JP2017004654A - battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack capable of reducing variation in capacity with a simple configuration.SOLUTION: A battery pack (1) includes: a cell pack (2) in which a plurality of single cell units (20) are connected in parallel to each other; a tab electrode (4) for electrically connecting respective single cells (22) of the cell pack (2); and a conductive plate (5) which has lower resistance than the tab electrode (4). The conductive plate (5) is electrically connected to an end electrode (4a). The current is distributed to each single cell unit (20) via the end electrode (4a) and an intermediate electrode (4b) from the conductive plate (5).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a stacked battery pack in which a plurality of unit cell units are stacked and connected in parallel.

  When a battery power supply device is mounted on various devices such as power tools, industrial labor-saving devices, and electric vehicles, the portability, convenience, environmental performance, and the like of the devices are improved. For this reason, the demand for equipment equipped with a battery power supply device is increasing. In particular, industrial labor-saving equipment (industrial robots) can be applied to various uses such as work-saving equipment, nursing care, and services, and therefore, the demand has been significantly increased. Along with this, there is an increasing demand for a wide variety of battery power supply devices suitable for various devices.

  For example, Patent Document 1 discloses an assembled battery in which a plurality of cells (batteries) are connected in parallel to extract electric power from lead terminals. Such an assembled battery can realize a high voltage and a high capacity by changing the number of cells in parallel and the number of batteries in each cell.

Japanese Unexamined Patent Publication No. 2004-3255 (released on January 29, 2004)

  However, the assembled battery described in Patent Document 1 has a problem that the configuration for reducing the variation in capacity due to cell deterioration becomes complicated.

  Specifically, the assembled battery described in Patent Document 1 focuses on the fact that the temperature rise tendency of the cells constituting the assembled battery depends on the heat radiation conditions, the heat generation amount, and the environmental temperature of the cells. Capacitance variation is reduced. For example, in the case of an assembled battery in which a plurality of cells are stacked, the heat dissipation efficiency is better for the outer cell than for the inner cell. That is, since the heat dissipation efficiency of the inner cell is lower than the heat dissipation efficiency of the outer cell, the temperature of the inner cell becomes relatively high. For this reason, the deterioration rate of the inner cell becomes larger than the deterioration rate of the outer cell. As a result, the variation in capacity between the inner cell and the outer cell increases, and the life characteristics of the assembled battery deteriorate.

  Therefore, in the assembled battery described in Patent Document 1, the connection resistance between the inner cell and the lead terminal is made larger than the connection resistance between the outer cell and the lead terminal using a bus bar. Further, the lengths of the positive electrode tab and the negative electrode tab provided in the inner cell are longer than the lengths of the positive electrode tab and the negative electrode tab of the outer cell. Thereby, the current value of charging / discharging becomes smaller in the inner cell than in the outer cell. That is, the amount of heat generated by the current is smaller in the inner cell than in the outer cell. As a result, the temperature rise of the inner cell can be suppressed, so that the temperature variation between the inner cell and the outer cell is reduced to suppress the capacity variation due to deterioration.

  However, in order to suppress the variation in capacity in this way, for each assembled battery, change the shape, material, thickness, etc. of the bus bar, or change the length of the positive electrode tab and the negative electrode tab, It is necessary to set the resistance value of each cell to a desired value. This complicates the configuration for reducing the variation in capacitance.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery pack that can reduce variation in capacity with a simple configuration.

  In order to solve the above-described problem, a battery pack according to one embodiment of the present invention includes an assembled battery in which a plurality of unit cell units each including at least one unit cell are connected in parallel, and each unit cell of the assembled battery. And a conductive member having a lower resistance than the tab electrode, wherein the conductive member is disposed on the current input side and the output side of each unit cell unit. It is electrically connected to the end portion of the electrode, and current is distributed from the conductive member to each single cell unit via the tab electrode.

  According to one embodiment of the present invention, it is possible to provide a battery pack that can reduce variation in capacity with a simple configuration.

1 is an exploded perspective view of a battery pack according to Embodiment 1 of the present invention. It is a perspective view of the assembled battery in the said battery pack. It is a graph which shows the result of having charged and discharged with respect to the said battery pack provided with the electrically conductive plate. It is a graph which shows the result of having charged and discharged with respect to the battery pack which is not provided with a conductive plate. It is a circuit diagram which shows schematic structure of the battery pack which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows schematic structure of the other battery pack which concerns on Embodiment 3 of this invention.

