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BSR PRO20-3 battery cut-off relay 12V 140A. set

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TMN Automotive

Fully automatic BSR cut-off relay

BSR PRO20-3 kit

12 volts / 140 amps continuous load

with 3 meters of 25mm² power cable

Working status immediately recognizable via LED


If a second or (secondary) additional battery is to be installed in a vehicle, the installation of an isolating relay is highly recommended.

The purpose of installing this relay is to disconnect the two batteries when the engine is off if the voltage drops below 12.8V. This ensures that the starter battery is not discharged if further energy is drawn from the additional battery.

When the engine is switched on, the charging voltage increases to over 13.3V (alternator control voltage ≥ 13.4), as a result of which the isolating relay closes the circuit and the starter and auxiliary batteries are charged at the same time. The same applies if the charging voltage of the additional battery increases to more than 13.3V due to a connected charger or a built-in solar system. So this BSR cut-off relay works bi-directionally in both directions.

This relay is suitable for CAN bus vehicles. No alternator control voltage d+ or ignition plus is required.

Areas of application:

  • car
  • buses
  • boats
  • caravans and camping
  • solar applications
  • CarHifi
  • Etc.

Product features TMN cut-off relay (BSR= Battery Sensitive Relay):

  • Continuous load: max. 140 amps
  • Housing color: transparent
  • Status Light / Color: Yes / Green
    • Status light ON: voltage above 13.3 VDC (circuit is closed)
    • Status light OFF: voltage below 12.8V DC (circuit is open)
  • Voltage: 12V
  • Dimensions: (LxWxH) approx. 67x67x53mm
  • Connections: 2x battery screw connections + 1x ground wire

Parts list installation set:

  • 1x BSR cut-off relay 140A
  • 1x pole terminal set +/- each with 2x M6 and 1x M8 connection
  • 3 meter 25mm² OFC full copper premium battery cable Color: red
  • 1 meter 25mm² OFC full copper premium ground cable Color: Black
  • 2x Mega fuse holder
  • 2x mega fuses 60A
  • 8x 25mm² tubular cable lugs M8
  • 1x grommet
  • 40cm shrink tubing

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