JP5498311B2 - Secondary battery device and data creation method used for capacity estimation - Google Patents

Description

  Embodiments of the present invention relate to a secondary battery device and a data creation method used for capacity estimation.

  In an electronic device in which a secondary battery cell or an assembled battery including a plurality of secondary battery cells is mounted, it is required to accurately estimate a remaining battery level (SOC: State of Charge). As a means for obtaining this SOC, a method has been studied in which the charge / discharge current of the secondary battery is integrated and the SOC value is estimated from the integrated amount.

  However, the estimated value by this method does not take into account the capacity deterioration of the secondary battery cell. Actually, capacity deterioration due to repeated aging and repeated charge / discharge (change in discharge characteristics) occurs, resulting in an error in the estimated value. Sometimes increased with deterioration. In order to reduce this error, a technique for learning a capacity that has deteriorated as appropriate has been proposed.

  In addition, a method of actually measuring the capacity from the end of charging to the end of discharging and newly updating the capacity as an actual capacity has been proposed. This method is a method of actually measuring the current capacity, and an accurate capacity can be obtained immediately after the update.

  However, in an actual use state, there is almost no opportunity to perform charge / discharge from the end of charge to the end of discharge within a short time in which the influence of self-discharge and the like can be ignored and under standard charge / discharge conditions. In particular, in electric vehicles and electric motorcycles, it is generally assumed that charging is performed before the end of discharge. In actual use conditions, the deterioration capacity is updated (measured) except for special occasions such as periodic inspections. Things are impossible.

  In addition, if the deterioration capacity due to charging / discharging in one cycle is a known value, the value obtained by subtracting the predetermined deterioration capacity according to the number of cycles is updated as the current capacity, or if it is stored without being used, A method has been proposed in which a value obtained by subtracting the deteriorated capacity corresponding to the storage period is updated as the current capacity using the storage temperature and the remaining amount as parameters. In this method, it is possible to estimate the current capacity at any time from data on the number of cycles, temperature, remaining battery level, and time.

JP 2002-236155 A JP 2002-236154 A JP 2007-315880 A

  However, the remaining battery level, which is one of the parameters, cannot be directly measured, but is an estimated value estimated based on the capacity. In other words, these parameters are mutual parameters, and when one of the estimation accuracy decreases (or is low), it affects each other, and the decrease in estimation accuracy may be amplified.

  An object of the present invention is to provide a secondary battery device that accurately performs capacity estimation in consideration of an actual deterioration state of a secondary battery cell, and a data generation method used for estimation.

  The secondary battery device according to the embodiment is arranged in temperature measuring means for a plurality of secondary battery cells, voltage measuring means for measuring a voltage between terminals of the secondary battery cells, and a current path of the plurality of secondary battery cells. Current measuring means, measured values measured by the temperature measuring means, voltage measuring means and current measuring means, storage means for storing characteristics of standard capacity of the secondary battery cell, and externally connected After the charger charges the secondary battery cell with the first current and the inter-terminal voltage of the secondary battery cell reaches the end-of-charge voltage, the secondary battery cell is charged with the second current smaller than the first current. When the inter-terminal voltage of the secondary battery cell reaches the end-of-charge voltage, the difference between the charge capacity at the end of charging by the first current and the charge capacity at the end of charging by the second current, or With the second current A charge capacity is calculated, a characteristic of the standard capacity of the secondary battery cell at the first current value is read from the storage means, a difference between the charge capacity or a charge capacity at the second current, and the second current And the current standard capacity from the characteristics of the standard capacity of the secondary battery cell at the first current value, using the value of the temperature at the end of charging with the second current. Means.

It is a figure which shows roughly the example of 1 structure of the secondary battery apparatus which concerns on embodiment. In the secondary battery apparatus which concerns on embodiment, it is a figure which shows an example of the relationship between an electric current integrated value at the time of performing step-down charge, and a secondary battery voltage. 5 is a flowchart for explaining an example of a method of creating data used for estimating the battery capacity of a secondary battery cell in the secondary battery device according to the embodiment. It is a figure which shows an example of the relationship between the value of 2 steps | paragraph electric current at the time of step-down charge, and an electric current integrated value. FIG. 5 is a diagram showing an example of the relationship between the intercept of the primary equation shown in FIG. 4 and a standard capacity. FIG. 5 is a diagram illustrating an example of a relationship between a temporary inclination and a standard capacity illustrated in FIG. 4. It is a figure for demonstrating an example of the table used for the capacity | capacitance estimation of a secondary battery cell in the secondary battery apparatus which concerns on embodiment.