Embodiment 1
Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a perspective view of a battery pack 1 according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the battery pack 1 includes an assembled battery 2, a protection circuit 3, a tab electrode 4, a conductive plate (conductive member) 5, and housings 6a and 6b.

  In the assembled battery 2, a plurality of unit cell units 20 having the same shape and configuration (seven units in FIG. 1) are stacked, and the unit cell units 20 are connected in parallel to each other.

  The unit cell unit 20 has a configuration in which a plurality (eight in FIG. 1) of unit cells 22 are arranged in series in a cell case 21. The cell case 21 holds the single cells 22 in parallel with each other. The shape of the cell case 21 may be set arbitrarily according to the shape of the unit cell 22 as long as the unit cells 22 can be arranged and held in series. The cell case 21 can be formed by molding plastic such as ABS resin, for example.

  The single battery 22 is formed of a cylindrical secondary battery (secondary battery cell). The positive electrode and the negative electrode of the unit cell 22 are arranged on the front surface S1 side or the back surface S2 side of the assembled battery 2 and are exposed from the cell case 21. The unit cells 22 are arranged in the cell case 21 so that the positive and negative electrodes exposed on the front surface S1 side or the back surface S2 side of the assembled battery 2 are alternately arranged in the series direction.

  In the present specification, the “secondary battery” means a battery that can be used as a battery by storing electricity by being charged, and may be any battery that can be used repeatedly. Typical unit cells 22 (secondary batteries) include lithium ion secondary batteries and nickel-cadmium storage batteries. The unit cell 22 includes a lithium ion polymer secondary battery, a nickel / hydrogen storage battery, a nickel / iron storage battery, a nickel / zinc storage battery, a silver oxide / zinc storage battery, and the like. In the present embodiment, the cylindrical unit cell 22 is used, but the unit cell 22 may have a rectangular shape, a flat shape, a button shape, a coin shape, or the like. Thus, the type and shape of the unit cell 22 are not particularly limited.

  Further, in the present embodiment, in order to set the rated cell voltage of the unit cell unit 20 to 3.2 V and the rated cell capacity to 3 Ah, seven unit cells 22 composed of lithium ion secondary battery cells are connected in series. ing. The number of unit cells 22 included in the unit cell unit 20 and the number of stacked unit cells 20 (number of parallel units) can be set according to the cell voltage and the cell capacity, and are not particularly limited. The capacity of the battery pack 1 (the assembled battery 2) can be increased or decreased by increasing or decreasing the number of stacked unit cells 20. Moreover, the voltage of each unit cell unit 20 can be increased or decreased by increasing or decreasing the number of unit cells 22 of each unit cell unit 20.

  Fixing members 23 are provided on the top surface S3 side and the bottom surface S4 side of the assembled battery 2, respectively. The battery unit 20 disposed on the top surface S3 side or the bottom surface S4 side of the assembled battery 2 is fixed to the fixing member 23. Thereby, the assembled battery 2 has a configuration in which the unit cell unit 20 is sandwiched between the fixing members 23.

  In the present embodiment, the first through portion 24a in which the first through portion 24a and the second through portion 24b are formed on the outer side surface (the side surface S5 of the assembled battery 2) of the cell case 21 of each unit cell unit 20. A bar-shaped penetrating member 25 is inserted into the opening in the parallel direction of the unit cell units 20. Furthermore, both ends of the penetrating member 24 are fixed to the fixing member 23 by screws or the like (not shown). Thereby, each unit cell unit 20 is mechanically fixed to the fixing member 23. On the other hand, the conductive plate 5 provided along the parallel direction of the unit cell units 20 is inserted into the opening of the second through portion 24b. Thus, the penetrating member 25 and the conductive plate 5 are provided in parallel to each other on the side surface S5 of the assembled battery 2 along the parallel direction of the unit cell units 20.

  The protection circuit 3 is disposed on the fixing member 23 on the top surface S3 side of the assembled battery 2, and the assembled battery 2 and the protection circuit 3 constitute a battery module. The position where the protection circuit 3 is attached to the assembled battery 2 is not limited to the top surface S3 side, and may be attached anywhere as long as it is insulated from each unit cell 22 of the assembled battery 2 and outside the assembled battery 2.

