JP2011258426A - Secondary battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a gas which is discharged from a secondary battery, from flowing into a car room, in simple duct configuration.SOLUTION: A flow channel TF is formed from a car room through a backflow prevention device, a duct, a separator, the surroundings of battery cells, the separator, the duct and a motor-driven fan 8 to the outside of the car. A cooling air taken from the inside of the car room flows through the flow channel. A portion in the flow channel through the surroundings of the battery cells, the inside of a separator 5B and the motor-driven fan to the outside of the car is also used for exhausting the gas discharged from the battery cells, and the discharged gas is quickly exhausted to the outside of the car by the motor-driven fan. When exhausting the gas, the backflow prevention device is closed, thereby preventing the gas from flowing through an inlet into the car room. The flow channel is applied to both the cooling air and the gas, so that the flow channel is simple and the configuration of a secondary battery pack can be simplified. Furthermore, the gas can be perfectly prevented by presence of the backflow prevention device from flowing into the car room.

Description

  The present invention relates to the structure of a battery pack for a secondary battery.

  An in-vehicle secondary battery mounted on an EV vehicle or an HV vehicle requires a plurality of unit batteries to be assembled into a large-capacity, high-power assembled battery. Usually, a plurality of unit batteries are included in a secondary battery pack. Storing. The secondary battery pack has a cooling air flow path for cooling each unit battery with air taken in from the passenger compartment, and gas discharged from the inside of the unit battery when an abnormality occurs in the unit battery. Gas discharge passages are provided. Since the gas discharged from the battery cell is high temperature and high pressure and is harmful to the human body, the gas cooling air flow path and the gas discharge flow path are separated from each other.

JP 2006-182264 A

  The secondary battery pack described in Patent Document 1 includes a cooling air supply duct and an exhaust gas pipe, and the exhaust gas pipe is connected to each battery cell.

  As described above, the gas discharged from the battery cell is collected without omission and discharged to the outside of the vehicle. Therefore, the configuration of the exhaust gas pipe becomes complicated, and the battery pack has a complicated structure and an increased size.

  The secondary battery pack according to the present invention includes a cell housing chamber in which a plurality of battery cells are housed, a take-in passage for taking cooling air into the cell housing chamber, the cooling air and gas discharged from the battery cells. A discharge passage that discharges from the storage chamber, and a backflow prevention device that is provided at the inlet of the intake passage and prevents the backflow of the gas under the condition that the internal pressure of the cell storage chamber is higher than the pressure at the inlet of the intake passage. It is characterized by having.

  According to the present invention, it is possible to prevent the gas released from the secondary battery from flowing into the vehicle interior with a simple duct configuration.

The front view which shows the vehicle carrying 1st Embodiment of the secondary battery pack by this invention. The external appearance perspective view which shows the secondary battery pack of FIG. FIG. 3 is an exploded perspective view of the secondary battery pack of FIG. 2. The disassembled perspective view which shows the non-return valve open state in the secondary battery pack of FIG. The partial expanded sectional view which shows the non-return valve open state in the secondary battery pack of FIG. The partial expanded sectional view which shows the non-return valve closed state in the secondary battery pack of FIG. The partial expanded sectional view which shows 2nd Embodiment of the secondary battery pack by this invention. The enlarged view which shows the 9A part in FIG. The external appearance perspective view which shows the non-return valve open state in the secondary battery pack of FIG. The partial expanded sectional view which shows 3rd Embodiment of the secondary battery pack by this invention. FIG. 11 is an enlarged view showing a 9A portion in FIG. 10. The enlarged view which shows the stopper in FIG. The external appearance perspective view which shows the non-return valve closed state in the secondary battery pack of FIG. The external appearance perspective view which shows the non-return valve open state in the secondary battery pack of FIG. The fragmentary perspective view which shows 4th Embodiment of the secondary battery pack by this invention. The figure which shows the front view and control circuit which show the inside of the secondary battery pack of 4th Embodiment. The flowchart which shows the opening / closing control procedure of the non-return valve of 4th Embodiment.

