**This article should not be taken as advice or instructions, it is merely a re-cap of how we did it**
A subject we knew very little about and as such a major (and potentially dangerous) part of the van’s construction, we did a tonne of research and reading on this topic. Some people would laugh off 12V electrics and comment that you can’t do any damage, others would fill you with heed about electrical fires.
We put so much thought into this topic, I can’t help but think other parts of the construction (insulation perhaps) suffered a bit. Between the very first plan to turning on the last switch and seeing the light shine, there were huge changes made, and many times along the way we made sure to check we were in the right direction.
And lastly, prior to finalising the connection between solar panel, battery, lights, amplifier, fridge and inverter, we had an electrician look over everything to ensure it would be OK. Safety first folk.
We started by learning the very basics. From here, we kept making our circuits more complicated to ensure we understood the theory behind it. Briefly now we’ll explain our learning curve and how we did it. BUT, remember this should not be taken as advice or instructions, it is merely a re-cap of how we did it.
From the battery’s ‘+’ (positive) terminal, take the power to the consumer (light, fan, pump etc). From the consumer, take the ground back to the battery’s ‘-‘ (negative) terminal. This creates the circuit and makes the consumer work. You never want to let the ‘+’ touch the ‘-‘, causing a short circuit. Once we had the hang of this, we put a switch between the battery and the consumer. You can also put the switch on the ‘-‘ side too, it’ll do exactly the same thing – cause a break in the circuit.
We then added another consumer to the circuit, both on the same switch and then on different switches.
Once we felt we understood all this, we set about trying to learn what else we didn’t know – which can be very tricky as you don’t know. Wire size, fuse size and type are prime examples.
For wire size we used an online calculator which was very useful – until the electrician told us to scrap using 1mm wires altogether and use 2.5mm as the minimum. This was controversial however, as two sources told us that you could run a lot on 1mm wires without a worry. We took the sparky’s word in the end though, even though it meant we had to pull out all the 1mm wires from the conduits and replace them with 2.5mm. Also the longer a circuit is, the thicker the wire needs to be, so we tried to minimise the length of wires where we could. To help us with this, we positioned ground points at strategic places in the van so the wire didn’t need to return to the battery. To ensure these were properly grounded, we used the voltmeter to test them all individually.
To gauge the fuse size we needed, we calculated the maximum power consumption per circuit and went with that, ensuring it was not above what the wire could handle, and if it was close, we erred on the side of caution and went down a fuse size. We then double checked these with the sparky. Every consumer needs a fuse – in the case something goes wrong, the fuse will cut the circuit and potentially stop a fire starting. It is also important to place the fuse as close to the power source as possible, but ensuring that each circuit has it’s own fuse.
We now began our discussions on what we wanted to run off the battery while travelling so we could gauge what size battery we would require. We struggled here as the battery works on amp hours (Ah) but usually consumers state their power consumption in watts. How many Ah is 45 watts? Don’t let the ‘hours’ in ‘amp hours’ confuse you as it did us, it just refers to how many amps the consumer will use per hour. Take the watts and divide by the voltage – which for us is 12. So a consumer that uses 45 watts is using 4 amps.
All we really wanted to run was our laptops, a few lights, a fan for showering, the amplifier and the fridge. We knew we’d need an inverter (to convert 12V to 220-240V in the case you wish to run a ‘household’ item) but – although convenient – this really isn’t the most efficient way to use 12V, so we wanted to limit our usage of inverter consumer’s where possible. We didn’t get very accurate answers for power consumption of the laptops or amplifier and we knew that the fan (being 7 watts) and the lights (being between 4 and 20 watts) used very little power so we ended up just making an educated guess with our predicted power consumption. The inverter we bought had a maximum power output of 300w, which we felt was suffice for anything that we may need to use it for.
So now let’s choose a battery. It’s not quite that easy unfortunately. We quickly discovered that there are many different varieties of 12V battery, each with quite differing features. So, which one to choose?
The most common one is a lead acid, which then comes in a few different ways.