  The protection circuit 3 monitors the battery voltage of each unit cell 22 and controls charging / discharging of each unit cell 22. Specifically, the voltage of the parallel unit consisting of a group of unit cells 22 arranged in the same row in the parallel direction of the unit cell units 20 is monitored. For example, since the battery pack 1 includes the single cell 22 made of a secondary battery, the protection circuit 3 controls the remaining battery level within a specified range. However, since it is difficult to directly measure the remaining battery level, the protection circuit 3 uses the fact that there is a correspondence between the remaining battery level and the battery voltage, so that the single cell 22 is connected based on the battery voltage. Control. Specifically, the protection circuit 3 monitors the battery voltage so that the unit cells 22 are not overcharged or overdischarged, and controls charging / discharging of each unit cell 22. “Overcharge” is a state where the battery level is outside the specified range and the voltage is high due to overcharging. “Overdischarge” is a state where the battery level is outside the specified range and low. This is a voltage state.

  The tab electrode 4 is arrange | positioned at the front surface S1 and the back surface S2 of the assembled battery 2 which the positive electrode or negative electrode of the cell 22 exposed. The tab electrode 4 electrically connects the unit cells 22 arranged in series or in parallel. Specifically, the front surface S1 of the assembled battery 2 is provided with two end electrodes 4a and three intermediate electrodes 4b disposed between the two end electrodes 4a. Three intermediate electrodes 4 b are provided on the back surface S <b> 2 of the assembled battery 2.

  The end electrode 4 a is provided so as to correspond to the unit cells 22 at both ends (current input side and output side) of each unit cell unit 20. The end electrode 4 a extends from end to end along the stacking direction of the unit cell units 20. The end electrodes 4a are in contact with the positive or negative electrodes of the unit cells 22 at both ends of each unit cell unit 20, and are connected by fastening with screws, welding, or the like. Thereby, the unit cells 22 at both ends of each unit cell unit 20 are electrically connected in parallel.

  The intermediate electrode 4 b is provided so as to correspond to the unit cells 22 other than both ends of each unit cell unit 20. In the present embodiment, each intermediate electrode 4 b is provided so as to have a width corresponding to two adjacent unit cells 22 arranged in series with the unit cell unit 20, and along the stacking direction of the unit cell units 20. Extending from end to end. That is, the intermediate electrode 4b is in contact with the positive electrode or the negative electrode of two adjacent unit cells 22 of the unit cell unit 20, and is connected by fastening with screws, welding, or the like. Further, the intermediate electrode 4 b is also in contact with the positive electrode or the negative electrode of the corresponding unit cells 22 in the same row in the parallel direction of the two unit cells 22 and the unit cell unit 20. Thereby, the unit cells 22 other than the both ends of each unit cell unit 20 are electrically connected in series or in parallel.

  In the present embodiment, the end electrode 4a and the intermediate electrode 4b have a unit shape (repeating unit) for each unit cell unit 20, and the unit shape is continuously provided for the number of stacked unit cell units 20. It has a repeated shape. For this reason, for example, if a progressive press die or the like is used, the end electrode 4a and the intermediate electrode 4b can be easily manufactured. Therefore, component costs can be reduced.

  In addition, when the number of stacked unit cells 20 is changed, it is only necessary to change the length (cutting position) of the end electrode 4a and the intermediate electrode 4b according to the number of stacked units. There is no need to change the press die. Therefore, the initial investment when changing the specifications of the battery pack 1 (changing the number of stacked unit cells 20) can be significantly reduced.

  In the present embodiment, the tab electrode 4 includes the end electrode 4a and the intermediate electrode 4b. However, the tab electrode 4 may be integrated.

  The conductive plate 5 is provided on both side surfaces S <b> 5 of the assembled battery 2 along the stacking direction of the unit cell units 20. That is, the battery pack 1 includes two conductive plates 5 on both side surfaces S5 of the assembled battery 2. The conductive plate 5 is electrically connected to the end electrodes 4 a provided on the current input side and the output side of each unit cell unit 20 and the protection circuit 3. Thereby, a current is distributed and supplied to each unit cell unit 20 via the conductive plate 5.