  Hereinafter, a secondary battery device and a data creation method used for capacity estimation according to an embodiment of the present invention will be described with reference to the drawings.

    FIG. 1 schematically shows a configuration example of the secondary battery device according to the present embodiment. A secondary battery device shown in FIG. 1 includes an assembled battery 1 including a plurality of secondary battery cells BT, a voltage measurement unit 2, a current measurement unit 3, a temperature measurement unit 4, an arithmetic control unit 5, and a storage unit. 6 is provided.

  The voltage measurement part 2 acquires the voltage of the positive electrode terminal and the voltage of a negative electrode terminal of each secondary battery cell BT, and measures the voltage between terminals. The voltage measuring unit 2 outputs the measured value of the terminal voltage to the calculation control unit 5.

  The current measuring unit 3 is connected in series to the current path of the assembled battery 1 and measures the charge / discharge current of the assembled battery 1. The current measuring unit 3 outputs the measured charge / discharge current value to the calculation control unit 5.

  The temperature measurement unit 4 includes a temperature sensor that is disposed in the vicinity of the plurality of secondary battery cells BT and detects the temperature of the plurality of secondary battery cells BT. The temperature measurement unit 4 outputs the temperature value detected by the temperature sensor to the calculation control unit 5.

  The arithmetic control unit 5 controls operations of the voltage measuring unit 2, the current measuring unit 3, and the temperature measuring unit 4. The arithmetic control unit 5 receives the terminal-to-terminal voltage, charge / discharge current, and temperature measurement data from the voltage measurement unit 2, the current measurement unit 3, and the temperature measurement unit 4, and outputs them to the storage unit 6.

  The storage unit 6 receives and stores measurement data from the arithmetic control unit 5 and includes a database DB of data used for capacity estimation of the secondary battery cell BT. In the database DB, for example, the characteristic data of the standard capacity of the secondary battery cell BT is recorded as a table from the measurement data and the calculation result when step-down charging is performed.

  FIG. 2 shows a flowchart for explaining an example of a method for estimating the capacity of the secondary battery cell BT in the secondary battery device. In this embodiment, the assembled battery 1 is step-down charged by a charger (not shown) connected to the outside of the secondary battery device.

  First, when a charger is connected to the secondary battery device, and charging of the assembled battery 1 with the first current (first stage charging) is started by the charger (step SP1), the arithmetic control unit 5 includes a voltage measuring unit. 2. The current measurement unit 3 and the temperature measurement unit 4 are controlled to measure the inter-terminal voltage, current, and temperature of each secondary battery cell BT (step SP2), and receive measurement data. The arithmetic control unit 5 starts calculating the current integrated value from the received measurement data, and records the measurement data and the current integrated value in the storage unit 6 together with the received time.

  FIG. 3 shows an example of the relationship between the voltage [V] between the terminals of the secondary battery cell BT and the charge capacity (current integrated value) [Ah] when the secondary battery cell BT is step-down charged. When charging of the secondary battery cell BT is continued with the first current, the voltage between the terminals of the secondary battery cell BT increases.

  The arithmetic control unit 5 determines whether or not the voltage between the terminals of the secondary battery cell BT reaches the end-of-charge voltage (step SP3), and when the end-of-charge voltage is reached, the charger determines that the end-of-charge voltage has been reached. Notice. When the charger receives notification from the arithmetic control unit 5 that the charging end voltage has been reached, the charger changes the charging current from the first current to the second current (first current> second current) and starts charging ( Step SP4).

  When the charger starts charging with the second current, the voltage between the terminals of the secondary battery cell BT once decreases and then increases again. This characteristic represents the fluctuation of the voltage between the terminals of the secondary battery cell BT due to the voltage drop, and is a characteristic suggesting the internal state. Further, when charging is performed at the end of constant voltage charging, it indicates that the chargeable capacity is larger when the current value is smaller.

  The calculation control unit 5 controls the voltage measurement unit 2, the current measurement unit 3, and the temperature measurement unit 4 to measure the voltage, current, and temperature between the terminals of each secondary battery cell BT (step SP5). ), Receive the measurement data. Subsequently, the arithmetic control unit 5 determines whether or not the line pressure between the terminals of the secondary battery cell BT reaches the charge end voltage (step SP6). When the charge end voltage is reached, the charge end voltage is supplied to the charger. Notify that you have reached When the charger receives notification from the arithmetic control unit 5 that the charge end voltage has been reached, the charger ends the second stage charging.

