Blue Sea 300A Red Mini m-Series On/Off Battery Switch w/ Key

Compact battery isolation for marine, RV and DC power systems

When space is tight but current demands are high, the Blue Sea mini m‑Series ON/OFF battery switch is designed to deliver reliable battery isolation in a compact footprint. It’s a practical choice for boat owners and installers who want a neat, serviceable way to disconnect a battery for maintenance, storage, fault-finding or improved safety—without resorting to oversized switchgear.

Rated to handle demanding DC loads, this single-circuit battery isolator suits a wide range of 12V, 24V and up to 48V DC systems. Use it to control a single battery feeding a single load group such as a house panel, inverter circuit, bow thruster feed, winch circuit (where appropriately engineered), or auxiliary power distribution. For many setups, adding a dedicated isolation point can help reduce the risk of parasitic drain, accidental short circuits during servicing, and confusion when troubleshooting onboard electrics.

Keyed ON/OFF operation for controlled access

This model includes a removable key, giving you a simple way to limit operation when the vessel is unattended or when you want only authorised users to energise critical circuits. It’s also handy in shared-use applications (workboats, club boats, fleet vehicles, camper fit-outs) where consistent procedures matter.

Built for marine environments and compliant installation

Blue Sea Systems components are widely specified in marine electrical builds for their focus on durability and installer-friendly design. This switch is ignition protected, making it suitable for installation aboard petrol-powered boats where electrical equipment must be designed to reduce the likelihood of ignition in fuel vapour environments (install to relevant standards and manufacturer guidance).

The casing is engineered for flexibility, supporting surface mounting as well as front or rear panel mounting. Breakout side panels assist with cable access and routing, helping you achieve a cleaner install—particularly valuable in compact battery compartments and console cavities.

Designed to handle high current in a small package

Despite its mini format, this switch is designed for substantial current handling, with a 300A continuous rating (and higher short-duration ratings for intermittent and starting loads). As with any high-current DC switching, final performance depends on correct cable sizing, termination quality, ventilation/ambient temperature, and overall installation practices.

Key features

• Single-circuit ON/OFF battery isolator for one battery to one load group
• Removable key for controlled access and added security
• Ignition protected for use in petrol-powered marine applications
• Compact mini m‑Series body suited to tight installs
• Versatile mounting: surface, front panel or rear panel
• Rear contact protection via isolating cover with snap-on sections

Ideal applications

• Boat battery master isolation (house or auxiliary bank)
• Caravan and RV DC isolation point for service and storage
• Off-grid DC systems requiring a simple ON/OFF disconnect
• Work vehicles and marine service rigs with controlled power access

Fit it once, service with confidence

If you’re upgrading your battery management or adding a proper isolation point to a new build, the Blue Sea mini m‑Series switch offers a professional, space-efficient solution with keyed operation and marine-ready design. Choose this switch to simplify maintenance, improve safety procedures, and keep your DC system organised—then install it as part of a well-designed wiring and protection plan.