JP2012138362A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack capable of making degrees of deterioration of a plurality of thin batteries which constitute a battery pack as uniform as possible.SOLUTION: The battery pack makes degrees of deterioration of a plurality of thin batteries as uniform as possible even if a temperature variation exists among temperatures of the plurality of thin batteries by reducing a residual capacity ratio more against a full charge capacity of each thin battery at charging and discharging for thin batteries 1B and 1C whose temperatures at charging and discharging are higher and by reducing a residual capacity ratio more against a full charge capacity of each thin battery at charging and discharging for thin batteries 1B and 1C which are positioned inside in a lamination direction.

Description

  The present invention relates to an assembled battery formed by laminating a plurality of thin batteries in which battery elements are housed in a film outer package, for example.

  Conventionally, an assembled battery formed by laminating a plurality of thin batteries is known in Patent Document 1 below.

  The assembled battery described in Patent Document 1 has a configuration in which a plurality of thin batteries are stacked and accommodated in a box, and the cell voltage of each thin battery of the plurality of thin batteries in the box becomes uniform. So that it is controlled.

JP 2003-346748 A

  However, in the above-described assembled battery, when the degree of deterioration of a specific thin battery becomes large, that is, when a large imbalance occurs in the degree of deterioration of the entire assembled battery, it is necessary to replace the thin battery having a large degree of deterioration. However, in order to replace a specific thin battery, a disassembly work such as taking out the assembled battery from the box and disassembling the assembled battery becomes necessary.

On the other hand, when the entire assembled battery is replaced, it is necessary to replace a thin battery that does not have a large degree of deterioration, which increases the cost. Thus, conventionally, it has been desired to make the deterioration degree of each thin battery constituting the assembled battery as uniform as possible.

  Then, this invention is proposed in view of the above-mentioned situation, and it aims at providing the assembled battery which makes the deterioration degree of the some thin battery which comprises an assembled battery uniform as much as possible.

  The present invention is an assembled battery formed by electrically connecting a plurality of thin batteries, the remaining capacity ratio with respect to the full charge capacity of each thin battery at the time of charging / discharging, the thin battery having a low temperature at the time of charging / discharging, A low remaining capacity ratio was set for a thin battery having a high temperature during charging and discharging.

  Further, the present invention relates to the remaining capacity ratio with respect to the full charge capacity of each thin battery at the time of charging / discharging, and the thin battery positioned on the outer side in the stacking direction has a lower remaining capacity ratio than the thin battery positioned on the inner side in the stacking direction. did.

  According to the assembled battery according to the present invention, the thin battery having a high temperature during charging / discharging reduces the remaining capacity ratio with respect to the full charge capacity of each thin battery during charging / discharging, or the thin battery positioned on the inner side in the stacking direction is By reducing the ratio of the remaining capacity to the full charge capacity of each thin battery during charging and discharging, even if there is a variation in temperature among multiple thin batteries, the degree of deterioration of the multiple thin batteries can be made as uniform as possible. Can do.

FIG. 3 is a plan view, a side view, and a circuit diagram showing a configuration of an assembled battery controlled by the present invention. It is a figure which shows the relationship between the temperature of a thin battery, and the raise rate of internal resistance. It is a figure which shows the relationship between the remaining capacity (SOC) of a thin battery, and the increase rate of internal resistance. It is a figure which shows the relationship between the usage time of the assembled battery to which this invention is applied, and the change of internal resistance, and the relationship between the usage time of the assembled battery which is a comparative example, and a change of internal resistance. It is a block diagram showing a configuration for actually detecting the temperature of a thin battery and controlling the voltage of the thin battery. It is a flowchart which shows the process sequence which controls the remaining capacity of each thin battery.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is applied to a control method for charging / discharging an assembled battery configured as shown in FIG. 1, for example.

  As shown in the plan view of the thin battery 1 constituting the assembled battery in FIG. 1 (a), each thin battery 1 accommodates a battery element by an exterior film 1a, and battery terminals 1b and 1c are externally provided from the battery element. It is formed by exposing and bonding the joint surface of the outer peripheral portion of the exterior film 1a around the battery element.

This assembled battery shall consist of the thin battery 1 of the same structure.

  As shown in the side view of FIG. 1B, the assembled battery has thin batteries 1A, 1D arranged outside the four thin batteries 1A, 1B, 1C, 1D in the vertical direction, and inside the stacking direction. Thin batteries 1B and 1C are provided.

