Leisure battery installation and Split Charge circuit.

Part 3 - 12v Secondary Fusebox.

The secondary fusebox is designed to distribute 12v positive from the leisure battery to you camping accesories such as interior lights, fridges, invertors etc.

The job of a fuse is to protect the wiring in an installation from catching fire. The fuse is essentially a small strip of metal which will get hot and melt in the case of a short or overload, breaking the circuit long before the cables can burn. Of course, the fuse and wire need to be of the correct rating at all times.

The most common mistake people make when thinking about leisure battery installations for the first time is that the term fusebox refers to the fusebox already in the vehicle. This is not the case: you will need a secondary fusebox if you plan to run more than one internal device. I will always refer to this fusebox as the Secondary Fusebox to avoid confusion.

The diagram below shows a simple diagram of how the secondary fusebox relates to the leisure battery installation.

If you consider yourself a bit of a dummy with electrickery, don't be put off by this drawing; it's really very simple.

• The earth of the leisure battery is shown as connected to the vehicle earth - this of course can be any metal part of the body or chassis near the battery installation point, provided the earth strap makes a good electrical contact to the metal.
• A live feed is taken from the postive (+ve) of the battery to the first terminal of the secondary fusebox. The other terminals are "commoned up" via a brass linking strip (see photos below)
• The other side of the fusebox, each individual terminal is now connected to the battery via a fuse, protecting the circuit. It is now a simple matter to run an appropriately rated wire from each terminal to feed a piece of equipment you wish to run from the battery.
• Note that the other side of the appliance or lamp you wish to connect can simply bolt to a convenient part of the bodywork to pick up an earth. You may wish to make one central earth point in the van and run a wire to each item to minimise holes!

Below is a set of photos showing a real-world example of a secondary fusebox.

6 Way Secondary Fusebox and fuses

Fusebox 6 way link.

The idea of the link is to "common up" the live feed coming in from the leisure battery, as you only need to connect this wire once to the common side of the fusebox. Of course, you can use 5 small bits of wire to do this job, but for the sake of a quid or so, this is much neater and easier to work with.

Once you open the fusebox, you will need to assemble it.

Use a screwdriver to prise open the 4 catches.

The fusebox, opened.

The fusebox with the common rail installed. I am not sure if this is the way it was designed to fit, but it looked wrong poking outside of the box....

And now with the 6 fuses installed. They will need to come out again for the final installation in the van, there are two holes in the back of the fusebox to allow you to screw it to a wooden cupboard etc.

You should now see that you only need to connect the thin wire from the +ve of the leisure battery to one of the terminals at the bottom, and you then have 6 seperately fused "output" terminals to run to each piece of 12v equipment.

For the record, my equipment will include:

1. Internal Light
2. "Bedside" spotlight
3. 3 Way Fridge
4. 12v socket for coolbox or invertor
5. Radio and Amplifier
6. Spare, or maybe another 12v socket for a hairdryer or TV!

>>Part 4 - The Relay...