JP2001359243A - Battery pack, battery system, and electrical element controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the output of a battery with high precision. SOLUTION: To a storage element 20, a plurality of power supply units 40a, 40b are connected in parallel. Delivering and receiving power between power elements 41a, 41b and a neutral point N side of the respective power units 40a, 40b can be controlled by time ratio of the closing conditions of switches 42, 43, according to the magnitude relation between the voltage of the power elements 41a, 41b and the voltage across the power supply units 40a, 40b. The output can be controlled for each of the respective power elements 41a, 41b, thus the control precision of the output of the battery pack 10 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembled battery having a plurality of power supply elements or electric elements, a battery system having a plurality of assembled batteries, and an electric element control device.

[0002]

2. Description of the Related Art Conventionally, an assembled battery having a plurality of power elements has been known. In conventional battery packs, it is difficult to increase the unit output voltage per power supply element with respect to a desired output voltage.Therefore, a plurality of power supply elements with a unit output voltage lower than the output voltage are connected in series, and the desired Output voltage is secured. One example of this is disclosed in JP-A-7-322516.

[0003]

However, in the above prior art, since a plurality of power supply elements are connected in series,
When the output of any one of the plurality of power elements is reduced due to performance degradation or the like, there is a problem that the output voltage of the battery is reduced by the amount of the output reduction of the power element. In addition, when the operating voltage of the accessories used in the battery system is different from the output voltage of the battery, a DC / DC converter is required.

[0004]

In view of the above-mentioned problems, according to the present invention, an assembled battery is a power storage element and a plurality of power supply units connected in parallel to the power storage element, wherein the power supply element outputs power. A power supply unit that is connected to each of the power supply elements and includes an open / close switch that controls a current flowing through the power supply unit by switching between open and closed states;
An open / close switch control unit that controls opening / closing of each of the open / close switches, and outputs power stored in the power storage element. In addition, the current to the electric element is controlled by the same method.

According to such a configuration, since the input / output of power can be controlled for each power element by controlling the on / off switch, for example, when one of the power elements drops in output, However, it is possible to improve the control accuracy of the battery output, for example, by increasing the output from another power supply unit that does not include the power supply element and suppressing a decrease in the output of the battery as a whole.

According to the present invention, the battery pack includes a neutral point selectively connected to the high voltage side or the low voltage side via a selection switch, and a selection switch control unit for controlling switching of the selection switch. Preferably, the power supply unit is connected between the neutral point and the high voltage side or the low voltage side. According to such a configuration, the output of the battery pack can be more easily and accurately controlled by controlling the potential of the neutral point.

In the present invention, the battery pack preferably includes a pair of output terminals provided at the neutral point and the high voltage side or the low voltage side. As described above, the potential at the neutral point is controlled to a desired value by the selection switch control unit. Therefore, by using the neutral point as an output terminal, this can be used as a power supply terminal of an external load.

[0008] In the present invention, it is preferable that a load element that is connected between the neutral point and the high voltage side or the low voltage side and consumes electric power is provided. According to such a configuration,
Since the voltage applied to the load element can be controlled using the selection switch, a voltage application mechanism and a voltage control mechanism for each load element can be omitted.

In the present invention, the battery pack preferably includes a load element for a battery pack as the load element. Here, the load element for the battery pack includes a load element necessary for driving the battery pack or a load element for adjusting the drive of the battery pack.For example, when the battery pack is a fuel cell, the hydrogen flow rate Pump for control, heater for methanol reformer,
Includes fuel cell cooling fans.

Further, according to the present invention, in the battery system, the assembled batteries are connected in series. According to such a configuration,
Since the output voltage shared by each battery pack can be reduced with respect to the output voltage of the battery system, the output control accuracy of each battery pack is improved, and the output control precision of the battery system having these battery packs is improved. can do.

Further, according to the present invention, the electric element control device comprises: a power storage element; a neutral point selectively connected to a high voltage side or a low voltage side of the power storage element via a selection switch; And a plurality of high-voltage or low-voltage sides of the power storage element, each of which generates, consumes, or stores electric power, and controls switching of the selection switch to control the potential of the neutral point. A selection switch control unit,
Is provided. According to such a configuration, the electric element control device can control the operation of a plurality or plural kinds of electric elements by controlling the potential of the neutral point. For this reason, the device configuration can be simplified as compared with the case where a control mechanism is provided for each electric element.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 is a schematic diagram of a battery system, FIG. 2 is a schematic configuration diagram of an assembled battery, and FIG. 3 is a circuit diagram of a load unit.

