KR20110084633A - Apparatus and method for estimating the life span of battery - Google Patents

Abstract

PURPOSE: An apparatus and a method for estimating the life span of battery are provided to calculate temperature, current, and voltage by deciding certain period which is a SOC(State Of Charge) variable during a charge or a discharge process of a battery, thereby predicting a lifetime of a battery. CONSTITUTION: Sensing units(111,112,113) sense the voltage, current, and temperature of a battery. A data processing unit(121) collects the voltage, current, and temperature data from the sensing units. An operation unit(122) calculates a first OCV(Open Circuit Voltage) value from the collected currents, voltage, and temperature, and obtains a first SOC value corresponding to the first OCV according to a fixed OCV-SOC table. The operation unit calculates the second OCV value from the collected currents, voltage, and temperature after a progress of a specified time period, and obtains a second SOC value corresponding to the second OCV according to the OCV-SOC table fixed in advance. The calculation unit calculates an integrated current quantity of a battery among specified time period, a deterioration capacity of a battery using the first and the second SOC value, and a battery life state using the deterioration capacity.

Description

Apparatus and Method for estimating the life span of battery}

The present invention relates to an apparatus and method for estimating battery life, and more particularly, to an apparatus and method for estimating battery life by measuring a decrease in battery capacity in a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle.

Recently, as environmental considerations become more important, hybrid cars, plug-in hybrid cars, and electric vehicles are in the spotlight. In particular, technology development for batteries that are essential for such automobiles is considered very important. However, such batteries generally have a lifespan. In other words, with the use of the car, the internal resistance naturally increases, reducing the power, and on the other hand, the overall charging capacity. When such a performance degradation occurs, it is important to measure the performance of such a battery because it may cause a reduction in fuel efficiency and performance of a hybrid vehicle or a plug-in hybrid vehicle.

In general, a battery management system (BMS) predicts a state of health (SOH) to properly adjust a battery's charge / discharge output and state of charge (SOC) usage strategy. This protects the battery and reduces battery failure in the vehicle.

However, in the related art, the method of performing SOH estimation through the internal resistance of the battery is mostly performed by deteriorating the performance of the battery. According to this conventional method, the change in battery internal resistance can estimate the degree of battery power fading, but it is difficult to accurately estimate battery capacity fading.

The present invention is proposed to solve the problems posed by the prior art, and an object of the present invention is to provide an apparatus and method for predicting the life of a battery according to the capacity reduction of the battery without using the internal resistance of the battery.

It is another object of the present invention to provide an apparatus and method for predicting the life of a battery as the capacity of the battery decreases without introducing additional equipment.

In order to achieve the above object, an embodiment of the present invention provides a battery life prediction apparatus. The battery life prediction apparatus includes at least one battery used in a hybrid vehicle, a plug-in hybrid vehicle, or an electric vehicle, a sensing unit that senses voltage, current, and temperature for the at least one battery, and a voltage, current from the sensing unit. And a data processor configured to collect temperature data, and calculate a first Open Circuit Voltage (OCV) value according to the collected current, voltage, and temperature, and calculates the first Open Circuit Voltage (SOC) value from the preset OCV-SOC table. The first SOC value corresponding to the OCV is obtained, and after a certain period of time, the second open circuit voltage (OCV) value is calculated according to the collected current, voltage, and temperature. Of Charge) to obtain a second SOC value corresponding to the second OCV, to calculate the current integration amount of at least one battery during a specific period, using the current integration amount, SOC1 and SOC2 Computing the deterioration capacity for at least one battery, and includes a calculation unit for calculating at least one battery life state using the deterioration capacity and the nominal capacity set at the time of shipment of the hybrid vehicle.

The apparatus may further include a memory unit configured to store data including at least one of a voltage, a current, a temperature, an OCV-SOC table, an SOC, an OCV, a degradation capacity, and a nominal capacity value.