  Next, an embodiment of a secondary battery pack according to the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the secondary battery pack 50 mounted in an electric vehicle is installed, for example, at the rear of the vehicle. In the secondary battery pack 50, as shown in FIG. 3, a plurality of thin rectangular battery cells 1 are arranged in parallel in a casing. A cooling air intake 54 and a discharge duct 52 are connected to the secondary battery pack 50, and the battery cell 1 is cooled by the cooling air introduced from the intake 54. The cooling air flowing into the secondary battery pack 50 is discharged outside the vehicle through the discharge duct 52. When the internal pressure of the battery cell rises, the battery cell 1 opens and discharges gas from the inside of the container. This gas is also discharged from the exhaust duct 52 through the same flow path as the cooling air to the outside of the vehicle.

  As shown in FIGS. 2 to 4, the secondary battery pack 50 has a base plate 3 arranged on the bottom surface, and a plurality of secondary battery battery cells 1 are arranged in series in the vehicle longitudinal direction on the base plate 3. It is arranged. The battery cell 1 is a flat rectangular parallelepiped shape, and the thickness direction is arrange | positioned along the vehicle front-back direction.

  The secondary battery pack 50 is provided with pressure plates 2A and 2B that rise vertically at the front and rear ends of the base plate 3, and the top plate 4 is connected to the upper ends of the pressure plates 2A and 2B. Further, separators 5 </ b> A and 5 </ b> B are provided on the side surface of the secondary battery pack 50. The base plate 3, the pressure plates 2A and 2B, the top plate 4, and the separators 5A and 5B constitute a substantially rectangular parallelepiped sealed container, that is, a cell storage chamber.

  The separators 5A and 5B are rectangular cylindrical cooling air passages that are elongated in the direction in which the battery cells are arranged, and a channel having a rectangular cross section is formed inside the separators 5A and 5B. An intake duct 6A in which a channel having a rectangular cross section similar to that of the separator 5A and a backflow prevention device 7 are sequentially connected to the front end portion of the separator 5A, and an intake port 54 is connected to the suction side of the backflow prevention device 7. ing. The rear end of the separator 5B is connected to a discharge duct 6B in which a channel having a rectangular section similar to that of the separator 5B is formed. The power fan 8 is connected to the outlet of the discharge duct 6B. The discharge duct 52 is a power fan. 8 is connected to the discharge side.

  Referring to FIG. 4, a plurality of slits SA and SB that are long in the vertical direction perpendicular to the flow path are arranged in parallel with the flow direction of the cooling air on the wall surface that separates the flow path inside the separators 5 </ b> A and 5 </ b> B from the cell storage chamber. Open. Thus, from the passenger compartment, the backflow prevention device 7, the intake duct 6A, the inside of the separator 5A, the slit SA of the separator 5A, the periphery of the battery cell 1, the slit SB of the separator 5B, the inside of the separator 5B, the discharge duct 6B, the power A flow path TF extending to the outside of the vehicle through the fan 8 and the duct 52 is formed, and cooling air drawn by the power fan 8 from the vehicle interior flows through the flow path TF.

  In the process from the slit SA to the slit SB, the cooling air passes around the battery cell 1 and cools the battery cell 1. In this embodiment, the slits SA and SB are arranged so as to face each other between the battery cells 1 juxtaposed, and the cooling air flowing out from the slit SA smoothly passes through the gap between the battery cells 1 to form the slit SB. Flow into. By dispersing the cooling air in the plurality of slits SA and SB and flowing the cooling air, it is possible to supply the cooling air having a substantially uniform flow rate for all the battery cells 1. Therefore, the cooling effect can be ensured efficiently.

  Note that the temperature of the battery cells can be made more uniform by taking measures such as decreasing the slit area downstream so that the cooling air flows evenly through the slits SA and SB arranged from the upstream to the downstream of the separators 5A and 5B.

  Further, in the flow path TF, the portion around the battery cell 1, the slit SB of the separator 5B, the inside of the separator 5B, the discharge duct 6B, the power fan 8, the duct 52, and the outside of the vehicle is the gas released from the battery cell 1. The exhaust gas used in combination with the exhaust is quickly exhausted out of the vehicle by the power fan 8. When the gas is discharged, the backflow prevention device 7 is shut off and the gas does not flow into the vehicle compartment from the intake 54.