The battery system 1 according to the present embodiment is configured by connecting a plurality of assembled batteries 10 in series. The positive electrode terminal t1 of each battery pack 10 and the negative electrode terminal t2 of the battery pack 10 adjacent thereto are connected. The positive electrode terminal t1 of the battery pack 10 on one end is connected to the positive electrode terminal T1 of the battery system 1, and The negative terminal of the battery system 1 is connected to the negative terminal of the battery pack 10. By thus connecting a plurality of assembled batteries in series, the output voltage per assembled battery with respect to the output voltage of the battery system can be reduced. The smaller the output voltage per assembled battery is, the smaller the variable width of the output becomes, so that the output control accuracy of the assembled battery can be improved. The output voltages of the battery packs 10 may be set so as to be all equal, or may be set individually for each battery pack 10.

The battery pack 10 includes a power storage element 2 for storing power.
0, and a plurality of power supply units (40a, 40b, 40c) connected in parallel to the power storage element 20. Each power supply unit (40a, 40
b, 40c) is stored, and this power is output from these output terminals T1, T2. In addition, the power supply unit (40a, 4
0b, 40c).

The battery pack 10 of the present embodiment comprises a storage element 20
And a neutral point N having an intermediate potential Vn between the high voltage side potential and the low voltage side potential. The neutral point N is alternately connected to the high voltage side and the low voltage side by switching the selection switches 30a and 30b. In the present embodiment, two switches, a high voltage side selection switch 30a connecting the neutral point N and the high voltage side, for example, a power MOSFET, and a low voltage side selection switch 30b connecting the neutral point N and the low voltage side, for example, a power MOSFET Are provided, and these are alternately closed to control the potential Vn of the neutral point N. The potential Vn of the neutral point N can be controlled by the ratio of the connection time between the neutral point N and the high voltage side or the low voltage side. That is, the potential Vn of the neutral point N increases as the time ratio of connection to the high voltage side increases, and the potential Vn of the neutral point N decreases as the time ratio of connection to the low voltage side increases.

Power supply unit (40a, 40b, 40c)
Are connected between the neutral point N and the high-pressure side or the low-pressure side, respectively. In the present embodiment, there are provided power supply units 40a and 40b connected between the neutral point N and the low voltage side, and a power supply unit 40c connected between the neutral point N and the high voltage side and the low voltage side. .

The power supply unit 40a is connected between the neutral point N and the low voltage side, and includes a chargeable / dischargeable power supply element 41a, for example, a lead storage battery. The power supply unit 40b includes a power supply element 41b that performs only discharge, for example, a fuel cell. In addition,
In the present embodiment, each of the power supply elements 41a and 41b is configured by connecting a plurality of, for example, three cells of a lead storage battery and a fuel cell in series.

The power supply units 40a and 40b have the same configuration except that the power supply elements 41a and 41b are different. That is, the power supply units 40a and 40b are connected in series with the power supply elements 41a and 41b, respectively, and control the current flowing through each of the power supply units 40a and 40b. A coil 44 connected in series with the first open / close switch 42;
b and a second open / close switch 43, for example, a power MOSFET, connected in parallel to the series connection of the coil 44 and controlling the current flowing through each of the power supply units 40a and 40b.
And. Since the open / close switches 42 and 43 are provided for each power supply element, each of the power supply elements 41
The output can be controlled for each of a and 41b. The first and second open / close switches 42 and 43 are controlled so as to be alternately closed.

The coil 44 has a function of holding a current passing therethrough. For this reason, the second open / close switch 43
When the second switch 43 is opened, the current flowing through the coil 44 when the switch is closed flows through the first switch 42 which is now closed. This current is output from each of the power supply units 40a and 40b.