Another embodiment of the present invention provides an apparatus for predicting the life of a battery. The battery life prediction method includes calculating a first Open Circuit Voltage (OCV) value according to the collected current, voltage, and temperature of at least one battery used in a hybrid vehicle, and preset OCV-Open Circuit Voltage (SOC). Obtaining a first SOC value corresponding to the first OCV from a state of charge table; and after a specific period of time, a second open circuit voltage (OCV) according to the recollected current, voltage, and temperature of the at least one battery. Calculating a value, obtaining a second SOC value corresponding to the second OCV according to a preset OCV-SOC (Open Circuit Voltage-State Of Charge) table, and calculating a current integration amount of at least one battery during a specific period. Calculating the deterioration capacity for at least one battery using the current integration amount, SOC1 and SOC2, and using the deterioration capacity and the nominal capacity set at the factory of the hybrid vehicle. Computing at least one battery life state is included.

At this time, the OCV-SOC table may be configured for each temperature.

At this time, the current integration amount is Δ Ah = Q × ( SOC2 - SOC1 ) (where Q is the deterioration capacity of the battery),

The deterioration capacity is calculated using Q = Δ Ah / ( SOC2 - SOC1 ) , where Δ Ah is the current integration amount,

Battery life state is SOH ( State Of Health ) (%) = Q / NC × 100% , where NC is the nominal dose.

Here, the current integration amount is Δ Ah (n) = Δ Ah (n-1) + I x t (where ΔAh (n) is the current current integration amount and ΔAh (n-1) is the previous current integration amount , I is the current and t is the elapsed time.

According to the present invention, the life of a battery can be predicted by calculating temperature, current, and voltage by determining a specific period during which the SOC changes during the charging or discharging of the battery without using the internal resistance of the battery.

In addition, another effect of the present invention is that it can be measured in the battery management system (BMS), it is possible to predict the life of the battery without the need to introduce additional equipment.

1 is a system configuration diagram for measuring the deterioration capacity of a battery according to an embodiment of the present invention.
FIG. 2 is a block diagram of a micro controller unit (MCU) unit of FIG. 1.
3 is a graph showing a SOC-OCV curve according to an embodiment of the present invention.
4 is a graph showing a SOC-OCV curve in a specific section of the charging mode according to an embodiment of the present invention.
5 is a flowchart schematically illustrating a process of obtaining a deterioration capacity Q and an SOH value according to Q during a period in which a BMS is turned on and off according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a system configuration diagram for measuring the deterioration capacity of a battery according to the present invention. In this system configuration diagram, the battery pack 100, sensing units 111 to 113 for sensing the voltage, current, and temperature of each battery in the battery pack, and data received from the sensing units 111 to 113 are charged. MCU (Micro Controller unit) unit 120 for measuring the capacity is included. Battery management system (BMS) unit 110, the vehicle controller 140 for receiving the charge capacity measured from the BMS unit 110 is configured. The functions and roles of these components are described as follows.

The battery pack 100 includes batteries 101 to 10n in series or in parallel. The battery pack 100 may be a hybrid battery such as a nickel metal battery or a lithium ion battery. Of course, in one embodiment of the present invention, for the sake of understanding, the battery pack 100 is configured as only one pack, but may be configured as a plurality of subpacks.

The BMS unit 110 includes the sensing units 111 to 113 and the MCU unit 120, and functions to measure the charging capacity of the battery pack 100. That is, the sensing units 111 to 113 may include a voltage sensing unit 111, a current sensing unit 112, and a temperature sensing unit for sensing current, voltage, and temperature of the batteries 101 to 10n in the battery pack 100. The unit 113 is comprised.

Of course, the temperature sensing unit 113 may sense the temperature of the battery pack 100 or the batteries 101 to 10n. Here, the current sensing unit 112 may be a Hall CT (Hall current transformer) that measures current using a Hall element and outputs an analog current signal corresponding to the measured current, but the present invention is not limited thereto. Other devices can be applied as long as they can sense current.

