Sapphire Energy
MRBF Battery Fuse Kit (Single/Double)
MRBF Battery Fuse Kit (Single/Double)
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MRBF Marine Battery Fuse Kit – Single & Double
Everything you need for compact, marine-grade battery fuse protection in one convenient package. Our MRBF Battery Fuse Kit combines a corrosion-resistant tinned copper fuse holder, a protective red silicone insulating cover, stainless steel hardware, and two matching MRBF fuse cartridges in your selected amperage.
Choose a Single or Double (Dual) fuse holder to suit your installation. The Single kit provides one installed fuse plus a convenient spare, while the Double kit includes two fuses to protect separate circuits from a common battery terminal or busbar.
Designed for marine, RV, LiFePO₄ battery, and off-grid applications, these compact terminal-mounted fuse kits offer high interrupt capacity, IP66 waterproof fuse construction, and ignition protection without the bulk of a traditional inline fuse block.
Why You'll Love It
- Complete Battery Protection Kit: Includes your selected holder, two matching MRBF fuses, silicone insulating cover, and stainless steel hardware.
- Single or Double Configuration: Choose one protected circuit with a spare fuse or two independently fused connections from a common mounting point.
- High Interrupt Capacity: MRBF fuses offer up to 10,000A interrupt capacity at 14V DC for protection against high-current electrical faults.
- IP66 Waterproof & Ignition Protected: Sealed marine-grade fuse cartridges resist dust and powerful water jets and feature ignition-protected construction.
- Marine-Grade Tinned Copper: Corrosion-resistant holder construction with secure M8 (5/16") fuse and cable connections.
- Compact & Serviceable: Mount fuse protection close to the battery and easily replace cartridges when required.
Choose Your MRBF Kit
Single Holder Kit: Includes one Single MRBF holder and two identical fuses. Install one fuse and keep the second as a spare.
Double Holder Kit: Includes one Double (Dual) MRBF holder and two identical fuses, allowing both positions to be used for independently protected circuits.
Select your preferred Holder and Amperage options to configure your kit.
Single vs. Double MRBF Fuse Kits
Both configurations include a tinned copper holder, protective silicone cover, stainless steel hardware, and two waterproof, ignition-protected MRBF fuses. The difference is how the two included fuses are used.
| Feature | Single Kit | Double Kit |
|---|---|---|
| Fuse Positions | 1 | 2 |
| Fuses Included | 2 | 2 |
| Protected Circuits | 1 | 2 |
| Holder Rating | 300A | 300A Total |
High Interrupt Capacity for Battery Protection
Batteries can deliver extremely high currents during a short circuit. The fuse's interrupt rating indicates the maximum prospective fault current it can safely interrupt under specified conditions.
The included MRBF fuses provide high interrupt capacity in a compact package, making them a practical choice for battery terminal and DC distribution protection.
| Operating Voltage | Interrupt Capacity |
|---|---|
| 14V DC | 10,000A (10kA) |
| 32V DC | 5,000A (5kA) |
| 58V DC | 2,000A (2kA) |
Interrupt capacity decreases at higher operating voltages. Always select a fuse with sufficient interrupt capacity for the available short-circuit current of your battery bank.
Marine-Grade Construction
The MRBF fuse holder features tinned copper conductive components for excellent electrical conductivity and corrosion resistance. Stainless steel fastening hardware securely retains the fuse and cable connections without serving as the primary current-carrying path.
The included MRBF fuse cartridges feature sealed ceramic construction with IP66 ingress protection against dust and powerful water jets, along with ignition-protected construction conforming to SAE J1171.
A flexible red silicone insulating cover helps shield exposed electrical connections from accidental contact, dust, and splashing water while allowing convenient access for fuse replacement.
Applications
- Marine Electrical Systems: Battery banks, DC distribution, and auxiliary onboard equipment.
- LiFePO₄ Battery Installations: Compact overcurrent protection where fuse voltage and interrupt ratings are suitable.
- RVs & Camper Vans: Space-saving protection for house batteries and mobile electrical systems.
- Off-Grid Solar Systems: Battery protection for cabins, tiny homes, and remote DC installations.
- Battery Busbars: Individually fused circuits from compatible distribution studs.
- Parallel Battery Banks: Individual battery cable protection where required by the system design.