  That is, since the flow path TF is applied to both cooling air and gas, the flow path TF is simple and the configuration of the secondary battery pack 50 can be simplified. Further, the presence of the backflow prevention device 7 described in detail below can completely prevent the gas from flowing into the vehicle interior.

  As described above, in the secondary battery pack according to the first embodiment, the plurality of battery cells 1 are arranged side by side in one direction in the cell storage chamber. The separator 5A, to which the intake duct 6A is connected to the entrance, extends in one direction on one side of the battery cell 1, and slits SA on the intake side are provided along the one direction at predetermined intervals. The separator 5B having the discharge duct 6B connected to the outlet extends in the one direction on the other side of the battery cell 1, and discharge slits SB are provided along the one direction at predetermined intervals. The cooling air flows into the cell housing chamber from the plurality of intake side slits SA, and the cooling air heat exchanged with the battery cell 1 is discharged out of the cell housing chamber through the discharge side slit SB.

  As shown in FIGS. 4 to 6, the backflow prevention device 7 has a duct 7 </ b> D that is inserted into the front end of the intake duct 6 </ b> A and connected to the intake duct 6 </ b> A. A blade-like check valve 9 is mounted on the rear end of the duct 7D so as to be swingable in the vertical direction. The check valve 9 has a hinge portion 9A at its upper end and a rectangular valve body 9B extending downward from the hinge portion 9A, and the upper edge of the opening 7M at the rear end of the duct 7D in the hinge portion 9A. It is pivotally attached to the department. The check valve 9 supports the valve body 9B in a swingable manner by the hinge portion 9A. A valve seat orthogonal to the flow path is formed in the opening 7M. The valve body 9B is in a suspended state due to its own weight. The opening 7M is closed by sitting on the valve seat of the opening 7M.

  That is, the backflow prevention device 7 includes an opening 7M that opens toward the intake duct 6A and has a valve seat, and a swingable valve body 9B that opens and closes the opening 7M. The valve body 9B has a suspension structure in which one end is pivotally supported by a hinge 9A, and the valve body 9B opens and closes according to the front-rear differential pressure. That is, when there is no front-rear differential pressure, the valve body 9B is seated on the valve seat and closes the opening 7M, and when the downstream pressure is low, the valve body 9B is separated from the valve seat and opens the opening 7M. Has been.

  When the power fan 8 is driven and the cooling air is taken into the duct 7D of the backflow prevention device 7, the valve body 9B is pushed in the direction of the intake duct 6A by the cooling air, and the valve body 9B jumps up in the downstream direction. Then, the opening 7M is opened (see FIG. 5).

  On the other hand, when an abnormality occurs in the battery cell 1 and the gas is released, the pressure around the battery cell 1, that is, the internal pressure of the cell storage chamber is increased by the gas, and the drawing of the valve body 9B in the downstream direction is stopped. Further, this pressure propagates into the intake duct 6A, pushes the valve body 9B toward the duct 7D, that is, toward the intake port 54, and seats the valve body 9B on the valve seat of the opening 7M. As a result, the opening 7M is closed and the inflow of gas into the passenger compartment is prevented (see FIG. 6).

  In order to enhance the responsiveness of opening and closing of the valve body 9B, the check valve 9 is preferably lightweight, and needs to have sufficient strength against gas pressure in the closed state (shut off state). For this reason, the check valve 9 is formed of, for example, a thin metal plate. By providing the backflow prevention device 7, the secondary battery pack 50 can completely prevent the gas from flowing into the passenger compartment.

  Further, the backflow prevention device 7 has a simple configuration in which a blade-like check valve 9 is pivotally attached to the duct 7D. Therefore, combined with use of both cooling air and gas in the flow path TF, the secondary battery pack 50 The configuration is simple.

  The first embodiment can prevent the gas released from the secondary battery from flowing into the vehicle interior by a simple duct structure. Furthermore, since a separate duct is unnecessary for gas discharge, the degree of freedom of the configuration and outer shape of the secondary battery pack including the arrangement and configuration of the flow path TF can be greatly expanded.

[Second Embodiment]
Next, a second embodiment of the secondary battery pack according to the present invention will be described with reference to FIGS. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the second embodiment, the hinge portion 9A is provided with an arm portion 9R having a predetermined radius from the rotating shaft 9C, and the valve body 9B is connected to the tip portion of the arm portion 9R. The valve body 9B is seated on a valve seat provided in the opening 7M and closes the opening 7M.

