David Root: I just built one of those discharger cut-off devices. I think that the Radioshack relay is not the way to go. Even though it is rated to release at 3.5v, it actually is releasing at 6.5v, and thats wired without a resistor. I suspect that the quality of this relay leaves alittle to be desired. I'm going to try one that is specific to a car application. Does your Bosch relay have a part or model number on it ? LC