JP2018081796A - Battery control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery control system capable of calculating a rate of capacity degradation owing to the precipitation of charge carriers with high accuracy.SOLUTION: A battery control system according to the present invention is arranged to execute the steps of: measuring a resistance increase rate ΔRof a secondary battery; estimating, based on temperature frequency distribution data including battery temperatures and an integration time held at each battery temperature, a resistance increase rate ΔRand a capacity degradation rate ΔCafter the degradation of a material owing to the abrasion thereof in the secondary battery; comparing the measured resistance increase rate ΔRwith the estimated resistance increase rate ΔRafter the material degradation; using a first map to calculate a capacity degradation rate ΔCowing to the precipitation of charge carriers when the compared resistance increase rates satisfy a relation given by ΔR≥ΔR; and using a second map different from the first map in feature to calculate a capacity degradation rate ΔCowing to the precipitation of the charge carriers when the compared resistance increase rates satisfy a relation given by ΔR<ΔR.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a battery control system for a secondary battery.

  A secondary battery such as a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a vehicle-mounted power source. In this type of secondary battery, charge and discharge are performed by transferring charge carriers (for example, lithium in the case of a lithium ion secondary battery) between a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material. Is called. That is, at the time of charging, the charge carrier is extracted from the positive electrode active material and released as ions into the electrolytic solution (electrolyte). At the time of charging, the charge carriers enter the structure of the negative electrode active material provided on the negative electrode side, where electrons that have passed through the external circuit are obtained from the positive electrode active material and occluded. Patent document 1 is mentioned as a prior art regarding the battery control of this kind of secondary battery.

JP 2011-222343 A

  Patent Document 1 is provided with a correlation map of internal resistance of aging and interval discharge amount, and at least one of the actually acquired interval discharge amount and waste portion resistance is converted and compared through the correlation map, and lithium deposition is performed. A battery system for determining the degree of is described. In this publication, it is assumed that the amount of decrease in the amount of discharge in the battery is the sum of the amount of decrease due to aging and the amount of decrease due to lithium deposition, and the degree of increase in internal resistance has little effect on the presence or absence of lithium deposition. Based on the knowledge that it is not performed, the reduction amount of the discharge amount due to only aged deterioration is estimated based on the value of the internal resistance value, and the degree of lithium deposition is determined by subtracting this from the overall reduction amount. However, according to the study by the present inventor, the internal resistance value also increases depending on the degree of lithium precipitation. Therefore, when the deterioration due to lithium precipitation exceeds a predetermined amount, the accuracy of estimation of lithium precipitation deterioration deteriorates, resulting in an error. A determination may occur. I want to accurately grasp the degree of lithium precipitation.

The battery control system for a secondary battery proposed here is a battery control system for a secondary battery including an electrode active material capable of reversibly occluding and releasing charge carriers. The battery control system includes a temperature sensor that detects a temperature of the secondary battery, a current sensor that detects a current flowing into and out of the secondary battery, a voltage sensor that detects a voltage of the secondary battery, and the charge carrier And a calculation unit for calculating the capacity deterioration rate ΔC _y caused by the precipitation of. The calculating unit measures a resistance increase rate ΔR _current of the secondary battery from the current value detected by the current sensor and the voltage value detected by the voltage sensor; and the battery detected by the temperature sensor Estimating a resistance increase rate ΔR _x and a capacity deterioration rate ΔC _x after material deterioration due to material wear of the secondary battery based on temperature frequency distribution information including temperature and accumulated time held at each battery temperature; The step of comparing the measured resistance increase rate ΔR _current with the estimated resistance increase rate ΔR _x after material degradation, and when the compared resistance increase rate satisfies the relationship ΔR _x ≧ ΔR _current , using the first map showing the correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate (ΔC x ₊ ΔC _y), the resistance increase ratio after the estimated material degradation [Delta] R _x and capacity degradation rate [Delta] C _x Al, calculating a capacity deterioration rate [Delta] C _y due to deposition of the charge carriers, wherein the compared resistance increase rate may satisfy the relationship ΔR x _{<ΔR current,} excessive precipitation of the charge carriers occurs And a map showing the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ), which is different from the first map, using the second map, The step of calculating the capacity deterioration rate ΔC _y resulting from the deposition of the charge carriers from the estimated resistance increase rate ΔR _x and capacity deterioration rate ΔC _x after material deterioration is executed. According to this configuration, the capacity deterioration rate ΔC _y resulting from the charge carrier deposition is calculated in consideration of the increase in resistance due to the charge carrier deposition, so that the calculation accuracy is improved.

