By Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD
“After frying a $400 inverter in my shed, I learned that central QLD heat demands derating cables by at least 20% to survive the summer.”
— Dave. Measure twice, buy once.
ArticlesCalculatorsSite PlannerShopBy Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD
“After frying a $400 inverter in my shed, I learned that central QLD heat demands derating cables by at least 20% to survive the summer.”
Build Your First Solar Power System — Essential knowledge for Australian off-grid living
A 12V solar system is the cheapest way to learn off-grid solar, with full kits from $150 AUD and complete setups under $500. The 20% cable derating rule matters in QLD heat, where undersized wiring causes voltage drop and fire risk. Start small, wire right, and expand later.
A step-by-step guide to building a 12V solar system from scratch, perfect for RVs, cabins, camping, and learning the fundamentals of solar power.
Video by DIY Solar Power with Will Prowse
If you have never touched a solar panel before, a 12V system is the best place to start. It is affordable (under $500 for a complete setup), forgiving of mistakes, and teaches you the same fundamental principles that apply to larger systems. Once you understand how a 100W panel charges a battery through a charge controller, you will be ready to scale up to 48V systems running an entire home.
Will Prowse's beginner tutorial is the most popular solar build guide on his channel, and for good reason. It walks through the entire process using a Renogy 100W starter kit, which includes the solar panel, charge controller, and all the wiring you need. Add a deep cycle battery and an inverter, and you have a complete power station that can charge phones, run lights, power a small fridge, or keep your camping setup going for days.
This article expands on Will's video with additional context for Australian users, battery selection advice, and practical tips that will help you avoid the most common beginner mistakes.
This all-in-one kit includes a 100W monocrystalline solar panel, a PWM charge controller, MC4 to bare-wire adapters, and mounting brackets. The charge controller has a 30A rating, which gives you room to expand to up to 400W of panels later without upgrading the controller.
The kit also includes the wires to connect the charge controller to both the solar panel and the battery. For a first build, this eliminates the guesswork of selecting compatible components.
A 100Ah battery at 12V gives you 1,200 watt-hours of total capacity. In practice, you should only discharge a sealed lead-acid battery to about 50%, so your usable capacity is around 600Wh. That is enough to run a few LED lights, charge devices, and power small appliances for a night of camping.
Sealed lead-acid batteries are affordable and widely available at auto parts stores, making them a great choice for a first system. Later, you can upgrade to LiFePO4 lithium batteries for more usable capacity and longer lifespan.
The inverter converts 12V DC from your battery into 240V AC (in Australia) that your appliances can use. A pure sine wave inverter is important because it produces clean power identical to the grid. Modified sine wave inverters are cheaper but can damage sensitive electronics and make some appliances buzz or run hot.
These connect the inverter to the battery. A bolt-on fuse (175A for a 1,500W inverter) is essential for safety. If a short circuit occurs, the fuse blows before the wires can overheat and catch fire. You can find these at any auto parts store.
Attach the included Z-brackets to the solar panel using the bolts, washers, and locking nuts provided. The correct order from front to back is: bolt, washer, washer, locking nut, washer, then the final nut. Tighten with a socket on the front and pliers or an adjustable wrench on the back. Then drill or screw the brackets onto your roof, rack, or mounting surface.
Screw the charge controller to a piece of plywood, a wall, or whatever surface works for your setup. Position it close to the battery to keep cable runs short. The controller should be in a ventilated area, not in direct sunlight.
Strip the insulation from the battery wires. Look at the charge controller: you will see a battery icon with positive and negative terminals. Use a flathead screwdriver to loosen the terminal screws, insert the stripped wire, and tighten down firmly. Connect negative (black) first, then positive (red). When the green light illuminates on the controller, you have a successful connection.
Take the MC4 adapter cables from the kit. Connect the negative cable to the panel first, then run it to the "solar panel negative" terminal on the charge controller. Repeat for the positive cable. When both are connected and the panel is in sunlight, a second green light (PV) should appear on the controller.
Two green lights with one flashing means the system is actively charging. You are in business.
The Renogy charge controller has a button to select battery type. Hold it down for seven seconds until the indicator starts flashing, then cycle through the options: green for sealed lead-acid, orange/yellow for gel, red for flooded, and blue for lithium. Since we are using a sealed lead-acid battery, set it to green. Wait 10 seconds without pressing anything and the setting will save.
