I have this and it works nice. It is not loud either when it switches over. The only thing I don't like is that the relay area that gets the trigger voltage (small nuts) gets very warm, almost hot, so I am thinking to put a bulb in series, but then it may not be enough to trigger the relay. I don't care or need the stupid control that sells separate, as it is ridiculously expensive. Aside from that the main power connections handle my battery current flow well. I using a kinetic600 that doesn't need a relay anyway since that technology battery does not drain main battery because it is a slightly higher voltage and charges quickly. I would suggest a regular small 12v relay to energize this relay because it probably takes more juice than a normal accessory out from your car or radio can handle.
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