Sapphire Energy
MRBF Marine Fuse Holder – Single & Dual (Double)
MRBF Marine Fuse Holder – Single & Dual (Double)
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MRBF Marine Battery Fuse Holder – Single & Double
Protect your battery and DC electrical systems with our premium tinned copper MRBF fuse holders. Designed for marine, RV, LiFePO₄ battery, and off-grid applications, these compact holders provide a convenient way to install high-current fuse protection directly at the battery terminal or busbar.
Available in Single and Double (Dual) configurations, each holder features a versatile mounting hole compatible with M8 (5/16") and M10 (3/8") studs, M8 (5/16") fuse and cable connection studs, stainless steel fastening hardware, and a flexible red silicone insulating cover to help protect exposed electrical connections.
Why You'll Love It
- Marine-Grade Tinned Copper: Excellent electrical conductivity and corrosion resistance for demanding DC installations.
- Single or Double Configuration: Choose one fuse position or protect two independent circuits from a shared battery or busbar connection.
- High Interrupt Rating: Compatible MRBF fuses offer up to 10,000A interrupt capacity at 14V DC.
- M8 Cable Connections: Standard 5/16" fuse terminal studs provide secure connections for compatible battery cable lugs.
- Protective Silicone Cover: Includes a flexible red insulating cover to help protect exposed connections from accidental contact, dust, and splashing water.
- Compact & Serviceable: Install overcurrent protection close to the power source and easily replace MRBF fuse cartridges when required.
Complete Your Installation
Fuse cartridges are sold separately. Pair your holder with our waterproof, ignition-protected MRBF battery fuses, conveniently packaged in 2-packs. Alternatively, choose a complete MRBF kit with your preferred holder configuration and fuse amperage.
Single vs. Double MRBF Fuse Holders
Both versions feature corrosion-resistant tinned copper construction, stainless steel hardware, and a protective silicone cover. Select the configuration that best suits your electrical system.
| Feature | Single Holder | Double Holder |
|---|---|---|
| SKU | FH-MRBF1 | FH-MRBF2 |
| Fuse Positions | 1 | 2 |
| Protected Circuits | 1 | 2 |
| Mounting Compatibility | M8 / M10 | M8 / M10 |
| Fuse/Cable Studs | M8 (5/16") | M8 (5/16") |
| Maximum Holder Rating | 300A | 300A Total |
| Protective Cover | Included | Included |
Built for Demanding DC Environments
MRBF (Marine Rated Battery Fuse) holders offer a compact alternative to conventional inline fuse holders. By mounting directly to a compatible battery terminal or busbar, they help reduce additional wiring and allow overcurrent protection to be located close to the power source.
The holder's tinned copper conductive components provide an efficient electrical path while offering enhanced corrosion resistance in marine and outdoor environments. Stainless steel fasteners provide secure mechanical connections without serving as the primary current-carrying path.
Each holder includes a flexible red silicone insulating cover that helps shield the fuse and terminal connections against accidental contact, dust, and splashing water. The cover can be removed for inspection or replacement of the fuse cartridges.
Applications
- Marine Electrical Systems: Battery banks, DC distribution, and auxiliary onboard equipment.
- LiFePO₄ Battery Installations: Compact overcurrent protection for compatible lithium battery systems.
- RVs & Camper Vans: Space-saving protection for house batteries and DC power systems.
- Off-Grid Solar Systems: Battery and DC distribution protection for cabins and remote installations.
- Battery Busbars: Direct mounting to compatible busbar studs for individually protected circuits.
- Auxiliary Battery Systems: Protection for vehicle accessories and additional DC loads.
Technical Specifications
| Product Type | MRBF Marine Battery Fuse Holder |
|---|---|
| Configurations | Single / Double (Dual) |
| Holder Material | Tinned Copper |
| Maximum Holder Current | 300A Total |
| Maximum Voltage | 58V DC |
| Mounting Hole | M10 (3/8") |
| Compatible Mounting Studs | M8 (5/16") / M10 (3/8") |
| Fuse/Cable Terminal Studs | M8 (5/16") |
| Fastening Hardware | Stainless Steel |
| Maximum Terminal Torque | 75 in-lb (8.5 N·m) |
| Compatible Fuse Type | MRBF Terminal Fuse |
| Holder Ignition Protection | No (with fuse: see FAQ) |
| Insulating Cover | Flexible Red Silicone |
| Installation | Battery Terminal / Busbar Stud |
| Fuses Included | No – Sold Separately |
What's Included
- 1 × MRBF Fuse Holder (Single or Double, as selected)
- 1 × Red Silicone Insulating Cover
- Stainless Steel Fuse-Retaining Hardware
Prefer a Complete MRBF Fuse Kit?
