Van Wiring System Off Of Leisure Battery

[Radventures]

Hey again chaps. How are we all? In your experience what is the best way to feed cables from under the bonnet to the back of a van? It's really got me stumped.

 

[Radventures]

I'm un-stumped! Managed to figure out a way if I drill a new hole behind the fuse box. I've worked out I'll need around 2.7m of cable to run from the starter battery to the battery to battery charger. Where, conveniently, is a shelf which I should be able to store everything else. So I'm tying to work out cable size:

Max cable current at an inverter efficiency of 85%, 600w max load and battery discharged to 11v: 600/0.85/11 = 64A from the battery.
Volt drop is then a distance of 2.7m, volt drop figure is 2.8v for a 16mm2 cable (from https://www.tlc-direct.co.uk/Figures/Tab4.7.htm) and the 64A from cable current: 2.7x4.4x64A = 0.484. In a 12v system this is just over 4% voltage drop right? If I can find a 3 or 4 core 16mm2 cable then (according to the linked table above) I can get the voltage drop down to 0.414 which should be okay right?

Is there anything else I'm forgetting? Thanks!

 

[Wilko]

Hi - just looking at the pics of your invertor in post #25 and LN comments in #26. The manufacturer supplied 12v lead looks like it might be 4mm2. Sometimes the supplied cables can be a bit light duty, but I'm not sure investing in multiple 16mm2 cables will be worth your effort. Your calc of about 0.4V drop for 64A over 2.7m of 16mm2 copper looks about right. But I just don't see that invertor in your pic being able to sustain that draw. Of course I can't read the spec etc so I may well be wrong. If you want, you could try connecting to 12v car battery and loading the 230V AC side with some lamps via a plugboard and see how it performs?

 

[Lucien Nunes]

There seems to be some confusion here! You say the 2.7m is the length of the B2BC input cable, but you then calculate the VD using the inverter current, not the B2BC input current. As it happens the maximum is a similar figure (60A) but that is only coincidence - they are separate circuits working at different voltages and currents. The B2BC will only be operating when the alternator is running, so the launch voltage at the starter batt should be >14V. So long as the VD doesn't reduce this below the minimum input voltage of the B2BC at 60A, the voltage at the inverter batt will always be correct. Decreasing VD a few more % will simply increase maximum output current from the B2BC by about the same amount so it's not worth busting a gut for.

The VD is likely to be a few % less than the tabulated value because the cables won't be running at full temp, because the current is limited below their CCC by the VD.

 

[Radventures]

Hey Wilko, thanks for chipping in. I was thinking 10mm2 for the inverter & leisure battery cables. Think that's about right? The 16mm2 I meant just for the starter battery > B2b charger (and b2b negative cable). Inverter is rated for 600/1200w. I've tested a couple of bits off of the 12v lighter and seems to be okay handling loads up to 300w so far. Can't imagine I'll be loading much more than that.

Lucien, I admit I struggled superbly with the calculations so that would explain the confusion. Although I am getting the gist a bit now after some research & your help. Thanks for clearing things up (again). Would you be so kind as to clarify what you mean by 'CCC'?

 

[Richard Burns]

Would you be so kind as to clarify what you mean by 'CCC'?

CCC = Current carrying capacity, the maximum current a cable can take on a continuous basis without exceeding the temperature at which the insulation would start to melt.

 

[Deleted member 26818]

I would normally use Tri-rated AWG 4 or 35mm2 for battery to starter cables.
Although, that's on Harley Davidson motorcycles, so it may be different for vans and other vehicles?

 

[Radventures]

Thanks for chipping in guys. I've started putting some wires in (unconnected) and cutting cables to size. A few questions have cropped up and I would be very grateful for some help. I'll upload pics for ease of explanation.

1. I'm wondering how I am going to take a single live wire from this inverter plug and turn it into two wires for two mains sockets? Also, if I leave the negative/ground for this plug unconnected it shouldn't matter right? The inverter negative will be linked to the battery terminal (from the 12v cable on the other side) I'm technically just using it as a live output from the inverter?



2. What's the best way to hook up this pair of wires? I've noticed in a lot of the circuits in the car there's a clip system. What are these called, as I'm struggling to find these online? Or is there a better way? Should I remove the two wires attached to the LEDs and solder on the 2.5mm2 wire I'm installing?



3. Is it best to return the earth (in this instance the negative cable if I'm right?) to the leisure battery negative (which will be earthed to chassis). I remember Lucien saying not to take this to the chassis earth so I'm a little confused.

4. This is the B2B charger. In the instructions it says if I 'link' the two connections here labelled 'battery' & 'temp' I activate the feature where the charger turns off and on automatically (pretty desirable right?). By link I assume it means simply connecting a wire between the two with the screw in sockets. Am I right/if so, what thickness should the wire be?


Many thanks!

 

[Radventures]

Also, I've just opened a thread asking for an electricians help with overseeing the installation at some point over the next week. If anyone in the Swindon (Broad Town specifically) area can help out (or you can recommend someone) that would be great.