JP2010212013A - Battery system, vehicle, and battery-loaded device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery system allowing a battery to discharge with a suitable discharge pattern, for example, to control progress of deterioration of the battery, as well as a vehicle and a battery-loaded device equipped with such a battery system. <P>SOLUTION: The battery system includes a lithium ion secondary battery having a power generating element and an electrolyte containing lithium salt, a discharge control means for controlling a discharge current DC from the lithium ion secondary battery, and a voltage detection means for detecting a battery voltage. The discharge control means has relation acquisition means S20, S30 for sequentially acquiring a relation between a lapsed time TD since the start of the discharge and the battery voltage in a series of discharge period JD during which the discharge current continues to flow, and controls an amount of the subsequent discharge current based on the already acquired relation between the lapsed time and the battery voltage in the series of the discharge period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery system comprising a lithium ion secondary battery having an electrolytic solution containing a power generation element and a lithium salt, and discharge control means for controlling the discharge current of the lithium ion secondary battery. The present invention relates to a vehicle equipped with such a battery system and a battery-equipped device.

In recent years, lithium ion secondary batteries (hereinafter also simply referred to as batteries) have been used as power sources for driving portable electronic devices such as hybrid vehicles, notebook computers, and video camcorders.
When such a battery is discharged with a relatively large discharge current, in a series of discharge periods in which the discharge current continues to flow, the battery voltage decreases greatly instantaneously immediately after the start of discharge (first stage), and then gradually There is known a characteristic indicating a two-stage battery voltage decrease mode of decreasing (second stage).
Of these, the first stage is considered to correspond to an energization resistance that does not depend on battery characteristics such as contact resistance between members constituting the battery. On the other hand, the second stage is considered to correspond to a period in which the lithium salt in the electrolyte solution is diffused due to the battery reaction.

  By the way, as a technique for controlling the battery, there is known a technique (Patent Document 1) that performs output restriction when the battery voltage during discharge falls below a lower limit voltage. Further, a technique (Patent Document 2) that controls discharge current from a square integrated value of discharge current is also known.

JP 7-255133 A JP 2006-149181 A

When the battery is discharged with a relatively large current of, for example, 10 C or more (hereinafter also referred to as high-rate discharge), the lithium salt concentration of the electrolyte impregnated in the power generation element gradually becomes non-uniform locally, and the concentration distribution Occurs. As a result, it has been found that since the lithium salt concentration of the electrolytic solution deviates from the optimum concentration, a deterioration phenomenon (hereinafter also referred to as high-rate deterioration) in which the internal resistance of the battery increases.
Further, this high rate deterioration is caused by the fact that the discharge current is too large in the second stage of the discharge period (described above) after a while from the start of the second stage, so that the diffusion of the lithium salt cannot catch up with the battery reaction. This is thought to be due to the non-uniformity of the lithium salt concentration.
Therefore, when such a phenomenon occurs, the lithium salt serving as a carrier in the battery reaction decreases, so that the battery voltage becomes lower than the battery voltage determined by the electrical energy stored chemically in the battery. I must. That is, a phenomenon occurs in which the battery voltage is accelerated at a later stage of the second stage.

In the battery, the high-rate discharge causes the battery deterioration due to the battery reaction accompanying the discharge, such as the lithium salt concentration of the electrolyte gradually becoming non-uniform locally.
However, in the above-described techniques (Patent Document 1 and Patent Document 2), battery deterioration including high-rate deterioration cannot be appropriately suppressed.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a battery system capable of discharging with a discharge pattern suitable for a battery, such as suppressing the progress of deterioration of the battery. And Moreover, it aims at providing a vehicle provided with such a battery system, and a battery mounting apparatus.

  One aspect of the present invention is a lithium ion secondary battery having a power generation element in which a separator is interposed between a positive electrode plate and a negative electrode plate, and an electrolyte solution impregnated in the power generation element and containing a lithium salt; A battery system comprising: a discharge control unit that controls a discharge current discharged from the lithium ion secondary battery; and a voltage detection unit that detects a battery voltage of the lithium ion secondary battery, wherein the discharge control unit includes: , Having a relationship acquisition means for sequentially obtaining the relationship between the elapsed time from the start of discharge and the battery voltage in a series of discharge periods in which the discharge current continues to flow, and already obtained in the series of discharge periods The battery system controls the magnitude of the discharge current of the subsequent lithium ion secondary battery based on the relationship between the elapsed time and the battery voltage.