It is a block diagram which shows the structure of the power supply system controlled by the battery control apparatus of the secondary battery which concerns on this embodiment. It is a graph which shows the relationship between an elapsed time days and a resistance increase rate. It is a graph which shows the relationship between the number of days elapsed and a capacity maintenance rate. It is a graph which shows the relationship between battery temperature T and deterioration rate (beta). It is a graph which shows battery temperature frequency distribution. Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). 7 is a flowchart illustrating an example of a capacity deterioration rate ΔC _y calculation processing routine.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than the matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, general technology related to the construction and manufacturing method of the positive electrode and the negative electrode, secondary batteries and other batteries) Etc.) can be grasped as a design matter of those skilled in the art based on the prior art in this field.

  Although not intended to be particularly limited, a preferred embodiment according to the battery control system of the present invention will be described below by taking as an example the case of mainly controlling a lithium ion secondary battery. In this specification, the term “lithium ion secondary battery” refers to a secondary battery that uses lithium ions (Li ions) as electrolyte ions and is charged / discharged by the movement of charges associated with lithium ions between the positive and negative electrodes. Say.

  FIG. 1 is a block diagram showing a configuration of a battery control system 1 controlled by a control device for a lithium ion secondary battery 10 according to the present embodiment. The control device of the lithium ion secondary battery 10 is suitably used for a vehicle (typically, an automobile including an electric motor such as an automobile, particularly a hybrid automobile, an electric automobile, or a fuel cell automobile).

  The battery control system 1 includes a lithium ion secondary battery 10, a load 20 connected to the lithium ion secondary battery 10, a temperature sensor (not shown) that detects the temperature of the secondary battery 10, and a current flowing in and out of the secondary battery 10. A current sensor (not shown) for detecting, a voltage sensor (not shown) for detecting the voltage of the secondary battery, and an electronic control unit (ECU) 30 may be included. The ECU 30 is configured to control the operation of the lithium ion secondary battery 10 connected to the load 20, and drives and controls the load 20 based on predetermined information. The load 20 connected to the lithium ion secondary battery 10 may include a power consumer (for example, a motor) that consumes the power stored in the battery 10. The load 20 may include a power supply device (charger) that supplies power that can charge the battery 10.

  The lithium ion secondary battery 10 includes a positive electrode and a negative electrode facing each other with a separator interposed therebetween, and an electrolyte containing lithium ions supplied between the positive and negative electrodes. The positive electrode and the negative electrode contain an electrode active material that can occlude and release lithium ions as charge carriers. When the battery 10 is charged, lithium ions are released from the positive electrode active material, and the lithium ions are occluded in the negative electrode active material through the electrolyte. On the contrary, when the battery 10 is discharged, lithium ions occluded in the negative electrode active material are released, and the lithium ions are occluded again in the positive electrode active material through the electrolyte. As the lithium ions move between the positive electrode active material and the negative electrode active material, electrons flow from the active material to the external terminal. Thereby, the load 20 is discharged.

Here, it is known that the lithium ion secondary battery generally deteriorates with use. According to the knowledge of the present inventor, the main causes of deterioration are considered to be material deterioration due to wear of the material of the secondary battery and deterioration due to lithium deposition at the negative electrode inside the secondary battery. When deterioration occurs with use, as shown in FIG. 2, the resistance increase rate ΔR _current calculated from the current flowing through the secondary battery and the voltage drop amount may increase with the passage of days. The resistance increase rate ΔR _current includes a resistance increase due to lithium deposition in addition to a resistance increase due to material deterioration (resistance increase rate ΔR _x ). Further, as shown in FIG. 3, the capacity maintenance rate can become a decreasing tendency (the capacity deterioration rate tends to increase) with the passage of days. The capacity deterioration rate includes a capacity deterioration due to lithium deposition (capacity deterioration rate ΔC _y ) in addition to a capacity deterioration due to material deterioration (capacity deterioration rate ΔC _x ). The present inventor determines the degree of lithium deposition (capacity degradation rate ΔC _y due to lithium deposition) from the secondary battery resistance increase rate ΔR _x and capacity degradation rate ΔC _x without disassembling the secondary battery. I'm considering doing that.