  The weight of the valve body 9B generates a moment for rotating the arm portion 9R downward, and the valve body 9B rotates at a high speed when pressure due to gas discharge occurs. This increases the responsiveness when closing the opening 7M. The backflow prevention device 7 is provided with a stopper 9S that contacts the valve body 9B that swings in the direction of the intake duct 6A and regulates the swing range of the valve body 9B, thereby preventing excessive swing of the valve body 9B. Has been.

  If the valve body 9B is excessively oscillated when the cooling air is introduced, the response time for closing the opening 7M becomes longer. However, the high responsiveness is always ensured by the oscillation range restriction by the stopper 9S. .

  By providing the arm portion 9R on the hinge portion 9A, the rotating shaft 9C can be disposed outside the duct 7D, that is, in the space 7R between the upper outer surface of the duct 7D and the upper inner surface of the intake duct 6A, and the stopper 9S can also be disposed above the upper surface of the duct 7D. Accordingly, the hinge portion 9A does not hinder the flow of cooling air.

  In addition to the effects of the first embodiment, the second embodiment has an effect of high responsiveness when shut off.

[Third Embodiment]
Next, a third embodiment of the secondary battery pack according to the present invention will be described with reference to FIGS. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the third embodiment, as in the first embodiment, the hinge portion 9A has a simple configuration consisting of only the rotating shaft 9C. On the other hand, in the suspended state, the opening portion is configured so that the valve body 9B reliably closes the opening portion 7M. 7M is given an inclination that inclines downward in the downstream direction. That is, the valve seat of the opening 7M is inclined toward the downstream side of the flow path from one end side where the valve body 9B is suspended toward the free end side. This improves the closing response at the time of gas discharge.

  Similarly to the second embodiment, the backflow prevention device 7 is provided with a stopper 9S that contacts the lower portion of the valve body 9B that swings in the direction of the intake duct 6A and regulates the swing range of the valve body 9B. Excessive swinging of the valve body 9B is prevented. Also in this respect, the closing response at the time of gas release is high.

  The third embodiment has an effect that the configuration of the check valve 9 is simple in addition to the same effect as the second embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the secondary battery pack according to the present invention will be described with reference to FIGS. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the fourth embodiment, similarly to the third embodiment, the hinge portion 9A has a simple configuration consisting of only the rotary shaft 9C, and in the suspended state, the valve body 9B closes the opening portion 7M so that the opening portion 7M is closed. In this way, an inclination is provided to incline in the downstream direction downward. Further, in the fourth embodiment, a solenoid (opening drive means) 13 that opens the check valve 9 and a spring 15 that opens the check valve 9 are provided.

  As shown in FIGS. 15 and 16, the rotary shaft 9C is provided with a spring 15 that urges the valve body 9B in the closing direction, and a solenoid 13 that pushes the valve body 9B in the opening direction on the outer upper surface of the duct 7D. Is installed. The solenoid 13 includes a piston 13P that can advance and retreat, and a slider 13S that extends toward the valve body 9B is attached to the tip of the piston 13P. The tip of the slider 13S is in contact with the blade 9B. When the solenoid 13 is excited, the piston 13P advances while resisting the elastic force of the spring 15, and the valve body 9B is swung in the opening direction by the slider 13S. On the other hand, when the solenoid 13 is demagnetized, the piston 13P moves backward and the rotating shaft 9C swings in the closing direction by the elastic force of the spring 15. The solenoid 13 and the hinge portion 9A are covered with a cover 14 to prevent dust and the like from adhering. This ensures a stable operation of the backflow prevention device 7.

  When the check valve 9 is closed, the elastic force of the spring 15 acts, and the opening 7M has an inclined valve seat, so that the response is very good.

  As shown in FIG. 16, a controller 170 is connected to the solenoid 13, and excitation and demagnetization of the solenoid 13 are controlled by the controller 170. The controller 170 includes a temperature sensor 172 that detects the surface temperature of the battery cell 1, a voltage sensor 174 that detects the output voltage of the battery cell 1, a current sensor 176 that detects the output current of the battery cell 1, and the secondary battery pack 50. A pressure sensor 178 for detecting the internal pressure is connected, and the control unit 170 controls the solenoid 13 based on the detection data of these sensors 172 to 178.

