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Home > 12v Power Accessory Socket & DC to DC USB Adapters / Converters > Mobile Installation Tools, Power Supplies & Accessories > 12v Voltage Sensing Automatic Power Off Switch

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12v Voltage Sensing Automatic Power Off Switch


You will never have to turn on or off your radio(s) again. This voltage sensing automatic switch is designed for 12 volt vehicle electrical systems with negative ground. It can switch up to 20 amps and carry up to 30 amp loads. The shutdown voltage can be set to one of four pre-programmed voltages (11.8, 12.1, 12.7, 13.05 volts) using two DIP switches and the shutdown delay can be set to one of four pre-programmed times (0, 5, 10, 20 minutes). The device is housed in a sturdy ABS plastic case.

What it Does and How it Works

This is basically a voltage controlled switch. When the vehicle voltage is higher than the unit's set point, the relay is turned on and power is provided to the load side. When the voltage drops below the unit's voltage set point and stays there for longer than the time set point, the Unit's relay turns off and power is removed from the load side.

The automatic switch has a bright yellow LED to indicate its status and it has a slide switch that can be used to turn the load on regardless of the input voltage.

Using the factory default settings, the Automatic switch will turn on the load when the vehicle voltage rises above 13.05 volts. This typically occurs within a few seconds of starting the vehicle. The load remains powered as long as the vehicle is on. When the engine is shut off, the vehicle voltage sinks below 13.05. The automatic switch waits until the voltage has been less than 13.05 volts for 10 minutes and then turns the load off.

The automatic switch is ideal for use with mobile APRS stations. It allows the radio to transmit a few position reports after the vehicle is shut off before turning off the radio and GPS to reduce clutter on the APRS channel and prevent the vehicle battery from discharging.


This Automatic Switch is installed between the vehicle battery and the DC load. Typically, the load is a amateur radio mobile transceiver and accessories. Standard installation involves installing this switch in the DC feed to the radio. This usually takes 10 minutes or less. If you want to change the factory set points, then you will need to remove the cover and flip a couple of small switches.

Switch Settings

The voltage threshold and the shutdown delay are configurable with DIP switches. The switch settings are shown below and are also printed on the bottom of the circuit board.


  • Dimensions: 3.3" (84 mm) long, 4.75" (121 mm) wide, 1.35" (34 mm) tall
  • Weight: 5.5 ounces (158 grams) with Anderson connectors
  • Input Voltage: 7-20 volts DC
  • Input Current: 1.734 mA @ 12.0 VDC with LED off and relay off
  • 60 mA @ 13.8 VDC with LED off and relay on
  • 61.25mA @ 12.7 VDC with LED on and relay on
  • Load Current: 30 amps holding, 20 amps switching
  • Internal Protection: Thermal, Over Current
  • Case Material: Flame retardant ABS plastic. UL's best flame rating of 94-5VA (case only).

  • Voltage Set Points: 11.8, 12.1, 12.7, 13.05 volts DC. Selectable by DIP switch.

    Time Delays: 0, 5, 10, 20 minutes. Selectable by DIP switch.

    12v Voltage Sensing Automatic Power Off Switch
    AP03-12-volt-accessory-automatic-power-off-switchRetail: $74.95Sale Price: $59.95 (You save: 20%)

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