As described above, it is possible to detect whether the battery voltage is decreasing during the discharge period, that is, whether the battery is performing high-rate discharge in a state where the battery is deteriorated from the relationship between the elapsed time from the start of discharge and the battery voltage. It is possible to know the suitability of the battery driving conditions during discharge (selection of the magnitude of the discharge current, etc.).
On the other hand, in the battery system described above, the discharge control means has a relationship acquisition means for sequentially obtaining the relationship between the elapsed time and the battery voltage in a series of discharge periods. Thereby, for example, in a battery that is performing high-rate discharge, it is possible to appropriately capture an acceleration decrease phenomenon in the second stage of the battery voltage described above. And according to this, appropriate discharge current control, such as restrict | limiting the magnitude | size of subsequent discharge current of a battery to a relatively small value, can be performed.
Thus, it is possible to cause discharge with a discharge pattern suitable for the battery, such as appropriately suppressing the progress of deterioration such as high-rate deterioration in the battery.

  Further, in the battery system described above, the relationship acquisition unit is a change amount per unit time of the battery voltage with respect to a square root of the elapsed time as a relationship between the elapsed time from the start of discharge and the battery voltage. A first relationship acquisition unit that sequentially obtains a first relationship that is a relationship of voltage change rates, wherein the discharge control unit is an initial unit that is obtained in an initial period of the series of discharge periods of the first relationship. A regression line that follows the first relationship and the voltage change rate obtained after the initial period are sequentially compared to determine whether the voltage change rate obtained after the initial period deviates from the regression line. It is preferable that the battery system has a deviation detecting means for detecting and a discharge current reducing means for reducing the magnitude of the discharge current flowing through the lithium ion secondary battery thereafter when the deviation is detected.

  By the way, in the battery in the state of the second stage described above, it has been found that there is a linear relationship between the square root of the elapsed time from the start of discharge and the voltage change rate, which is the amount of change per unit time of the battery voltage. It was. When the discharge current is large, for example, in the case of high-rate discharge, the voltage change rate deviates from the regression line indicating this linear relationship in the latter stage of the second stage, that is, the battery voltage is accelerated in the second stage. It has also been found that there is a case where a phenomenon of deterioration occurs. In this case, in the power generation element of the battery, the concentration of the lithium salt contained in the electrolyte is locally uneven, and a portion where the lithium salt concentration is high or thin is generated. It has also been found that resistance increases.

  Based on this knowledge, in the battery system described above, the relationship acquisition unit is a first relationship acquisition unit that sequentially obtains the relationship (first relationship) between the square root of the elapsed time and the voltage change rate, and the discharge control unit is configured as described above. It has a deviation detection means and a discharge current reduction means. For this reason, the phenomenon in which the voltage change rate deviates from the regression line can be properly captured. And according to this, control of the discharge current suitable for a battery, such as restrict | limiting the magnitude | size of subsequent discharge current to a small value, can be performed. Thereby, in a power generation element, it can suppress that a local nonuniformity arises in the lithium salt density | concentration of electrolyte solution, and can suppress that a battery deteriorates.

  The initial period refers to the initial period of the second stage of the discharge period, that is, the period in which the battery voltage is gradually decreasing after the first stage. A period of 1 to 0.5 seconds is applicable. The initial first relationship refers to the relationship between the square root of elapsed time and the voltage change rate in the initial period.

  Furthermore, another aspect of the present invention provides a lithium ion secondary having a power generation element in which a separator is interposed between a positive electrode plate and a negative electrode plate, and an electrolytic solution impregnated in the power generation element and containing a lithium salt. A battery, discharge control means for controlling a discharge current discharged from the lithium ion secondary battery, charge state detection means for detecting a charge state of the lithium ion secondary battery, and battery temperature of the lithium ion secondary battery A battery temperature detecting means for detecting the discharge current and a discharge current detecting means for detecting the magnitude of the discharge current discharged from the lithium ion secondary battery, wherein the discharge control means comprises the discharge current The lithium ion secondary battery is allowed to use the detected state of charge, the battery temperature, and the magnitude of the discharge current in a series of discharge periods in which the current continues to flow. The discharge allowable period acquisition means for obtaining the discharge allowable period from the start of discharge, and the length of the series of discharge periods is equal to or longer than the discharge allowable period, and then flows through the subsequent lithium ion secondary battery And a post-elapse discharge current reduction means for reducing the magnitude of the discharge current.

In the battery system described above, the discharge control means includes the discharge allowable period acquisition means and the discharge current reduction means after elapse. For this reason, when the length of a series of discharge periods (elapsed time from the start of discharge) becomes equal to or longer than the discharge allowable period, the magnitude of the discharge current flowing through the subsequent batteries is reduced. Thereby, it is possible to prevent a phenomenon such as a battery voltage acceleratingly decreasing in the latter stage of the second stage.
Thus, it is possible to cause discharge with a discharge pattern suitable for the battery, such as appropriately suppressing the progress of deterioration such as high-rate deterioration in the battery.