We chose an Exide sealed gel, 210 amp hours weighing in at a massive 70kg. We decided on the sealed gel – although being more expensive than it’s predecessor – there is no chance it’ll leak gas as it charges and it is maintenance free. Seeing as you should try not to use your battery beyond 50% of it’s capacity (as it’ll shorten it’s lifespan) we were counting with 105 amps per day (24 hours).
We knew we wanted solar panels too, but had no idea how many we’d need, or what wattage we would need. We used a rule of thumb after reading different peoples experiences, that a 100 watt solar panel will generate 8 amps in full sunshine, for 5 hours a day.
Based on these maths, we decided to go for 2x100w solar panels, hoping to get 80amps out of the pair each day. As our back-up plan we’d also be installing a VSR (volt sensing relay), which works off the alternator – it just taps into this to direct some of the current to the leisure battery (exactly as it charges your normal car’s battery). Although being told “it is completely useless, you may as well throw it away” we’ve found it to work an absolute treat. It will take the battery from 60% charge to full from just a 20 minute drive.
Now that we had all this information, we set about figuring out what parts we needed to make it all work. This was much more challenging than one might think! As Paul didn’t know what each item was called in English, it made it almost impossible to get what we wanted in Hungarian. Fortunately we found a lady who was incredibly helpful and spent a good couple of hours – all the while we were unable to decide whether or not the products were the right ones – talking to her. The bag was a bit like a pot luck draw when we got home.
When we were finally satisfied we had enough to get started, we began. We started by planning all the circuits. The planning of the circuits through the van went through many, many different stages. Once we were satisfied the circuits were good, we laid out the conduits through the van, ready to pass all the wires through. Firstly we made sure that we labelled them (at both ends) to make sure we could figure out what was what down the line. For the most part, the wires ran from the ‘control board’ (explained next) to their switch, before continuing on to the consumer.
The control board is literally a board we used to house all the components of the electrical system – the solar charge controller, the VSR, the fuse boxes and the cut off switch – and connects them all. We’ll briefly explain this below, but see the photo (below top left) for a visual interpretation. Initially we made this on a scrap piece of OSB – which we were OK with, but not entirely convinced – perhaps it was a blessing in disguise when the electrician very strongly suggested we change it over to a piece of fire retardant material. This allowed us to put much more thought into it, and get a result that was neat, tidy and we were 100% happy with.
From the solar panels – which we connected in parallel (meaning the negatives are connected together as are the positives, before coming inside the van) – a ‘+’ and ‘-‘ wire come into the solar charge controller (a device that is used to look after the battery). A + wire runs between the solar charge controller and the battery, with a large switch (used to isolate the power from the battery reaching any of the consumers) and a fuse. And lastly a + wire runs from the solar charge controller to the consumers, in our case a positive ‘bar’ to distribute the power to different fuses and the fuse boxes. We put a switch on virtually everything so we had full control over deciding whether or not a consumer was on or not – but the switches don’t all sit on the control board.
All wire ends require crimping with their specific ends depending on their connections, (and there are thousands! And very confusing if you’ve never paid too much attention to them before). For the most part, the wires and ends that need crimping are small, and you can buy a small wire-crimping tool for not too much, but the bigger wires will need a heftier tool, which costs a fair bit, and chances are you’ll only need to use it a handful of times. We decided it wasn’t worth buying it for this, so used a hammer and flat headed screw driver – which worked fine – it just wasn’t so easy to get the heat shrink tape on after.
When we initially installed the wires, we calculated what we thought would be enough excess at the end to reach the final destination, and as we built the units in we fed the wires through holes and along the frame.
Six weeks into our trip and all the electrics still work – yes, even we are a little surprised! The choice on battery seems to be good. We haven’t run into any power difficulties relating to the battery being flat or the efficiency of the solar panels. Occasionally we’ll turn the VSR on if we hit problems with consecutive cloudy days, but for the most part we leave this disconnected – and we haven’t had to tap into shore power at all yet.