Method and system for determining the capacity of a battery
First Claim
1. A method for estimating a capacity of a battery, comprising:
- estimating a steady-state voltage, an internal resistance, and an internal voltage drop of the battery caused by a density difference in a battery acid;
initializing a model describing the battery in order to estimate the capacity in accordance with estimated values of the steady-state voltage, the internal resistance, and the internal voltage drop of the battery;
stimulating the initialized model with a predefined load current characteristic in order to obtain a voltage response of the initialized model, representing a battery voltage, given the predefined load current characteristic; and
estimating the capacity of the battery by comparing the voltage response of the initialized model with a predefinable minimal battery voltage.
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Abstract
A method for estimating the capacity of a battery, including the following steps: estimation of a steady-state voltage UR, an internal resistance R1 and an internal voltage drop UK of the battery, caused by a density difference in the battery acid; initialization of a model describing the battery in order to estimate the capacity, using estimated values UR, R1 and UK; stimulation of the initialized model with predefined load current characteristic IBatt,stim, in particular a simulated load current characteristic of a consumer in operative connection with the battery, in order to obtain a voltage response UBatt,pred of the model, representing the battery voltage given the predefined load current characteristic; comparison of the voltage response UBatt,pred of the model with a predefinable, minimal battery voltage UBatt,limit, and estimation of the capacity of the battery by comparing UBatt,pred and Ubatt,limit.
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Citations
11 Claims
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1. A method for estimating a capacity of a battery, comprising:
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estimating a steady-state voltage, an internal resistance, and an internal voltage drop of the battery caused by a density difference in a battery acid;
initializing a model describing the battery in order to estimate the capacity in accordance with estimated values of the steady-state voltage, the internal resistance, and the internal voltage drop of the battery;
stimulating the initialized model with a predefined load current characteristic in order to obtain a voltage response of the initialized model, representing a battery voltage, given the predefined load current characteristic; and
estimating the capacity of the battery by comparing the voltage response of the initialized model with a predefinable minimal battery voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7)
the predefined load current characteristic includes a simulated load current characteristic of a consumer in operative connection with the battery.
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3. The method according to claim 1, further comprising:
determining the steady-state voltage, the internal resistance, and the internal voltage drop of the battery by a monitoring device that produces the estimated values for the steady-state voltage, the internal resistance, and the internal voltage drop of the battery on the basis of at least one of a measured battery voltage, a measured battery temperature, and a measured battery current in accordance with the initialized model describing the battery.
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4. The method according to claim 3, wherein:
the monitoring device includes a Kalman filter.
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5. The method according to claim 1, wherein:
in the comparison of the voltage response with the predefinable minimal battery voltage, a minimal value over time of the voltage response is used.
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6. The method according to claim 5, further comprising:
determining the capacity of the battery in accordance with a formula;
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7. The method according to claim 1, further comprising:
determining a load state of the battery on the basis of the estimated value for the steady-state voltage.
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8. A system for estimating a capacity of a battery, comprising:
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a predictor for estimating a battery voltage occurring given a particular load current characteristic, in which a steady-state voltage, an internal resistance an internal voltage drop caused by a density difference in a battery acid, and a particular load current characteristic are able to be supplied as input variables to a model used by the predictor to represent the battery, wherein;
an estimated battery voltage is obtained from the model as a response representing an estimation of the battery voltage with respect to the particular load current characteristic, and the estimated battery voltage is compared to a limiting voltage in order to estimate the capacity of the battery. - View Dependent Claims (9, 10, 11)
the battery includes a motor vehicle starter battery.
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10. The system according to claim 8, further comprising:
a monitoring device for estimating the steady-state voltage, the internal resistance, and the internal voltage drop caused by the density difference in the battery acid.
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11. The system according to claim 10, wherein:
the monitoring device includes a Kalman filter.
Specification