  Connection lines 2A, 2B, 2C, 2D, and 2E are drawn out from the battery terminals 1b and 1c of the thin batteries 1A, 1B, 1C, and 1D, respectively. For example, the connection line 2A drawn from the thin battery 1A is connected to the positive electrode of the electric device (not shown), and the connection line 2E drawn from the thin battery 1D is connected to the negative electrode of the electric device to supply power to the electric device. Supply. As shown in FIG. 1C, this assembled battery is formed by connecting thin batteries 1A, 1B, 1C, and 1D in series.

Such an assembled battery charges and discharges power by each of the thin batteries 1A, 1B, 1C, and 1D when power is supplied to the electrical equipment. Therefore, if currents of the same value flow through the stacked thin batteries 1A, 1B, 1C, 1D, the amounts of heat generated are substantially the same. In this case, among the plurality of thin batteries 1A, 1B, 1C, and 1D constituting the assembled battery, the temperature of the thin batteries 1B and 1C disposed on the inner side in the stacking direction is the temperature of the thin batteries 1A and 1D on the outer side in the stacking direction. It becomes higher than the temperature. FIG. 2 shows the temperature during storage and the rate of increase in internal resistance of the thin battery when the remaining capacity (SOC) of the thin battery is stored at 50% for half a year. As shown in FIG. As the temperature during power charging / discharging increases, the rate of increase in internal resistance [%] (that is, the degree of deterioration) increases. FIG. 3 is a diagram showing the remaining capacity of the thin battery 1 and the rate of increase in internal resistance when the thin battery 1 is stored for six months at each temperature (25 ° C., 45 ° C., 55 ° C.). As shown in FIG. 3, as the remaining capacity (SOC (State Of Charge)) [%] of the thin battery 1 increases, the rate of increase in internal resistance [%] (that is, the degree of deterioration) increases.

  Therefore, by arranging the thin battery 1 on the outer side in the stacking direction, the heat generated during charging / discharging is easily dissipated, and the remaining capacity of the thin batteries 1A, 1D at which the temperature during power charging / discharging does not increase is reduced. The battery pack is made higher than the remaining capacity of the thin batteries 1B and 1C, which are arranged on the inner side in the stacking direction than the batteries 1A and 1D, and the heat generated during charging / discharging is difficult to dissipate and the temperature during power charging / discharging increases. The variation in the deterioration degree (internal resistance increase rate) of the plurality of thin batteries 1A, 1B, 1C, 1D constituting the battery can be suppressed. Alternatively, since it is known that there is a correlation between the remaining capacity (SOC) of the thin battery and the open circuit voltage, as shown in FIG. The open circuit voltage of 1C may be set lower than the open circuit voltages of the thin batteries 1A and 1D in which the temperature during power charging / discharging is not higher than that of the thin batteries 1B and 1C.

  In other words, in other words, the remaining capacity of the thin batteries 1B and 1C where the temperature during power charging / discharging becomes higher is lower than that of the thin batteries 1A and 1D where the temperature during power charging / discharging is not higher than that of the thin batteries 1B and 1C. The thin batteries 1B and 1C have a lower open-circuit voltage than the remaining capacity or the temperature at the time of power charging / discharging is higher than that of the thin batteries 1A and 1D. It is the same as making it higher than the open circuit voltage.

  The rate of increase in internal resistance is the percentage of increase in internal resistance after deterioration when the internal resistance of the battery at the time of a new product is 1. In other words, the internal resistance of the battery at the time of a new product is expressed as R0. When the internal resistance after deterioration is R1, it is a numerical value represented by (R1-R0) / R0 × 100.

  In the example shown in FIG. 1 (c), the average open circuit voltage of the thin batteries 1A, 1B, 1C, 1D is 4 [V], and the open circuit voltage of the thin batteries 1B, 1C at which the temperature during power charging / discharging becomes high is 3. The open circuit voltage of the thin batteries 1 </ b> A and 1 </ b> D at which the temperature during power charging / discharging does not increase is set to 4.05 [V]. Alternatively, the average remaining capacity of the thin batteries 1A, 1B, 1C, and 1D is set to 80 [%], the remaining capacity of the thin batteries 1B and 1C that increase the temperature during power charging and discharging is set to 75 [%], and the power charging and discharging is performed. The remaining capacity of the thin batteries 1A and 1D where the temperature does not increase is set to 85 [%]. Here, the higher the remaining capacity of the thin battery 1, the higher the open circuit voltage. Conversely, the higher the open circuit voltage, the higher the remaining capacity of the thin battery 1, and there is a correlation between the open circuit voltage and the remaining capacity. There is a relationship.