  When a short circuit occurs inside the battery cell 1, the output voltage and output current decrease, and the surface temperature increases. Further, when gas is ejected as a result of the short circuit, the pressure in the secondary battery pack 50 increases. Further, when a slight short circuit occurs inside the battery cell 1, the output voltage does not change and the output current decreases. Further, the control unit 170 is connected to the power fan 8 and controls the rotational speed of the power fan 8. Thereby, it is possible to cope with overheating of the battery cell 1 in a state where no short circuit occurs.

  As shown in FIG. 17, the control unit 170 controls the solenoid 13 and the power fan 8 through the following steps. The process of FIG. 17 is executed by a program stored in the control unit 170.

  In step S1801, the detection data of the sensors 172 to 178 is fetched, and the process proceeds to step S1802. In step S1802, based on the detection data of temperature sensor 172, it is determined whether the surface temperature of battery cell 1 is within a safe range. If it is determined that the surface temperature of the battery cell 1 is higher than the safe range, the solenoid 13 is demagnetized in step S1811, the flow path is closed by the check valve 9, and the process is terminated.

  If the surface temperature is within the safe range, the process proceeds to step S1803, and it is determined whether or not the surface temperature of the battery cell 1 is within a high temperature range within the safe range. If it is determined in step 1803 that the surface temperature of the battery cell 1 is a high temperature within the safe range, the process proceeds to step 1804, where the rotational speed of the power fan 8 is set high and the cooling effect by the cooling air is enhanced. If it is determined that the surface temperature of the battery cell 1 is not a high temperature within the safe range, the process proceeds to step 1805, the rotation speed of the power fan 8 is set to the standard rotation speed, and the process proceeds to step S1806. As a result, the backflow prevention device 7 can be shut off based on the abnormal surface temperature.

  In step S1806, based on the detection data of the pressure sensor 178, it is determined whether the pressure in the secondary battery pack 50 is abnormal. If the pressure is abnormal, the process proceeds to step S1811, the solenoid 13 is demagnetized, the flow path is closed by the check valve 9, and the process is terminated. If it is determined in step 1806 that the pressure is not abnormal, the process proceeds to step S1807.

  In step 1807, it is determined whether the output voltage of the battery cell 1 is abnormal based on the detection data of the voltage sensor 174. If the voltage is abnormal, the process proceeds to step S1811, the solenoid 13 is demagnetized, the flow path is closed by the check valve 9, and the process is terminated. If the output voltage of the battery cell 1 is not abnormal, the process proceeds to step S1808.

  In step S1808, based on the detection data of the current sensor 176, it is determined whether the output current of the battery cell 1 is decreasing. If it is determined that the output current is decreasing, the process advances to step S1809 to determine whether the output current of the battery cell 1 is decreasing to an abnormal range. If it is determined that the pressure has fallen to an abnormal range, the process proceeds to step S1811, the solenoid 13 is demagnetized, the flow path is closed by the check valve 9, and the process is terminated. If it is determined that the output current of the battery cell 1 has not decreased to an abnormal range, the process proceeds to step S1810, where an alarm indicating that a slight short circuit may have occurred is issued, and the process ends. To do.

  In the fourth embodiment, in addition to the same effects as those of the first embodiment, the spring 15 can ensure higher responsiveness when closed. In addition, since the check valve 9 is closed based on various detection data of the sensors 172 to 178, that is, a condition in which the internal pressure of the cell storage chamber is higher than the pressure at the entrance of the duct 7D is determined. Therefore, since the check valve 9 is controlled to be opened and closed by the solenoid 13 which is a valve driving device, it is possible to reliably detect an abnormal situation such as gas generation and reliably prevent the gas from flowing back into the vehicle interior. There is an effect that can be. Furthermore, an effect that a sign of a short circuit can be detected by detecting a current drop is also obtained.

[Modification]
The above embodiment can be modified as follows.
(1) In the embodiment, one backflow prevention device is provided in the preceding stage of the intake duct 6A. However, one or more backflow prevention devices may be provided in the intake duct 6A.

