All prices are in Australian Dollar (AUD)
I wanted a solar option that would ensure my 200Ah battery is always topped up even when the sun is being shy! Solar is much more affordable these days and it’s much cheaper to buy more solar than lithium battery storage.
As you may know I plan to live off grid as much as possible, water will be the only thing I need to stock up from at mains supply. This setup may look excessive, but I thought I would spend a couple of extra hundred dollars on the solar just to be absolutely sure my power requirements will be met. In Australia we do get a lot of sun so this should definitely be enough.
It was a little tricky finding panels that would fit in the remaining roof space after the maxx fans were installed, but I found panels that were the perfect size. I bought 5 x 100w panels (500w) and 4 x 20w panels (80w). The 100w panels are all connected in parallel to each other in their own circuit, and the 20w panels are connected in parallel also in their own seperate circuit.
I had to wire them seperately because they’re rated at different Voltages, Wattages & Amperages. Each circuit will run down to a seperate charge controller to avoid mismatched panels causing efficiency limitations.
The panels are bolted to 60mm x 60mm x 3mm aluminium angle, and are hinged on one side to allow access underneath for cleaning and maintenance. The aluminium is adhered to the van using Sikaflex 221, which is extremely strong and does not require any priming. (I have heard Sikaflex 225 is even stronger but I spoke to a rep from Sikaflex and he was confident Sikaflex 221 would do the job).
Series vs Parallel
There are pros and cons to wiring in both series or parallel. I used to install solar on domestic houses and we would always wire a group of panels in series, and parallel that group to another group of panels.
Electricity can be more easily understood by comparing it to plumbing. Voltage is the same as water pressure, how much push or force are pushing the electrons. Amperage (current) can be thought of as water flow, how many electrons are flowing through a conductor. Resistance can be thought of as a block in the water pipe, how much resistance there is for the electrons to move.
All electrical circuits have a resistance, even if they’re minute. In general, the longer the cable run or smaller the cable, the higher the resitance. There is a phenomenon known as voltage drop, the voltage at the start of the cable is different to the end because there are losses of voltage or “pressure” due to resistance of the cable.
Motorhome cable lengths are obviously much shorter than domestic houses, but lower voltages (12V, 24V) are more common in motorhomes which are still prone to voltage drop even across shorter runs and are subject to higher current flow.
I won’t go too into depth but in general the higher the voltage, the less voltage drop and less current flow. The lower the voltage the higher the voltage drop and higher the current flow. This is why automotive cabling is generally much thicker because it’s at a lower voltage but has to handle much higher amps. Google “Ohm’s Law” and this will explain it in much more detail.
Ohm’s Law – (P = V x I)
P (watts) = V (volts) x I (amps) to calculate watts.
I (amps) = P (watts) / V (volts) to calculate amperage.
I will explain the difference between series and parallel. For the theoretical example we will use a system of 5 panels, each rated at 18V and 100W each in perfect conditions (which is the same as the 5 x 100w panels circuit on my van).
System wattage = 500W
System Voltage = 90V
System Amperage = 5.55A
Note: Solar panel technology is always increasing and it’s becoming more common for panels to not be as effected by shading and on the rest of the system with bypass diodes etc. Some systems won’t be as effected as others, but this is just a general explantation.
In a series system the voltage is the sum of all the panels voltages, however the amperage remains the value of the lowest amperage panel (in this case 5.55A).
When a panel becomes shaded, its output generally drops. This can be thought of as a “bottleneck” in a series system, where the other 4 panels are thriving in full sun but because 1 panel is shaded the whole system drops to the output of the shaded panel. So if the shaded panel is now operating at 50% output, all the panels are operating at 50% output collectively.
This is the con with series, however the pro to the system is the voltage of the system is operating at the sum of each panel. This brings the voltage much higher and is creating more “pressure” to push electrons. As said before, this means the system is less subject to voltage drop and there will be less amperage flowing in the system, which means you can use smaller cables.
System wattage = 500W
System Voltage = 18V
System Amperage = 27.75A
As you can see the system voltage is the same as a single panel, but the system amperage is the sum of each individual panel. This is because each panel has its own path or circuit, rather than having to flow through each other panel before reaching its destination.
The pros to this setup is if one panel is shaded, it only effects that one panel. This panel could be shaded and is operating at 50% output but the other 4 panels are operating at 100% in full sun.
The cons to this setup is the system is subject to higher voltage drop and will incure higher currents (amperages), and you may need to use larger cable.
Each setup has it’s own downfalls and benifits, I prosume you are using a solar panel setup on your campervan or RV. Some wire in series and some wire in parallel and both do the job just fine, it depends on your needs, location, panel quality etc.
There is no right way or wrong way. I wired mine up in parallel as I wanted the system to not be as effected by shading when I park up near trees etc. If this isn’t working out I can always change it to a series configuration at no cost.
Here is a wiring diagram to how I wired my panels in parallel.
How do you know how much solar you will need?
You will need to figure out the maximum demand of your system to meet your electrical storage needs. Also, plan for the worst cloudiest days as your system will work great on sunny days, but also needs to be able to handle days without solid sunshine.
The type of batteries you buy for storage and how much Amp hours they store all come into play too. My battery is a 200Ah Lithium Ion Deep Cycle Battery with a Depth of Discharge (DoD) up to 80%, this means I have 160 usable amp hours.