The microcontroller unit 120 receives the voltage, current, and temperature values of each of the batteries 101 to 10n sensed by the sensing units 111 to 113, and the state of charge of the corresponding batteries 101 to 10n. Value is calculated in real time, and the deterioration capacity of the batteries 101 to 10n is calculated for a period of time, and a battery state of health (SOH) value is calculated. The configuration of the MCU for this calculation process is shown in FIG. This will be described later. The SOC, SOH value, charge capacity value, and the like are stored in the memory unit 130 and transmitted to the vehicle controller 140.

The memory unit 130 may be a memory provided in the MCU unit 120 and may be a separate memory. Therefore, nonvolatile devices such as hard disk drives, flash memory, electrically erasable programmable read-only memory (EEPROM), static RAM (SRAM), ferro-electric RAM (FRAM), phase-change RAM (PRAM), magnetic RAM (MRAM), and so on. Memory can be used.

The vehicle controller 140 performs a function for optimally controlling main system performance required for driving an electric vehicle. To this end, a controller area network (CAN) communication method is used between the vehicle controller 140 and the MCU unit 120 to transmit the SOC and SOH values of the battery to the vehicle controller 140.

FIG. 2 is a block diagram of the MCU unit of FIG. 1. The MCU unit 120 receives the voltage, current, and temperature values of a specific section from the data processing unit 121 for processing data transmitted from the sensing units 111 to 113, and receives the SOC and SOH values from the data processing unit 121. The calculating part 122 which calculates, the memory part 130 which stores these values as data, etc. are comprised.

The calculator 122 receives the voltage, current, and temperature values sensed by the sensing units 111 to 113 through the data processing unit 121 to determine specific sections from these values, thereby real-time SOC values. It estimates and calculates the charge capacity of the batteries 101-10n from this, and determines the lifetime SOH of the batteries 101-10n according to the fall of the calculated deterioration capacity. Of course, these values are stored in real time in the memory unit 130 and transmitted to the vehicle controller 140.

Next, a process of estimating the life of the battery by measuring the deterioration capacity of the batteries 101 to 10n will be described. First, for convenience of understanding of an embodiment of the present invention, a diagram of measuring voltage, current, and temperature of the batteries 101 to 10n in a specific section will be described with reference to FIGS. 3 and 4.

3 is a graph showing a SOC-OCV (state Of Charge-Open Circuit Voltage) curve according to an embodiment of the present invention. It is a graph of SOC-OCV table by temperature. For example, it may be a SOC-OCV graph at room temperature (25 ° C). Of course, the SOC-OCV table is preset and stored in the memory unit 130 in the BMS unit 110 of FIG. An example of such an SOC-OCV look-up table is shown in Table 1.

SOC (%)  -15 ℃  -10 ℃ 0 ℃ 25 45 ℃ 0 3.1 3.1 3.01 3.01 3.0 10 3.5 3.47 3.45 3.4 ... 20 3.7 3.6 3.6 ... ... 40 3.8 ... ... ... ... ... ... ... 100 4.15 ... ...

Of course, Table 1 above is shown for the understanding of the embodiment of the present invention is only one example, it may be configured differently. Therefore, when SOC (%) and -OCV of only-15 ℃ in Table 1 above is connected to the SOC-OCV graph as shown in Figure 3 is calculated.

In general, the method for obtaining the battery SOC (%) is as follows.

[ Equation  One]

battery SOC (%) = (Remaining capacity / Q) × 100 (%)

Where Q is the deterioration capacity of the battery.

Battery cell electromotive force (OCV) is calculated based on temperature, current and voltage at a particular point. When the battery cell electromotive force (OCV) is calculated, the SOC corresponding to this OCV is found in the SOC-OCV table and the value is set as the SOC (%) value.

In addition, along with the SOC (%) value, the equation for calculating Q, which is the deterioration capacity of the battery (abbreviatedly also referred to as the battery capacity), is as follows.

