Extending the Leads of the FUSION Charger
The FORM Charge Fusion is designed to be permanently mounted near your battery bank, but some marine installs need a longer DC run than the factory cable allows, for example, when a battery sits in a different compartment from the charger. This article walks you through extending a Fusion bank's DC leads safely while keeping the factory waterproof rating intact.
Before You Begin
- Disconnect the bank's leads from the battery before cutting any wire.
- 10 AWG marine-grade tinned copper wire (matches the factory cable; 12 AWG is acceptable per the manual, but 10 AWG is preferred).
- Adhesive-lined heat-shrink tubing sized to the wire.
- Wire strippers, crimp tool, and a heat gun.
- Marine-grade butt splice connectors, or solder (your preference).
- A multimeter to verify polarity after the splice.
Plan Your Run
A few minutes of planning saves rework and keeps your install inside the manual's safety limits. Before cutting anything, confirm your layout meets all four of these rules:
- Total DC run must not exceed 15 feet -- measured from the charger's bank output to the battery terminals.
- Splice location: between the fork where the factory cable splits into positive and negative leads, and the inline fuse holder. One splice per conductor -- do positive and negative separately, not as a single combined splice. The inline fuse holder on the factory cable must stay within 7 inches of the battery terminals.
- If you're extending multiple banks, each bank's extension follows these same rules independently.
Extension Steps
1. Measure your run. With the charger temporarily placed where you plan to mount it, measure from the bank's fork down to the battery terminals. Confirm your total is under 15 feet before you cut anything.
2. Disconnect and cut. With the bank's leads disconnected from the battery, cut the factory cable between the fork and the fuse holder. Keep the fuse holder on the battery-side portion so it stays within 7 inches of the battery terminals.
3. Splice in the extension wire. Strip both ends of the cut factory cable and both ends of your 10 AWG extension wire. Crimp or solder a marine-grade butt splice on each conductor -- positive to positive, negative to negative. Do each conductor separately.
4. Heat-shrink the splices. Slide adhesive-lined heat-shrink tubing over each splice and shrink with a heat gun. The adhesive should ooze slightly from the ends -- that's the waterproof seal forming. Do not skip this step.
5. Waterproof the battery connection. On marine and wet installs, finish the ring-terminal connection at the battery with dielectric grease or marine silicone to keep moisture out of the crimp. Route the extended cable so splices sit above the bilge waterline wherever possible.
Test Before Use
Reconnect the extended leads to the battery, plug the Fusion into a properly grounded outlet, and confirm the bank's blue POWER LED and green CONNECTION LED come on as expected. If the CONNECTION LED doesn't come on, check your splice polarity with a multimeter before troubleshooting anything else.
Common Mistakes to Avoid
- Moving the fuse holder away from the battery. The 7-inch rule exists to protect the long extension run from a short circuit. Do not relocate the fuse holder to the charger side of the splice.
- Exceeding the 15-foot total DC run. Voltage drop and heat dissipation are designed around this limit; longer runs can cause undercharging or cable heating.
- Using automotive (untinned) wire in marine installs. Marine environments corrode untinned copper fast. Use tinned copper for any boat install.
- Skipping the adhesive-lined heat-shrink. Regular heat-shrink without adhesive is not waterproof. On a boat, this is not optional.
If you are not comfortable cutting into factory cables or crimping and soldering splices in a marine environment, we recommend having a qualified marine technician perform the extension.