  The discharge allowable period refers to a predetermined period as a period from the start of discharge until the discharge current is reduced by the discharge current lowering means after a lapse of time in a series of discharge periods. This discharge allowable period is a period given according to the state of charge, battery temperature, and discharge current, and is obtained in advance under, for example, the three conditions of charge state, battery temperature, and discharge current. The time until the voltage change rate deviates from the above-described regression line can be used.

  Furthermore, another aspect of the present invention is a vehicle including any one of the battery systems described above.

  Since the vehicle described above includes any one of the battery systems described above, appropriate discharge current control can be performed in accordance with the time change of the battery voltage or the length of a series of discharge periods. Therefore, a vehicle capable of discharging with a discharge pattern suitable for the battery, such as appropriately suppressing the progress of deterioration such as high rate deterioration in the battery, can be obtained.

  The vehicle may be a vehicle that uses electric energy from a battery for all or part of its power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, a forklift, an electric Wheelchairs, electric assist bicycles, and electric scooters.

  Furthermore, the other aspect of this invention is a battery mounting apparatus provided with one of the battery systems mentioned above.

  Since the above-described battery-equipped device includes any one of the battery systems described above, appropriate discharge current control can be performed according to changes in the battery voltage over time or the length of a series of discharge periods. Therefore, a battery-equipped device capable of discharging with a discharge pattern suitable for the battery, such as appropriately suppressing the progress of deterioration such as high-rate deterioration in the battery, can be obtained.

  The battery-equipped device may be any device equipped with a battery and using it as at least one of the energy sources. For example, a battery such as a personal computer, a mobile phone, a battery-driven electric tool, an uninterruptible power supply, Various household appliances, office equipment, and industrial equipment driven by

1 is a perspective view of a vehicle according to Embodiments 1 and 2. FIG. 1 is a perspective view of a lithium ion secondary battery according to Embodiment 1. FIG. It is sectional drawing (AA cross section of FIG. 2) of the lithium ion secondary battery of Embodiment 1. It is a graph which shows the relationship between the discharge time of a lithium ion secondary battery, and a battery voltage. It is a graph which shows the relationship between the square root discharge time of a lithium ion secondary battery, and a voltage change rate. 3 is a flowchart of the first embodiment. 3 is a flowchart of the first embodiment. It is a graph which shows the relationship between the square root discharge time of a lithium ion secondary battery, and a voltage change rate. 4 is a perspective view of a lithium ion secondary battery according to Embodiment 2. FIG. It is a graph which shows the relationship between the discharge time of a lithium ion secondary battery, and a battery voltage. It is a graph which shows the relationship between the square root discharge time of a lithium ion secondary battery, and battery voltage. It is a graph which shows the relationship between the energization allowable period of a lithium ion secondary battery, and discharge current. 6 is a flowchart of Embodiment 2. It is a perspective view of the hammer drill of Embodiment 3.

(Embodiment 1)
Next, Embodiment 1 of the present invention will be described with reference to the drawings.
First, the vehicle 100 according to the first embodiment will be described. FIG. 1 shows a perspective view of the vehicle 100.
The vehicle 100 controls a plurality of batteries 1 and 1 forming an assembled battery 120, a battery monitoring device 122 that detects each battery voltage VT of the plurality of batteries 1 and 1, and a discharge current DC of the batteries 1 and 1. A control device 130 is provided. In addition to these, the hybrid electric vehicle includes an engine 150, a front motor 141, a rear motor 142, a cable 160, a first inverter 171, a second inverter 172, and a vehicle body 190. The battery system M1 according to the first embodiment includes the batteries 1, 1, the battery monitoring device 122, and the control device 130.

  The control device 130 of the vehicle 100 has a CPU, ROM, and RAM (not shown) and includes a microcomputer that operates according to a predetermined program. The control device 130 communicates with a front motor 141, a rear motor 142, an engine 150, a first inverter 171, a second inverter 172, and a battery monitoring device 122 mounted inside the vehicle 100. The control device 130 controls the front motor 141, the rear motor 142, the engine 150, the first inverter 171 and the second inverter 172. Further, the control device 130 controls the discharge current DC discharged from the battery 1.

The assembled battery 120 of the vehicle 100 includes a battery unit 121 in which a plurality of batteries 1 and 1 are arranged, and a battery monitoring device 122 (see FIG. 1). Among these, the battery monitoring apparatus 122 detects the battery voltage VT of each battery 1 and 1 using the sensing wire which is not illustrated.
Further, the battery unit 121 accommodates a plurality of batteries 1 and 1 connected in series with each other by bolt fastening with a bus bar (not shown).

