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TMN-Handels GmbH

BSR 20-3 battery cut-off relay 12V/140A. Set "3m cable"

Regular price 74,95 €*
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TMN Automotive

Fully automatic cut-off relay

BSR 20-3 kit

with 3 meter 25mm² power cable

12 volts / 140 amps continuous load


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 TMN BSR cut-off relay 140A
  • 1x pole terminal set +/-
  • 3 meter 25mm² OFC full copper premium battery cable Color: red
  • 1 meter 25mm² OFC full copper premium ground cable Color: black
  • 2x MIDI fuse holder
  • 2x MIDI fuses 60A
  • 8x 25mm² tubular cable lugs M6
  • 1x grommet
  • 35cm shrink tubing

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