Here, according to the knowledge of the present inventor, the influence of lithium deposition on the resistance increase rate ΔR _current is different between the normal deterioration state where lithium deposition is small and the abnormal deterioration state where lithium is excessively precipitated. Specifically, in the normal deterioration state with little lithium deposition, the resistance increase rate ΔR _current does not increase so much even if lithium is deposited, but in the abnormal deterioration state in which lithium is excessively deposited, the resistance increase rate ΔR _current is Shows an increasing tendency as it precipitates. On the other hand, since deterioration due to material wear depends on the thermal history, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x due to material deterioration can be estimated by using the thermal load and deterioration rate applied to the battery. Therefore, by comparing the resistance increase rate ΔR _x due to material deterioration estimated from the thermal history with the actually measured resistance increase rate ΔR _current , is the secondary battery in a normal deterioration state with little lithium deposition? Alternatively, it can be determined whether or not the battery is in an abnormally deteriorated state in which lithium is excessively deposited. Then, by using an appropriate correlation map according to each deterioration state, the degree of lithium precipitation (capacity deterioration rate due to lithium precipitation) from the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _{x of the} secondary battery. ΔC _y ) can be determined.

From the above knowledge, in the battery control system 1 disclosed herein, the ECU 30 determines the resistance increase rate ΔR _{current of the} secondary battery from the current value detected by the current sensor and the voltage value detected by the voltage sensor. _Is measured (ΔR _current measurement step). Further, based on the temperature frequency distribution information including the battery temperature detected by the temperature sensor and the accumulated time held at each battery temperature, the resistance increase rate ΔR _x and the capacity deterioration rate after material deterioration due to material wear of the secondary battery ΔC _x is estimated (ΔR _x and ΔC _x estimation step). Then, the measured resistance increase rate ΔR _current is compared with the estimated resistance increase rate ΔR _x after material deterioration (comparison step). Here, when the compared resistance increase rate satisfies the relationship ΔR _x ≧ ΔR _current , the ECU 30 shows a first correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ). Using the map, the capacity deterioration rate ΔC _y resulting from the precipitation of lithium is calculated from the estimated resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration. On the other hand, when the compared resistance increase rate satisfies the relationship ΔR _x <ΔR _current , the ECU 30 determines that excessive precipitation of lithium has occurred, and uses the second map having characteristics different from the first map, A capacity deterioration rate ΔC _y resulting from lithium deposition is calculated from the estimated resistance increase rate ΔR _x and capacity deterioration rate ΔC _x after material deterioration (ΔC _y calculation step). Then, it is determined whether or not the calculated capacity deterioration rate ΔC _y exceeds the Li deposition allowable amount ΔC _limit . If the capacity deterioration rate ΔC _y exceeds the allowable amount ΔC _limit , the battery is used. Is stopped (judgment step).

  The typical configuration of the ECU 30 stores at least a ROM (Read Only Memory) storing a program for performing such control, a CPU (Central Processing Unit) capable of executing the program, and temporarily stores data. A random access memory (RAM) and an input / output port (not shown) are included. The secondary battery 10 is provided with the above-described current sensor, voltage sensor, and temperature sensor. The ECU 30 receives output signals from the sensors via the input port. And ECU30 acquires the information of the electric current value which goes in and out of the secondary battery 10, the voltage value, and battery temperature based on the output signal from each sensor. The ECU 30 constitutes the calculation unit of this embodiment.

<ΔR _current measurement step>
In the ΔR _current measurement step, the ECU 30 calculates the resistance increase rate ΔR _current of the secondary battery from the current I _x flowing through the lithium ion secondary battery 10 during charging / discharging from the load 20 and the battery voltage drop ΔV _x. taking measurement.

<ΔR _x and ΔC _x estimation step>
In the ΔR _x and ΔC _x estimation step, the ECU 30 determines the resistance increase rate ΔR _x after the material deterioration and the capacity deterioration in the secondary battery based on the temperature frequency distribution information including the battery temperature and the accumulated time held at each battery temperature. Estimate the rate ΔC _x . According to the inventor's knowledge, the deterioration due to material wear depends on the thermal history. Therefore, if the thermal load applied to the battery and the deterioration rate are used, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC due to the material deterioration are used. _x can be estimated. Specifically, as shown in the temperature-accelerated Arrhenius model of FIG. 4, the deterioration rate β tends to increase as the battery temperature increases. By using this correlation, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration can be estimated from the temperature frequency distribution information and the deterioration rate β.

  In this embodiment, as shown in FIG. 4, data indicating the relationship between the battery temperature and the deterioration rate is stored in a ROM in the form of a map, and a predetermined battery temperature (for example, a temperature range) is stored with reference to this map. ). Such data can be obtained from the transition of the resistance increase rate and the capacity deterioration rate at certain time intervals when a plurality of secondary batteries are prepared and subjected to an endurance test under various temperature conditions.