  The plurality of batteries 1 and 1 are wound lithium ion secondary batteries having a power generation element 20 including a positive electrode plate 21, a negative electrode plate 22, and a separator 23 (see FIG. 2). The power generation element 20 is housed in a rectangular box-shaped battery case 10.

  In the power generation element 20, a strip-like positive electrode plate 21 and a negative electrode plate 22 are wound in a flat shape via a strip-like separator 23 made of polyethylene (see FIG. 2). 3, the power generation element 20 includes a positive electrode lead portion 21f of a positive electrode plate 21 extending leftward in FIG. 3, and a negative electrode lead portion of a negative electrode plate 22 extending rightward in FIG. 22f. The positive electrode lead portion 21f is joined to a plate-shaped positive electrode current collecting member 71 bent in a crank shape (see FIG. 2). Note that a positive electrode terminal portion 71A located on the front end side (upward in FIG. 2) of the positive electrode current collecting member 71 protrudes upward from the battery case 10 in FIG. The negative electrode lead portion 22f is joined to a plate-shaped negative electrode current collecting member 72 bent in a crank shape (see FIG. 2). Note that a negative electrode terminal portion 72A located on the tip end side (upward in FIG. 2) of the negative electrode current collecting member 72 protrudes upward from the battery case 10 in FIG.

Further, the power generation element 20 is impregnated with an electrolytic solution 30 containing a lithium salt. This electrolytic solution 30 is an organic electrolytic solution in which LiPF ₆ is added as a solute to a mixed organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are adjusted to EC: EMC = 3: 7 by volume ratio. is there.

By the way, when the battery 1 is discharged, in a series of discharge periods in which the discharge current at the time of discharging continues to flow, the battery voltage VT decreases greatly immediately after the start of discharge (first stage), and then gradually decreases ( This shows a two-stage reduction characteristic (second stage).
This will be specifically described with reference to a graph showing a change with time of the battery voltage VT of the battery 1 shown in FIG.
For the battery 1 whose battery voltage VT is the initial voltage VL, the discharge is started at the discharge time TD = 0. Then, after the time of 0.1 second (TD = 0.1) has elapsed from the start of discharge (TD = 0), the battery voltage VT rapidly decreases to the voltage VM (first stage).
Subsequently (TD> 0.1), the battery voltage VT of the battery 1 gradually decreases from the first stage starting from the voltage VM (second stage).

  As the relationship between the discharge time TD and the battery voltage VT in the second stage, the horizontal axis represents the square root discharge time TDH, which is the square root of the discharge time TD, and the vertical axis represents the unit time of the battery voltage VT (this embodiment 1). It has been found that there is a linear relationship between the voltage change rate VV, which is the amount of change per second). That is, as shown in the graph of FIG. 5, when the square root of the discharge time TD is taken on the horizontal axis, the voltage change rate VV decreases linearly.

  However, it has been found that if the battery 1 in the second stage is continuously discharged, the linear relationship may be lost between the square root discharge time TDH and the voltage change rate VV in the latter stage of the second stage. That is, as indicated by the broken line in FIG. 5, the voltage change rate VV of the battery 1 changes so as to deviate from the extension of the straight line (the dashed line in FIG. 5) after the square root discharge time TDH reaches T2H. There are things to do. In this case, as shown by a broken line in FIG. 4, this corresponds to the battery voltage VT acceleratingly decreasing in the latter part of the discharge period. Furthermore, in such a case, it has been found that the concentration of the lithium salt of the electrolytic solution 30 impregnated in the power generation element 20 of the battery 1 gradually becomes non-uniform in location and a concentration distribution is generated. Such a concentration distribution of the lithium salt is one of the causes for increasing the internal resistance of the battery 1.

  Based on the above knowledge, the control of the battery 1 in the battery system M1 of Embodiment 1 will be described in detail with reference to the flowcharts of FIGS.

First, in the main routine shown in FIG. 6, when the operation of the vehicle 100 is started (key-on) (step S1), the control device 130 of the vehicle 100 is activated. In the subsequent step S2, it is determined whether or not the battery 1 is discharged as the vehicle 100 travels.
If NO, that is, if the battery 1 is not discharged, step S2 is repeated. On the other hand, if YES, that is, if the battery 1 is discharged, the battery 1 is discharged, and the process proceeds to the first relationship acquisition subroutine of step S20.