[ Equation  2]

△ Ah  = Q × ( SOC2   - SOC1 )

이다. Where? Ah is the current integration amount,

to be.

Equation 2 is summarized as follows.

[ Equation  3]

Q = △ Ah  / ( SOC2   - SOC1 )

Therefore, the deterioration capacity Q is a value obtained by dividing ΔAh by the difference of SOC2-SOC1.

Then, FIG. 4 schematically illustrates a method of determining a specific period and obtaining corresponding SOC1 and SOC2. That is, referring to FIG. 4, a specific period in x, y plane coordinates is displayed in the x coordinate as T1 400 and T2 410, and OCV1 420 and 0CV2 430 are displayed in the y coordinate.

Of course, as shown in Table 1, in order to calculate the values of SOC1 and SOC2, OCV1 and OCV2 must first be calculated, and these OCV1 and OCV2 are the temperature, current, and voltage at T1 400 and T2 410, respectively. Is calculated based on

 Once OCV1 420 and OCV2 430 are obtained, the values of SOC1 and SOC2 corresponding thereto can be obtained from Table 1 above. For example, suppose that OCV1 is obtained from T1. If the current temperature of the batteries 101 to 10n is -15 ° C and OCV1 is 3.8V, the corresponding SOC1 becomes 40 (%). Of course, SOC2 is also obtained in the same way.

Therefore, when OCV1 and OCV2 are obtained, the deterioration capacity Q can be obtained using Equation (3). When the deterioration capacity (Q) is obtained, the equation for obtaining SOH (%) is as follows.

[ Equation  4]

SOH (%) = Q / NC  × 100 (%)

Here, NC is the nominal capacity of the battery, and the nominal capacity is the value when the battery is shipped from the factory. Usually, the battery capacity of a hybrid electric vehicle is about 6 Ah-7 Ah, but one embodiment of the present invention is not limited thereto. Of course, the deterioration capacity Q refers to the capacity of the deteriorated battery as the battery (101 to 10n in FIG. 1) is used.

Therefore, by using Equations 3 and 3 above, it is possible to predict the SOH of the battery (101 to 10n in FIG. 1) in real time.

Then, the results of comparing the SOH (%) estimated by using the above 1 to 4 and the actually measured SOH (%) are shown in Table 2 below.

Test Items Estimated SOH (%) Actual SOH (%) % Error One 89.6 87.7  1.8 2 90.7 87.7  -3.0 3 92.0 87.7  4.2 4 97.5 93.5  -4.0 5 102.8 101.9  -0.9 ... ... ... ...

Here, the test item refers to a case in which the current or the charging mode is changed. That is, test item 1 may be expressed as 6A constant charging, and test item 2 may be expressed as 1KW constant power charging.

Of course, the data in Table 2 may vary depending on conditions, and one embodiment of the present invention is not limited thereto.

Next, a flowchart schematically showing a process of obtaining an SOH value with reference to FIGS. 1 to 4 and Equations 1 to 4 is shown in FIG. 5. That is, FIG. 5 is a flowchart illustrating a process of obtaining a deterioration capacity Q and an SOH value according to Q during a period in which a BMS is turned on and off according to an embodiment of the present invention.

When the BMS unit 110 (in FIG. 1) is turned on, the MCU unit 120 initializes by setting Flag = 0 (step S500). That is, when the electric vehicle is started, the BMS unit 110 (in FIG. 1) is also in an on state.

At this time, the process of obtaining the SOH according to an embodiment of the present invention is performed in a calculation cycle method that is increased by 1 second according to n = n + 1 (step S510).

The calculating part (122 of FIG. 2) of an MCU part determines whether Flag is 1 (step S520).

As a result, if Flag is not 1, SOC calculated in the range of 15 ° C <T <30 ° C, 20% <SOC <40%, -2A <I <2A, specific period T and sensed current I It is determined whether n corresponds (step S530). Here, 15 <T <30 means T1 is 15 and T2 means 30. Of course, these figures are for the convenience of understanding of one embodiment of the present invention will be understood by those skilled in the art is not limited thereto.

