Voltage Sensing Relay - 12V 125 Amp Dual Sense.

VSR features:

When the voltage of a battery bank reaches 13.7 volts, the VSR engages, allowing two battery banks (start and house) to be charged simultaneously. When the voltage drops below 12.8 volts (eg. the engine is stopped), the VSR disengages, separating the batteries. This system eliminates the possibility of draining the start battery and protects sensitive electronic equipment powered from the house battery from harmful engine start up spikes.

Advantages of fitting a VSR over conventional diode isolators:
Easy 3 wire connection at the battery. No need to bypass existing alternator wiring.
VSRs have no volt drop. Conventional diode isolators incur a minimum of 0.6 volt drop.
Compact size - no large heat sink
Cost effective solution

Continuous current: 125 Amps
Intermittent current: 150 Amps

Dimensions (mm): 69L x 69W x 50H