The first relationship acquisition subroutine in step S20 will be described with reference to FIG.
First, in step S21, the discharge time TD (that is, the elapsed time from the start of discharge) of the battery 1 and the battery voltage VT of the battery 1 are measured.
Subsequently, in step S22, a first relationship W indicating the relationship between the square root discharge time TDH and the voltage change rate VV is acquired. Specifically, the square root discharge time TDH is calculated from the discharge time TD, and the voltage change rate VV is calculated from the battery voltage VT obtained last time and this time, respectively. The square root discharge time TDH and the voltage change rate VV are stored in relation to each other. The relationship between the square root discharge time TDH and the voltage change rate VV is a first relationship W (a relationship in which the horizontal axis can be expressed in a graph of the square root discharge time TDH and the vertical axis in the voltage change rate VV). After this step S22, the process returns to the main routine.

In step S3 of the main routine, it is determined whether or not the battery 1 is to be continuously discharged.
Here, if NO, that is, if the battery 1 is not continuously discharged, the process proceeds to step S11, where a series of discharge periods JD in the battery 1 is terminated, and the process returns to step S2. On the other hand, if YES, that is, if the discharge is continued, the process proceeds to step S4, where it is determined whether or not the discharge time TD has passed the initial period TF. The initial period TF corresponds to the initial period of the second stage in the series of discharge periods JD, and is 0.5 seconds in the first embodiment.

If NO, that is, if the discharge time TD has not yet passed the initial period TF, the process returns to step S20 and the first relationship acquisition subroutine is performed again. For this reason, the first relationship acquisition subroutine S20 is sequentially performed (in the first embodiment, every 0.10 seconds).
On the other hand, if YES, that is, if the discharge time TD has passed the initial period TF, the process proceeds to step S5.

  Next, in step S5, the square root discharge time TDH and the voltage change are obtained using the initial first relation WP which is the plurality of first relations W (the relation between the square root discharge time TDH and the voltage change rate VV) acquired in the initial period TF. The equation of the regression line LN1 with the velocity VV is calculated (LN1: VV = −a · TDH + b (a and b are constants)). FIG. 8 shows the initial first relation WP as a graph of the square root discharge time TDH on the horizontal axis and the voltage change rate VV on the vertical axis.

After step S6 described above, the process proceeds to a first relationship acquisition subroutine S30 similar to the first relationship acquisition subroutine described above.
Subsequently, in step S7, it is determined whether or not the battery 1 is continuously discharged.
Here, if NO, that is, if the battery 1 is not continuously discharged, the process proceeds to step S11, where a series of discharge periods JD in the battery 1 is terminated, and the process returns to step S2. On the other hand, if YES, that is, if the discharge is continued, the process proceeds to step S7, and the voltage change rate VV in the square root discharge time TDH, that is, the square root discharge time TDH and the voltage change rate related in the first relationship acquisition subroutine S30 described above. It is determined whether or not the voltage change rate VV has deviated from the regression line LN1 using the first relationship W which is a relationship with VV.
Note that the voltage change rate VV deviates from the regression line LN1 is that the difference between the regression voltage change rate VVK obtained using the regression line LN1 from the square root discharge time TDH and the actually obtained voltage change rate VV is a predetermined determination. This is a case where the value is larger than the value K (| VVK−VV |> K).

  If NO, that is, if the first relationship W is not deviated from the regression line LN1, the process returns to step S30, and the first relationship acquisition subroutine is performed again. On the other hand, if YES, that is, if the first relationship W deviates from the regression line LN1, the process proceeds to step S8, and the magnitude of the discharge current DC of the battery 1 is limited to be small.

Next, in step S9, it is determined whether or not the battery 1 is continuously discharged.
Here, if YES, that is, if the discharge is continued, step S9 is repeated. On the other hand, if NO, that is, if the battery 1 is not continuously discharged, the process proceeds to step S10, the restriction of the discharge current DC is released, the series of discharge periods JD is terminated (step S11), and the process returns to step S2.

  The first relationship acquisition subroutines S20 and S30 are the relationship acquisition means when the control device 130 of the first embodiment is the discharge control means, the battery monitoring device 122 is the voltage detection means, and the discharge time TD is the elapsed time from the start of discharge. This corresponds to (first relation acquisition means). Step S7 corresponds to the deviation detection means, and step S8 corresponds to the discharge current reduction means.

