High-Capacity 24V Battery Management for Marine and Heavy-Duty Systems

Managing multiple battery banks in 24V systems requires robust, reliable switching technology. The Blue Sea ML-Series Automatic Charging Relay (ACR) provides a superior solution for automatically managing the charging of two large battery banks, such as a start battery and a house bank. Designed for high-amperage applications, this unit removes the need for manual switching, ensuring your batteries are charged when a source is active and isolated when discharging to prevent accidental depletion of your starting power.

Magnetic Latching Technology for Maximum Efficiency

Unlike standard continuous-duty solenoids that generate heat and consume significant power just to stay closed, the ML-Series utilises a magnetic latching (bi-stable) mechanism. This advanced design draws very low current (less than 40mA) to monitor terminal voltage in both the "ON" or "OFF" states. It only draws moderate current for a fraction of a second when changing states. This ensures that your energy goes into charging your batteries, not heating up the relay, making it essential for energy-conscious off-grid and marine setups.

Dual Sensing and Smart Isolation

This ACR features intelligent dual sensing technology, meaning it monitors voltage on both battery banks. If you are charging your house bank via a solar array or a shore charger, the relay will close to top up the start battery. Conversely, when the engine alternator is running, it combines the banks to charge the house battery.

For sensitive electronics, the unit offers configurable Start Isolation. This feature temporarily isolates the house loads from the engine circuit during cranking, protecting navigation units, sonar, and other sensitive equipment from voltage sags and spikes.

Manual Control for Safety and Service

While the operation is fully automatic, the integrated yellow manual control knob provides complete peace of mind. It allows for:

• Lock Off: Isolate batteries completely for safe servicing or storage.
• Manual On: Combine batteries for emergency starting if the start battery is low.
• Auto: The default set-and-forget mode for daily operation.

Built for High-Output Environments

With a continuous rating of 500 Amperes, this relay is engineered to support modern high-output alternators commonly found on large vessels, heavy trucks, and commercial vehicles. The robust construction features 3/8"-16 (Approx. M10) tin-plated copper stud terminals which provide maximum conductivity and corrosion resistance. These long terminals allow for multiple cable lugs to be connected securely (accepting up to 4/0 AWG or approx. 120mm² cables).

Key Features

• 500A Continuous Rating: Handles heavy loads and high-output charging sources reliably.
• Magnetic Latch (Bi-Stable): Ultra-low power consumption with no heat generation in the hold state.
• Dual Sensing: Bi-directional charging manages inputs from alternators and solar/shore chargers.
• Silver Alloy Contacts: Ensures high reliability for switching live loads up to 300A.
• LED Output: Compatible with remote LEDs to indicate combined, isolated, or lockout states.
• Engine Isolation: Can be configured to isolate two engines while running to protect individual engine electronics.
• IP66 Rating: Protected against powerful water jets, suitable for harsh marine environments.

Note: This unit is the 24V DC model. The ML-Series Remote Control Contura Switch is not included with this SKU (BS-7623B) and is available separately if remote operation is required.

Optimise Your 24V Power System

Ensure your batteries are charged efficiently and your starting power is always protected. Upgrade to the Blue Sea ML-Series 24V ACR for professional-grade battery management.