  Thus, when the open circuit voltage or the remaining capacity is changed between the thin batteries 1B and 1C in which the temperature during power charging / discharging becomes high and the thin batteries 1A and 1D in which the temperature during power charging / discharging does not become high (this application), a plurality of FIG. 4 shows the relationship between the usage time of the assembled battery and the change in internal resistance when the thin battery 1 has the same open circuit voltage or remaining capacity (comparative example). In addition, as conditions for measuring the change of the internal resistance shown in FIG. 4, the operation of the four steps of charging, charging suspension, discharging, and discharging stop is repeated, and the current of each thin battery 1 at the time of charging / discharging is set as a constant current. .

  The discharge condition is a current value of 10 CA (current value that discharges the entire capacity in 6 minutes), the discharge end voltage is 2.5 [V], and the charge condition is a current value of 10 CA (discharges the entire capacity in 6 minutes). Current value), the charging voltage is 4.2 [V], and the pause time is 1 minute. The internal resistance was obtained by measuring a voltage drop when the thin battery 1 was discharged with a constant current, and measuring a direct current resistance using Ohm's law from the constant current and the voltage value.

  According to FIG. 4 obtained by such measurement, the increase rate of the internal resistance of the present application is gentler than the increase rate of the internal resistance shown as the comparative example.

  The reason why the difference in the increase rate of the internal resistance will be described. By charging and discharging, the temperature of each thin battery 1 rises, but the thin batteries 1A and 1D on the outer side in the stacking direction have better heat dissipation than the thin batteries 1B and 1C on the inner side in the stacking direction. The temperature of the thin batteries 1B and 1C is higher than that of the thin batteries 1A and 1D on the outer side in the stacking direction. In particular, as in the comparative example, when the remaining capacity or the open circuit voltage of the plurality of thin batteries 1 is the same, the internal resistance of the thin batteries 1B and 1C on the inner side in the stacking direction is the same as the thin batteries 1A and 1D on the outer side in the stacking direction. Higher than the internal resistance. Therefore, in the assembled battery in the comparative example, the life of the thin batteries 1B and 1C on the inner side in the stacking direction is the life of the assembled battery itself.

  On the other hand, when the remaining capacity or open circuit voltage of the thin batteries 1B and 1C on the inner side in the stacking direction is lower than the remaining capacity or open circuit voltage of the thin batteries 1A and 1D on the outer side of the stacking direction as in the present application, Since the difference between the internal resistance increase rate of the thin batteries 1A, 1D on the outer side in the direction and the internal resistance increase rate of the thin batteries 1B, 1C on the inner side in the stacking direction can be reduced, The battery life can be improved.

  That is, since the remaining capacity or open circuit voltage of the thin batteries 1A, 1D outside the stacking direction is higher than the remaining capacity or open circuit voltage of the thin batteries 1B, 1C inside the stacking direction, the thin battery 1A outside the stacking direction. , 1D is close to that of the thin batteries 1B, 1C on the inner side in the stacking direction. In the above-described example, the difference between the remaining capacity of the thin batteries 1B and 1C where the temperature during power charging / discharging is high and the remaining capacity of the thin batteries 1A and 1D where the temperature during power charging / discharging is not high is determined for each thin battery 1. By making it within 10% of the maximum capacity, the life of the thin batteries 1A, 1D outside the stacking direction and the life of the thin batteries 1B, 1C inside the stacking direction can be made equal. Further, the difference between the open circuit voltage of the thin batteries 1B and 1C where the temperature during power charging / discharging is high and the open circuit voltage of the thin batteries 1A and 1D where the temperature during power charging / discharging is not high is within 0.1 [V]. Thus, the life of the thin batteries 1A and 1D on the outer side in the stacking direction can be made equal to the life of the thin batteries 1B and 1C on the inner side in the stacking direction.

  In addition, the remaining capacity or open circuit voltage of the thin batteries 1B and 1C in which the temperature during power charging / discharging becomes higher than the above remaining capacity difference or open circuit voltage difference, and the thin batteries 1A and 1D in which the temperature during power charging / discharging does not increase. If the difference between the remaining capacity or the open circuit voltage of the battery is excessively large, the temperature difference between the thin batteries 1B, 1C on the inner side in the stacking direction and the thin batteries 1A, 1D on the outer side in the stacking direction is smaller than that of the thin batteries 1B, 1C on the inner side in the stacking direction. The difference in temperature between the thin batteries 1A and 1D on the outer side in the stacking direction and the difference in the open circuit voltage is increased, and the rate of increase in internal resistance of the thin batteries 1A and 1D on the outer side in the stacking direction increases. The increase rate of the internal resistance of the inner thin batteries 1B and 1C will be larger. Therefore, as described above, the difference between the remaining capacity of the thin batteries 1B and 1C where the temperature during power charging / discharging is high and the remaining capacity of the thin batteries 1A and 1D where the temperature during power charging / discharging is not high is determined for each thin battery. The open circuit voltage of the thin batteries 1B and 1C within 10% of the maximum capacity of the battery 1 or the temperature during power charge / discharge and the open circuit voltage of the thin batteries 1A and 1D where the temperature during power charge / discharge does not increase The difference is preferably within 0.1 [V].

