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Automotive Security circuit to cause power failure - isolated dual batteries

Discussion in 'Power Electronics' started by wayne.workman2012, Aug 31, 2015.

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  1. wayne.workman2012


    Aug 31, 2015
    Hello everyone, this is my first post here. I'm somewhat familiar with very basic circuitry but I need some help with this particular problem.

    I'm setting up a low-power computer with wifi in my car (something like a Raspberry Pi) and I am intending to power it via a secondary battery and a four-terminal solenoid battery isolator.

    However - if any car doors or hatches open - I want the device to be turned off for security reasons.

    I have been thinking this might be possible with the use of two relays. One normally open relay and one normally closed relay - wired in series. The normally closed would have it's controller power wired in parallel to the dome light, while the normally open relay's controller wires would be connected to the engine starting battery. This way, if either the dome lights come on or the main battery is disconnected, my computer will turn off immediately due to the power being cut.

    Is this possible? Does the circuit I described make sense? Can one power source be used to control the open/closed state of another power source?

    Also - is it absolutely necessary to use a deep cycle or marine battery as the second battery? I know they put off toxic fumes when they are being charged! I'd really like to use something like a sealed 65ah solar battery or something similar.

    Any advice is very appreciated, Thanks,
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