MRBF Terminal Fuse Kit (300A) - for TITAN Lithium Batteries

MRBF Terminal Fuse Kit (300A) - for TITAN Lithium Batteries300A 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 5190 300A MRBF Terminal Fuse 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). Why we recommend it UK caravan, motorhome and

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 5190 300A MRBF Terminal Fuse

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).

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.

Important: read before installing

Heads up. This is a short-circuit compliance fuse - not a cable-protection fuse.

The 300A rating was chosen for one reason: to satisfy BS 7671's worst-case short-circuit requirement (and the AIC rules that come with it) without nuisance-tripping on the legitimate inrush currents that a normal lithium install pulls - inverter startup spikes, induction hob ignition, electric winches, big DC-DC chargers running in parallel. It 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 300A 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'd rather a tighter primary rating, MRBF terminal fuses are available from 30A up to 300A in the exact same physical format. We do not currently stock the smaller ratings; Blue Sea Systems, T1 Terminals and most marine suppliers carry them. The block in this kit accepts any of those fuses without modification.

If you're unsure how to size the rest of 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 number we ship.

Specifications

Spare parts available separately: MRBF Terminal Fuse Block · MRBF 300A Fuse

Technical reference

Drawings & curves sourced from Blue Sea Systems product documentation.