  Next, another embodiment of the present invention will be described. In the above-described embodiment, the remaining capacity difference or the open circuit voltage difference between the thin batteries 1B and 1C (inside the stacking direction) and the thin batteries 1A and 1D (inside the stacking direction) where the temperature during power charging / discharging becomes high in advance is not high. In this embodiment, as shown in FIG. 5, the temperature of each thin battery 1A, 1B, 1C, 1D is actually set to the temperature detectors 3A, 3B, The remaining capacity or open circuit voltage of each thin battery 1A, 1B, 1C, 1D is controlled by the bypass circuits 4A, 4B, 4C, 4D.

  The temperature detectors 3A, 3B, 3C, 3D are provided corresponding to the thin batteries 1A, 1B, 1C, 1D, and are temperature sensors that detect the surface temperature of the thin batteries 1A, 1B, 1C, 1D. The temperature detectors 3A, 3B, 3C, 3D not only measure the temperature of the thin batteries 1A, 1B, 1C, 1D directly, but also calculate the internal resistance of each thin battery 1A, 1B, 1C, 1D. You may estimate the temperature of each thin battery 1A, 1B, 1C, 1D. The detection outputs of the temperature detectors 3A, 3B, 3C, 3D are supplied to the bypass circuits 4A, 4B, 4C, 4D via connection lines (not shown).

  The bypass circuits 4A, 4B, 4C, and 4D are provided corresponding to the thin batteries 1A, 1B, 1C, and 1D, and bypass current flowing through the thin batteries 1A, 1B, 1C, and 1D during power charging / discharging. It consists of a switch circuit. The bypass circuits 4A, 4B, 4C, 4D adjust the remaining capacity of each thin battery 1A, 1B, 1C, 1D by bypassing the current flowing through each thin battery 1A, 1B, 1C, 1D.

  In this way, the temperature detectors 3A, 3B, 3C, 3D and the bypass circuits 4A, 4B, 4C, 4D, as shown in FIG. 6, each thin battery 1A, The temperature of 1B, 1C, 1D is detected, and the operation after step S2 is repeated. This process is activated in response to the start of power supply from the assembled battery to the electrical device when the electrical device connected to the assembled battery is activated.

  In step S1, when the temperature of the thin battery 1 is estimated from the internal resistance of each thin battery 1A, 1B, 1C, 1D, the temperature detectors 3A, 3B, 3C, 3D use the thin batteries 1A, 1B, 1C, 1D. Since the internal resistance increases as the temperature of the battery increases, the relationship between the battery temperature and the internal resistance is previously mapped and stored, and the internal resistance is obtained from the slope of the current I (current) -V (voltage) characteristics. The current battery temperature may be estimated by referring to the map from the internal resistance. In addition, as a method for obtaining the internal resistance from the IV characteristics, a method for obtaining the internal resistance from the slope when the current I and the voltage V in a predetermined period are measured at a plurality of points and linearly regressing the current I and the voltage is detected. There are known techniques such as a method for obtaining the internal resistance from the slope of the straight line connecting the IV points.

  In the next step S2, the battery temperature detected by each temperature detector 3A, 3B, 3C, 3D is acquired by a controller (not shown), the temperature variation of each thin battery in the assembled battery is calculated, and in step S3, the temperature variation If it is determined that there is no temperature variation, the process ends. If it is determined that there is a temperature variation, the process proceeds to step S4. Note that all battery temperatures detected by the temperature detectors 3A, 3B, 3C, and 3D are read by the bypass circuits 4A, 4B, 4C, and 4D, and temperature variations are determined by the bypass circuits 4A, 4B, 4C, and 4D. Also good.