As described above, the battery system M1 of the vehicle 100 according to the first embodiment has the relationship between the discharge time TD and the battery voltage VT, specifically, the square root discharge time TDH and the voltage change rate VV in the series of discharge periods JD. The relationship acquisition means S20 and S30 which obtain the 1st relationship W which is these relationships sequentially are provided. Thereby, for example, in the battery 1 that is performing high-rate discharge, it is possible to appropriately detect an acceleration decrease phenomenon in the second stage of the battery voltage VT described above. Accordingly, after this detection, it is possible to perform appropriate discharge current control such as limiting the discharge current DC of the battery 1 to a relatively small value.
Thus, the battery 1 can be discharged with a discharge pattern suitable for the battery 1 such as appropriately suppressing the progress of deterioration such as high rate deterioration.

  The relationship acquisition means S20 and S30 are first relationship acquisition means S20 and S30 that sequentially obtain a first relationship W that is a relationship between the square root discharge time TDH and the voltage change rate VV. The battery system M1 is a divergence detection means. S7 and discharge current lowering means S8. For this reason, the phenomenon in which the voltage change rate VV deviates from the regression line LN1 can be properly captured. The discharge current DC appropriate for the battery 1 can be controlled in accordance with the divergence phenomenon of the voltage change rate VV. Thereby, in the power generation element 20 of the battery 1, it is possible to suppress the occurrence of local non-uniformity in the lithium salt concentration of the electrolytic solution 30 and to suppress the deterioration of the battery 1.

  In addition, since the vehicle 100 according to the first embodiment includes the battery system M1, it is possible to perform appropriate discharge current control according to the time change (voltage change speed VV) of the battery voltage VT. Therefore, the vehicle 100 capable of discharging with a discharge pattern suitable for the battery 1 such as appropriately suppressing the progress of deterioration such as high rate deterioration in the battery 1 can be obtained.

(Embodiment 2)
Next, a vehicle 200 according to the second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, the control device 130 in the battery system M2 detects the charge allowable period from the start of discharge according to the charge state of the battery, the battery temperature and the magnitude of the discharge current, and the battery temperature of the battery. The second embodiment is different from the first embodiment in that it has a thermocouple.

  As shown in FIG. 9, the battery 2 according to the second embodiment includes, in addition to the battery 1 according to the first embodiment described above, the vicinity of the center of the first main surface 10 </ b> F facing the front in FIG. 9 in the battery case 10. Further, a thermocouple 40 is arranged. The thermocouple 40 is fixed to the battery case 10 with an insulating tape TP. The thermocouple 40 is connected to the battery monitoring device 122, and the battery temperature TM information is transmitted to the control device 130 through the battery monitoring device 122.

  By the way, the control device 130 according to the second embodiment has a map MP that summarizes the energization allowable period TG for each battery temperature TM, for each charge state SC, and for each magnitude of the discharge current DC of the battery 1. Is remembered. The energization allowable period TG is a predetermined period as a grace period from the start of discharge until the discharge current DC is limited to be small in a series of discharge periods JD of the battery 2. Further, in the second embodiment, as the discharge allowable period TG, the charge state SC, the battery temperature TM, and the magnitude of the discharge current DC are respectively determined in advance as shown in the first embodiment. The time from the start of discharge until the voltage change rate VV deviates from the regression line is used.

A method for creating the map MP of the energization allowable period TG will be specifically described.
First, a battery 2 having a predetermined battery temperature TMV and a predetermined charge state SCV is prepared, and a discharge test is performed in which a predetermined discharge current DCV is passed. By this test, the change with time of the battery voltage VT of the battery 1 shown in FIG. 4 was obtained.
The test result is shifted by the battery voltage VT when time T1 (0.1 second in the second embodiment) has elapsed from the start of discharge (discharge time TD = 0). That is, the vertical axis of the graph is moved so that the voltage VM at time T1 becomes 0 V (see FIG. 10).

Next, the horizontal axis of the graph shown in FIG. 10 is changed from the discharge time TD to the square root discharge time TDH to make a graph showing the battery voltage VT at the square root discharge time TDH (see FIG. 11). The time T1 is the square root time T1H.
Then, although the relationship between the square root discharge time TDH and the battery voltage VT shows a linear relationship, it can be seen that a curve relationship is shown in the later stage of discharge. Therefore, a linear regression line LN2 is determined using each battery voltage VT in the square root discharge time TDH in the range of the first square root time T1H (√0.1) to √0.5.
Then, the regression line LN2 and the battery voltage VT at the square root discharge time TDH are overlapped. Thereby, the deviation square root discharge time TDG in which the battery voltage VT in the square root discharge time TDH deviates from the regression line LN2 is known (see FIG. 10). A numerical value obtained by squaring the deviation square root discharge time TDG is set as the above-described energization allowable period TG at a predetermined battery temperature TMV, a predetermined charge state SCV, and a predetermined discharge current DCV.

