Vehicle security system siren with backup rechargeable battery

摘要

A vehicle security siren that includes a rechargeable back-up battery and an electronic circuit that minimizes current drain from the vehicle's battery by controlling the rate at which the siren's back-up battery is charged by the vehicle's battery. The circuit charges the siren's battery at a relatively high rate when the vehicle engine is running or the ignition is on, and by a low charging rate at other times. This multi-level charging rate preserves the vehicle's battery charge particularly if the vehicle is not driven for any extended time period. The circuit includes a back-up battery condition detector that issues a warning signal in the event of failure of the back-up battery. The circuit also limits the maximum siren duration in the event that either the vehicle's battery or the security system is disconnected from the siren.