As a result of the determination in step S530, if the above values are within the range, Flag = 1 is set (S532), and OCV1 and SOC1 are calculated in turn (steps S534 and S536). Of course, SOC1 is calculated rather than calculated, as shown in the SOC-OCV curve of Figure 4, when OCV1 is obtained, SOC1 corresponding to this OCV1 is obtained from the SOC-OCV curve.

When OCV1 and SOC1 are calculated, the amount of current accumulated during charge / discharge time is set to 0 (step S538). In other words, initialization is performed. Thereafter, the flow advances to step S510.

In other words, after OCV1 and SOC1 are calculated, OCV2 and SOC2 are calculated after a specific period, and the current integration amount is set to 0 for this purpose. Of course, the method of calculating OCV2 and S0C2 also calculates OCV2 based on the sensed temperature, voltage, and current, and obtains the SOC2 value corresponding to OCV2 calculated from the SOC-OCV curve.

On the contrary, if it is determined in step S530 that it is not within the range of 15 ° C <T <30 ° C, 20% <SOC <40%, -2A <I <2A, step S510 is performed.

On the other hand, if Flag is 1 in step S520, the current integration amount is calculated (step S540). That is, the current integration amount is expressed as follows.

[ Equation  5]

△ Ah (n) = △ Ah (n-1) + I × t

Here, Δ Ah (n) is the current current integration amount, Δ Ah (n-1) is the previous current integration amount, I is the current, and t is the elapsed time. That is, the current current integration amount is a value obtained by adding the charge amount I * t during the elapsed time to the previous current integration amount.

In other words, if OCV1 and OCV2 are found, It is possible to calculate ΔAh, which is the current integration amount. In detail, as described with reference to FIGS. 1 and 2, the MCU unit 120 receives and processes data from the voltage sensing unit 111, the current sensing unit 112, and the temperature sensing unit 113. It is possible to sense the current of the batteries 101 to 10n and to integrate it during the period.

5, SOC calculated in the range of 15 ° C <T <30 ° C, 70% <SOC <90%, -2A <I <2A, specific period T and sensed current I It is determined whether or not it corresponds (step S550). Here, 15 ° C <T <30 ° C means T1 is 15 and T2 means 30. Of course, these figures are for the convenience of understanding of one embodiment of the present invention will be understood by those skilled in the art is not limited thereto.

If it is determined that these SOCs, T and I are not within the above ranges, step S510 is performed in which one second is further increased in the calculation period n = n + 1.

In contrast, if SOC, T, and I are in the above range as a result of the determination in step S550, OCV2, SOC2, SOH are sequentially calculated (steps S560 to S580). In other words, using the calculated difference between SOC1 and SOC2 and the current integration amount? Ah, the deterioration capacity Q value is calculated. The calculated deterioration capacity (Q) is divided by the nominal capacity (NC) and multiplied by 100% to calculate SOH (%), which is the life of the battery.

Once the SOH (%) is calculated, the SOH estimation process ends (S590).

The above flowchart is for the convenience of understanding the exemplary embodiment of the present invention, and it should be understood that the order may proceed differently. For example, the setting of the flag of step S532 to 1 may be performed after step S538.

1 to 5 illustrate only the case where the battery (101 to 10n of FIG. 1) is in the charge mode state, but may also be applied to the case where the battery is in another mode (eg, discharge mode, etc.). The charging mode state may be constant current (CC), constant voltage (CV), and constant power (CP).

Although one preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the scope of the present invention is not limited to these embodiments, it will be understood by those skilled in the art that numerous modifications are possible. Accordingly, the scope of the invention should be defined by the appended claims and equivalents thereof.

