Method and device for measuring pure resistance of on-vehicle battery by periodically measuring a discharge current and terminal voltage while a rush current flows into a constant load
First Claim
1. A method of measuring a pure resistance of an on-vehicle battery for supplying electric power to loads in the vehicle comprising the steps of:
- periodically measuring a discharge current and terminal voltage of the battery while a rush current flows into a predetermined constant, the rush current first monotonically increasing from zero to a peak value and subsequently monotonically decreasing from the peak value to a steady value;
computing a first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current, said current-voltage characteristic indicating a correlation between the discharge current and terminal voltage of the battery; and
computing an intermediate value of two values of the terminal voltage change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component when the first and second approximate expressions include the voltage drop, wherein the intermediate value computed is measured as the pure resistance of the battery.
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Abstract
A discharge current and terminal voltage of the battery are periodically measured while a rush current flows into a predetermined constant load of the loads. The rush current first monotonically increases from zero to a peak value and subsequently monotonically decreases from the peak value to a steady value. A first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current are computed. An intermediate value of two values of the terminal voltage change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component is computed when the first and second approximate expressions include the voltage drop. The intermediate value computed is measured as the pure resistance of the battery.
14 Citations
13 Claims
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1. A method of measuring a pure resistance of an on-vehicle battery for supplying electric power to loads in the vehicle comprising the steps of:
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periodically measuring a discharge current and terminal voltage of the battery while a rush current flows into a predetermined constant, the rush current first monotonically increasing from zero to a peak value and subsequently monotonically decreasing from the peak value to a steady value;
computing a first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current, said current-voltage characteristic indicating a correlation between the discharge current and terminal voltage of the battery; and
computing an intermediate value of two values of the terminal voltage change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component when the first and second approximate expressions include the voltage drop, wherein the intermediate value computed is measured as the pure resistance of the battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
calculating a first difference in the terminal voltage of the battery between the first and second approximate expressions at a point of the discharge current being zero;
calculating a second difference between voltage values at a current value being zero and at a current value being twice the peak current value calculated on the basis of said difference expression;
calculating a third difference between voltage values at the peak current value and at twice the peak current value; and
computing the voltage drop by multiplying the first difference by the ratio of the third difference to the second difference.
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12. The method as claimed in any one of claims 1-3, wherein when the rush current, which monotonically increases up to a peak value in a short period of time without an occurrence of concentration polarization, flows into the constant load, the first approximate expression is linear and a gradient of the first approximate expression is used for computing the intermediate value.
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13. A device for measuring a pure resistance of an on-vehicle battery for supplying electric power to loads in the vehicle comprising:
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measuring means for periodically measuring a discharge current and terminal voltage of the battery while a rush current flows into a predetermined constant load of the loads, the rush current first monotonically increasing from zero to a peak value and subsequently monotonically decreasing from the peak value to a steady value;
first computing means for computing a first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current, said current-voltage characteristic indicating a correlation between the discharge current and terminal voltage of the battery measured by the measuring means; and
second computing means for computing an intermediate value of two values of the terminal voltage, change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component when the first and second approximate expression include the voltage drop, wherein the intermediate value computed by the second computing means is measured as the pure resistance of the battery.
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Specification