Mouse Over to Zoom
Click to Enlarge

BLUE SEA SYSTEMSML-Series Heavy Duty Automatic Charging Relay


In stock online.
Only 5 in stock!
Model # 9369059 | Mfg # 7620UPC # 632085076207


ML-Series Heavy Duty Automatic Charging Relay

Name Value
Amperage 500 Amps
Cold Cranking Amps 2500 Amps
Color Black
Dimensions 2 7/8" Length x 2 7/8" Width x 3" Height
Voltage 12 Volts/24 Volts DC
Warranty Details Lifetime
Type Charger

Product Overview

500 Amp magnetic latching (bi-stable) Automatic Charging Relay will automatically combine batteries during charging and isolate batteries when discharging or when starting engine.

The ML-ACR (Magnetic Latch-Automatic Charging Relay) and ML-RBS (Remote Battery Switch, sold separately), when paired, provide complete battery management of large battery banks with the push of a button. In addition to automatically sharing the charge from an engine’s alternator between the start and auxiliary battery, the ML-ACR control switch combines batteries momentarily to assist with starting in the event an engine battery is low. With the optional Blue Sea Systems 9160 Paralleling Link Bus (sold separately), multiple remote battery switches can be easily connected to the ML-ACR for a complete remote battery management subsystem.

An automatic charge relay (ACR) performs several tasks. It combines two battery banks to charge them from a single source, and isolates each bank as required to prevent accidental discharge and protect sensitive circuits. The Blue Sea Systems ML-series ACR adds some additional features and allows the user to choose how the battery banks are isolated.

Blue Sea Systems designed the ML-Series heavy duty Automatic Charge Relay to manage large battery banks with push-button convenience. The ACR is mounted close to batteries and battery switches to reduce heavy cable runs and simplify installation. An Ignition protection rating allows the ACR to be installed in the engine room of gasoline powered boats. An included remote switch controls the ACR and requires as little as 20 AWG wire; saving time and expense of running heavy gauge cable.

The ML-Series offers some additional control at the remote switch. The included Contura style switch allows the user to select ON, AUTO, and OFF: to combine the two banks in emergency situation, select automatic mode, and turn off or isolate the ACR. Users can set the system up for Start Isolation to isolate the house bank and protect sensitive electronics or Engine Isolation to isolate the engines to protect sensitive engine electronics.

Key Features

  • Magnetic Latch (ML)—ACR draws very low current (<40mA to monitor terminal voltage) in the “ON” or “OFF” states, and draws moderate current for very short time when changing state
  • Allows two battery banks to be efficiently charged from a single charging source without external regulators or isolators
  • Dual sensing; senses charge in each battery bank
  • Start Isolation or Engine Isolation allow uses to select bank to be isolated during current spikes to protect sensitive electronics or engine control systems
  • Ignition protected; can be installed in engine rooms of gasoline powered boats
  • Operated using remote switch; eliminates long heavy gauge cable runs
  • Remote switch (included) provides emergency combine feature to start the engine or make a radio call
  • LED indicators on switch designate mode of operation
  • Can be easily connected to ML series battery switches using link bus plates
  • Lifetime warranty

ACR Specifications

  • Nominal voltage: 12V
  • Engine Isolation: Yes
  • Amperage Operating Current: 13mA
  • Amperage Operating Current when changing state: <7.0A
  • Live Current Switching: 300A @ 12V DC
  • Continuous Rating: 500A
  • Intermittent Rating: 700A
  • Cable Size to Meet Rating: 4/0AWG
  • Terminal Stud Size: 3/8"
  • Weight: 2.04 lbs.
  • Approvals: Meets ISO 8846 and SAE J1171 external ignition protection requirements, CE marked, Rated IP66

Relay Contact Position

  • Combine 30 sec: 13.5V
  • Combine 90 sec: 13.0V
  • Open 10 sec: 12.35V
  • Open 30 sec: 12.75V
  • Open High: 16.2V


Wiring Diagram

Dimensional Drawings

Troubleshooting Guide

 WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.


The West Advisor articles have answered boaters' questions and provided solutions to boating problems for more than 20 years. West Marine has compiled one of the Web's most comprehensive collections of technical boating information articles.

Related West Advisor Articles


Product Q & A