100: battery pack, 101 to 10n: battery
111: voltage sensing unit, 112: current sensing unit
113: temperature sensing unit, 110: BMS (Battery Management System) unit
120: microcontroller unit (MCU) unit,
130: memory unit 140: vehicle controller
121: data processing unit 122: calculation unit

Claims (9)

At least one battery used in a hybrid car, plug-in hybrid car, or electric vehicle,
A sensing unit configured to sense a voltage, a current, and a temperature of the at least one battery;
A data processor for collecting the voltage, current, and temperature data from the sensing unit;
A first open circuit voltage (OCV) value is calculated according to the collected current, voltage, and temperature, and a first SOC value corresponding to the first OCV is calculated from a preset open circuit voltage-state of charge (OCV) table. Calculate a second Open Circuit Voltage (OCV) value according to the collected current, voltage, and temperature after a specific period of time, and set the second Open Circuit Voltage (SOC) table according to a preset OCV-SOC (Open Circuit Voltage-State Of Charge) table. A second SOC value corresponding to OCV is obtained, a current integration amount of the at least one battery is calculated during the specific period, and a degradation capacity of the at least one battery is calculated using the current integration amount, SOC1 and SOC2. And a calculator configured to calculate the at least one battery life state using the deterioration capacity.
Life prediction device of a battery comprising a. The method of claim 1,
The OCV-SOC table is configured for each temperature, and the specific section is a life prediction device of a battery in which the at least one battery is in a discharge or charge mode. The method according to claim 1 or 2,
And a memory unit for storing data including at least one of voltage, current, temperature, OCV-SOC table, SOC, OCV, degradation capacity, and nominal capacity value. The method according to claim 1 or 2,
The current integration amount is
ΔAh = Q × (SOC2-SOC1), where Q is the deterioration capacity of the battery,
The deterioration capacity is,
Q = ΔAh / (SOC2-SOC1) (where ΔAh is the current integration),
The battery life state is,
Battery life prediction device calculated using SOH (State Of Health) (%) = Q / NC × 100 (%), where NC is the nominal capacity set at the factory of the hybrid vehicle. The method of claim 4, wherein
The current integration amount is
ΔAh (n) = ΔAh (n-1) + I × t (where ΔAh (n) is the current current integration, ΔAh (n-1) is the previous current integration, I is the current, t is Device for predicting the life of a battery calculated using elapsed time). The first Open Circuit Voltage (OCV) value is calculated according to the collected current, voltage, and temperature of at least one battery used in the hybrid vehicle, the plug-in hybrid vehicle, or the electric vehicle, and the preset OCV-SOC (Open Circuit Voltage-State) is calculated. Obtaining a first SOC value corresponding to the first OCV in an Of Charge table;
After a certain period of time, a second Open Circuit Voltage (OCV) value is calculated according to the re-collected current, voltage, and temperature of the at least one battery, and a preset OCV-SOC (Open Circuit Voltage-State Of Charge) table Obtaining a second SOC value corresponding to the second OCV according to the following;
Calculating a current integration amount of the at least one battery during the specific period;
Calculating a deterioration capacity for the at least one battery using the current integration amount, SOC1 and SOC2;
Calculating the at least one battery life state using the deterioration capacity
Life prediction method of a battery comprising a. The method according to claim 6,
The specific period is a method for predicting the life of a battery in which the at least one battery is in a discharge or charge mode. The method according to claim 6 or 7,
The current integration amount is
ΔAh = Q × (SOC2-SOC1), where Q is the deterioration capacity of the battery,
The deterioration capacity is,
Q = ΔAh / (SOC2-SOC1) (where ΔAh is the current integration),
The battery life state is,
A method of estimating the life of a battery, calculated using SOH (%) = Q / NC × 100 (%), where NC is the nominal capacity set at the factory of the hybrid vehicle. The method of claim 8,
The current integration amount is
ΔAh (n) = ΔAh (n-1) + I × t (where ΔAh (n) is the current current integration, ΔAh (n-1) is the previous current integration, I is the current, t is A method of predicting the life of a battery, calculated using elapsed time.

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