Battery state of charge monitor

A method of monitoring the state of an electrical energy source comprising the steps of:

• sensing the direction and amount of current flow into and out of the energy source as a first signal;
• providing an integrating circuit including a capacitive element having an effective capacity of more than 0.01 farad and a time constant resistor through which the capacitor charges or discharges, a supply voltage input, and an input for receiving the first signal from the current sensor;
• energizing the circuit by operative connection of the supply voltage input to the energy source being monitored, the circuit having a minimum drain current that is less than or equal to 1.0 mA;
• and
• charging the capacitive element in response to the first signal in one direction, at a charge rate that is in proportion to the amount of the first signal, and discharging the capacitive element in response to the first signal in the opposite direction, at a discharge rate that is in proportion to the amount of the first signal, thereby providing an integrated first signal corresponding to the state of charge of the energy source.

An apparatus for monitoring the state of an electrical energy source comprising:

• a current sensor for producing an output current signal related to the magnitude and direction of the current flowing to or from said energy source;
• an integrator circuit having a feedback path including a charge storing capacitive element with low self leakage, a resistor which in conjunction with the capacitive element provides a time constant for integrating the output current signal on a continuous basis as the current flows to and from said energy source, and an output for providing the integrated output signal stored in the capacitive element corresponding to the state of charge of the energy source;
• the capacitive element being charged at a rate proportional to the magnitude of the sensed current when the current flow is in one direction and discharged at a rate proportional to the magnitude of the sensed current when the current flow is in the opposite direction;
• means for sensing and processing the sensed magnitude and direction of the output signal and the amplitude of the integrated output signal, thereby to indicate the charge condition of the energy source;
• a device to monitor a temperature corresponding to the temperature of the energy source;
• and
• a circuit, responsive to the monitored temperature, providing a first signal corresponding to the capacity of the energy source at the monitored temperature.

A method of monitoring the state of an electrical energy source comprising the steps of:

• sensing the direction and amount of current flow into and out of the energy source;
• integrating the net amount of said current flow continuously as current flows into and out of said energy source;
• the step of integrating comprising charging a capacitive element having an effective capacity of 0.01 farad or more in response to current flow in one direction, at a charge rate that is in proportion to the amount of current flow, and discharging the capacitive element in response to current flow in the opposite direction at a discharge rate that is in proportion to the amount of current flow, thereby providing an integrated output signal corresponding to the state of charge;
• and
• determining whether or not the energy source has a short condition in response to the sensed charging current flow and the sensed integrated output signal.

A method of monitoring the state of an electrical energy source comprising the steps of:

• sensing the direction and amplitude of current flow into and out of the energy source as a first signal;
• providing an integrator circuit having a feedback path including a charge storing capacitive element with low self leakage, and a resistor which in conjunction with the capacitive element provides an integration time constant;
• charging the capacitive element in response to the first signal in one direction, at a charge rate that is in proportion to the amount of the first signal, and discharging the capacitive element in response to the first signal in the opposite direction, at a discharge rate that is in proportion to the amount of the first signal, thereby providing an integrated output signal stored in the capacitive element corresponding to the state of charge of the energy source;
• sensing and processing the direction and amplitude of the first signal and the amplitude of the integrated output signal, thereby to indicate the condition of the electrical energy source;
• monitoring a temperature corresponding to the temperature of the electrical energy source;
• and
• providing a signal corresponding to the state of the electrical energy source at the monitored temperature.

An apparatus for monitoring the state of an electrical energy source having a charge capacity that changes with the temperature comprising:

• a current sensor for producing a first signal related to the magnitude and direction of the current flowing to or from said energy source;
• a capacitive element having a capacitance of 0.01 farad or more connected to said current sensor for integrating said first signal on a continuous basis as the current flows to and from said energy source, said capacitive element charging at a rate proportional to the magnitude of the sensed current when the current flow is in one direction and discharging at a rate proportional to the magnitude of the sensed current when the current flow is in the opposite direction and producing a second signal corresponding to the state of charge of the energy source;
• a device for monitoring a temperature corresponding to the temperature of the energy source;
• and
• a circuit, responsive to the second signal and the sensed temperature, for providing a third signal corresponding to the capacity of the energy source at the sensed temperature.

A method of monitoring the state of an electrical energy source comprising the steps of:

• sensing the direction and amount of current flow into and out of the energy source;
• integrating the net amount of said current flow continuously as current flows into and out of said energy source and providing a first signal corresponding to the net charge in the energy source;
• the step of integrating comprising charging a capacitive element having an effective capacity of more than 0.01 farad in response to current flow in one direction, at a charge rate that is in proportion to the amount of current flow, and discharging the capacitive element in response to current flow in the opposite direction, at a discharge rate that is in proportion to the amount of current flow;
• monitoring a temperature corresponding to the temperature of the energy source;
• and
• adjusting the first signal in response to the sensed temperature and providing a second signal corresponding to the charge capacity of the energy source at the sensed temperature.

An apparatus for monitoring the state of an electrical energy source comprising:

• a current sensor for producing an output signal related to the magnitude and direction of the current flowing to or from said energy source;
• an operational amplifier having a capacitive element in the feedback path and a time constant resistor through which the output signal is integrated on a continuous basis as the current flows to and from said energy source and an output for providing the integrated output signal corresponding to the state of charge of the energy source, the capacitive element having an effective capacitance of 0.01 farad or more and charging at a rate proportional to the magnitude of the sensed current when the current flow is in one direction, discharging at a rate proportional to the magnitude of the sensed current when the current flow is in the opposite direction, and having a self-discharge rate when no sensed current flows to or from the energy source;
• and
• a circuit for detecting a short circuit in the energy source.

An apparatus for monitoring the state of an electrical energy source comprising:

• a current sensor for producing an output signal related to the magnitude and direction of the current flowing to or from said energy source;
• an operational amplifier having a capacitive element in the feedback path and a time constant resistor through which the output signal is integrated on a continuous basis as the current flows to and from said energy source and an output for providing the integrated output signal corresponding to the state of charge of the energy source, the capacitive element charging at a rate proportional to the magnitude of the sensed current when the current flow is in one direction, and discharging at a rate proportional to the magnitude of the sensed current when the current flow is in the opposite direction;
• and
• means for determining whether or not the energy source is defective in response to the charging current flow and the integrated output signal.

A method of monitoring the state of an electrical energy source comprising the steps of:

• sensing the direction and amount of current flow into and out of the energy source;
• integrating the net amount of said current flow continuously as current flows into and out of said energy source;
• the step of integrating comprising charging a capacitive element in response to current flow in one direction, at a charge rate that is in proportion to the amount of current flow, and discharging the capacitive element in response to current flow in the opposite direction at a discharge rate that is in proportion to the amount of current flow, thereby providing an integrated output signal corresponding to the state of charge of the energy source;
• and
• determining whether or not the energy source is defective in response to the charging current flow and the integrated output signal.