Next, with respect to the battery 2 in the predetermined battery temperature TMV and the predetermined charge state SCV, a discharge test similar to the above is performed by changing the magnitude of the discharge current DC, and the energization allowable period TG under these conditions is performed. Get. In this way, a graph showing the relationship between the energization allowable period TG and the magnitude of the discharge current DC at a predetermined battery temperature TMV and a predetermined charging state SCV is completed (see FIG. 12).
Further, the same discharge test as described above is performed while changing the battery temperature TM and the state of charge SC. In this manner, a plurality of graphs showing the relationship between the energization allowable period TG and the magnitude of the discharge current DC at each battery temperature TM (-30 to 60 ° C.) and each state of charge SC (0 to 100%) are completed. . Accordingly, a map MP of the energization allowable period TG is created according to the battery temperature TM, the charge state SC, and the magnitude of the discharge current DC. So remember this.

  The control device 130 that accommodates the map MP of the energization allowable period TG described above controls the discharge current DC of the battery 2 in the battery system M2 of Embodiment 2 in detail with reference to the flowchart of FIG. To do.

First, when the operation of the vehicle 200 is started (key-on) (step S41), the control device 130 of the vehicle 200 is activated. In a succeeding step S42, it is determined whether or not the battery 2 is to be discharged.
If NO, that is, if the battery 2 is not discharged, step S42 is repeated. On the other hand, if YES, that is, if the battery 2 is to be discharged, the process proceeds to step S43, where the battery temperature TM, the charge state SC, and the magnitude of the discharge current DC of the battery 2 are detected.

  Specifically, the battery temperature TM of the battery 2 is detected using the above-described thermocouple 40 (see FIG. 9). Further, the charge state SC of the battery 2 is calculated from the integrated value of the charge / discharge current accumulated in the control device 130. The magnitude of the discharge current DC can be determined from the command value that the control device 130 commands the inverters 171 and 172.

Subsequently, in step S44, an energization allowable period TG is acquired. Specifically, energization under conditions that all match the battery temperature TM, charge state SC, and discharge current DC of the battery 2 obtained in step S43 from the map MP of the energization allowable period TG accommodated in the control device 130. The allowable period TG is selected.
Then, it progresses to step S45, the discharge of the battery 2 is started, and the discharge time TD of the battery 2 is measured (step S46).

Next, in step S47, it is determined whether or not the battery 2 is to be continuously discharged.
Here, if NO, that is, if the battery 2 is not continuously discharged, the process proceeds to step S52, where a series of discharge periods JD in the battery 2 is terminated, and the process returns to step S42. On the other hand, if YES, that is, if the discharge is continued, the process proceeds to step S48, and it is determined whether or not the difference obtained by subtracting the energization allowable period TG from the discharge time TD is 0 or more.

  If NO, that is, if the difference obtained by subtracting the energization allowable period TG from the discharge time TD is negative, the process returns to step S46. On the other hand, if YES, that is, if the difference obtained by subtracting the energization allowable period TG from the discharge time TD is 0 or more, the process proceeds to step S49, and the magnitude of the discharge current DC of the battery 2 is limited to be small.

Next, it progresses to step S50 and it is discriminate | determined whether the battery 2 is discharged continuously.
If YES, that is, if the discharge is continued, step S50 is repeated with the discharge current DC limited. On the other hand, if NO, that is, if the battery 2 is not continuously discharged, the process proceeds to step S51, the restriction of the discharge current DC is released, a series of discharge periods JD are terminated (step S52), and the process returns to step S42.

  Note that the control device 130 of the second embodiment is the charge state detection means and discharge current detection means, the thermocouple 40 is the battery temperature detection means, step S44 is the discharge allowable period acquisition means, and the discharge current decreases after step S49 has elapsed. It corresponds to each means.

As described above, the battery system M2 of the vehicle 200 according to the second embodiment includes the above-described discharge allowable period acquisition unit S44 and the post-elapse discharge current reduction unit S49. For this reason, even when the discharge time TD is equal to or longer than the allowable discharge period TG (that is, the difference obtained by subtracting the allowable discharge period TG from the discharge time TD is equal to or greater than 0), for example, the battery after step S49 in the flowchart shown in FIG. 2 can be reduced, and the battery voltage VT can be prevented from accelerating in the second stage.
Thus, the battery 2 can be discharged with a discharge pattern suitable for the battery 2 such as appropriately suppressing the progress of deterioration such as high-rate deterioration.

  In addition, since the vehicle 200 according to the second embodiment includes the battery system M2, appropriate discharge current control can be performed according to the length of the series of discharge periods JD (discharge time TD). Therefore, the vehicle 200 can be discharged with a discharge pattern suitable for the battery 2 such as appropriately suppressing the progress of deterioration such as high-rate deterioration in the battery 1.

