Arco Starting & Charging BI-1203-3A Battery Isolator 120A 1 Alternator 3 Battery

The Arco Marine BI-1203-3A is a solid-state battery isolator designed for marine inboard and outboard applications. This unit handles 1 alternator and 3 batteries with a maximum current rating of 120 amps. It's rated for use with 10 to 350-amp alternators on 12, 24, or 32-volt negative ground systems and includes an exciter terminal for proper voltage regulation.

Key Features:

• 120-amp maximum capacity with 1 alternator and 3 battery configuration
• Solid-state design allows current flow in one direction only, preventing higher-charged batteries from discharging into lower-charged batteries
• Automatic proportional charging—both batteries receive charge according to their individual needs whenever the engine is running
• Compatible with battery selector switches without requiring position changes for dual-battery charging
• Rated for 10 to 350-amp alternators on 12V, 24V, or 32V negative ground systems
• Includes exciter terminal for voltage regulation

This battery isolator provides intelligent charge distribution, automatically directing alternator output to the batteries that need it most regardless of selector switch position. Ideal for marine vessels requiring reliable dual or triple battery management.

Important Compatibility Note: This battery isolator cannot be used on 12-volt charging systems with 24-volt trolling motors or newer outboard engines equipped with rectifier-regulator charging systems.