  The conductive plate 5 is not particularly limited as long as the conductive plate 5 is made of a material having conductivity and lower resistance than the tab electrode 4. For example, examples of the material constituting the conductive plate 5 include metals such as aluminum, copper, iron, gold, and titanium, or alloys such as bronze and stainless steel. The conductive plate 5 is preferably a metal plate made of such a metal, and more preferably a metal plate having a uniform thickness and a uniform width in the stacking direction of the unit cell units 20. In particular, when the tab electrode 4 is spot welded to the unit cell 22, the tab electrode 4 is generally made of nickel. In this case, the conductive plate 5 is more preferably made of aluminum having a resistance smaller than that of nickel. Thus, the conductive plate 5 is most preferably an aluminum plate made of aluminum that is inexpensive and has high electrical conductivity.

  The length of the conductive plate 5 can be arbitrarily set as long as a current can be supplied to each unit cell unit 20. However, as shown in FIG. 1, the length of the conductive plate 5 is preferably a length corresponding to the number of unit cell units 20 in parallel (the length in the parallel direction). Thereby, the length of the conductive plate 5 falls within the range of the length of the side surface S5 of the assembled battery 2.

  The casings 6a and 6b are cases in which the assembled battery 2, the protection circuit 3, the tab electrode 4, and the conductive plate 5 are accommodated. The housing 6a covers the top surface S3 and both side surfaces S5 of the assembled battery 2, and the housing 6b covers the front surface S1, the back surface S2, and the bottom surface S4 of the assembled battery 2. The casings 6a and 6b are made of sheet metal parts or the like. A connector 61 is formed in the housing 6 a, and the battery pack 1 is charged or discharged when current flows in or out through the connector 61.

  Next, the relationship between the assembled battery 2, the tab electrode 4 and the conductive plate 5 will be described based on FIG. 2. FIG. 2 is a perspective view of the assembled battery 2 in the battery pack 1.

  As shown in FIG. 2, the front surface S1 of the assembled battery 2 is provided with two end electrodes 4a and three intermediate electrodes 4b arranged between the two end electrodes 4a. Both the end electrode 4 a and the intermediate electrode 4 b extend along the parallel direction of the unit cell units 20. The end electrode 4a has a bent portion 4c that is bent along the side surface S5 of the battery pack 2 from the contact position with the unit cell 22 (see FIG. 1) at both ends (current input side and output side) of the unit cell unit 20. doing. The conductive plate 5 is provided on the side surface S5 of the assembled battery 2 along the parallel direction of the unit cell units 20 and is electrically connected to the bent portion 4c of the tab electrode 4. The bent portion 4c and the conductive plate 5 can be electrically connected, for example, by fastening with screws, welding, or the like, but the connection method is not particularly limited. In FIG. 2, the bent portion 4 c and the conductive plate 5 are electrically connected to each other by a screw 51 that penetrates the bent portion 4 c and the conductive plate 5.

  As described above, according to the present embodiment, the battery pack 1 includes the conductive plate 5 having a resistance lower than that of the tab electrode 4 that electrically connects each unit cell 22 of the assembled battery 2. Further, the conductive plate 5 is electrically connected to the tab electrode 4 at the current input side and output side positions (both ends) of each unit cell unit 20. Thereby, it will be in a state with small resistance until just before the assembled battery 2 (single cell unit 20). For this reason, at the time of charging / discharging the battery pack, current is distributed from the conductive plate 5 to each unit cell unit 20 via the tab electrode 4. As a result, since the current flows through each unit cell unit 20 almost uniformly, the voltage of the group of unit cells 22 (parallel units) arranged in the same row in the parallel direction of each unit cell unit 20 also becomes substantially uniform.

  Therefore, the battery pack 1 of the present embodiment does not need to change the shape of the tab electrode 4 or the length of the lead wire unlike the invention described in Patent Document 1, and the In addition, the capacity variation of the battery pack 1 can be reduced by a simple configuration in which the low-resistance conductive plate 5 is provided. Therefore, even if charging / discharging is repeatedly used continuously (in other words, even if the number of cycles of the battery pack 1 is increased), it is possible to suppress a decrease in capacity due to battery deterioration.

