Method and apparatus for monitoring battery voltage

A method for monitoring the charge on a battery and for maintaining such charge between upper and lower threshold voltages, fully below the ideal, fully charged voltage for the battery and for shutting off charging current to the battery when the battery voltage falls below a minimum voltage less than said lower threshold and at which the battery is considered defective, comprising the steps of:

• providing a reference voltage that is related to such ideal voltage,
• sensing the voltage of the battery being monitored to provide a sensed voltage,
• comparing the sensed voltage with the reference voltage to provide a first signal representing a battery voltage above said ideal voltage, a second signal representing a battery voltage below said ideal voltage, and a third signal representing a battery voltage at or below said minimum voltage,
• supplying current to the battery in response to said second signal but shutting off the supply of current in response to said first signal whereby current flow into the battery oscillates between on and off conditions as the battery voltage respectively falls below and rises above said ideal voltage, and
• shutting off the supply of current to the battery in response to the third signal.

A method of maintaining a charge on a battery after the battery has been charged to a voltage which is equal or close to its ideal standby voltage by controlling the supply and interruption of current flow to the battery, comprising:

• providing a reference voltage that is related to such ideal voltage;
• sensing the voltage of the battery to provide first and second sensed voltages representative of the actual voltage of the battery being monitored;
• comparing the first sensed voltage with the reference voltage to provide first and second signals respectively depending on whether the first sensed voltage is greater or less than the reference voltage, said first and second signals respectively representing maximum and intermediate battery voltages above an upper threshold slightly greater than said ideal voltage and below a lower threshold slightly less than said ideal voltage;
• comparing the second sensed voltage with the reference voltage to provide a third signal when the second sensed voltage is less than the reference voltage, said third signal representing a minimum battery voltage less than said intermediate battery voltage;
• supplying current to the battery in response to said second signal;
• interrupting the flow of current to the battery in response to the first and third signals,
• said comparing step causing an oscillation between said first and second signals when the first sensed voltage is nearly equal to the reference voltage thereby to supply current to the battery in pulses between said upper and lower thresholds.

A method for maintaining an ideal full charge on a lead-acid battery by supplying the battery with charging current when the battery voltage is between upper and lower threshold voltages respectively above and below said ideal charge and when the battery voltage is between the lower threshold voltage and a predetermined minimum voltage representing a defective battery or crossed wires, and so as not to supply current to the battery when the battery voltage is above the upper threshold or below the predetermined minimum, comprising:

• providing a reference voltage that has a predetermined relationship to such ideal battery voltage at the ambient temperature of the battery and thereby to said upper and lower threshold voltages at such temperatures,
• sensing the voltage of the battery being monitored to provide a first monitoring voltage which represents the actual voltage of the battery when it is in a range from above said upper threshold voltage to said predetermined minimum voltage,
• sensing the voltage of the battery being monitored to provide a second monitoring voltage which represents the actual voltage of the battery below said predetermined minimum voltage,
• comparing the first and second monitoring voltages with the reference voltage,
• supplying current to the battery when said comparison with the first monitoring voltage indicates that the battery voltage is between said predetermined minimum voltage and said upper threshold voltage, and
• ceasing the supply of current to the battery when said comparison with the first monitoring voltage indicates that the battery voltage is above said upper threshold voltage and when said comparison with the second monitoring voltage indicates that the battery voltage is below said predetermined minimum voltage.

An apparatus for monitoring the voltage on a lead-acid battery so as to supply the battery with charging current when the battery voltage is between upper and lower threshold voltages respectively above and below an ideal voltage for the battery and when the battery voltage is between the lower threshold voltage and a predetermined minimum voltage representing a defective battery or crossed wires, and so as not to supply current to the battery when the battery voltage is above the upper threshold or below the predetermined minimum, comprising:

• means for providing a temperature -dependent reference voltage that has a predetermined relationship to such ideal battery voltage and thereby to said upper and lower threshold voltages and a fixed reference voltage,
• first means for sensing the voltage of the battery being monitored to provide a first monitoring voltage which represents the actual voltage of the battery when it is in a range of voltages from above said upper threshold voltage to said predetermined minimum voltage,
• second means for sensing the voltage of the battery being monitored to provide a second monitoring voltage which represents the actual voltage of the battery below said predetermined minimum voltage,
• controlling comparator means responsive to the first and second sensing means for respectively comparing the first and second monitoring voltages with the temperature-dependent reference voltage to provide output signals representative of the voltages sensed, and
• switching comparator means responsive to the controlling comparing means for comparing said output signals with the fixed reference voltage to supply current to the battery when the first monitoring voltage is representative of a battery voltage between said upper threshold voltage and said minimum voltage, to cease the supply of current to the battery when the first monitoring voltage is representative of a battery voltage above said upper threshold voltage and to cease the supply of current to the battery when the second monitoring voltage is representative of a battery voltage below said predetermined minimum voltage.

An apparatus for monitoring the voltage on a battery so as to supply the battery with charging current when the battery voltage is between upper and lower thresholds respectively above and below an ideal voltage for the battery, comprising:

• means for providing a reference voltage that is related to such ideal battery voltage,
• means for establishing a voltage which represents the actual voltage of the battery being monitored,
• means for comparing the established voltage with the reference voltage, and
• means for supplying current in pulses to the battery when the established voltage is representative of a battery voltage above said lower threshold.