MRBF Terminal Fuse Kit

Artikelomschrijving:

100A-300A · 58V DC · 10kA AIC · Marine-Rated · Ignition-Protected

Recommended for BS 7671 compliance on every TITAN install.

What's in the kit

• 1 × Blue Sea 5191 MRBF Terminal Fuse Block
• 1 × Blue Sea MRBF Terminal Fuse in your chosen rating (100A, 150A, 200A, 250A or 300A)
• Low-height (DIN) fitment only: 1 × Durite cargo-style positive terminal (5-100-01) with vertical stud

Mounts directly on the M8 positive terminal of any TITAN battery. The block isolates the fuse from accidental shorts and accepts standard 5/16" ring terminals (or stacked terminals via the M8 stud).

Standard or Low-height (DIN)?

Standard mounts the fuse block upright on the battery post - the simplest install if you have clearance above the battery.

Low-height (DIN) is for height-restricted fitments - under-seat and tray installs where the standard block won't clear. It adds a Durite cargo-style terminal that moves the connection point out towards the edge of the casing, letting the MRBF block mount inverted off the side of the battery instead of on top:

• Total height: 195mm including the terminal stud (vs ~215mm with the standard upright block on a 190mm DIN battery)
• Width at the fuse point: 205mm - the block sits proud of the side of the case, so allow for it in the tray
• Vertical 5/16" Whitworth stud (M10 equivalent) with 13mm nuts - all nuts included for the terminal and the block
• Same Blue Sea block and fuse as the standard kit - nothing about the protection changes, only the mounting

As with the standard kit, your main positive battery cable needs an M8 or M10 eyelet on the end to connect to the fuse holder. Most TITAN owners don't need this option - if your battery bay has normal clearance, choose Standard.

Why we recommend it

UK caravan, motorhome and marine installs fall under BS 7671, which requires a fuse capable of safely interrupting a worst-case short-circuit current. Our BMS shuts down on a short in normal use, but the regulation looks at worst case - and lithium short-circuits can theoretically reach 3,000-6,000A. Standard blade or MEGA fuses cannot interrupt that current; only marine-rated MRBF or Class T fuses are AIC-rated to do so.

Without a compliant fuse, an insurance claim has an easy line of defence. We sell this kit at minimal mark-up because we'd rather you were covered than not.

Which rating should I choose?

Not sure? Choose 300A. It satisfies the BS 7671 worst-case short-circuit requirement without nuisance-tripping on the legitimate inrush currents a normal lithium install pulls - inverter startup spikes, induction hob ignition, electric winches, big DC-DC chargers running in parallel. It is the rating we fit by default.

Want the main fuse matched to your cable? That's what the 100A-250A options are for. Pick the lowest rating that comfortably exceeds your maximum continuous system draw, and that does not exceed the continuous rating of your main positive cable. Two checks before you go tighter:

• An MRBF fuse holds 100% of its rating and tolerates brief surges well beyond it (135% for up to about 15 minutes), so size to your continuous load, not the worst momentary spike.
• If you run an inverter, check its startup surge against the rating - a big inverter on a tight fuse is the classic nuisance-trip.

All five ratings are the same physical fuse with the same 58V DC and interrupt ratings - only the trip current (and body colour) changes. The block accepts any of them without modification, so you can change rating later by swapping the fuse alone.

Important: read before installing

Heads up. The 300A option is a short-circuit compliance fuse - not a cable-protection fuse.

At 300A, the fuse is not sized to protect any one specific cable or load downstream of the battery. You remain responsible for the rest of the install. In practice that means one of the following:

• Cabling between this fuse and your distribution / busbar rated for at least the fuse's rating continuous, or
• A correctly-sized secondary fuse close to each load - blade, MEGA, mini-ANL or similar - sized to the cable feeding that load.

If you're unsure how to size your install, please get in touch before fitting. We're happy to talk it through - but the duty of matching fuse rating to cable rating and load demand sits with the installer / owner. Don't assume 300A is the right number for your wiring just because it's the default we recommend.

Specifications

Spare parts available separately: MRBF Terminal Fuse Block · MRBF Terminal Fuses (100A-300A)

Technical reference

Drawings & curves sourced from Blue Sea Systems product documentation. Dimensions and trip curves apply to all ratings; trip currents scale with the nominal rating.