Technical Specifications
| Holder Configuration | Single / Double (Dual) |
|---|---|
| Holder Material | Tinned Copper |
| Maximum Holder Current | 300A Total |
| Maximum Voltage | 58V DC |
| Mounting Compatibility | M8 & M10 (5/16" & 3/8") |
| Fuse/Cable Terminal Studs | M8 (5/16") |
| Maximum Terminal Torque | 75 in-lb (8.5 N·m) |
| Fuse Construction | Sealed Ceramic Cartridge |
| Fuse Quantity | 2 – Matching Amperage |
| Interrupt Ratings | 10,000A (14V DC) 5,000A (32V DC) 2,000A (58V DC) |
| Fuse Ingress Protection | IP66 |
| Fuse Ignition Protection | SAE J1171 |
| Fuse Dimensions | 23.0 x 27.8 x 16.3 mm 0.91" x 1.09" x 0.64" |
| Insulating Cover | Flexible Red Silicone |
What's Included
- 1 × MRBF Fuse Holder (Single or Double, as selected)
- 2 × IP66 MRBF Fuse Cartridges (matching selected amperage)
- 1 × Red Silicone Insulating Cover
- Stainless Steel Fuse-Retaining Hardware
Already Have an MRBF Installation?
Need replacement fuses or another holder? Our MRBF components are also available separately. Choose replacement fuses in convenient 2-packs or add another Single or Double tinned copper holder.
Frequently Asked Questions
What's the difference between the Single and Double MRBF Fuse Kits?
Both kits include a tinned copper MRBF fuse holder, two matching fuses, stainless steel hardware, and a red silicone insulating cover.
The Single kit has one fuse position, allowing you to install one fuse and keep the second as a spare.
The Double (Dual) kit has two fuse positions, allowing both included fuses to be installed simultaneously to protect two separate circuits.
Can I select two different fuse amperages for the Double kit?
Each kit includes two identical MRBF fuses in the amperage selected when ordering.
The Double holder can accommodate different fuse amperages in its two positions. If your circuits require different ratings, additional MRBF fuses can be purchased separately in convenient 2-packs.
When installing different ratings, position the smaller-rated fuse on the outermost (furthest) fuse position.
Can I mount the MRBF holder directly onto a battery terminal?
Yes. The holder has an M10 (3/8") mounting hole that accommodates compatible M8 (5/16") or M10 (3/8") battery studs, as well as busbar connections.
When installing on an M8 stud, use a suitable flat washer to support the larger mounting hole. Ensure clean contact surfaces, secure fastening, and sufficient thread engagement.
Can I install an MRBF fuse directly onto a battery terminal without the holder?
No. Always use a compatible MRBF fuse holder. Installing a fuse directly onto a battery terminal allows the mounting bolt to create an electrical path that bypasses the fuse element entirely.
This effectively renders the fuse useless. During a short circuit, current can flow through the bolt rather than the fuse, leaving the connected wiring without the intended overcurrent protection.
A proper MRBF holder uses an electrically isolated terminal stud to ensure current passes through the fuse element before reaching the cable.
Are these MRBF fuses and holders compatible with Blue Sea Systems products?
Yes. These components use the standard MRBF configuration and are compatible with Blue Sea Systems MRBF fuses and fuse holders.
Always verify fuse amperage, voltage rating, mounting compatibility, and holder current limits for your installation.
Are the MRBF fuses waterproof and ignition protected?
Yes. The included MRBF fuse cartridges feature IP66 ingress protection, providing dust-tight construction and resistance to powerful water jets.
The fuses also feature ignition-protected construction conforming to SAE J1171. The fuse holder includes a protective silicone cover, but the complete holder assembly is not a sealed waterproof enclosure.
Can I use this kit with a LiFePO₄ battery?
Yes. MRBF fuse kits are suitable for LiFePO₄ battery systems when the selected fuse has the appropriate amperage, voltage rating, and interrupt capacity.
The holder and fuses have a maximum rating of 58V DC. Some nominal 48V LiFePO₄ systems can exceed this voltage during charging, so verify the maximum system voltage before installation.
At 58V DC, the fuses have an interrupt capacity of 2,000A. Battery banks with higher available fault currents may require a higher-interrupt-capacity fuse, such as Class-T.
What is the maximum current rating of the Double holder?
The Double holder has a maximum combined current rating of 300A total across both fuse positions.
The sum of the currents flowing through its common connection must remain within this limit, regardless of the individual fuse amperages installed. Each circuit must also be protected by an appropriately sized fuse.
What size cable lugs and mounting studs are required?
The fuse and cable terminals use M8 (5/16") studs, requiring compatible cable lugs.
The holder's main mounting hole is M10 (3/8") and accommodates compatible M8 or M10 battery and busbar studs.
What is the maximum tightening torque?
The manufacturer's specified maximum fuse-terminal torque is 75 in-lb (8.5 N·m).
Use an appropriate torque wrench, avoid overtightening, and ensure all contact surfaces are clean and properly assembled.
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