Moreover, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration can be calculated by integrating and summing the accumulated time held at each battery temperature and the deterioration rate at each battery temperature. Here, the accumulated time held at each battery temperature can be obtained by integrating for each predetermined battery temperature how much the secondary battery is held at a predetermined battery temperature (for example, a temperature range). In addition, even if the battery is not charging / discharging (it is not used), the increase in resistance and the capacity deterioration due to material deterioration can occur. Therefore, it is preferable to count the accumulated time both when the battery is used (for example, when the vehicle is running) and when the battery is not used (for example, when the vehicle is stopped). The obtained temperature frequency distribution information may be stored in the ROM in the form of a map or table as shown in FIG.

<Comparison step>
In the comparison step, the ECU 30 compares the resistance increase rate ΔR _current measured in the ΔR _current measurement step with the resistance increase rate ΔR _x after material deterioration estimated in the ΔR _x and ΔC _x estimation steps.

<ΔC _y calculation step>
In the ΔC _y calculation step, the ECU 30 determines that excessive precipitation of lithium does not occur when the rate of increase in resistance compared in the comparison step satisfies the relationship of ΔR _x ≧ ΔR _current , and increases the resistance after the estimated material deterioration Based on the rate ΔR _x and the capacity deterioration rate ΔC _x , the capacity deterioration rate ΔC _y caused by lithium deposition is calculated. Specifically, as shown in FIG. 6, data indicating the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) under the condition where excessive precipitation of lithium does not occur. Is obtained in advance by a preliminary experiment or the like and stored in the ROM in the form of a first map (Line 1). Then, referring to the first map, a total capacity deterioration rate (ΔC _x + ΔC _y ) corresponding to the estimated resistance increase rate ΔR _x after material deterioration is estimated, and the estimated total capacity deterioration rate (ΔC _x + ΔC _y). ) Is subtracted from the capacity deterioration rate ΔC _x after material deterioration, to calculate the capacity deterioration rate ΔC _y resulting from lithium deposition.

In the ΔC _y calculation step, the ECU 30 determines that excessive precipitation of lithium occurs when the resistance increase rate compared in the comparison step satisfies the relationship ΔR _x <ΔR _current , and what is the first map? Using a second map having different characteristics, a capacity deterioration rate ΔC _y resulting from lithium deposition is calculated based on the estimated resistance increase rate ΔR _x and capacity deterioration rate ΔC _x after material deterioration. Specifically, as shown in FIG. 7, data showing the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) under the condition where excessive precipitation of lithium occurs. Is obtained in advance by a preliminary experiment or the like and stored in the ROM in the form of a second map (Line 2). In this embodiment, Line 2 of the second map has a total capacity deterioration rate (ΔC _x + ΔC _y ) corresponding to the resistance increase rate ΔR _x after material deterioration is larger than Line 1 of the first map (that is, shifts to the right). ) Is set as follows. Then, with reference to this second map, the total capacity deterioration rate (ΔC _x + ΔC _y ) corresponding to the estimated resistance increase rate ΔR _x after material deterioration is estimated, and the estimated total capacity deterioration rate (ΔC _x + ΔC _y). ) Is subtracted from the capacity deterioration rate ΔC _x after material deterioration, thereby calculating the capacity deterioration rate ΔC _y caused by lithium deposition.

Here, in spite of excessive precipitation of lithium (that is, ΔR _x <ΔR _current ), if the capacity deterioration rate ΔC _y caused by lithium precipitation is calculated using the first map, FIG. As shown in FIG. 4, since the capacity deterioration rate ΔC _y is calculated to be less than the actual value, it is determined that the battery can still be used even though the capacity deterioration rate ΔC _y exceeds the Li deposition allowable amount ΔC _limit. there is a possibility. In contrast, by calculating the [Delta] R _current and [Delta] R _x from the magnitude relationship selects the second map capacity degradation rate [Delta] C _y of appropriately determine the capacity deterioration rate [Delta] C _y exceeds the allowable amount [Delta] C _limit The use of the battery can be stopped reliably.

<Judgment step>
In the determination step, the ECU 30 determines whether or not the value of the capacity deterioration rate ΔC _y calculated in the ΔC _y calculation step exceeds the Li precipitation allowable amount ΔC _limit , and the capacity deterioration rate ΔC _y exceeds the allowable amount ΔC _limit . If so, stop using the battery. On the other hand, when the capacity deterioration rate ΔC _y does not exceed the allowable amount ΔC _limit , the use of the battery is continued.