Choose a Single or Double holder and your preferred fuse amperage. Every kit includes the selected holder, silicone cover, stainless steel hardware, and two matching MRBF fuses.
With the Single kit, install one fuse and keep the second as a spare. With the Double kit, both fuses can be installed to protect two circuits.
Frequently Asked Questions
What is the difference between a Single and Double MRBF fuse holder?
The Single holder accommodates one MRBF fuse to protect one circuit. The Double (Dual) holder accommodates two MRBF fuses, allowing two independently fused circuits to share a common battery terminal or busbar connection.
The Double holder has a maximum combined current rating of 300A total, regardless of the individual fuse amperages installed.
Can the Double holder use two different fuse amperages?
Yes. Each position can use a different MRBF fuse amperage appropriate for its connected circuit.
When using different ratings, we recommend installing the smaller-rated fuse on the outermost (furthest) fuse position.
Combined current through both circuits must not exceed the holder's 300A total rating.
Are these holders compatible with Blue Sea Systems MRBF fuses?
Yes. These holders accept standard MRBF fuse cartridges, including Blue Sea Systems MRBF fuses and our own marine-rated MRBF fuses.
Can I install an MRBF fuse holder directly onto a battery terminal?
Yes. The holder has an M10 (3/8") mounting hole and accommodates compatible M8 (5/16") and M10 (3/8") battery terminal studs, as well as busbar connections.
When mounting on an M8 stud, use a suitable flat washer to support the larger mounting hole. Ensure the holder makes full electrical contact with the mounting surface and that all hardware is securely fastened.
Can I install an MRBF fuse directly onto a battery terminal without a holder?
No. Always use a compatible MRBF fuse holder. Installing the fuse directly onto a battery terminal allows the mounting bolt to create an electrical path around the fuse element, effectively bypassing it.
This renders the fuse ineffective because current can flow through the bolt instead of the fuse. During a short circuit, the fuse may not interrupt the current, leaving the connected wiring without the intended protection.
A proper MRBF holder electrically isolates the fastening hardware and ensures current flows through the fuse element before reaching the connected cable.
What size cable lugs do I need?
The fuse and cable connection studs are M8 (5/16"). Use cable lugs with matching M8 or 5/16" mounting holes.
The holder's main mounting hole is M10 (3/8"), allowing installation onto compatible M8 or M10 studs.
Are the MRBF holders waterproof?
Each holder includes a flexible red silicone insulating cover that helps protect exposed connections from accidental contact, dust, and splashing water.
Our compatible MRBF fuse cartridges have been tested to IP66, providing dust-tight protection and resistance to powerful water jets. The complete holder assembly should not be considered a sealed waterproof enclosure.
Are these holders ignition protected?
The holder itself is not independently ignition protected. When properly installed with a compatible ignition-protected MRBF terminal fuse, the assembly is designed for applications requiring ignition-protected fuse protection.
Our MRBF fuses feature ignition-protected construction suitable for appropriate marine installations.
Can I use these holders with LiFePO₄ batteries?
Yes. MRBF holders can be used with LiFePO₄ batteries when fitted with appropriately rated fuses.
The holder and compatible MRBF fuses are rated for 58V DC maximum. The selected fuse must also have sufficient interrupt capacity for the battery bank's available short-circuit current.
For installations with particularly high prospective fault currents, a higher-interrupt-capacity fuse such as a suitably rated Class-T fuse may be required.
What is the maximum tightening torque for the fuse terminal?
The manufacturer's specified maximum terminal torque is 75 in-lb (approximately 8.5 N·m).
Use a suitable torque wrench and do not exceed this value. Ensure all contact surfaces are clean and the fuse, cable lug, washers, and fastening hardware are assembled correctly.
Are MRBF fuses included with the holders?
No. The holder includes its silicone insulating cover and stainless steel fastening hardware, but fuse cartridges are sold separately.
For a complete installation, our MRBF kits include your choice of Single or Double holder and two matching MRBF fuses.
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