Overview

The Blue Sea Systems 7610 is a 120A SI-Series automatic charging relay with start isolation for 12V and 24V DC battery systems. It combines two battery banks when charging voltage is present and separates them when charging stops, so a start battery and a house bank can share charging without remaining linked under discharge. Auto-ranging input, dual sensing, and an IP67-rated housing make it a practical fit for boats that deal with spray, vibration, and mixed charging layouts.

On board, its main job is to keep charging automatic while reducing the voltage sag and spike issues that can reach house electronics during engine cranking. Start isolation opens the relay during crank events, and under-voltage lockout prevents it from closing below 9.5V on 12V systems or 19V on 24V systems. The relay is ignition protected for gasoline-powered boats and is rated for 120A continuous service, with a 210A intermittent rating for 5 minutes.

Key features

• 12V and 24V auto-ranging operation for boats with either system voltage
• 120A continuous rating and 210A intermittent rating for 5 minutes
• Dual sensing responds to charging voltage on either battery bank
• Start isolation opens the relay during engine cranking to keep house loads off the start circuit
• IP67-rated housing with hermetically sealed contacts for wet marine spaces
• Ignition protected for installation on gasoline-powered boats
• Built-in LED shows combined status, and quick-connect terminals support ground, SI, and an optional remote indicator lamp
• 3/8 in - 16 tinned copper studs with 7/8 in stud length for battery cable lugs

Installation and fit

This relay fits boats with separate start and house banks that are charged by an alternator, an onboard charger, or another DC charging source. Because it senses charging on either bank, it works in layouts where the charge source lands on the engine battery on one boat and the house side on another. It is a strong match for cruising boats, fishing boats, and sailboats that want automatic battery charging without needing to manage the banks by hand every time the engine starts or a charger comes online.

The 7610 should be used as a charging relay, not as a path for starter motor current. If your system needs an emergency parallel function for cranking, that should be handled by a switch or combining setup rated for starting loads. When planning the install, the main checks are cable lug fit on the 3/8 in studs, fuse protection for the connected cables, and enough mounting clearance for the relay body and cover. It can live in places that see washdown or splash, though a dry protected mounting location is still the better choice when space allows.