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Battery disconnect device
| Details |
Inventors: Sloan, Jeffrey M.;
Assignee:
Primary Examiner: Hickey; R. J.
Assistant Examiner:
Attorney, Agent or Firm: Gifford, Groh, Sprinkle, Patmore and Anderson
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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DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION With reference first to FIG.
1, a preferred embodiment of the device of a circuit 10 of the present invention is thereshown for use with a battery 12 which is electrically connected through a switch 14 to an electrical load 16.
The switch 14 will subsequently be described in greater detail.
Additionally, the battery 12 is used with a motor vehicle having an engine, such as an automobile, and the load 16 comprises the electrical components of the vehicle.
These electrical components include, for example, headlights, radio, hazard lights and the like.
Still referring to FIG.
1, the circuit 10 includes a microprocessor 18 which operates under control of a computer program.
The computer program for driving or controlling the microprocessor 18 will be subsequently described in greater detail.
Typically, the computer program is contained in read only memory (ROM) contained in the microprocessor, but external ROM can be alternatively used.
Additionally, although the circuit 10 is preferably microprocessor based, it can alternatively be hard wired logic, ASIC technology, discrete components, or the like without deviation from the spirit or scope of the present invention.
Still referring to FIG.
1, the battery 12 is connected through a diode 200 and voltage regulator 202 to the power supply input 204 and 206 of the microprocessor 18.
The negative terminal of the battery 12 is connected to the ground terminal 206 of the microprocessor.
A varistor 234 is also connected in parallel across the positive and negative terminals of the battery 12 to protect the circuit 10 from voltage spikes.
A crystal 208 and resistor 210 parallel combination are also coupled to a clock input of the microprocessor 18.
The crystal 208 and resistor 210 provide the appropriate oscillator frequency to the microprocessor 18 in the conventional fashion.
The positive terminal of the battery 12 is connected through the diode 200 and the voltage disorder network comprising resistors 212, 213, and 214 to one input 218 of a voltage comparator 216
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