In such a configuration, the power supply element 41
a, 41b and the neutral point N side exchange power with the power supply element 4
It changes based on the magnitude relationship between the voltages of 1a and 41b and the voltage between both ends of the power supply units 40a and 40b, and the time ratio of opening and closing of the on / off switches 42 and 43. That is, the power supply element 4
If the potentials of the positive electrodes 1a and 41b on the positive electrode side are higher than the potential Vn of the neutral point N (that is, if the voltage of the power supply elements 41a and 41b is larger than the potential difference between both ends of the power supply units 40a and 40b), the first switching is performed. The higher the time ratio in the closed state of the switch 42, the more the neutral point N
The current output to the side increases, and the first open / close switch 42
The current flowing into the power supply elements 41a and 41b from the neutral point N increases as the time ratio of the closed state decreases.

On the other hand, when the potentials on the positive electrode side of the power supply elements 41a and 41b are lower than the potential Vn at the neutral point N (that is, when the voltage of the power supply elements 41a and 41b is lower than the power supply units 40a and 40b).
0b), the current flowing from the neutral point N to the power supply elements 41a and 41b increases as the time ratio of the closed state of the first on / off switch 42 increases, and the first The current output from the power supply elements 41a and 41b to the neutral point N increases as the time ratio of the closed state of the on / off switch 42 decreases.

The power supply unit 40c includes a power supply element 41c for charging and discharging, for example, a lead storage battery for driving auxiliary equipment. The positive side of the power supply element 41c is connected to the neutral point N, and the negative side is the midpoint of two open / close switches 45 and 46 connected in series between the high voltage side and the low voltage side via the coil 44. Np
Connected to. The on / off switches 45 and 46 are provided with respective protection diodes in parallel.

The transmission and reception of power between the power supply element 41c and the neutral point N side is based on the magnitude relationship between the potential difference between the neutral point N and the high voltage side or the low voltage side, the voltage of the power supply element 41c, and the open / close switch 4c.
5, 46 based on the open / close time ratio. That is, when the potential difference between the neutral point N and the low-voltage side is larger than the voltage of the power supply element 41c, the current flowing from the neutral point N side to the power supply element 41c increases as the time ratio of the closed state of the open / close switch 46 increases. When the potential difference between the neutral point N and the low voltage side is smaller than the voltage of the power supply element 41c, the current output from the power supply element 41c to the neutral point N side increases.

In the configuration of the power supply unit 40c, the potential Vn of the neutral point N is controlled so that the potential difference between the neutral point N and the high voltage side is different from the potential difference between the neutral point N and the low voltage side. In this case, two kinds of voltages can be easily applied to the power supply element 41c by switching between opening and closing of the two open / close switches 45 and 46.

The battery pack 10 includes load units 50a and 50b that consume power. In the present embodiment, a load element 51a (for example, a hydrogen flow rate control pump of a fuel cell)
And a load unit 50b including a load element 51b (eg, a heater for a methanol reformer of a fuel cell) are connected between the neutral point N and the low pressure side. In this way, by incorporating the load elements for the assembled battery into the battery system, the entire system can be made more compact than when these are separately configured.

The load units 50a and 50b have the same configuration except that the load elements 51a and 51b are different. That is, each of the load units 50a and 50b includes an open / close switch 52 such as a power MOSFET connected in series to the load elements 51a and 51b, and a load element 51, respectively.
a, a coil 51 connected in series between the switch 51 and the on / off switch 52; and a diode 53 connected in parallel to the series connection of the load elements 51a, 51b and the coil 54. Note that an open / close switch may be provided instead of the diode 53.

When the open / close switch 52 is in the open state, a return circuit CL is formed in which current flows through the load elements 51a, 51b, the diode 53, and the coil 54 in this order.
At this time, the coil 54 functions to maintain the return current.
That is, with such a configuration, the current flowing through the load elements 51a and 51b can be held and recirculated, and the power can be effectively used without waste.

In such a configuration, the open / close switch 5
As the time ratio of the closed state of the load element 2 increases, the load element 51
The current flowing into the load elements 51a, 51b increases as the ratio of the closing time of the on / off switch 52 decreases.
The current flowing into 51b decreases.

The control unit 60 includes selection switches 30a, 30
b, and each open / close switch (42, 4)
3, 45, 46) to control the power supply unit (4
0a, 40b, 40c) and the storage element 20, and controls the operation of the load units 50a, 50b.