(2) In the embodiment, the cooling air is sucked and taken in by the power fan 8 provided in the discharge duct 6B. However, a configuration in which the cooling air is pushed into the take-in duct 6A may be employed. In this case, it is preferable to dispose the power fan 8 at a position away from the passenger compartment, considering the quietness of the passenger compartment.

(3) In the embodiment, the solenoid 13 is employed as the opening drive means, but an air cylinder, a hydraulic cylinder, a linear motor, a link mechanism driven by a motor, and other various drive means can be employed.

(4) Although the flat rectangular battery cell has been described in the embodiment, the present invention can also be applied to a secondary battery pack using a cylindrical secondary battery.
(5) Although the separators 5A and 5B are arranged on the left and right sides of the battery cell 1, they may be arranged on the upper and lower surfaces, respectively.
(6) In the embodiment, the configuration in which the cooling air is taken from the vehicle interior of the vehicle has been described. However, the present invention can be applied to secondary battery packs used in various environments in which emission gas inflow should be prevented. .

1: Battery cell 2A, 2B: Pressure plate
3: Base plate 4: Top plate 5A, 5B: Separator 6A: Intake duct 6B: Discharge duct 7: Backflow prevention device 7D: Duct 7M: Opening
8: Power fan 9: Check valve 9A: Hinge part 9B: Valve body 9C: Rotating shaft 9R: Arm part 9S: Stopper 13: Solenoid 13P: Piston 13S: Slider 14: Cover 15: Spring 50: Secondary battery pack 52 : Duct 54: Intake port 170: Control unit 172: Temperature sensor 174: Voltage sensor 176: Current sensor 178: Pressure sensor

Claims (6)

A cell storage chamber in which a plurality of battery cells are stored;
An intake passage for taking cooling air into the cell storage chamber;
A discharge passage for discharging the cooling air and the gas discharged from the battery cell from the cell storage chamber;
A backflow prevention device provided at the inlet of the intake passage and configured to prevent a backflow of the gas when an internal pressure of the cell storage chamber becomes higher than a pressure at the entrance of the intake passage. Next battery pack. The secondary battery pack according to claim 1,
It is further equipped with a power fan for taking in cooling air,
The backflow prevention device includes a check valve installed between the inlet of the intake passage and the cell storage chamber,
The check valve has a suspension-type valve body that is pivotally supported at one end, and a flow path is formed when the pressure upstream of the check valve is high according to the differential pressure across the check valve. A secondary battery pack that is configured to open and close the flow path when the downstream pressure is high. The secondary battery pack according to claim 2,
When the power fan stops and no differential pressure is generated before and after the check valve, the valve body is configured to be seated on the valve seat of the check valve by its own weight and close the flow path. A secondary battery pack characterized by comprising: The secondary battery pack according to claim 3,
The secondary battery pack, wherein the valve seat is inclined toward the downstream side of the flow path from one end side for suspending the valve body toward the free end side. The secondary battery pack according to claim 1,
The backflow prevention device includes a check valve installed between an inlet of the intake passage and the cell storage chamber, a biasing member that biases the check valve in a flow path closing direction, and the check valve The valve drive device that drives the energizing member against the energizing force of the energizing member and the condition that the internal pressure of the cell storage chamber is higher than the pressure at the entrance of the intake passage, and the determination result And a control unit that controls the opening and closing of the check valve by the valve driving device. The secondary battery pack according to any one of claims 1 to 5,
The plurality of battery cells are arranged side by side in one direction in the cell housing chamber,
The intake passage has an intake passage extending in the flow direction of the cooling air on one side of the battery cell, and a wall surface separating the intake passage and the cell storage chamber is provided in the flow direction of the cooling air. A take-side slit is provided at a predetermined interval along the
The discharge passage has a discharge flow path extending in the flow direction of cooling air on the other side of the battery cell, and a wall surface separating the discharge flow path and the cell storage chamber has a flow direction of the cooling air. Discharge slits are provided at predetermined intervals along the
The cooling air introduced into the intake flow channel flows into the cell storage chamber from a plurality of intake side slits, and the cooling air heat exchanged with the battery cells enters the discharge flow channel from the discharge side slit. A secondary battery pack configured to be discharged.

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