running 12 volts from the front, to outside rear of the vehicle..

[Towpack]

just to confirm towpack, do you mean 25mm2 or 25 mm dia cable?

25mm2.

 

[StarCruiser]

133A full load current. Just in (max 136A based on 90 degree centigrade rated flexible single insulated and sheathed cable) for continuous loading on a 25mm2 which will drop 0.27v per metre run per pair. Which is 1.3v over 5 metres. 35mm drops .18v per metre which is 0.94v over the 5m. Taking a bolt to the chassis each end in addition to the copper cable would help get the voltage drop down further.

.94v is 7.8% of the battery voltage at 12V and 6.5% at 14.4v charging voltage. As this will be from a private supply (truck not mains) then as it is not for lighting then 'Other uses' apply and the maximum allowed is 8%. At 14.4v charging voltage, the value of 1.3v for the 25mm2 would be 9% which is too much. In any case the worst case would apply at 12v nominal which is worse at 10.8%.

Of course if the battery were near the load, then 25mm would be sufficient. A Durite 140A charger relay would cope with the load.

Hope this helps

Richard.

 

[chapel gate]

thanks towpack, and cheers for the calcs starcruiser. the cable I have is 10mm diameter. some of the conversion charts state this as 25mm2.

so if I earth to the chassis this helps reduce the "run"? (but take the positive off the offside battery)
i have seen the durite split charger that you mention starcruiser.

am i good to go at this? or will i turn the cruiser into a mobile 1 bar heater?

 

[StarCruiser]

10mm dia is probably 25, possibly 35, usually stamped on the outside these days. If you run a pair and link to the chassis also this will decrease the resistance of the negative. Will it make an appreciable difference? A little. All depends how you want to do it. Electric glowing cruiser? Nah. [emoji6]

 

[Dave2000]

I would run the two cables and be done with it Mike, I think as per StarCruiser it will not make a lot of difference, if it did then this means your cables are not heavy enough.

I seem to remember back from the science lab days that we had always believed current flows from + to -, and this is known as 'conventional current', the reality is the current runs from - to +. As all diagrams and knowledge bases assumed the earlier was correct it would cause to much of a problem to 'retrain' everyone to think 'backwards' as it were.

Now I could be having one of my 'low sugar moments' but IIRC this was (is) the case, hence the reason earths are as important as positives ....I think.

regards

Dave

 

[Chris]

I learned that in O level physics Dave. They basically too an educated guess about current direction and in this case they got it wrong but it was all a bit late in the day.

 

[Dave2000]

Thanks for the verification Chris, in 'my head' the pos to neg sits easier when wiring etc. Now off to the garage to repair a major failure of the LC.......the washers for the screen are not working

regards

Dave

 

[Chris]

Yes, well technically although the same thing, it's the direction of flow of electrons. But doesn't change the philosophy red = live, don't touch it to earth.

 

[StarCruiser]

In any circuit, the negative will take the same current as the positive. Earthing to chassis at both ends adds the conductivity of the chassis and thereby lowers the resistance slightly. The current available at the motor will be slightly greater as the resistance of the whole circuit has been decreased. Would probably not make a huge difference in practice.

 

[chapel gate]

Cheers chaps.