Blue Sea Systems VSR ML Series Auto Charge Relay 500A 24V BS-7621B

Sale price$487.00


500 Amp magnetic latching (bi-stable) relay automatically combines batteries during charging and isolates batteries when discharging and when starting engine


  • Manual control switch provides an added level of safety allowing control with or without power, and offering LOCK OFF capability for servicing
  • Automatically manages the charging of two large battery banks
  • Allows paralleling of battery banks for emergency starting
  • 500 Ampere continuous rating to support high-output alternators
  • 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
  • Dual sensing—senses charge on both battery banks
  • Start Isolation (SI)—can be configured for temporary isolation of House loads from Engine circuit during engine cranking to protect sensitive electronics
  • Engine Isolation (EI)—can be configured for isolation of two engines while both are running to protect engine electronics and maximize alternator output
  • Senses charging on two battery banks
  • LED output to remotely indicate when batteries are combined, isolated, in voltage lockout, or in Start or Engine isolation
  • 3/8″-16 tin-plated copper studs for maximum conductivity and corrosion resistance
  • 7/8″ (22mm) stud length accepts multiple cable terminals
  • Silver alloy contacts provide high reliability for switching live loads
  • Label recesses for circuit identification
  • ML-Series Remote Control Contura Switch is not supplied with Solenoid. PN 2146 available as a seperate item.


Control Circuit Connection  Tinned Wire
Nominal Voltage 24V DC
Manual Control 
Engine Isolation  Yes
Mounting #10
Start Assist  Yes
Start Isolation  Yes
Amperage Operating Current
Amperage Operating Current when changing state <7.0A
Terminal Stud Torque 140 in-lb (15.82 Nm)
Continuous Rating 
Intermittent Rating  700A (5 min)
Cranking Rating 30 sec  1450A DC
Minimum Operating Temperature -10° C
Maximum Operating Temperature 60° C
Cable Size to Meet Ratings 4/0 AWG x 2
Live Current Switching 300A @ 12V DC
Switching Cycles 100000
Terminal Ring Diameter Clearance 1.12in (28.45 mm)
Terminal Stud Length 1.50in (38.1 mm)
Terminal Stud Size 3/8" - 16 (M10)
Wire Size 20 AWG
Relay Contact Position
Combine 30 sec 27.0V
Combine 90 sec 26.0V
Open 10 sec 24.7V
Open 30 sec 25.5V
Open High 32.4V
Weight 2.08lb (0.94 kg)

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