Blue Sea Systems BatteryLink Automatic Charging Relay, 12/24V DC, 120A

Overview

The Blue Sea Systems 7611 is a BatteryLink automatic charging relay for 12/24V DC systems that manages two battery banks and carries 120A continuously, with a 210A intermittent rating for 5 minutes. It combines the banks when a charging source is present and separates them when charging drops away, so a start battery and an auxiliary battery can share charge without being tied together all the time.

This relay fits boats that run a dedicated start battery alongside a house or auxiliary bank and want both banks to charge from the same alternator or charger. It is IP67-rated, ignition protected, and built with 3/8"-16 (M10) tinned copper studs with 7/8 in (22 mm) stud length, which gives useful terminal space when more than one cable lug needs to land at the connection.

Key features

• 12/24V DC auto-ranging operation for boats wired on either nominal system voltage
• 120A continuous rating and 210A intermittent rating for 5 minutes
• Dual sensing across two battery banks so charging on either bank can trigger combining
• Auxiliary Battery Priority connection can keep the banks combined longer while the engine is running so the auxiliary bank gets more charging time
• IP67 enclosure and ignition protection for marine electrical spaces, including gasoline-powered boats
• 3/8"-16 (M10) tinned copper studs with 7/8 in (22 mm) stud length and support for cable up to 1/0 AWG
• Side and bottom knockouts, clip-on insulated cover, and built-in LED status indication

Installation and setup

Mount it in a dry, protected location when possible and avoid placing it directly above the battery banks. That helps reduce corrosion at the connections and keeps the relay easier to inspect and service over time.

The main setup is straightforward: one battery bank connects to each main stud and the unit is grounded through a 1A in-line fuse. Quick-connect terminals are provided for ground, Auxiliary Battery Priority, and an optional remote LED if you want to monitor relay status away from the battery compartment.

Compatibility and fit

This is a good fit for boats with separate start and house banks where automatic charge sharing matters more than manual battery switching. It will sense charge on either bank, which works well on systems that may see input from an alternator, shore charger, or another charging source tied into one side of the system.

It is not intended to carry engine starting current. On boats where emergency parallel starting is part of the battery plan, this relay should be used alongside a battery switching setup that includes a combine or parallel function.

Use on board

This relay makes sense on center consoles, fishing boats, cruising sailboats, and similar setups where electronics, pumps, lighting, or other house loads are fed from a separate bank. It helps keep the charging side automatic while still leaving the start battery isolated once charging is no longer present.

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