The operation of the battery control system 1 configured as described above will be described. FIG. 9 is a flowchart showing an example of a capacity deterioration rate ΔC _y calculation processing routine executed by the ECU 30 of the battery control system 1 according to the present embodiment. This routine is executed, for example, immediately after the secondary battery is mounted on the vehicle.

When the capacity deterioration rate ΔC _y calculation process shown in FIG. 9 is executed, the CPU of the ECU 30 first calculates the current I _x flowing through the secondary battery and the battery voltage for the lithium ion secondary battery (cell) 10 to be controlled. The resistance increase rate ΔR _current of the secondary battery is measured from the drop amount ΔV _x (step S10). In addition, temperature frequency distribution information including the battery temperature and the accumulated time held at each battery temperature is acquired, and the secondary battery is referred to by referring to the data indicating the relationship between the battery temperature and the deterioration rate stored in the ROM. The resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration due to material wear at (S20) are estimated.

Next, in step S30, the ECU 30 compares the resistance increase rate ΔR _current measured in step S10 with the resistance increase rate ΔR _x after aging estimated in step S20. If the compared resistance increase rate satisfies the relationship of ΔR _x ≧ ΔR _current (in the case of Yes), it is determined that lithium is not excessively precipitated, and the process proceeds to step S40. In step S40, the ECU 30 estimates using the first map (Line 1) indicating the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) stored in the ROM. From the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration, the capacity deterioration rate ΔC _y due to lithium deposition is calculated. On the other hand, if the compared resistance increase rate does not satisfy the relationship of ΔR _x ≧ ΔR _current (in the case of No), it is determined that excessive precipitation of lithium has occurred, and the process proceeds to step S50. In step S50, the ECU 30 estimates using the second map (Line 2) indicating the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) stored in the ROM. From the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration, the capacity deterioration rate ΔC _y due to lithium deposition is calculated.

In step S60, the ECU 30 determines whether or not the calculated capacity deterioration rate ΔC _y due to lithium precipitation exceeds the Li precipitation allowable amount ΔC _limit (that is, ΔC _y > ΔC _limit ). When the capacity deterioration rate ΔC _y exceeds the allowable amount ΔC _limit (Yes), the process proceeds to step S70 and the use of the battery is stopped. On the other hand, if the capacity deterioration rate ΔC _y does not exceed the allowable amount ΔC _limit (No), the process proceeds to step S80 and the use of the battery is continued.

According to the above embodiment, the capacity deterioration rate ΔC _y resulting from lithium deposition is calculated in consideration of an increase in resistance due to deposition of lithium as a charge carrier, so that the calculation accuracy is improved. Based on the calculated capacity deterioration rate ΔC _y , it is possible to determine whether or not the battery can be used without erroneous determination.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 1 Battery control system 10 Lithium ion secondary battery 20 Load 30 ECU

Claims (1)

A battery control system for a secondary battery comprising an electrode active material capable of reversibly occluding and releasing charge carriers,
A temperature sensor for detecting a temperature of the secondary battery;
A current sensor for detecting current flowing in and out of the secondary battery;
A voltage sensor for detecting a voltage of the secondary battery;
A calculation unit for calculating a capacity deterioration rate ΔC _y caused by the deposition of the charge carriers,
The calculation unit includes:
Measuring a resistance increase rate ΔR _current of the secondary battery from a current value detected by the current sensor and a voltage value detected by the voltage sensor;
Based on the temperature frequency distribution information including the battery temperature detected by the temperature sensor and the accumulated time held at each battery temperature, the resistance increase rate ΔR _x and the capacity deterioration rate after material deterioration due to material wear of the secondary battery Estimating ΔC _x ;
Comparing the measured resistance increase rate ΔR _current with the estimated resistance increase rate ΔR _x after material degradation;
When the compared resistance increase rate satisfies the relationship ΔR _x ≧ ΔR _current , the first map showing the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) is used. Calculating a capacity deterioration rate ΔC _y resulting from the deposition of the charge carriers from the estimated resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration;
If the compared resistance increase rate satisfies the relationship ΔR _x <ΔR _current , it is determined that excessive precipitation of the charge carriers occurs, and the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) and a second map having a characteristic different from that of the first map, the charge increasing rate ΔR _x after the material deterioration and the capacity deterioration rate ΔC _{x are used} to calculate the charge. A battery control system configured to perform a step of calculating a capacity deterioration rate ΔC _y resulting from the deposition of the carrier.

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