Dreaming of off-grid freedom in your campervan? Adding solar panels is one of the best upgrades you can make to stay powered up wherever you park. Whether you're charging devices, running a fridge, or powering lights, a solar setup will give you independence and peace of mind.
This guide walks you through a real installation using a solar controller (or DC to DC charger with solar input). We'll cover each step — from panel placement to final testing — using practical examples and photos from a live install.
Understanding Your Dual Battery and Solar Setup
A dual battery system means your vehicle has two batteries:
- Starter battery: Powers your engine and standard vehicle electronics. Usually under the bonnet, but in older vans like Toyota HiAce or VW Transporter, it may be under a seat.
- Auxiliary battery (house battery): Powers your camping gear — fridge, lights, fans, USB ports — without risking a flat starter battery when parked.
While driving, the alternator charges your auxiliary battery. When parked, solar keeps it topped up so you're not stranded without power.
To manage this, you'll need a device that controls how the auxiliary battery is charged. You have two common options:
- DC-DC charger with solar input – Handles both alternator and solar charging. Best for smart alternators (newer vans and 4WDs).
- Solar controller (PWM or MPPT) – Manages solar charging only. Can be paired with a basic isolator for alternator charging. Ideal for older vehicles or budget setups.
If you’re unsure what kind of alternator your vehicle has, check your vehicle manual or ask your mechanic. For smart alternators or lithium batteries, a DC-DC charger is strongly recommended.
What You’ll Need
- 12V Solar Panel (rigid, flexible or portable)
- Solar Controller or DC-DC charger
- Deep cycle battery (AGM or lithium)
- Wiring (usually 6mm² or 8 B&S)
- 30A fuse or circuit breaker
- Anderson plugs (optional)
- Mounting brackets or roof racks
- Cable glands or entry ports
- Basic tools: drill, wire stripper, crimper, multimeter, screwdriver
Step 1: Plan Your Setup
Sketch out a basic wiring diagram and decide where each component will go:
- Solar Panel: Roof-mounted for set-and-forget charging, or portable for flexibility. See our guide on fixed vs portable panels.
- Solar Controller or DC-DC Charger: Mount close to your auxiliary battery to reduce voltage drop.
- Cables: Route from panel to controller, then controller to auxiliary battery. Use conduit or cable glands when passing through metal or walls.
- Auxiliary Battery: Secure in a ventilated location (under a seat, drawer, or battery box). A battery box can keep cables organised and often includes USB ports, circuit protection, and Anderson inputs.
Step 2: Mount the Solar Panel
If you're using a fixed rigid panel, mount it to your van roof using:
- Z-brackets on a flat roof
- Roof racks or crossbars with U-bolts or clamps
- Adhesive brackets (no drilling required)
Photo: Rigid panel mounted with adhesive brackets
Make sure the panel is secure and ideally angled slightly for water runoff and sun exposure.
If you're installing a flexible panel, it must have airflow underneath. Without ventilation, it may overheat and lose performance over time. Use spacers or matting to raise it slightly off the roof.
Read more: How to Mount Flexible Panels Without Overheating
Photo: Flexible panel installed with spacer tape for ventilation
Step 3: Run the Solar Cables Inside
To run the cable from the roof into your van, you'll usually need to drill a hole (ideally near your solar panel). Use a waterproof cable gland to keep the entry point sealed and weatherproof.
How to install a cable gland:
- Drill a hole just large enough for the cable
- Feed the cable through the gland and position it on the roof
- Apply UV-resistant sealant like Sikaflex around the hole and base
- Tighten the gland to compress the rubber seal around the cable
- Let it cure for 24 hours before driving or washing
Tip: Label your positive and negative cables before routing them through the gland.
Photo: Cable entry gland sealed with silicone
Step 4: Install Your Charging Setup
There are two common options depending on your setup:
- Step 4A: Using a solar controller (PWM or MPPT)
- Step 4B: Using a DC-DC charger with solar input
Step 4A – Using a Solar Controller
Mount the solar controller close to your auxiliary battery to minimise voltage drop and keep wiring short.
Wiring order matters:
- Connect battery to the controller first (positive and negative)
- Then connect solar panel to the controller (positive and negative)
This order is important — most solar controllers must detect battery voltage to operate correctly. Connecting solar first can cause faults or prevent startup.
A PWM controller works for small, budget setups. An MPPT controller is more efficient, especially if you're using a high-voltage panel or want better performance in variable sunlight.
If you want to charge your battery while driving, you can add a battery isolator between the starter and auxiliary battery. The isolator links both batteries when the engine is running, and separates them when it's off.
- Solar-only setup → no isolator needed
- Solar + alternator charging → add a basic isolator
Photo: Basic solar controller wiring diagram
Step 4B – Using a DC-DC Charger with Solar Input
Install the DC-DC charger close to your auxiliary battery in a ventilated spot. These units have three main inputs:
- Alternator (or ignition wire)
- Solar panel
- Auxiliary battery
Connect in this order:
- Battery first
- Then alternator input
- Then solar panel input
DC-DC chargers automatically switch between charging from the alternator or solar, depending on whether the engine is running. Make sure to fuse all inputs, and if possible, wire solar last to avoid live voltage during install.
Photo: Redarc DC-DC charger mounted inside van
Step 5: Fuse the System
Protect your system by adding a 30A inline fuse or circuit breaker on the positive wire between your solar controller and auxiliary battery. This prevents overheating or fire risk in case of a short circuit.
If you're using Anderson plugs, place the fuse inline before the plug to keep your system safe during disconnect.
You can also add a fuse box or 12V distribution panel if you're powering multiple appliances (fridge, lights, water pump). This makes it easier to isolate individual circuits for maintenance or troubleshooting.
Photo: Fuse box for multiple loads
Step 6: Secure and Test Your Connections
Now that everything is connected, it’s time to double-check and test:
- All connections are tight and secure
- No exposed copper or loose wires
- Solar panel is receiving sunlight
Use a multimeter to verify that the battery voltage is rising. Most modern solar controllers will also display input voltage and charging status — many even have Bluetooth apps for monitoring.
Photo: Solar controller showing live input and charging voltage
Step 7: Tidy Up Your Setup
Secure all cables using zip ties, conduit, or mounts. Avoid sharp edges, leave some slack for vibration, and keep everything clean and organised.
Label your components (especially if you're using Anderson plugs or multiple fuses) and sketch a final wiring diagram for future reference.
Photo: Auxiliary battery installation
Final Thoughts
Installing a solar panel setup in your campervan is a rewarding DIY project that gives you the freedom to travel off-grid without worrying about power. Once everything’s installed and working, your system quietly charges in the background every time the sun is out — no noise, no fuel, no fuss.
If you're not confident with wiring or working with electrical systems, always consult a professional — especially when dealing with lithium batteries or high current devices.
Related Blog Posts
Want to keep learning? Explore more guides:
- How to Install Flexible Solar Panels in Vehicles – A Complete Guide
- A Step-by-Step Guide to Setting Up a Dual Battery System
- How to Choose the Best Panel for Free Camping in Australia
- The Ultimate Cheat Sheet for Portable Inverter Generators
- How to Charge Electronic Devices While Camping
Join the Conversation
Have questions about your camper solar setup? Or want to share your own dual battery build? Drop a comment below — we’d love to hear how you power your adventures.
Need Help Choosing the Right Gear?
Still unsure? Send us a message — we're happy to help.