The control unit 60 includes the detected storage element 20
, The detected potential Vn of the neutral point N, the detected voltage values (Va, Vb, Vc) of the power supply elements (41a, 41b, 41c), and the detected load elements 51a,
51b operating status signal, output voltage command signal V *, output command signals Pa *, Pb for each load element 51a, 51b
*, And an output command signal Ic * for the auxiliary battery 41c.
Is entered. Here, the operation status signal is a load element 51
a, 51b indicating the output status of the pump 51a. For example, in the case of the pump 51a, the output flow rate of the pump 51a, the heater 51
In the case of b, it is the temperature of the heating unit. The output voltage command signal V * and the output command signals Pa *, Pb *, Ic * are
It is input from an external device such as an ECU. Based on the input detection value and command signal, the control unit 60 controls the control signals sa and b of the selection switches 30a and 30b and the control signals (s) of the open / close switches (42, 43, 45, 46, and 52).
1, s2, s3, s4, s5). In the present embodiment, the potential at the neutral point N is detected as a potential difference Vn between the low voltage side and the neutral point N.

The control unit 60 compares the output voltage command signal V * with the detected voltage V across the storage element 20 and controls the voltage V across the both ends to match the output voltage command signal V *. When the voltage V between both ends is lower than the output voltage command signal V *, control is performed so that the current output from each power supply unit (40a, 40b, 40c) to the power storage element 20 increases. More specifically, for example, the power supply elements 41a, 41b
Are larger than the potential difference between both ends of the power supply units 40a and 40b (that is, Vn in this embodiment), the time ratio of the closed state of the first open / close switch 42 is increased (that is, the second open / close state). The time ratio of the closed state of the switch 43 is reduced), and conversely, the voltages Va,
When Vb is smaller than the potential difference between both ends of the power supply units 40a and 40b (that is, Vn), the time ratio of the closed state of the first open / close switch 42 is reduced (that is, the second open / close switch 4).
3). Further, the potential of the neutral point N is controlled by controlling the selection switches 30a and 30b,
The magnitude relationship between the voltages Va and Vb of the power supply elements 41a and 41b and the potential difference Vn between both ends of the power supply units 40a and 40b may be adjusted. On the other hand, when the voltage V between both ends is higher than the output voltage command signal V *, each power supply unit (40a, 40a)
b, 40c) to control the current output to the electricity storage element 20 to decrease.

The control unit 60 controls each power supply element (41a,
The output of each power supply element (41a, 41b, 41c) is controlled based on the detected voltage value (Va, Vb, Vc) of (41b, 41c). For example, when the output of the power supply element 41a has decreased, the open / close switches 42 and 43 of the power supply unit 40a are increased so that the current flowing into the power supply element 41a increases.
Control. At this time, the other power supply elements 40b, 40c
Power supply units 40b,
The on / off switches (42, 43, 45, 46) of the 40c may be controlled, or the selection switches 30a, 3
0b may be controlled to control the potential Vn at the neutral point N.

The control unit 60 compares the output command signal Vc * for the auxiliary battery 41c with the detected voltage Vc across the auxiliary battery 20 to determine the voltage Vc across the auxiliary battery 41c.
Control is performed so as to conform to the output command signal Vc * for c. For example, in response to the output command signal Vc *, the auxiliary battery 41
When the output voltage Vc of c is low, the controller 60 charges the auxiliary battery 41c, that is, in the present embodiment, increases the current flowing from the neutral point N to the auxiliary battery 41c. , And controls the open / close switches 45 and 46 or the selection switches 30a and 30b.

The control unit 60 controls each of the load elements 51a, 5a.
The output command signals Pa * and Pb * for 1b are compared with the detected operation status signals Pa and Pb, and the operation status is controlled so as to conform to the output command. For example, the output command signal P
If the outputs detected from the operation status signals Pa and Pb are insufficient for a * and Pb *, the control unit 60 determines that the voltage between both ends of each load element 51a and 51b increases.
It controls the open / close switch 52 and the selection switches 30a and 30b.

Next, regarding a second embodiment of the present invention,
This will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram of the battery pack according to the present embodiment.