  Next, the arithmetic control unit 5 determines the difference between the charge capacity at the end of the first stage charge and the charge capacity at the end of the second stage charge (Δ capacity) or the charge capacity at the second current (Δ capacity). Is calculated (step SP7). Subsequently, the arithmetic control unit 5 reads the database DB from the storage unit 6 (step SP8), and estimates the standard capacity at the end of the two-stage charging using the database DB (step SP9).

  FIG. 7 shows an example of a table recorded as a database DB in the storage unit 6. In the database DB of the storage unit 6, the characteristic data of the standard capacity of the secondary battery cell BT corresponding to the Δ capacity, the value of the second current, and the temperature at the end of the second stage charging are recorded as a table. Furthermore, if necessary, the first current has a plurality of levels, and a table is prepared for each value of the first current.

  Further, the calculation control unit 5 determines the remaining capacity (SOC: state of charge) after completion of charging from the standard capacity estimated as the final charge termination condition (current, temperature) and the known characteristics recorded in the database DB. Is calculated (SP10), and the SOC is transmitted to the host control means (not shown) (SP11).

  When capacity estimation is performed as described above, capacity data can be updated relatively frequently in the actual use state, and since there are no parameters that affect each other, a decrease in estimation accuracy is suppressed.

  Below, the creation method of the data contained in database DB is demonstrated. If necessary, the first current is set to a plurality of levels, and the following is performed for each value of the first current. First, a secondary battery device is connected to a charger to perform a second stage charge with a plurality of second currents, and a charge capacity at the end of the first stage charge and a charge capacity at the end of the second stage charge. The relationship between the difference (Δ capacity) or the charge capacity at the second current (Δ capacity) and the value of the second current is approximated by a linear function.

  FIG. 4 shows an example of a function when the relationship between the value of Δcapacitance and the second current is approximated by a linear function. FIG. 4 shows a plurality of linear functions for three cases where the degree of deterioration of the secondary battery cell BT is different. The slope of the linear function is smaller as the deterioration of the secondary battery cell BT is earlier, and the slope is larger as the deterioration is later. Further, the value of the intercept of the linear function is larger as the deterioration of the secondary battery cell BT is earlier, and is smaller as the deterioration is later. Thus, the slope of the linear function and the value of the intercept change according to the degree of deterioration of the secondary battery cell BT.

  FIG. 5 shows an example of the relationship between the intercept of the linear function of the value of Δ capacity and the second current and the standard capacity at the first current. The larger the intercept value, the smaller the standard capacity. For example, the standard capacity is a capacity when a constant current (CC) charge / discharge (1C_CC charge / discharge) is performed with a current of 1 C in an environment of 25 ° C.

  Therefore, assuming that the temperature characteristic of the temporary function of FIG. 5 is the database DB in advance, the current standard capacity can be calculated from the second current, the Δ capacity, and the temperature when the charging is terminated in the second stage charging. For example, as a model formula, the current standard capacity is expressed by the following formula, and the standard capacity can be calculated by substituting the intercept calculated from the values of the Δ capacity and the second current. At this time, A and B are functions of the temperature T, and are obtained from the battery temperature at the end of charging and DB.

Current standard capacity = A (T) × intercept + B (T) (1) Formula Also, it is not a model formula like formula (1), but has a relationship between standard capacity, intercept and temperature as a table. Similarly, standard capacity is required. In this way, the standard capacity is calculated, and the standard capacity corresponding to the Δ capacity, the second current, and the temperature is recorded in the database. By setting the standard capacity at this time to, for example, 1 C_CC charge / discharge capacity at 25 ° C., it can be used as an index of capacity deterioration.

  The present embodiment is effective when charging up to the end-of-charge voltage relatively frequently. For example, it is effective when charging a secondary battery cell mounted on a camera, a mobile phone, a notebook PC, an electric motorcycle, or an electric vehicle. In particular, in the case of electric motorcycles and electric automobiles that have a large battery capacity and require a long time for full charge, step down to perform full charge with small current (second current) after rapid charge with large current (first current). It is assumed that the battery is frequently charged, and the current capacity data can be updated frequently. As a result, the remaining battery level can be estimated with high accuracy.

  In addition, in the secondary battery device of the present embodiment, only the known database and the current measurement data are used, and the mutual estimation parameter is not included in the capacity estimation parameter. Low) affects each other, and the decrease in estimation accuracy is suppressed from being amplified.

  In the data creation method included in the database DB, data for obtaining the standard capacity is created using the intercept of the linear function of the value of the Δ capacity and the second current. The standard capacity may be obtained using the slope of a linear function of the value.

