BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a testing technology for battery, and more particularly, to a method for rapidly estimating for a remaining capacity of a battery.

2. Description of the Prior Art

With the gradual depletion of petrochemical energy and the continuous improvement of power battery technology, people are paying more and more attention to issues such as energy conservation, carbon reduction, green energy, and environmental sustainability on facing the destruction of the ecological environment and extreme climate changing. The market share of electric vehicles, such as electric bus, electric car, and electric motorcycle, is rising due to the support of many governments worldwide. It is, thus, expected that the electric vehicle will become mature and popular in a few years. The power battery will become the main power source for the driving of electric vehicles and electricity, etc. However, these power batteries will gradually age and degrade with the usage time. There are many causes, which are observable indicators such as the reduction of remaining capacity of the battery and the battery Internal impedance increases, to the aging and degradation of batteries in the prior art.

In the prior art, as to a power battery pack of an electric vehicle, when the remaining capacity of the battery pack is less than 70%-80% of the nominal capacity of the battery pack leaving the factory, the prior art determines that the battery pack is not suitable for the electric vehicle, and the requirements of practical applications and security may not meet anymore. Therefore, the electric vehicle vendor and other related applications expect a method for estimating a status of aging and degrading and the performance of the battery, which are used to be the basis that the battery may be phased out and adapted for another purpose. After the processes such as battery classification, screening, matching, and reorganization mentioned above, for example, the degraded batteries can be used in energy storage systems to achieve the advantages of extending the battery's full life cycle, improving use efficiency, and reducing initial purchase costs. In addition, how to quickly and accurately evaluate the remaining capacity of the used electric vehicle battery will also be a bottleneck to the used electric vehicle trading market due to the increasing number of electric vehicles in the future. Therefore, the present invention discloses a method for rapidly estimating for a remaining capacity of a battery, which will be an excellent reference for evaluating the remaining capacity of the battery in the future

U.S. Patent Publication No. 2007/0252600 (Diagnosis method for state-of-health of batteries) discloses a method for diagnosing the state of health of the battery (SoH), which uses a constant current to discharge a battery for a long time, and measures the battery's voltage and voltage changing rate to evaluate the health of the battery. Therefore, US Pub. 2007/0252600 cannot meet the urgent need to rapidly diagnose the remaining capacity of a battery. U.S. Patent Publication No. 2009/0128097 (Method and system for tracking battery state of health) also discloses a method for determining the state of health of a battery; that is, calculating the battery charge via the charging period and the discharging period and comparing or analyzing with the pre-set capacity of the battery. Similarly, US Pub. 2009/0128097 cannot meet the urgent need to rapidly diagnose the remaining capacity of a battery due to the long diagnosing time. U.S. Pat. No. 6,281,683 (Rapid determination of present and potential battery capacity) also discloses a method using a plurality of discharge current pulses and a plurality of leaving-along periods, and then measuring the battery voltage during the pulse current period and the battery open-circuit voltage (Voc) during the leaving-along period respectively, and calculating the voltage difference between each pulse by lookup table or equations to measure the remaining capacity and the maximum charging capacity of the battery. However, the state of the battery during the battery test was not taken into consideration; moreover, the realistic open-circuit voltage of the battery cannot be accurately measured, causing the estimation errors, because the leaving-along period is too short. TW Patent Application No. 098127249 also discloses a method with establishing a controlled discharge path inside the battery module. The battery discharge current is a constant value despite the variation of system loading current. The internal resistance measurement, which is made by establishing this constant battery current, can be the base of the relation between the pre-set internal resistance and capacity, and to the estimation for the capacity of the battery by looking up the table. The method merely takes the discharging status of the battery instead of aging and degrading and other conditions into consideration. It thus would cause the uncertainty of the discharge voltage measurement. Besides, the realistic open-circuit voltage of the battery cannot be accurately measured in a short time, which causes the calculation errors to the internal resistance. Therefore, the methods and devices in the prior art for diagnosing the status of the battery and its application have limitations and shortcomings, comprising: measuring accurately the remaining capacity of the battery during a whole of charging and discharging period taking a long time to diagnose, which cannot obtain the status of battery instantly.

In traditional battery remaining capacity (RC) estimation methods, the remaining capacity of the battery is estimated by increasing or decreasing the initial battery remaining capacity value, wherein the initial remaining capacity of the battery is determined according to the open-circuit voltage and read from the lookup table. Besides, the degree of increase (or decrease) in the remaining capacity of the battery is obtained by (Coulomb) counting the charges entering or leaving the battery. Specifically, batteries typically have specific voltage-capacity characteristics. In the lookup table, the remaining capacity of the battery is corresponding to the reference voltage by charging the battery, which has been completely discharged, till the open-circuit voltage reaching the reference voltage and counting the charge entering to the battery during charging. Thus, the counted Coulomb charge is corresponding to the remaining capacity of the battery at the reference voltage. However, due to the accumulated error of the Coulomb counting, the lookup table is not accurate. Besides, when the battery is completely discharged, the battery has a residual capacity (RES), which changes with the battery's voltage, current, temperature, etc., reducing the accuracy in the estimation process.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the present invention to provide a method for rapidly estimating for a remaining capacity of a battery, which could fast and accurately calculate the remaining capacity of the battery under test, which can be the basis of battery lifetime estimation and battery usage analysis.

The present invention discloses a method for rapidly estimating for a remaining capacity of a battery, comprising performing a constant current charge to the battery under test in a first period, instantly capturing a voltage and a temperature of a positive electrode of the battery under test in a default frequency, and generating a voltage-time graph; after leaving the battery under test along for a second period, and instantly capturing the voltage and the temperature of the positive electrode of the battery under test in the default frequency; calculating a voltage rising rate of the battery under test during a constant current charging period; calculating a voltage drop rate of the battery under test during a leaving-along period; calculating a critical sample time; applying the critical sample time, and comparing the voltage-time graph measured in the constant current charging period, to obtain a critical sampling voltage; calculating a voltage difference slope of the battery under test; calculating a charging time, which is consumed by charging the battery under test from a lower bound voltage to an upper bound voltage with the constant current; calculating a compensation ratio value on the remaining capacity of the battery under test; and calculating the remaining capacity of the battery under test.

In an embodiment of the present invention, the first period is 180-240 seconds.

In an embodiment of the present invention, the second period is 30-60 seconds.

In an embodiment of the present invention, the default frequency ≥1 Hz.

In an embodiment of the present invention, the battery under test in an environmental temperature is in a safe temperature of the battery under test.

In an embodiment of the present invention, the constant current for charging is 0.2 C-2 C.

In order to make the objects, technical solutions and advantages of the present invention become more apparent, the following relies on the accompanying drawings and embodiments to describe the present invention in further detail.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

