Size solar from daily energy use rather than battery capacity alone. Estimate the watt-hours consumed by refrigeration, lighting, pumps, electronics and other loads over 24 hours, then allow for controller losses, panel temperature, cable losses, shading and the fact that a panel rarely produces its nameplate output all day. A larger battery does not necessarily require a larger solar array if daily consumption is modest, but a small array may take several days to recover a heavily discharged bank. Australian solar conditions are generally favourable, yet roof angle, heat and partial shade can have a major effect. If the system must operate through several cloudy days, combine adequate battery storage with enough panel capacity to recover it when good sunlight returns.

Both can charge batteries when correctly matched, but they suit different systems. PWM controllers are simple and economical where panel voltage closely suits the battery system and the array is relatively small. MPPT controllers actively track the panel's maximum power point and convert higher panel voltage into useful charging current, which can provide better harvest—particularly with larger arrays, cooler panel temperatures or systems where panel operating voltage is well above battery voltage. The controller must be rated for the battery bank voltage, maximum solar open-circuit voltage and array current or wattage. For a Trolltek lithium battery, also ensure the controller offers a suitable LiFePO4 charging profile or can be configured to the required voltages.

No. A suitable solar charge controller should be installed between the solar array and the battery. Solar panel voltage varies with sunlight and temperature and can exceed the voltage a battery should receive. The controller regulates charging and provides the correct voltage behaviour for the battery chemistry. Select the controller from the battery voltage and the array's electrical specifications, particularly maximum open-circuit voltage and current. Provide appropriate fusing or circuit protection and an isolation method where required. For multiple panels, the decision to connect them in series or parallel changes array voltage and current, so it must remain within the controller's input limits. Do not base the design only on the panel's advertised wattage.

Partial shading is one of the most common causes. A shadow from an aerial, roof rack, hatch or tree can reduce panel output far more than expected. Other causes include dirty panels, excessive panel temperature, loose MC4-style connectors, undersized cabling, a controller set to the wrong battery profile or a battery that is already near full charge. Measure solar input voltage and charging current at the controller rather than judging performance from sunlight alone. Also check whether the panel rating is being compared with realistic operating conditions; nameplate wattage is measured under standard test conditions that may not match a hot Australian roof. If output has suddenly dropped compared with the same installation previously, inspect connections and individual panel performance.

Mount panels where they are securely supported, ventilated and as free from regular shading as practical. Cable should be UV-resistant where exposed, protected from sharp edges and sized for the array current, length and acceptable voltage drop. Use compatible weatherproof connectors and avoid leaving plug connections where water can collect. Any roof or deck penetration needs an appropriate gland and sealing method for the surface material. Provide isolation and over-current protection where required by the system design. On boats, corrosion resistance becomes especially important; on 4WDs and trailers, allow for vibration and cable movement. Before permanently fixing panels, confirm the proposed wiring configuration remains within the charge controller's maximum input voltage at the lowest expected panel temperature.