12 Volt Power

One of the biggest pains when we are out and about is the lack of power. With all my vehicles, I have had to add in adapters that plug into the cigarette lighter to give additional capacity for charging phones, running Sat-Nav’s and so on. After a bit of digging around on the Internet, I have decided to (in my next vehicle!) add an extra battery in the boot, along with its own Power Distribution Board. It sounds daunting, but looks fairly straightforward.

As my current vehicle has quite a few 12 volt power outlets (3 in total – front, back and boot) and 7 USB power sockets, this is not currently an absolute necessity, however I am looking to take a step backwards and buy an older 4×4 that I can work on, and this is one of the main things I want to try.

I am currently compiling a heap of parts, and will start by making a trial board first. The Second Battery setup will be the last step in this process, and it is also the most expensive in terms of parts required. I will be putting links to my YouTube videos of this endeavor here, along with PDF’s of how I did the wiring, and a list of the parts I used and where they were sourced from.

The long term idea of this is that we are self sufficient in power when we are travelling around, camping and doing the shows with Ford & Field. I am aiming to have a system that charges the second (Leisure or Deep Cycle) battery from both the vehicles alternator as well as from Solar panels. Wish me luck! 10th April 2021.

First Update: I have now got some parts arriving, primarily the fuse box and the Relay. Spent some time this morning putting a wiring diagram together, so I know what to put where. This is going to be ‘Phase 1’. I will construct this part of the Power Distribution Board, and test it on a leisure battery that I have running off solar panels in my garage. Once that is done it will be time to start buying and adding the accessory power outlets, and anything else (perhaps a CB?) that needs to be permanently wired into the car. This is my wiring diagram:

Hopefully it will work, but I will let you know the results once I have put it all together.

So Far all parts have been located on Amazon. I have found a couple of 12 volt specialist websites here in the UK that will be my next port of call for cables and so on, but again, full supplier list, kit used and cost will be posted at the end. I will also do a YouTube video once production starts. I will also post some downloadable PDF files of any wiring diagrams and equipment check-lists that I put together, as it will make life easier for anyone wanting to give this a go.

If you notice anything wrong on the wiring diagram, feel free to email me. 11th April 2021.

The Fuse Box and Relay have arrived:

The Midi Inline Fuse, Connectors and Marine Heat Shrink, Midi fuse and Connectors have now also arrived, and I picked up a couple of other bits. Just need the Inline Fuse Holder (which is on the way) and the cable, which I will be ordering next week as the supplier is currently closed down whilst it moves warehouse.

Looking forward to trying it all out! 12th April 2021.

The Inline Fuse holder for the 80 amp fuse arrived on the 13th April, so it is literally a case of waiting for the wire supplier to come back online so I can begin in earnest. While researching all this I came across more critical safety information:

1 – Fuse Size. To work out what fuse you require in each of the slots on the fuse box, you need to take the total amount of Watts required and divide this by the Volts (which in this system is always 12 volts). You take the resulting figure, which is the Amps, and times it by 1.5 to get the fuse size. The fuse must not be more than 1.5 times the amps required. You could always err on the side of caution and just times the Load by 1.25 to get a smaller fuse.

The formula looks like this: (Watts divided by Volts) x 1.5 = Fuse Size (in Amps)

Some accessories will already have an amperage rating, like the Twin USB sockets which generally draw 3.1 amps. With these, just add them all together and times by 1.5 (or 1.25 if you prefer) to get the fuse size.

2 – Wire Thickness. Your wire must be able to handle more amps than the fuse, this way if there is a surge of power, the wire will tolerate it and the fuse will then blow, thereby preventing the wire from melting and causing a fire. Always over engineer the wire and go for a much larger thickness than required.

Update: Two lengths of wire have now been ordered (3m of black and the same of red), 16 mm² and 110 amps. Should be here this week. I have also got a sheet of plywood, ready to put it all together on. 19th April 2021.

All the bits are here, and after another side trip to Halfords, I have began to put together a prototype of the final board. The accessory panels have also arrived, which was supposed to be Phase 2, but I have also stared wiring them up. Ran out of crimps which was frustrating, but the good news is that my 1980’s Crimps are working just fine with everything so far, including the large Tinned Copper Lug Terminals that I thought I may need a special crimper for. I also found a nice hack on YouTube where a vice was used to crimp these lugs. I gave it a go and it seemed to work. Just got to cut the chipboard up now and put it all together. 25th April 2021.

The prototype board is now built! It took a while to update this as things have been hectic of late. Once I have hooked it all up to a battery, I will let you know how (if!) it works. Please ignore the hack and slash of the woodwork, this is just to prove it works. 1st June 2021.