Hardkorr DCDC Charger Wiring Kit (Suits 40A DCDC)

The correct wire gauge depends on the maximum current your charging system produces and the distance between your batteries. For most dual battery setups using a 25A to 40A charger, 6 B&S (roughly 13.5mm²) is the industry standard for maintaining efficiency and minimizing voltage drop.

Using cable that is too thin will cause power to be lost as heat before it reaches your auxiliary battery, which leads to slow charging and potentially damaged components. If you are mounting your second battery in a trailer or at the rear of a long wagon, stepping up to a heavier gauge like 4 B&S is a smart move. This ensures the full voltage from your charger reaches the cells, keeping your fridge running and your batteries healthy.

Explore our range of heavy-duty Battery Cable for custom runs, or find a match for your kit in our DCDC Chargers collection.

Choosing between a pre made kit and a DIY approach depends on your experience level and how custom your vehicle layout needs to be. Pre made wiring kits are a smart move for those wanting a fast and safe installation with pre crimped terminals and correctly sized fuses already in place.

A DIY build is better if you are routing cables through tight spaces or require exact custom lengths that standard kits do not provide. However, building your own leads requires specialized tools like a heavy duty cable crimper to maintain a safe connection. For most travelers, a high quality kit reduces the risk of wiring errors and provides a clean finish without the need for extra gear.

Browse our complete Dual Battery Systems to see how these kits fit your rig, or explore our Crimping Tools if you prefer to build a custom setup.

Match your fuse size to the maximum current rating of your charger while considering the safety limits of your cable. For a standard 25A DC to DC charger, a 40A or 50A fuse is typically used to provide a safe buffer for peaks without the risk of nuisance tripping during a long drive.

You must install a fuse at both ends of the main positive cable, as close to the starter and auxiliary battery terminals as possible. This is a critical safety measure because both batteries can dump their full power into a short circuit if the cable is damaged. Using the correct fuse prevents overheating in your wiring and protects your vehicle from potential electrical fires on rough corrugated tracks.

Find the right protection in our Circuit Breakers & Fuses collection, or see your live charging data with our Battery Monitors.

Roam Gear uses Australian made KEY cable because it is specifically designed for the extreme heat, vibration, and salt air conditions found across Australia. Standard imported cables often use lower grade copper or thinner insulation that can fail when exposed to constant outback vibrations or engine bay temperatures.

By using tinned copper cable manufactured in South Australia, these kits provide superior corrosion resistance and better electrical conductivity. This is critical for marine environments or remote touring where resilience is a deal breaker. Using high quality materials makes certain that your power system remains safe and stays functional throughout your trip.

Explore our range to see how these components improve your next build.