Importance

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Abstract

A device for use in conjunction with a battery in a motor vehicle which is connected to an electrical load. The device includes a microprocessor which iteratively inputs the value of the battery voltage as well as the ambient temperature surrounding the battery. The microprocessor also sets a cut off voltage level which increases proportionately with elapsed time from the last system reset of the device and preferably adjusts the cut off voltage level as a function of the ambient temperature of the battery. The cut off voltage level is set so that when the battery reaches the cut off voltage, sufficient energy remains in the battery for engine ignition, i.e. engine starting. The microprocessor then iteratively compares the battery voltage signal with the cut off voltage level and generates an output signal whenever the battery voltage is less than or equal to the cut off voltage level. The output signal initiates a timer which counts down a relatively short period of time, for example two minutes. At the end of the two minute period and assuming that a system reset did not occur during the activation of the timer, the device generates a battery disconnect signal which disconnects the battery from the electrical load of the vehicle. In this fashion, the device of the present invention ensures that the battery retains sufficient electrical charge or energy for subsequent vehicle ignition. The device also is responsive to an ignition attempt or the activation of a switch on the dashboard of the vehicle to reconnect the electrical load to the battery.

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First Claim