  In the present embodiment, the side surface S5 of the assembled battery 2 is provided with the conductive plate 5 and the bent portion 4c formed on the end electrode 4a of the tab electrode 4, and the side surface S5 of the assembled battery 2 is The conductive plate 5 and the bent portion 4c are electrically connected. Accordingly, the conductive plate 5 and the tab electrode 4 other than the bent portion 4c are not arranged on the same surface (front surface S1). Therefore, a short circuit at the time of charging / discharging of the battery pack 1 can be prevented. Further, the conductive plate 5 can be arranged using the space on the side surface S5 of the assembled battery 2.

  In this embodiment, since the length of the conductive plate 5 corresponds to the number of the unit cell units 20 in parallel, the length of the conductive plate 5 does not exceed the length of the unit cell units 20 in the parallel direction. Therefore, the battery pack 1 in which the conductive plate 5 is within the range of the outer size of the assembled battery 2 can be provided even if the number of parallel cell units 20 is increased. Furthermore, since it is only necessary to change the length of the conductive plate 5 even if the number of the unit cell units 20 is changed, the members can be made common and the manufacturing cost can be reduced.

  Moreover, in this embodiment, since the width | variety and thickness of the conductive plate 5 are uniform along the parallel direction of the cell unit 20, the shape of the conductive plate 5 can be simplified. Further, since the conductive plate 5 has a single shape, not only the cost is reduced, but also the mounting structure is simplified and the workability is improved.

  In the present embodiment, since the conductive member is made of a metal plate, it is possible to form a conductive member that can be easily processed.

  In the present embodiment, since the protection circuit 3 is provided, charging / discharging can be controlled so as not to fall into an overcharge or overdischarge state. Therefore, the battery pack 1 with high safety can be provided.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the present embodiment, the results of charging and discharging the battery pack 1 of Embodiment 1 under the charge / discharge conditions shown in Table 1 will be described. The 8 series × 7 parallel (8S7P) described in Table 1 is a battery pack 1 (see FIG. 1) having a unit cell unit 20 in which eight unit cells 22 are connected in series and a battery pack 2 including seven units in parallel. Show. The tab electrode 4 was a nickel plate, and the conductive plate 5 was an aluminum plate having a width of 20 mm × length of 200 mm × thickness of 3 mm. For comparison, the battery pack 1 was also charged and discharged under the same conditions for the configuration without the conductive plate 5. In addition, all the battery packs used the new thing which charged.

  Tables 2 and 3 show the measurement results of the voltage value at 1 hour after the start of charge / discharge and the capacity after the end of charge / discharge. Table 2 shows the result of the battery pack 1 and Table 3 shows the conductive plate 5. The result of the battery pack without it is shown. In addition, the both ends in Table 2 and Table 3 are the unit cells 22 on the input side and the output side of the assembled battery 2 (unit cell unit 20).

  On the other hand, FIG. 3 is a graph showing the results of charging and discharging the battery pack 1 having the conductive plate 5. FIG. 4 is a graph showing the results of charging and discharging a battery pack that does not include the conductive plate 5.

  As shown in Table 2 and FIG. 3, in the battery pack 1 provided with the conductive plate 5, the current flowed uniformly into or out of each unit cell 22 of the assembled battery 2. For this reason, the voltage of the parallel unit which consists of the group of the cell 22 arrange | positioned in the same row in the parallel direction of each cell unit 20 became uniform. The effective capacity was about 98% of the nominal capacity.

  On the other hand, as shown in Table 3 and FIG. 4, in the battery pack that does not include the conductive plate 5, the charging voltage of the parallel units at both ends of the assembled battery 2 was larger than the charging voltage of the parallel units other than both ends. On the contrary, the discharge voltage of the parallel units at both ends was smaller than that of the parallel units other than both ends. For this reason, effective capacity fell to about 96% of nominal capacity. If charging / discharging is repeated in this state, deterioration of only the parallel units at both ends is promoted, and there is a concern about further capacity reduction.

  As described above, when the battery pack 1 including the conductive plate 5 is charged / discharged, current is collectively distributed from the conductive plate 5 to each single cell unit 20 via the tab electrode 4. As a result, since the current flows through each unit cell unit 20 substantially uniformly, it is confirmed that the voltage of the group of unit cells 22 (parallel units) arranged in the same row in the parallel direction of each unit cell unit 20 is also substantially uniform. It was done.