  FIG. 6 shows an example of the relationship between the slope of the linear function of the values of the Δ capacity and the second current and the standard capacity at the first current. The standard capacity increases as the slope of the linear function increases.

  Therefore, assuming that the temperature characteristic of the temporary function of FIG. 6 is the database DB in advance, the current standard capacity can be calculated from the charging current, the Δ capacity, and the temperature when the charging is terminated in the second stage charging. For example, as a model formula, the current standard capacity is expressed by the following formula, and the standard capacity can be calculated by substituting the slope calculated from the values of the Δ capacity and the second current. At this time, A ′ and B ′ are functions of the temperature T, and are obtained from the battery temperature at the end of charging and DB.

Current standard capacity = A ′ (T) × slope + B ′ (T) (2) Formula Also, not a model formula such as formula (2), but the relationship between standard capacity, slope and temperature as a table Even if you have it, you will be asked for a standard capacity. In this way, the standard capacity is calculated, and the standard capacity corresponding to the Δ capacity, the second current, and the temperature is recorded in the storage unit 6 as the database DB.

  Thus, even if the data to be recorded in the database DB is created using the slope of the linear function of the values of the Δ capacity and the second current, the same effect as when using the intercept can be obtained.

  Furthermore, the data to be recorded in the database DB may be created using both the slope and intercept of the linear function of the values of the Δ capacity and the second current. In this case, the same effect as that obtained when only the section is used can be obtained.

  According to the embodiment, it is possible to provide a secondary battery device that accurately performs capacity estimation in consideration of an actual deterioration state of a secondary battery cell, and a data creation method used for estimation.

  In the above embodiment, step-down charging in which the charging current is changed in two stages has been described as an example. However, the present invention can also be applied to the case where step-down charging in three or more stages is performed. In that case, by estimating the standard capacity and the SOC using the current value after reaching the end-of-charge voltage as the second current value, the same effect as in the above embodiment can be obtained.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  BT ... secondary battery cell, DB ... database, 1 ... assembled battery, 2 ... voltage measurement unit (voltage measurement unit), 3 ... current measurement unit (current measurement unit), 4 ... temperature measurement unit (temperature measurement unit), 5 ... calculation control unit (calculation unit), 6 ... storage unit (storage unit).

Claims (4)

Temperature measuring means for a plurality of secondary battery cells;
Voltage measuring means for measuring a voltage between terminals of the secondary battery cell;
Current measuring means disposed in a current path of the plurality of secondary battery cells;
A storage means for storing measured values measured by the temperature measuring means, the voltage measuring means and the current measuring means; and a standard capacity characteristic of the secondary battery cell;
After the charger connected to the outside charges the secondary battery cell with the first current and the voltage between the terminals of the secondary battery cell reaches the end-of-charge voltage, the second battery with the second current smaller than the first current is used. Charging capacity at the end of charging with the first current and charging capacity at the end of charging with the second current when the voltage between the terminals of the secondary battery cell reaches the charging end voltage due to charging of the secondary battery cell Or the charge capacity at the second current is calculated, the characteristic at the first current value of the standard capacity of the secondary battery cell is read from the storage means, and the difference between the charge capacity or the second Using the values of the charge capacity at current, the second current, and the temperature at the end of charging by the second current, the current capacity of the secondary battery cell from the characteristics at the first current value Arithmetic configured to calculate standard capacity When the secondary battery system, characterized in that it comprises a.   The calculation means is configured to calculate a remaining capacity after the end of charging with the second current from the second current value, a temperature at the end of charging with the second current, and the standard capacity. The secondary battery device according to claim 1. The secondary battery cell is charged with a charging capacity when the voltage between the terminals of the secondary battery cell reaches the end-of-charge voltage by the first current, and a second current smaller than the first current after the charging by the first current is completed. The difference between the charge capacity when charging until the terminal voltage of the battery reaches the charge end voltage is calculated,
Approximating the relationship between the second current and the charge capacity difference by a linear function,
A method for creating data used for capacity estimation, wherein the standard capacity of the secondary battery cell is calculated using the intercept of the linear function and the temperature at the end of charging by the second current. The secondary battery cell is charged with a charging capacity when the voltage between the terminals of the secondary battery cell reaches the end-of-charge voltage by the first current, and a second current smaller than the first current after the charging by the first current is completed. The difference between the charge capacity when charging until the terminal voltage of the battery reaches the charge end voltage is calculated,
Approximating the relationship between the second current and the charge capacity difference by a linear function,
A method for creating data used for capacity estimation, wherein the standard capacity of the secondary battery cell is calculated using the slope of the linear function and the temperature at the end of charging by the second current.

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