Switching between alternative power sources

Alan_at_Hahndorf Registered Users Posts: 2

Although not strictly wind and solar, I'm looking for a 12 volt DC switch that will automatically switch power to an auxiliary battery when the vehicle's engine is turned off and revert back to running the car fridge from the vehicle's alternator, once the vehicle starts operating again.

Is there such an animal and if so, what is it called?

The auxiliary battery is being charged through a 15A DC-DC controller and I want to maximise the recharging of that battery by running the car fridge from the excess current produced by the alternator, when on the move.



  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    It's called a single pole double throw relay, the coil would be powered by an ignition circuit, see link, just substitute 12VDC 
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  • Alan_at_Hahndorf
    Alan_at_Hahndorf Registered Users Posts: 2

    Dear mcgivor,

    Thank you very much for your answer and for being so prompt.

    Really appreciated.


  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    Describe your setup in more detail.  You may already have the device you need in the vehicle. That is, a vehicle battery supplies power to the 12VDC system (radio, lights, etc.) when engine is not running.  Start the engine, DC voltage climbs above approx. 13VDC, and the battery is no longer supplying power.

    What power source is the controller using (you said not strictly wind or solar).
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