(Embodiment 3)
Further, the hammer drill 300 of the third embodiment is equipped with a battery pack 310 incorporating either of the battery systems M1 and M2 described above, and has a battery pack 310 and a main body 320 as shown in FIG. It is a battery-equipped device. The battery pack 310 is detachably accommodated in the pack accommodation portion 321 of the main body 320 of the hammer drill 300.

  In addition, since the hammer drill 300 according to the third embodiment includes the battery systems M1 and M2, the time change (voltage change rate VV) of the battery voltage VT or the length of the series of discharge periods JD (discharge time). Depending on (TD), appropriate discharge current control can be performed. Therefore, the hammer drill 300 capable of discharging with a discharge pattern suitable for the battery 1 or the battery 2 such as appropriately suppressing the progress of deterioration such as high rate deterioration in the battery 1 or the battery 2 can be obtained.

  In the above, the present invention has been described with reference to the first embodiment, the second embodiment, and the third embodiment. However, the present invention is not limited to the above-described embodiment, and may be appropriately changed without departing from the gist thereof. Needless to say, this is applicable.

1, 2 batteries (lithium ion secondary batteries)
20 Power generation element 21 Positive electrode plate 22 Negative electrode plate 23 Separator 30 Electrolytic solution 40 Thermocouple (battery temperature detection means)
100, 200 Vehicle 122 Battery monitoring device (voltage detection means)
130 Control device (discharge control means)
300 Battery-equipped equipment 310 Battery pack (battery system)
DC discharge current JD A series of discharge periods LN1, LN2 regression line M1, M2 battery system SC charge state TD discharge time (elapsed time)
TDH square root discharge time (square root of elapsed time)
TF initial period TG discharge allowable period TM battery temperature VT battery voltage VV voltage change speed W first relation WP initial first relation

Claims (5)

A power generation element having a separator interposed between the positive electrode plate and the negative electrode plate, and
A lithium ion secondary battery having an electrolyte solution impregnated in the power generation element and containing a lithium salt;
A discharge control means for controlling a discharge current discharged from the lithium ion secondary battery;
A voltage detection means for detecting a battery voltage of the lithium ion secondary battery, and a battery system comprising:
The discharge control means includes
In a series of discharge periods in which the discharge current continues to flow, it has relationship acquisition means for sequentially obtaining the relationship between the elapsed time from the start of discharge and the battery voltage,
A battery system that controls the magnitude of the discharge current of the subsequent lithium ion secondary battery based on the relationship between the elapsed time and the battery voltage that has already been obtained within the series of discharge periods. The battery system according to claim 1,
The relationship acquisition means
As the relationship between the elapsed time from the start of the discharge and the battery voltage, a first relationship that is a relationship of a voltage change rate that is a change amount per unit time of the battery voltage with respect to a square root of the elapsed time is sequentially obtained. Relationship acquisition means,
The discharge control means includes
Of the first relationship, the regression line following the initial first relationship obtained in the initial period of the series of discharge periods and the voltage change rate obtained after the initial period are sequentially compared, Deviation detection means for detecting whether or not the voltage change rate obtained after the initial period has deviated from the regression line;
A battery system comprising: a discharge current reducing unit that reduces the magnitude of the discharge current flowing through the lithium ion secondary battery thereafter when the deviation is detected. A power generation element having a separator interposed between the positive electrode plate and the negative electrode plate, and
A lithium ion secondary battery having an electrolyte solution impregnated in the power generation element and containing a lithium salt;
A discharge control means for controlling a discharge current discharged from the lithium ion secondary battery;
Charging state detection means for detecting the charging state of the lithium ion secondary battery;
Battery temperature detecting means for detecting the battery temperature of the lithium ion secondary battery;
A discharge current detection means for detecting the magnitude of a discharge current discharged from the lithium ion secondary battery, and a battery system comprising:
The discharge control means includes
In a series of discharge periods in which the discharge current continues to flow,
A discharge permissible period obtaining means for obtaining a discharge permissible period from the start of discharge, which is permitted to the lithium ion secondary battery, using the detected state of charge, the battery temperature and the magnitude of the discharge current;
And a discharge current reducing means for reducing the magnitude of the discharge current flowing through the lithium ion secondary battery thereafter when the length of the series of discharge periods is equal to or longer than the discharge allowable period. Battery system. A vehicle comprising the battery system according to any one of claims 1 to 3. A battery-equipped device comprising the battery system according to any one of claims 1 to 3.

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