  Moreover, in this embodiment, since the tab electrode 4 consists of a nickel plate, while being able to form the thin tab electrode 4, it can weld to the positive electrode or negative electrode of the cell 22 reliably. Further, since the conductive plate 5 is made of an aluminum plate, it is possible to form the conductive plate 5 that is inexpensive and has high electrical conductivity.

  Note that, in a battery pack that does not include the conductive plate 5, a current flows into the end electrode 4a. That is, after a current flows in the parallel direction of the unit cell units 20 via the end electrodes 4a, a current flows in the series direction of the unit cell units 20. For this reason, the wiring resistance increases as the distance from the unit cell unit 20 on the inflow side increases in the parallel direction. As a result, it is considered that the balance of current flowing through the single cells 22 in the parallel units at both ends is broken.

[Embodiment 3]
The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 5 is a circuit diagram showing a schematic configuration of a battery pack 1a according to Embodiment 3 of the present invention. FIG. 6 is a circuit diagram showing a schematic configuration of another battery pack 1b according to Embodiment 3 of the present invention.

  The battery pack 1 according to the first embodiment has a configuration in which seven unit cell units 20 including eight unit cells 22 are connected in parallel. However, the unit cell unit 20 is not limited to a configuration including a plurality of unit cells 22, and may be configured to include one unit cell 22. Moreover, the parallel number of the unit cell units 20 should just be two or more.

  For example, as illustrated in FIG. 5, the battery pack 1 a may have a configuration in which three unit cell units 20 including one unit cell 22 are connected in parallel. As shown in FIG. 6, the battery pack 1 b may have a configuration in which five unit cell units 20 including one unit cell 22 are connected in parallel.

  In such battery packs 1a and 1b, similarly to the battery pack 1, the capacity variation of the battery packs 1a and 1b can be reduced by a simple configuration in which the conductive plate 5 having a resistance lower than that of the tab electrode 4 is provided. it can.

  Further, in the battery packs 1a and 1b, since the length of the conductive plate 5 corresponds to the number of the unit cell units 20 in parallel, the length of the conductive plate 5 exceeds the length of the unit cell unit 20 in the parallel direction. Absent. Therefore, the battery pack 1 in which the conductive plate 5 is within the range of the outer size of the assembled battery 2 can be provided even if the number of parallel cell units 20 is increased. Furthermore, since it is only necessary to change the length of the conductive plate 5 even if the number of the unit cell units 20 is changed, the members can be made common and the manufacturing cost can be reduced.

[Embodiment 4]
Another embodiment of the present invention will be described as follows. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the present embodiment, a configuration in which the tab electrode 4 is a nickel plate, the conductive plate 5 is an aluminum plate, and the tab electrode 4 is spot-welded to the unit cell 22 in the battery pack 1 of the first embodiment will be described.

  As described above, in the battery pack 1, the conductive plate 5 has a lower resistance than the tab electrode 4. The resistance value of the conductive plate 5 may be smaller than the resistance value of the tab electrode 4, but is preferably less than 1/100 of the resistance value of the tab electrode 4. The resistance value of a nickel plate having a width of 29.0 mm × a length of 14.0 mm × a thickness of 0.1 mm is 1.54 mΩ, and the resistance value of an aluminum plate having a width of 29.0 mm × a length of 25.0 mm × a thickness of 3 mm is It was 0.01 mΩ. Therefore, when the tab electrode 4 is a nickel plate and the conductive plate 5 is an aluminum plate, the resistance value of the conductive plate 5 is about two orders of magnitude smaller than the resistance value of the tab electrode 4. As a result, the current is more evenly distributed to the unit cell units 20 and flows, so that the voltage of the group of unit cells 22 (parallel units) arranged in the same row in the parallel direction of the unit cell units 20 is also more uniform. .

  In the battery pack 1, in order to electrically connect the end electrode 4 a of the tab electrode 4 and the conductive plate 5, the bent portion 4 c of the end electrode 4 a and the screw 51 that penetrates the conductive plate 5 are used. (See FIG. 2). In the case of electrical connection by screwing, the material constituting the tab electrode 4 and the conductive plate 5 is not particularly limited as long as the resistance value satisfies tab electrode 4> conductive plate 5. That is, the tab electrode 4 is a nickel plate, and the conductive plate 5 is not limited to an aluminum plate. On the other hand, when the end electrode 4a and the conductive plate 5 are electrically connected by spot welding, welding cannot be performed if the tab electrode 4 is a nickel plate and the conductive plate 5 is an aluminum plate.

