The subject matter herein generally relates to a method and apparatus of estimating a state of health (SOH) of a battery.
A concept of state of health (SOH) is defined as an index for indicating the strength of a battery for electric vehicles, etc. The battery has an aging effect. The SOH detects a current state of the battery by predicting an aging degree in advance.
Implementations of the present technology will now be described, by way of example only, with reference to the attached figures.
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure.
The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like.
The present disclosure is described in relation to a method and an apparatus for estimating state of health (SOH) of a battery.
At block 101, an internal resistance (R) of a battery can be measured. A voltage value and a current value of the battery can be measured via a voltage sensing unit and a current sensing unit. The internal resistance can be calculated according to the measured current value and voltage value. The internal resistance can be also measured by an alternating current impedance method.
At block 102, a voltage drop (ΔV) can be calculated via multiplying the measured internal resistance by a preset current lower limit value (I) at the available capacity.
At block 103, an OCV lower limit value can be calculated via adding the ΔV and a voltage lower limit (V) at the available capacity.
At block 104, a correlation table (shown in
At block 105, a SOC lower limit value (SOC_1) can be obtained according to the calculated OCV lower limit value and the established correlation table.
At block 106, a SOH value at the moment can be calculated by a relationship of SOH=100%−SOC_1. Therefore, the estimating SOH of a battery can be completed.
The memory unit 210 can store the correlation table of the OCV value and the SOC.
The voltage sensing unit 220 and current sensing unit 230 can measure current and voltage of a battery according to the control of the controller 240, and makes it possible to calculate the internal resistance of a battery. In general, the internal resistance of the battery is to sum up impedance such as a direct current (DC) resistance, or a spreading resistance etc., and is difficult to measure in real time. For this reason, it is good to measure only a component of pure DC resistance. It is preferable to measure the resistance within a rapid time period, but the measurement time is arbitrarily set to one second in consideration of hardware and a calculation time of other information.
When estimating SOH of a battery, the controller 240 can control the voltage sensing unit 220 and the current sensing unit 230 to measure a voltage and a current of the battery at the moment. The measured voltage and current can be transmitted to the microprocessor unit 250 via the controller 240. Simultaneously, the controller 240 can control the memory unit 210 to transmit the correlation table to the microprocessor unit 250.
The internal resistance of the battery can be calculated via the microprocessor unit 250 according to the measured voltage and current. A ΔV value of the battery can be calculated via the microprocessor unit 250 according to the calculated internal resistance. An OCV lower limit value can be calculated via the microprocessor unit 250 according to the calculated the ΔV. A SOC lower limit value (SOC_1) can be obtained via the microprocessor unit 250 according to the calculated OCV lower limit value and the established correlation table in the memory unit 210. The SOH value can be calculated via the microprocessor unit 250 according to the calculated SOC_1.
The apparatus of SOH of the battery 200 which can be combined with the method of estimating SOH of the battery will now be described. When SOH estimation is requested, the controller 240 can obtain a voltage and a current of a battery via the voltage sensing unit 220 and the current sensing unit 230. The measured voltage and current can be transmitted to the microprocessor unit 250 via the controller 240. The internal resistance of the battery can be calculated via microprocessor unit 250 according to the measured voltage and current (101).
A ΔV value of the battery can be calculated via the microprocessor unit 250 according to the calculated internal resistance (102).
An OCV lower limit value can be calculated via the microprocessor unit 250 according to the calculated ΔV (103).
A SOC lower limit value (SOC_1) can be obtained via the microprocessor unit 250 according to the calculated OCV lower limit value and the established correlation table in the memory unit 210 (104, 105).
The SOH value can be calculated via the microprocessor unit 250 according to the calculated SOC_1 (106).
As described above, the SOH of the battery can be directly estimated by the relationship of the measured internal resistance and the OCV. The method of estimating SOH of the battery is simple, and the apparatus of estimating SOH of the battery is cost effective.
The embodiments shown and described above are only examples. Many details are often found in the art such as the other features of a method and an apparatus of estimating SOH of a battery. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the details, including in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.
Number | Date | Country | Kind |
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103112203 | Apr 2014 | TW | national |