In the battery pack 11 according to the present embodiment, at least one electric element unit 70d is connected between the low voltage side of the power storage element 20 and the neutral point N, and the high voltage side of the power storage element 20 is connected to the neutral point N. Is connected to at least one electric element unit 70u. These electric element units 70d, 7
0u can be configured as a circuit including any one of electric elements for generating, consuming, or storing electric power, for example, the power supply unit 40 of the first embodiment.
a, 40b, or the same circuit configuration as the load units 50a, 50b. Also in this embodiment, similarly to the first embodiment, the control unit 60 controls the selection switches 30a and 30b to control the potential Vn of the neutral point N, and the control unit 60 similarly controls each electric element unit. Open / close switches (not shown) included in 70d and 70u are controlled to control the transfer of electric power between each electric element and the electric storage element 20 or between each electric element.
The control unit 60 performs these controls in the same manner as in the first embodiment, by detecting each detection value or signal (for example, the power storage element 20).
, The voltage value of the high-voltage side of the storage element, the potential Vn of the neutral point, the voltage value of each electric element, the operation status signal, the output voltage command signal, or the output command signal).

In this embodiment, the output terminals t1, t
2 and output terminals t at the neutral point N and the low voltage side, respectively.
3, t4 are provided. According to such a configuration, the potential of the neutral point N can be controlled to a predetermined value, and this can be used for supplying power to an external load.

Next, regarding a third embodiment of the present invention,
This will be described with reference to the drawings. FIG. 5 is a schematic configuration diagram of the battery pack according to the present embodiment.

In the battery pack 12 according to the present embodiment, a plurality of electric element units 70t are connected between the neutral point N and the low voltage side or the high voltage side of the power storage element 20. Each of the electric element units 70t can be configured as a circuit including any one of electric elements that generate, consume, or store electric power. For example, the electric power unit 4 of the first embodiment can be configured.
0c, that is, an electric element having one end connected to the neutral point N and a selection switch for selectively connecting the other end of the electric element to the low voltage side or the high voltage side of the electric storage element 20. And a circuit configuration having the following. The control of each unit by the control unit 60 is the same as in the first or second embodiment.

Next, regarding a fourth embodiment of the present invention,
This will be described with reference to the drawings. FIG. 6 is a schematic configuration diagram of the battery pack according to the present embodiment.

In the battery pack 13 according to the present embodiment, the electric element unit 70t is connected between the neutral point N and the low voltage side or the high voltage side of the power storage element 20, and the low voltage side of the power storage element 20 is connected to the neutral point. N is connected to the electric element unit 70d,
An electric element unit 70u is connected between the high voltage side of the electric storage element 20 and the neutral point N. Each of these electric elements 70t,
70d, 70u can have the same configuration as the electric element units 70t, 70d, 70u of the second or third embodiment described above. The control of each unit by the control unit 60 is the same as in the first, second, or third embodiment.

The present invention is not limited to the above embodiment. The connection form of the electric element includes: 1) connection between the neutral point N and the high voltage side of the main power storage element 20 [for example, an electric element included in the electric element unit 70u of the second embodiment], 2) neutral point N and the low voltage side of the main power storage element 20 [for example, the power supply elements 41a, 41b,
Load units 51a, 51b, etc.] or 3) selectively connecting the neutral point N to either the high voltage side or the low voltage side of the main power storage element 20 [for example, the power supply element 41c of the first embodiment]. Types are included, and without being limited to the above-described embodiment, a plurality of electric elements can be incorporated by any one of the connection forms 1) to 3). Further, these connection forms may be appropriately mixed.
Further, the electric element connected in the connection form 1) or 2) may be directly connected to the neutral point N or the high voltage side or the low voltage side of the power storage element 20 without intervening a switch.

The potential of the neutral point N can be set to an appropriate value in accordance with the electric element to be connected, and the potential difference between the neutral point N and the high voltage side of the storage element 20 and the neutral point The potential difference between N and the low voltage side of power storage element 20 can be set as different values. With this, it is possible to incorporate electric elements having different potential differences required for the operation, for example, different rated voltages, and selectively act on a plurality of, for example, two kinds of different potential differences with respect to the electric elements connected by the above-mentioned connection form 3). Can be done.

As a power supply element, for example, various types of chemical batteries (for example, nickel-metal hydride batteries, lithium ion batteries, etc.) or AC power supplies can be connected. These power supplies can be applied regardless of whether charging is possible.
As a load element, for example, an EHC heater or A
A transformer for a C100 volt power supply can also be connected.
Further, as the power storage element, for example, an electric double layer capacitor or the like may be used, or the power storage element may be configured as a chargeable / dischargeable battery instead of the capacitor.