  When the tab electrode 4 is spot-welded to the unit cell 22, the tab electrode 4 is preferably a nickel plate. Spot welding is welding that uses heat generated by electrical resistance. For this reason, it is more suitable for welding to comprise the tab electrode 4 from the metal which has a certain amount of electrical resistance (electric conductivity is low) rather than comprising from good conductors, such as copper or silver. On the other hand, if the thermal conductivity of the tab electrode 4 is high, the heat of the welded part will immediately escape. For this reason, it becomes difficult to weld the tab electrode 4 and the unit cell 22. When considering the relationship between such electrical conductivity and thermal conductivity, nickel is one of the constituent materials of the tab electrode 4 suitable for spot welding.

[Summary]
The battery packs 1, 1 a, and 1 b according to the first aspect of the present invention include a battery pack 2 in which a plurality of battery cell units 20 including at least one battery cell 22 are connected in parallel, and each battery cell of the battery pack 2. 22 is electrically connected to the tab electrode 4 (the end electrode 4a / intermediate electrode 4b), and a conductive member (conductive plate 5) having a resistance lower than that of the tab electrode 4. The unit cell unit 20 is electrically connected to the end portion (end electrode 4a) of the tab electrode 4 disposed on the current input side and the output side of each unit cell unit 20, and from the conductive member via the tab electrode 4 A current is distributed to each unit cell unit 20.

  According to said structure, the battery pack is equipped with the electroconductive member of low resistance rather than the tab electrode which electrically connects each cell of an assembled battery. Further, this conductive member is electrically connected to the tab electrode at the current input side and output side positions of each unit cell unit. Thereby, it will be in a state with small resistance until just before an assembled battery (single cell unit). For this reason, at the time of charge / discharge of the battery pack, current is distributed from the conductive member to each unit cell unit through the tab electrode. As a result, since current flows through each unit cell unit substantially uniformly, the voltage of the unit cell group (parallel unit) arranged in the same row in the parallel direction of each unit cell unit also becomes substantially uniform.

  Therefore, the battery pack of the present invention does not need to change the shape of the tab electrode or the length of the lead wire unlike the invention described in Patent Document 1, and has a lower resistance than the tab electrode. With a simple configuration in which the conductive member is provided, the capacity variation of the battery pack can be reduced. Therefore, even if charging / discharging is repeatedly used continuously (in other words, even if the number of cycles of the battery pack increases), it is possible to suppress a decrease in capacity due to battery deterioration.

  The battery packs 1, 1 a, 1 b according to aspect 2 of the present invention are the above-described aspect 1, wherein the end portions of the tab electrode 4 (end portion electrodes 4 a) are single-sided on the current input side and output side of the unit cell unit 20. It has a bent portion 4c bent along the outer side surface (side surface S5) of the assembled battery 2 from the contact position with the battery 22, and the conductive member (conductive plate 5) extends along the parallel direction of the unit cell units 20. In addition, the battery may be provided on the outer surface of the assembled battery 2 and electrically connected to the bent portion 4c of the tab electrode 4.

  According to said structure, the electrically conductive member and the bending part formed in the edge part of a tab electrode are provided in the outer surface of the assembled battery, and an electrically conductive member and a bent part are provided in the outer surface of an assembled battery. Electrically connected. Thus, the conductive member and the tab electrode other than the bent portion are not arranged on the same plane. Therefore, it is possible to prevent a short circuit during charging / discharging of the battery pack. Moreover, a conductive member can be arrange | positioned using the space of the outer surface of an assembled battery.

  In the battery packs 1, 1a, 1b according to the third aspect of the present invention, in the first or second aspect, the length of the conductive member (conductive plate 5) is a length corresponding to the parallel number of the unit cell units 20. The structure which has become may be sufficient.

