Setting up a DC circuit is actually super easy! I truly believe that if someone is truly motivated, even without previous experience, they can setup their own solar/DC circuit.
Since this will be an independent system and could be used anywhere, not just in a Skoolie, adapt the installation as your system requires.
Solar Panels to the Solar Charge Controller
If you’re unsure about Solar Panels, check out our brief explanation, here. 12v DC electrical systems are NOT complex; at the most basic level, you have two sides, a positive (red) and a negative (black), just like a car battery.
We’ll start our planning at the rooftop solar panel combiner box, where all of the solar panels positive and negative lines combine, to power the solar charge controller.
You can see in the example on the right, all of the smaller #8 gauge negative leads (from individual solar panels) are connected to a larger all black #4 gauge wire.
On the positive side, you can see each panel has a circuit breaker before connecting to the larger #4 gauge positive wire (with Red tape). The circuit breakers are important! If an individual solar panel malfunctions, it will trip the circuit breaker instead of potentially taking out the whole system or starting a fire! It’s better to plan for the worst and end up with reduced power, over no power.
The larger #4 gauge wires are used to transmit electricity as efficiently as possible, without the larger gauge wire, you essentially bottleneck the system and reduce its ability to transmit energy from the solar panels.The length of wire needed to join the combiner box to your solar charge controller will also effect the gauge of wire needed, therefore it is important to keep components as close as safely, and reasonably possible. You will need to determine which gauge of wire you need based upon the amount of Amps (Amperage) you are planning to transmit. I will find a link asap to explain voltage and amperage by distance in wires.
Solar Charge Controller to Battery Bank
We will probably use #2 gauge welding wire from the MPPT charger to the battery bank bus bars, and from the bus bars to the individual batteries. Some may think this is overkill, but a well designed system is less likely to fail, and provides easy maintenance when required.
The battery bank will be connected together using Bus Bars. Bus Bars are simple, take 2, and place them on either side of the battery bank, 1 side is for all of the positive connections, and the other side is for all of the negative connections. This removes the need to have wires crisscross over each other. This is known as a parallel circuit, the voltage stays the same, but the capacity of the battery bank increases with each additional battery.
At times it may be preferable to connect battery banks in Series, to increase their Voltage. Remember though, batteries wired in Series will increase the Voltage, but it will not increase the capacity.
Connecting your appliance to the bus bar, instead of an individual battery, will give you the full capacity and power of the battery bank, as well as balance the load on each cell. As such, the bus bars will also be used to supply power to the 12v fuse panel and our 120v Inverter.
Solar Power to Run Your Skoolie
Don’t wrack your brain for too long trying to figure out how we charge the batteries while using them. If the power coming in from the Solar Panels, is greater than the power required, the excess is used to charge the batteries. Inversely, if the power coming from the solar panels is NOT enough for the required load, such as at night, ALL of your power needs will come from your battery bank. Unless, you’re Grid-tied, in which case you would draw power from the grid.
- If (Power In > Power Out) Than (Batteries Charge)
- If (Power In < Power Out) Than (Batteries Drain)
From the Bus Bars, a positive and a negative wire will be connected to a 12v Fuse Box. 12v appliances such as water pumps, LED lighting, etc. will be powered through the 12v fuse box. All grouped components should have individual fuses; water pumps, fans, LEDs, etc. Fortunately this inexpensive 12V Fuse Panel provides space for 12 fuses, as well as common positive and negative poles to connect to the Bus Bar.
With 12 Spaces, we will have enough for necessities, with spares for expansion…
- #1 Indoor LED Lighting (10 Amp Fuse)
- #2 Outdoor LED Lighting (15 Amp Fuse)
- #3 Fresh & Grey Water Pump (20 Amp Fuse)
- #4 12v to 5v Converters, 3A each (15 Amp Fuse)
For our cell phones and tablets, I’ll install several female USB ports around the bus; powered by these 12v to 5v 3A Converters. For the laptop and tv, along with any other needs, we will be using an AC-DC inverter hardwired to a 120v Fuse Panel. The inverter will be connected directly to the battery bank bus bar due to the high power draw. A larger Fuse is required between the battery bank and the inverter, due to the increased power consumption of the inverter.
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