In the first to fourth embodiments,
In either case, the control unit 60 controls the selection switches 30a, 3
0b or an open / close switch or a selection switch included in each electric element unit is controlled, and thereby, the transfer of electric power between the electric storage element 20 and the electric element or between the electric elements is controlled. That is, the assembled battery and the battery system according to the above-described embodiment can be said to be an electric element control device that controls a plurality of electric elements connected in parallel to the main electric storage element (that is, the electric storage element 20). With such a configuration, input / output control of power to various electric elements can be performed by an integrated circuit configuration. Therefore, compared to a case where a control mechanism is individually provided for a plurality of electric elements, the device configuration is Can be further simplified, and the power control of each electric element can be efficiently and accurately performed by controlling the selection switch and / or controlling the opening / closing switch provided for each electric element or the opening / closing control of the selection switch. . When configured as an electric element control device, an output terminal as an assembled battery or a battery system is not necessarily required.

[0046]

As described above, according to the present invention,
By controlling the open / close switch or the selection switch, it is possible to individually control the transfer of power between the main power storage element and a plurality of electric elements connected in parallel to the main power storage element, so that the output of the battery pack and the battery system including the same can be controlled. Control accuracy can be further improved. Further, it is possible to realize an electric element control device in which a plurality of electric elements are compactly integrated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a battery system according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a schematic configuration of the battery pack according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a load unit of the battery pack according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating a schematic configuration of an assembled battery according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a schematic configuration of a battery pack according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram illustrating a schematic configuration of an assembled battery according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 battery system, 10 assembled batteries, 20 power storage elements, 3
0a, 30b selection switch, 40a, 40b, 40
c, 40d, 40u power supply units, 41a, 41b,
41c power element, 42, 43, 45, 46, 52 open / close switch, 44, 54 coil, 50a, 50b load unit, 51a, 51b load element, N neutral point,
T1, T2 Output terminals of the battery system, t1, t2, t
Output terminal of 3,4 battery pack.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunari Moriya 41, Chuchu-ji, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. No. 41, Chochu Yokomichi 1 Toyota Central Research Laboratory Co., Ltd. (72) Inventor Shoichi Sasaki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Junwa Shamoto Toyota Toyota City, Aichi Prefecture No. 1 Toyota Motor Co., Ltd. (72) Inventor Masayuki Komatsu No. 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. F-term (reference) 5G003 BA04 DA07 DA16 FA08 GA01 GB03 5H030 AS20 BB22 BB23 BB27 FF44

Claims (7)

[Claims] 1. A power storage element, and a plurality of power supply units connected in parallel to the power storage element, wherein the power supply element outputs power, and the power supply unit is connected to each of the power supply elements and flows through the power supply unit by switching between opening and closing. An assembled battery, comprising: a power supply unit including an open / close switch for controlling current; and an open / close switch control unit for controlling opening / closing of each open / close switch, and outputting power stored in the power storage element. 2. A power supply unit comprising: a neutral point selectively connected to the high voltage side or the low voltage side via a selection switch; and a selection switch control unit that controls switching of the selection switch. The battery pack according to claim 1, wherein the battery pack is connected between the neutral point and the high voltage side or the low voltage side. 3. The semiconductor device according to claim 1, further comprising a pair of output terminals provided at the neutral point and the high voltage side or the low voltage side.
The battery pack according to item 1. 4. The battery pack according to claim 2, further comprising a load element connected between the neutral point and the high voltage side or the low voltage side and consuming power. 5. The battery pack according to claim 4, wherein the load element includes a load element for driving a battery pack. 6. A battery system including a plurality of assembled batteries connected in series, wherein the assembled battery is a power storage element and a plurality of power supply units connected in parallel to the power storage element, and outputs electric power. A power supply unit including a power supply element, an open / close switch connected to each of the power supply elements, and controlling a current flowing through the power supply unit by switching between open / close states; and an open / close switch control unit for controlling opening / closing of each open / close switch. When,
A battery system comprising: 7. A power storage element, a neutral point selectively connected to a high voltage side or a low voltage side of the power storage element via a selection switch, a neutral point and a high voltage side or a low voltage side of the power storage element. A plurality of electric elements, each of which generates, consumes, or stores electric power, and a selection switch control unit that controls switching of the selection switch to control the potential of the neutral point. apparatus.