  According to said structure, since the length of a conductive member and the number of parallel of a single cell unit respond | correspond, the length of a conductive member does not exceed the length of the parallel direction of a single cell unit. Therefore, even if the number of unit cell units is increased, it is possible to provide a battery pack in which the conductive member is within the range of the outer size of the assembled battery. Furthermore, since it is only necessary to change the length of the conductive member even if the number of the unit cell units is changed, it is possible to make the members common and to reduce the manufacturing cost.

  In the battery packs 1, 1a, and 1b according to the fourth aspect of the present invention, in the first to third aspects, the conductive member (conductive plate 5) may be formed of a metal plate.

  According to said structure, since a conductive member consists of a metal plate, a conductive member with easy process etc. can be formed.

  The battery packs 1, 1a, 1b according to the fifth aspect of the present invention are the first to fourth aspects, wherein the conductive member (conductive plate 5) is made of an aluminum plate, and the tab electrode 4 (end electrode 4a / intermediate electrode). 4b) may be composed of a nickel plate.

  According to said structure, since a tab electrode consists of a nickel plate, while being able to form a thin tab electrode, it can weld reliably to the positive electrode or negative electrode of a cell. Further, since the conductive member is made of an aluminum plate, it is possible to form a conductive member that is inexpensive and has high electrical conductivity.

  Battery packs 1, 1a, 1b according to aspect 6 of the present invention are the above-described aspects 1-5, wherein the conductive member (conductive plate 5) has a width and thickness along the parallel direction of the unit cell unit 20. The structure may be uniform.

  According to said structure, since the width | variety and thickness of an electroconductive member are uniform along the parallel direction of a cell unit, the shape of an electroconductive member can be simplified. Further, since the conductive member has a single shape, not only the cost is reduced, but also the mounting structure is simplified and the workability is improved.

  The battery pack 1, 1a, 1b according to aspect 7 of the present invention includes the protection circuit 3 that controls the charge / discharge of each unit cell by monitoring the battery voltage of each unit cell 22 in the above-described embodiments 1-6, The conductive member (conductive plate 5) may be configured to be electrically connected to the end portion (end electrode 4 a) of the tab electrode 4 and the protection circuit 3.

  According to said structure, since the protective circuit is provided, charging / discharging can be controlled so that it may not fall into an overcharge or overdischarge state. Therefore, a highly safe battery pack can be provided.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

  The present invention can be used for various applications such as electric tools, industrial labor-saving equipment, and electric vehicles. In addition, as long as electrical specifications such as voltage, capacity, or current are satisfied, it can be used for other purposes such as power storage.

DESCRIPTION OF SYMBOLS 1 Battery pack 1a Battery pack 1b Battery pack 2 Battery assembly 3 Protection circuit 4 Tab electrode 4a End electrode 4b Intermediate electrode 4c Bending part 5 Conductive plate 20 Single cell unit 22 Single cell S1 Front surface S2 Rear surface S3 Top surface S4 Bottom surface S5 Side surface

Claims (7)

An assembled battery in which a plurality of cell units each including at least one cell are connected in parallel;
A tab electrode for electrically connecting each unit cell of the assembled battery;
A conductive member having a lower resistance than the tab electrode,
The conductive member is electrically connected to an end portion of the tab electrode arranged on the current input side and the output side of each unit cell unit,
A battery pack characterized in that a current is distributed from the conductive member to each unit cell unit via the tab electrode. The end portion of the tab electrode has a bent portion that is bent along the outer surface of the assembled battery from the position of contact with the current input side and output side cells of the unit cell unit,
The conductive member is provided on an outer surface of the assembled battery along a parallel direction of the unit cell units, and is electrically connected to a bent portion of the tab electrode. The battery pack described in.   3. The battery pack according to claim 1, wherein a length of the conductive member is a length corresponding to a parallel number of the unit cell units.   The battery pack according to claim 1, wherein the conductive member is made of a metal plate. The conductive member is made of an aluminum plate,
The battery pack according to any one of claims 1 to 4, wherein the tab electrode is made of a nickel plate.   The battery pack according to claim 1, wherein the conductive member has a uniform width and thickness along a parallel direction of the unit cell units. A protection circuit that monitors the battery voltage of each unit cell and controls charging / discharging of each unit cell,
The battery pack according to claim 1, wherein the conductive member is electrically connected to an end portion of the tab electrode and the protection circuit.

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