Blue Sea 7622 ML-ACR Automatic Charging Relay with Manual Control 12V DC 500A

Automatic Dual-Bank Battery Management

The Blue Sea 7622 ML-ACR takes the guesswork out of managing two battery banks. When the relay senses charging voltage on either bank — above 13.5V for 30 seconds or above 13.0V for 90 seconds — it automatically combines both banks so your alternator or charger feeds them simultaneously. When voltage drops below charging thresholds, the relay isolates the banks, ensuring your starting battery stays topped up and your house bank doesn't drain it overnight.

This dual-sensing capability means the relay responds to charge from either bank, whether it comes from the engine alternator, a shore-power charger, or a solar panel. The result is a fully automated charging system that keeps both banks healthy without requiring you to flip switches or remember to reconnect after anchoring.

Magnetic Latching Technology for Minimal Current Draw

Unlike conventional solenoid-based relays that draw continuous current to hold their contacts closed, the ML-ACR uses a magnetic latching (bi-stable) coil. In either the ON or OFF state, the relay draws less than 13 mA — barely more than a small LED. It only draws moderate current (less than 7A) for approximately 20 milliseconds when changing state. This means the relay itself places virtually no load on your batteries, which is especially important for boats that sit at anchor or on a mooring for extended periods.

Manual Override and Remote Control

The 7622 model includes both a manual override knob mounted directly on the relay and an ML-Series Remote Control Contura Switch (PN 2146) for helm-mounted operation. The manual knob provides three critical functions: push-to-latch ON for emergency battery combining, release to isolate, and a LOCK OFF position that physically prevents the relay from closing — ideal when you need to service your electrical system safely. A cable tie can be passed through the knob's hole to secure it in the LOCK OFF position.

The included Contura switch offers sustained ON-OFF-ON operation from a convenient panel location. Switching to ON combines both banks for emergency starting power. Switching to OFF isolates them manually. The centre AUTO position returns the relay to fully automatic operation. Dual LEDs in the switch provide at-a-glance status: steady on when combined, off when isolated, slow blink during start or engine isolation, and rapid blink during voltage lockout conditions.

Start Isolation and Engine Isolation Modes

The ML-ACR can be configured for one of two optional isolation modes using the included wire harness — Start Isolation or Engine Isolation (but not both simultaneously).

• Start Isolation (SI) — Temporarily isolates house loads from the engine circuit for 3–5 minutes during cranking. This prevents voltage sags and spikes from the starter motor from reaching sensitive house electronics such as chartplotters, radios, and navigation instruments.
• Engine Isolation (EI) — Keeps two (or three) running engines electrically separated to reduce noise and communication cross-talk between engine electronics, and to maximise total alternator output. This mode is particularly useful when the engine manufacturer requires electrical isolation between powerplants.

Voltage Lockout Protection

Built-in undervoltage and overvoltage lockout safeguards prevent the relay from combining batteries under abnormal conditions. If either battery bank drops below 9.6V, the relay will not combine — protecting a healthy bank from being dragged down by a severely depleted one. Similarly, if either bank exceeds 16.2V, the relay opens to prevent damage from an overcharging alternator or faulty regulator. The remote Contura switch LEDs provide a rapid blink pattern to alert you when a lockout condition is active.

Heavy-Duty Construction for Marine Environments

Rated at 500A continuous when wired with dual 4/0 AWG cables, the ML-ACR is built to handle high-output alternators and large battery banks. The 3/8"-16 tin-plated copper studs resist corrosion and provide excellent conductivity, while silver alloy contacts ensure reliable switching of live loads over 100,000 cycles. The 7/8" (22 mm) stud length accommodates multiple stacked cable terminals, giving you flexibility in complex installations.

The relay meets ISO 8846 and SAE J1171 external ignition protection requirements and is CE marked and rated IP66, meaning it is protected against powerful water jets. For best results, mount the unit in a dry, protected location as close to both battery banks as possible to minimise voltage drop in the connecting cables. Avoid mounting directly above vented lead-acid batteries where corrosive gases could reach the terminals.