  In the next step S4, the remaining capacity of each thin battery 1A, 1B, 1C, 1D is adjusted by adjusting the voltage of each thin battery 1A, 1B, 1C, 1D by each bypass circuit 4A, 4B, 4C, 4D. To do. For example, when the temperature of the thin batteries 1B and 1C inside the stacking direction is 1 ° C. higher than the temperature of the thin batteries 1A and 1D outside the stacking direction, the remaining capacity of the thin batteries 1B and 1C inside the stacking direction is Discharge about 1% to 2%. For example, the voltage is decreased by 10 mV to 20 mV.

  In step S4, the temperature of each thin battery 1A, 1B, 1C, 1D is detected by the temperature detectors 3A, 3B, 3C, 3D, and the thin battery having the highest temperature by the bypass circuits 4A, 4B, 4C, 4D. The remaining capacity of the battery may be changed low, or the temperature of each thin battery 1A, 1B, 1C, 1D is detected by the temperature detectors 3A, 3B, 3C, 3D, and the bypass circuits 4A, 4B, 4C, 4D are used. You may change the open circuit voltage of the thin battery with the highest temperature low.

  Accordingly, even if the degree of increase in internal resistance increases as the battery temperature shown in FIG. 2 increases, it is canceled out by increasing the degree of decrease in internal resistance by reducing the SOC, and each thin battery 1A, 1B. , 1C, 1D are brought close to the same degree of deterioration. Therefore, in this assembled battery, the deterioration degree of the plurality of thin batteries 1A, 1B, 1C, 1D constituting the assembled battery is made uniform as much as possible, and the life of the thin batteries 1B, 1C in which the temperature during power charging / discharging becomes high is increased. It is possible to avoid shortening the life of the assembled battery. In addition, since the life of the thin batteries 1A, 1B, 1C, 1D constituting the assembled battery can be made substantially uniform, it is not necessary to replace only the thin batteries 1B, 1C where the temperature during power charging / discharging becomes high, The management cost of the assembled battery can also be reduced.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

  That is, in the above-described assembled battery, an example in which thin batteries are stacked has been described. However, even when a plurality of thin batteries are accommodated in a box and the boxes are stacked, the temperature during power charging / discharging of the thin battery is low. Since there will be a box that rises and a box where the temperature during power charging / discharging of the thin battery 1 does not rise, by controlling the remaining capacity or open circuit voltage as described above, the average remaining capacity of each box or The average open circuit voltage can be controlled.

  Further, in the above-described embodiment, an explanation is given by taking an assembled battery in which four thin batteries are stacked as an example. However, the number of thin batteries is not limited to four, and a thin battery with a higher temperature has a higher SOC or If the idea of the present invention of reducing the open circuit voltage is applied, the number of thin batteries can be changed as appropriate.

1A, 1B, 1C, 1D Thin battery 1a Exterior film 1b, 1c Battery terminal 2A, 2B, 2C, 2D, 2E Connection line 3A, 3B, 3C, 3D Temperature detector 4A, 4B, 4C, 4D Bypass circuit

Claims (5)

An assembled battery formed by electrically connecting a plurality of thin batteries,
The ratio of remaining capacity to the full charge capacity of each thin battery at the time of charging / discharging is characterized by a low remaining capacity ratio of the thin battery having a low temperature at the time of charging / discharging compared to the thin battery having a high temperature at the time of charging / discharging. The assembled battery. A battery pack in which a plurality of thin batteries are stacked in the thickness direction of the thin battery and electrically connected,
The remaining capacity ratio with respect to the full charge capacity of each thin battery at the time of charge / discharge is characterized in that the thin battery positioned on the outer side in the stacking direction has a lower remaining capacity ratio than the thin battery positioned on the inner side in the stacking direction. Assembled battery. The assembled battery according to claim 1,
The assembled battery, wherein the plurality of thin batteries are stacked in the thickness direction of the thin batteries. The assembled battery according to claim 1 or 3,
Provided with temperature detection means for detecting the temperature at the time of charging and discharging each thin battery,
Based on the temperature of the plurality of thin batteries detected by the temperature detection means, the thin battery having a low temperature during charging / discharging has a remaining capacity ratio to the full charge capacity with respect to the thin battery having a high temperature during charging / discharging. A battery pack comprising: a remaining capacity control means for controlling a remaining capacity ratio of each of the thin batteries so as to be low. The assembled battery according to any one of claims 1 to 4,
Among the plurality of thin batteries, the remaining capacity ratio with respect to the full charge capacity of the thin battery having the lowest temperature during charging / discharging is the remaining capacity ratio with respect to the full charge capacity of the thin battery having the highest temperature during charging / discharging, A battery pack having a difference of 10% or less.