Circuit and method for determining battery impedance increase with aging
First Claim
1. A method of determining an internal impedance of a battery, comprising:
- (a) analyzing current flowing through the battery or a voltage of the battery to determine if a transient condition due to a change of a load is occurring;
(b) if a transient condition has been detected in step (a), determining when the transient condition has ended;
(c) measuring a voltage of the battery while a current flows through the battery, and measuring the current;
(d) determining a present depth of discharge (DOD) of the battery;
(e) determining a value of open circuit voltage of the battery for the present DOD; and
(f) computing the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by the current.
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Accused Products
Abstract
An internal impedance of a battery (30) is automatically determined by operating a processor (13) to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring and determining when the transient condition has ended. A voltage of the battery is measured while a steady current is being supplied by the battery. The present depth of discharge (DOD) of the battery is determined and a database is accessed to determine a corresponding value of open circuit voltage. The internal impedance is computed by dividing the difference between the measured voltage of the battery and the open circuit voltage at the present DOD by an average value of the steady current. A remaining run-time of the battery can be determined using a total zero-current capacity of the battery, integrating the current to determine a net transfer of charge from the battery, determining a value of total run-time that would be required to reduce the voltage of the battery to a predetermined lower limit, determining the duration of the integrating, and determining the remaining run-time by subtracting the duration of the integrating from the total run-time.
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Citations
37 Claims
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1. A method of determining an internal impedance of a battery, comprising:
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(a) analyzing current flowing through the battery or a voltage of the battery to determine if a transient condition due to a change of a load is occurring;
(b) if a transient condition has been detected in step (a), determining when the transient condition has ended;
(c) measuring a voltage of the battery while a current flows through the battery, and measuring the current;
(d) determining a present depth of discharge (DOD) of the battery;
(e) determining a value of open circuit voltage of the battery for the present DOD; and
(f) computing the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by the current.
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2. A method of determining an internal impedance of a battery, comprising:
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(a) operating a processor to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring;
(b) if a transient condition has been detected in step (a), operating the processor to determine when the transient condition has ended;
(c) operating the processor to measure a voltage of the battery while a steady current is being supplied by the battery;
(d) operating the processor to determine the present depth of discharge (DOD) of the battery;
(e) operating the processor to access a database stored in a memory to determine a value of open circuit voltage of the battery for the present DOD; and
(f) operating the processor to compute the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by an average value of the steady current. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of determining a remaining run-time of a battery, comprising:
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(a) determining an internal impedance of the battery by i. operating a processor to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring, ii. if a transient condition has been detected, operating the processor to determine when the transient condition has ended, iii. operating the processor to measure a voltage of the battery while a steady current is being supplied by the battery, iv. operating the processor to determine the present depth of discharge (DOD) of the battery, v. operating the processor to access a database stored in a memory to determine a value of open circuit voltage of the battery for the present DOD, and iv. operating the processor to compute the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by an average value of the steady current; and
(b) determining a remaining run-time of the battery by obtaining or using a previously obtained value of a present total zero-current capacity Qmax of the battery, integrating the current to determine a net transfer of charge from the battery, determining a value of total run-time that would be required to reduce the voltage of the battery to a predetermined lower limit, determining the duration of the integrating, and determining the remaining run-time by subtracting the duration of the integrating from the total run-time.
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18. A system for determining an internal impedance of a battery, comprising:
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(a) a processor coupled to a digital bus, and a memory for storing data representing the relationship between the OCV (open circuit voltage) and DOD (depth of discharge) of the battery, a first ADC, and a second ADC all coupled to the digital bus;
(b) a first program stored in the memory for execution by the processor for i. analyzing current flowing through the battery to determine if a transient condition due to a change of the current is occurring and determining when the transient condition has ended, and ii. controlling the first ADC to measure a voltage of the battery while a steady current flows through the battery, the first ADC being coupled to the battery;
(c) a second program stored in the memory for execution by the processor for i. determining a present depth of discharge (DOD) of the battery, and ii. determining a value of open circuit voltage of the battery for the present DOD; and
(d) a third program stored in the memory for execution by the processor for computing the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by an average value of the steady current. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A system for determining a remaining run-time of a battery, comprising:
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(a) a processor coupled to a digital bus, and a memory for storing data representing the relationship between the OCV (open circuit voltage) and DOD (depth of discharge) of the battery, a first ADC, and a second ADC all coupled to the digital bus;
(b) a first program stored in the memory for execution by the processor for determining an internal impedance of the battery by analyzing current flowing through the battery to determine if a transient condition due to change of current is occurring, determining when the transient condition has ended, measuring a voltage of the battery while a steady current is being supplied by the battery, determining the present depth of discharge (DOD) of the battery, accessing a database stored in a memory to determine a value of open circuit voltage of the battery for the present DOD, and computing the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by an average value of the steady current; and
(c) a second program stored in the memory for execution by the processor for determining a remaining run-time of the battery by obtaining or using a previously obtained value of a present total zero-current capacity Qmax of the battery, integrating the current to determine a net transfer of charge from the battery, determining a value of total run-time that would be required to reduce the voltage of the battery to a predetermined lower limit, determining the duration of the integrating, and determining the remaining run-time by subtracting the duration of the integrating from the total run-time.
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34. A system for determining an internal impedance of a battery, comprising:
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(a) means for operating a processor to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring;
(b) means for operating the processor to determine when a detected transient condition has ended;
(c) means for operating the processor to measure a voltage of the battery while a steady current is being supplied by the battery;
(d) means for operating the processor to determine the present depth of discharge (DOD) of the battery;
(e) means for operating the processor to access a database stored in a memory to determine a value of open circuit voltage of the battery for the present DOD; and
(f) means for operating the processor to compute the internal impedance by dividing the difference between the measured voltage of the battery and the value of the open circuit voltage at the present DOD by an average value of the steady current. - View Dependent Claims (35, 36, 37)
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Specification