If you buy lead acid or AGM batteries, these generally have a DoD of 50%. So if you have 200Ah of storage, you really only have 100Ah of usable storage before it starts to really damage your battery.
I added up all the electrical appliances I could think of and worked out their amp draw and how many hours per day these would be running, which is called the Duty Cycle. Once I figured this figure out per day, I added a little bit on top of that just to be safe.
If you will be using an DC to AC inverter to run AC loads, as stated before the current draw on the DC side of the inverter will be far greater than the AC side to run for example a toaster. To calculate the DC amps draw for your maximum demand, I used this calculator.
It’s much cheaper to buy more solar wattage compared to buying more battery storage, especially if you are going with a lithium battery setup.
I will go much more into depth in the future blog post Electrical Pt.2 about the entire electrical system, storage, different batteries and real world tests and results.
I purchased all my solar panels, lithium ion battery and battery management system as one bulk package through Battery World Enoggera. They are all Enerdrive products, but battery would are one of Enerdrive’s outlets as the public cannot buy direct from Enerdrive.
As stated each circuit of solar panels will wire into 2 seperate charge controllers. I have listed the 5 x 100w charge controller in this post but will list the 4 x 20w charge controller in the future electrical fit off post as that charge controller has multiple uses.
The other bits and pieces were purchased from bunnings or independant suppliers.
Warning! Solar panels can cause dangerous electric shock particularly when connected in series. Only work with solar panels if you are competent and know what you’re doing.
1. The first thing I did was drill the hinge holes a little larger to allow the bolts I’m using to countersink flush.
2. Next I drilled and bolted 2 x 100w panels together down the middle.
3. I marked where the hinges would go, then drilled the holes and bolted them on. I used a countersunk bolt, washer and nylock nut.
4. I marked out the holes on the angle, then bolted that on.
5. When I mounted the angle on the other side I realised I needed to be able to access the nylock not underneath the panel to allow it to hinge.
Note: I drilled the bolt on a 45 degree angle in each corner to get around this. I may change these to Riv-Nuts in the future.
6. Once I’d finished bolting all the hinges and aluminium angle to the solar panels, I prepped the surfaces on the roof of the van that would be making contact with the alumium angle.
I did this by using a ScotchBrite dishwasher cloth to rough up the surface, followed by cleaning it thoroughly with isopropyl alcohol.
7. Once prepped I did the exact same thing on the base of the aluminium angles.
8. I placed the first set of solar panels in place, and used some electrical tape to mark the end of the angle. This is so I knew how much Sikaflex to put down for the first panels.
9. Once marked I moved the solar panels and laid down a generous amount of Sikaflex 221 in a zig zag motion. I cut the tip on a 45 degree angle, and then flat at the very tip for easy application.
Note: I used scrap 75mm piano hinges to stick underneath each of the 4 corners of aluminium angle, to raise the angle of the van roof roughly 2-3mm so the Sikaflex cures with some body to it.
10. I repeated this process with the rest of the panels.
11. Once all the panels were in placed, I let them cure for 48 hours and covered them with a tarp in case it rained. Once cured, I tested them by pulling up quite hard on the panels, not budging.
Just to be sure I lifted each panel up and applied a 2nd layer of sikaflex 221, really just to make sure the inside had maximum sikaflex adhesion as well.
12. Once the 2nd layer was applied, I let it cure for another 48 hours. Then I drilled 2 x 25mm holes in the back where there is a large cavity on the inside of the van.
I used Sikaflex to secure 2 pieces of 25mm corro to run each solar string through, and Sikaflex’d down the wiring entry enclosures, the enclosures come with 2 waterproof glands. I mounted them 180 degrees from the normal way because I didn’t want ugly cable visible entering the enclosure from the back.
I used 4mm solar cable for each solar string, but may upgrade the 5 x 100w to a 6mm in the future if the current creates heat issues.
13. I then taped the ends of the incoming solar cable separately before connecting all the panels together. I had to fit off some MC4 positive and negative connectors, and used tri junction MC4 connectors to parallel the 5 x 100w panels.
For the 4 x 20w panels I simply used BP connectors and taped them well with electrical tape. Once all the panels were connected I zip tied the joins up to the panels to keep them off the roof surface.
Now finish bolting the panels back into place and you’re complete! They’re still pretty stealthy from the bottom.
14. I then mounted a piece of custom bent aluminium on a special machine to the front solar panel as a wind diffuser to stop unwanted air pressure building up underneath the panels whilst driving.
I mounted this to the panel with 3 large bolts with a washer and a nylock nut.
I tested the 5 x 100w circuit late in the afternoon when the sun was nearly set, about 90 degrees to the panels and they were still outputting full voltage!
Some of these prices are discounted either from bulk buy or trade price. All prices are in AUD$
|580W Solar Panels||1||1204||1204|
|Aluminium Angle 60mm x 60mm||1||68.31||68.31|
|Solar Cable 4mm (12m)||12||2.75||33|
|Piano Hinge Zinc Plated 100mm||16||1.51||24.16|
|60mm M6 Hex bolt||4||3.63||14.52|
|Rubber Washers M6||1||9.34||9.34|
|White Solar enclosure||2||15||30|
|Tri Connector (Pos & Neg Pair)||2||23||46|
|MC4 Connector (Pos & Neg Pair)||4||4||16|