford made HT leads from string coated with carbon dust. The carbon would separate out into islands inside the insulation causing lots of unseen spark gaps and coughing and spluttering of the engine. Unless you knew about the carbon wires, it was very difficult to fault find. I was taught that by a Ford garage workshop foreman. First, change the HT cables for copper ones. That was before carbon/silicone wires.