Power point in Boot - Whats the best way to do this?

[BRE Fabrications LTD]

Right, so I'm about to sort the cable issue on my VIAIR Install (viewtopic.php?f=65&t=10557)

But what I'd like to do is run 50mm cable to the boot for a power point( I am planning on installing a leisure battery at some point as well as an Inverter, hence the cable size) and then wire my compressor into that. Only thing is I'm not sure what the best way to do this would be.

I'm thinking of doing what Chris has done and mount a mega fuse on the firewall. Now this is where I get stuck.

1. What size mega fuse should I run?
2. In the boot should I just mount an Auxiliary fuse box?
3. If so what type?
4. Do I need to install relays on anything? In other words should the secondary fuse box be switched?
6. Do I need to run a + & - cable to the secondary fuse box or can I just run a + cable and ground off of the bodywork?
7. If I do need to run two cables then should I run the - from the battery and + from the Aux power point under the bonnet?
8. Have I gotten this completely wrong or is there anything I have completely missed?

Any help/info much appreciated.

Cheers
Ryan

 

[sae70]

This is what I did for the supply to my compressor in the boot viewtopic.php?f=14&t=9414&p=62948 but this was with a pair of 10mm cables for a 50amp supply 50mm cables would be a struggle run in this way

I remember 'Steve H' posting about how he had run heavy cabling for the boot from the engine bay through one of his chassis rails

I have run a feed wire for my amp through the chassis rail on the drivers side. I found that 20mm flexible conduit fits through the cut outs in the chassis and can be fed through to the front of the rail from the back of the truck. It goes over the stiffening tube quite easily. I brought it out from the chassis under the drivers floor pan and then followed the rear heater pipes up into the engine bay along the inner wing to the battery. At the rear of the truck there is a grommet to take the wiring for the bumper lights into the truck behind the rear panel. I just fed the end of the conduit into the same hole and up into the void behind the panel. Then pushed the wire through from the engine bay into the rear. I will be fitting a 4 way splitter onto the end of this to power the amp, a permant live power socket and a charging socket to top up batterys for 12v caravaning weekends.

Pictures of his installation are here viewtopic.php?f=14&t=9122

 

[sae70]

I just remembered that it was rescently discussed about only running the positive wire & using the Chassis & body as the earth return path! If this is possible then it would save a pile of time & money

Here's the mention of it in this thread viewtopic.php?f=29&t=10801&p=80128

I used to compete in stereo competitions, on a break at the minute from them.

We used get marked on wiring and had specific rules/conditions, more to help/entice people to do installs to a good standard, lerge cables, proper discrimination with fusing, terminations etc.
never said anything about running a neg adn positive to 2nd battery in the back, always happy use the chassis as a common point.
But on the bright side, if you fitted another battery you could always go the other way!!!

Hope the wagon performs for ya when testing!!!
Have fun

 

[Jon Wildsmith]

Put your 250amp mega fuse as close to the battery as is practical, when you get to the rear these 300amp connecting blocks are what I use, the 1st one with 2 terminals and you don't need another mega fuse at the back until you add another battery. Having the junction box above makes it easy to run a smaller cable size into a fuse box and another run of 50mm to your solenoid and aux battery when you get that far. When you add the aux battery put another 250amp fuse close to it like the front.

 

[Ronanjordan]

What said there sounds good to me,
It's what I'd do.
Just remember to add a neg off ur main battery to have enough current flow back!
Lots of people forget this.

Also, if you decide to use 1 cable from the positive and use chassis as a huge negative,
Make sure you get good contact, maybe even sand off the paint where u bolt the cable to!!

 

[Chris]

I have mine wired with two cables and everything that comes off it uses two cables. That way there should be no leakage anywhere. It's effectively a closed loop. Once the split charge has opened, there is no route back to the starting batteries either. I just like it tidied that way. More cable yes, but There you go. If you had a problem with the main power feed, you have always got sufficient cable next to it to run a bypass in the field as it were.
I have 2 mega fuses in now. There is one either side of where the cable comes into the cabin. That way the main battery would be cut off if it earthed and so would the aux battery coming the other way if the charge breaker was closed.

Not an auto electrician, of course, but an overland prep chap told me to keep it all closed loop.

Chris

 

[Graham]

Hello Ryan,

50mm cable is a fair old size, and may be a little difficult.
Any way, I am sure it will be more than sufficient for your leisure battery and extras.

I run a pair of 35mm welding cables.
I know some have simply kept to simple and used the chassis as the earth, but to dismiss any possible future problems, with a proposed high current use, I would suggest you use a pos, and a neg. cable.
In my circumstance, the pos. is fused at the battery with a 175 amp fuse, (my cable capacity 225 amps) this came directly off the pos. of the battery.

Here is a very interesting data fact sheet.
I am sure this will help you decide if 50mm is what you need.

http://www.eland.co.uk/documents/H01N2D%20Cables.pdf

A 35mm on 100% full load, constantly would provide 225 amps
A 50mm on 100% full load, constantly would provide 285 amps

This data fact sheet also gives the current carry capacity on a percentage time basis, ie, if your just running a high load on an intermitant useages, short time winching?

G.

 

[BRE Fabrications LTD]

Thanks for the info guys, much appreciated.

I am going to stick with the 50mm welding cable, + & - directly from the battery. For the meterage I'm going to be buying the cost is negligible.

Any suggestions as to what type of fuse box I should go for? Are will a Halfords job do the trick? And is it necessary to have a switch controlling the power to the back?

 

[Chris]

Ryan, I think it's always advisable to have a cut off for any battery system. I have one of those rally removable key master switches on mine. I made a bracket and mounted it under the bonnet next to the driver battery. This allows me to disconnect the aux in the bot if I need to without worrying about live leads flying about everywhere.

For a fuse box, VWP do loads. For lighter duty items I use one of their little plastic boxes that takes blade fuses. I ran a live to the box then took a piece of wire and pushed it through all of the terminals on one side and soldered it in. This makes a common bus if you like. All the other terminals will now be live through fuses of my choice. Anything bigger than that (more then 30 amp) will come directly from the battery and go through a midi fuse mounted somewhere specifically for that device. Bought a second VIAIR pump today from Matt Savage and that will have a dedicated supply. They pull 30 amps each so I shall run one big dedicated cable to the pumps and then spilt it onto the factory cable supplied via a nice big proper relay controlled by a pressure switch.

Chris

 

[BRE Fabrications LTD]

Thanks again for the info Chris. The idea of a cut off under the bonnet seems a good one. I guess I could just as well do that while I do the other wiring. That way the work needed to be done under the bonnet for when I do install an Aux battery is complete.

I've ordered the bits off of VWP's so just waiting for it now. I'll update on how I get on when my goods arrive.

Be sure to give us an update on how your VIAIR setup performs once you have the second compressor wired up. I'm keen to see the difference once the wiring on mine is sorted because at the mo it's pretty gay

 

[Chris]

Ryan, been playing with it today. Woof! What a difference when you stick the other compressor on line! I have also decided to run to the tank with 7mm bore not 4mm as standard. I have some tank fittings that will work with the compressor. You do the math, but two 7mm bore instead of one 4mm bore. These pumps do their best flow at the lowest pressure. And I figure that some of that pressure is generated by the thin pipe. You can have high pressure low volume, low pressure high volume or what I am aiming for high pressure high volume. With the two pumps running into a Tee today, the volume and pressure coming out of one 4mm pipe was enough to blast paint off the grille! I'll start a thread once I get all set out. But so far very pleased with decision to get the extra pump.

Chris