Specifications

• Nominal Voltage: 12V DC
• Continuous Rating (with 2× 4/0 AWG cable): 500A DC
• Intermittent Rating — 5 min. (with 2× 4/0 AWG cable): 700A DC
• Cranking Rating — 30 sec. (with 2× 4/0 AWG cable): 1,450A DC
• Amperage Operating Current — Continuous: < 13 mA
• Amperage Operating Current — When Changing State: < 7.0A DC (20 ms)
• Contact Circuit Voltage: 16V DC Max.
• Combine Voltage Threshold (30 sec.): 13.5V
• Combine Voltage Threshold (90 sec.): 13.0V
• Open Low Voltage Threshold (10 sec.): 12.35V
• Open Low Voltage Threshold (30 sec.): 12.75V
• Open High Voltage Threshold: 16.2V
• Undervoltage Lockout: 9.6V
• Overvoltage Lockout: 16.2V
• Switching Cycles: 100,000
• Coil Function: Magnetic Latching Bi-Stable
• Terminal Stud Size: 3/8"-16 (M10)
• Terminal Stud Length: 7/8" (22 mm)
• Maximum Terminal Stud Torque: 140 in-lb (15.8 Nm)
• Terminal Ring Diameter Clearance: 1.12" (28.4 mm)
• Cable Size to Meet Ratings: 4/0 AWG (120 mm²) × 2
• Mounting Hardware: #10 or M5
• Control Circuit Connection: Tinned Wire
• Weight: 2.04 lb (0.93 kg)
• Dimensions (L × W × H): 5.47" × 4.50" × 2.03" (138.94 mm × 114.30 mm × 51.56 mm)
• Included Remote Control Switch: PN 2146 — Sustained SPDT ON-OFF-ON
• Remote Switch Mounting Hole: 1.45" × 0.83" (36.83 mm × 21.08 mm)
• Remote Switch LED Rating: 100,000 hours half-life
• Remote Switch Seals: Internal and external gasket panel seal
• Remote Switch Front IP Rating: IP67 when mounted with gasket
• ACR IP Rating: IP66
• Regulatory: CE marked; Meets ISO 8846 and SAE J1171 external ignition protection requirements
• Remote Switch Regulatory: Meets UL 1500 and ISO 8846 external ignition protection requirements
• Operating Temperature Range: -40°C (-40°F) to 85°C (185°F)

Key Features

• Automatic dual-bank charging — combines batteries when charging is detected and isolates them when discharging, so you never have to manually manage battery banks
• Manual override knob with LOCK OFF — provides physical control with or without power, and secures the relay for safe electrical servicing
• Included helm-mounted Contura switch — gives instant access to emergency cross-connect, manual isolation, and automatic mode from the cockpit
• Magnetic latching relay design — draws virtually no current in either state, preserving battery capacity during long periods at anchor or winter storage
• Dual-sensing on both banks — detects charging from either battery bank regardless of the source, ensuring both banks receive charge
• Configurable Start Isolation — temporarily separates house electronics from engine cranking transients, protecting sensitive navigation and communication gear
• Configurable Engine Isolation — keeps multiple running engines electrically separated to reduce cross-talk and maximise alternator output
• Undervoltage and overvoltage lockout — prevents combining under abnormal voltage conditions, protecting healthy batteries from damaged or overcharging systems
• LED status indication via remote switch — provides clear visual feedback on combined, isolated, lockout, and override states at a glance
• Silver alloy contacts rated for 100,000 switching cycles — ensures long-term reliability when switching live loads in demanding marine environments
• Ignition-protected design — safe for installation in engine compartments and other areas where fuel vapours may be present
• Compatible with ML-Series Remote Battery Switches — pairs with optional Paralleling Link Bus (PN 9160) for a complete remote battery management subsystem