What is a Voltage Sensitive Relay?

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A voltage sensitive relay (VSR) is a relay. It is used for automotive, truck and marine applications.

A voltage sensitive relay senses the input voltage generated and automatically connects/disconnects the appliance or circuit at pre-set voltages for a variety of applications.
It is typically used to prevent over-discharging of car battery and is very common in a dual battery system.

A VSR is usually classified into 12V / 24V range with varying amperage. A single sense relay only detects voltage at one pole while a dual sense relay detects voltage at both poles. An ignition-protected voltage sensitive relay can withstand repetitive engine cranking transients without significant effect. VSRs are inexpensive and offer little or no voltage drop. However, the relay may chatter (repeatedly open/close at very short intervals) if the voltage is not stable.

KT has released a range of Battery Master Switches and Voltage Sensitive Relays, Now available.
Contact KT on 1300 559 953 or email us for more information.


Model: KTVSR135
KT Voltage Sensitive Relay for Dual Battery Systems (VSR)

  • Protects The Primary Starting Battery
  • 135A, Voltage Cut In: 13.7V
  • Cut Out: 12.8V
  • LED Indicator Alert When Unit Is Active
  • Fully Resin Sealed
  • Suitable for Automotive & Marine Use
  • Mounting Hardware included

The Voltage Sensitive Relay (VSR) allows two batteries to be charged at the same time.

When the engine is started and the starting battery reaches 13.7V, the Voltage Sensitive Relay engages, allowing two battery banks (start and house) to be charged simultaneously. When the voltage drops below 12.8V (eg; the engine is stopped), the VSR disengages, separating the batteries.