Before connecting the inverter, disconnect one of the solar panel cables from the charge controller. This is a safety precaution: you do not want live solar input while you are working on battery connections.
Connect the positive (red) cable to the inverter first, then the negative (black). Attach the bolt-on fuse to the positive cable. Now connect to the battery: the fuse end goes to the positive terminal, the negative cable goes to the negative terminal. You will see a small spark when connecting the positive, and that is completely normal.
Reconnect the solar panel cable to the charge controller. Press the power button on the inverter. Plug in an appliance. If everything works, congratulations: you have just built your first solar power system.
Discharging a sealed lead-acid battery below 50% (about 12.2V at rest) will significantly reduce its lifespan. Running it flat to 0% can permanently damage it in a single event. Invest in a simple battery voltage monitor or capacity gauge to keep tabs on your state of charge. When the resting voltage drops to 12.2V, it is time to stop drawing power and let the sun do its work.
Will points out that the Renogy kit does not include a fused line between the charge controller and battery, which is a minor oversight. For the 30A charge controller in this kit, add a 35A or 40A inline fuse on the positive wire between the controller and battery. This costs a few dollars and adds an important layer of protection.
If you are using lead-acid batteries (sealed, gel, or flooded), the charge controller needs a temperature sensor to adjust charging voltage based on ambient temperature. Lead-acid batteries are sensitive to temperature, and charging at the wrong voltage in hot or cold conditions will shorten their life dramatically. The Renogy controller has a port for this sensor. Buy one, plug it in, and place it near the battery.
100 watts of solar is a solid starting point, but you may find you need more power. Here is how to scale:
Buy MC4 branch connectors (Y-connectors) and add a second or third 100W panel in parallel. The Renogy PWM charge controller supports up to 400W of solar input total. Beyond that, you will want to upgrade to an MPPT charge controller, which is more efficient and handles higher voltages.
When you are ready to invest more, swapping your sealed lead-acid battery for a 100Ah LiFePO4 gives you nearly double the usable capacity (you can safely discharge to 80% or even 90% instead of 50%), about four times the cycle life, and roughly half the weight. Change the charge controller battery setting to lithium (blue light) and you are good to go.
If your power needs grow beyond what a 12V system can handle, it is time to move to a 48V architecture with an all-in-one inverter. Check out our 10kW system crash course for the full walkthrough.
| Application | What You Can Power | Runtime Estimate |
|---|---|---|
| Weekend camping | Phone charging, LED lights, small fan | 2 to 3 days without sun |
| Caravan/RV | Lights, water pump, phone/laptop charging | Ongoing with daily sun |
| Remote cabin | LED lighting, radio, device charging | Ongoing with daily sun |
| Emergency backup | Phone charging, LED lights, CPAP machine | 1 to 2 nights per charge |
| Garden shed | Lights, small power tools (intermittent) | Daytime use with sun |
Setting realistic expectations is important. A single 100W panel with a 100Ah lead-acid battery is not designed for:
For those loads, you need a larger system. Our master off-grid calculator will help you figure out exactly what size setup your lifestyle requires.
A 12V system is low voltage and generally does not require an electrician in Australia. However, a few local factors are worth noting:
Solar Calculator Master Off-Grid Calculator
Worth a watch: Offgrid Solar Beginner Crash Course: Build a 10,000W Solar System · DIY Solar Power with Will Prowse
The article kicks off at $150 for a starter kit, which gets you the core bits to learn the fundamentals. I tell readers the real cost depends on what you want to run and how much battery storage you add — costs climb quickly once you go beyond the basics.
Not a chance mate. I cover this in the 'What This System Cannot Do' section — a 100W starter is built for LED lights, phone charging, small pumps, that sort of thing. It's a learning platform for RVs, cabins and camping, not a whole-house power source.
For a basic 12V setup like a camping kit or a small shed, plenty of people do it themselves — that's what my step-by-step build guide is for. But I've included a whole section on when to call a professional, because anything involving mains voltage, big battery banks, or permanent house wiring needs a licensed sparky.
It's good for the small stuff — LED lights, charging phones and laptops, running a small water pump for a cabin or campsite. I see it as a way to learn the fundamentals before you scale up to something bigger, not as a replacement for mains power.
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.