阅读说明：本技术 蓄电元件的保护装置 (Protection device for electricity storage element ) 是由 今中佑树 于 2018-05-29 设计创作，主要内容包括：本发明提供一种蓄电元件的保护装置,为保护蓄电元件不受过充电、过放电等异常的影响而将开闭器切换为切断状态后,应切换为通电状态时,迅速地切换为通电状态,并抑制用于切换的消耗电流。保护装置具备BMS(40),该BMS(40)具备：开闭器(47),设置在将电池组(30)和电气设备(3)连接的电流路径(41)中；控制部(42),在预测到电池组(30)异常的情况下将开闭器(47)切换为断开；和旁路路径(46),具有仅在对电池组(30)进行充电的方向上流过电流的寄生二极管(49B)及仅在进行放电的方向上流过电流的寄生二极管(50B)的至少一者,并与开闭器(47)并联连接,在旁路路径(46)中,通过流过给定的电流值的电流而利用磁通将开闭器(47)切换为接通的第2励磁线圈(51)与寄生二极管(49B)及寄生二极管(50B)串联连接。(The invention provides a protection device for an electric storage element, which can quickly switch to a conduction state and restrain the current consumption for switching when switching to a conduction state after switching a shutter to a cut-off state to protect the electric storage element from the influence of abnormality such as overcharge and overdischarge. The protection device is provided with a BMS (40), wherein the BMS (40) is provided with: a switch (47) provided in a current path (41) connecting the battery pack (30) and the electrical device (3); a control unit (42) that switches the shutter (47) off when an abnormality in the battery pack (30) is predicted; and a bypass path (46) which has at least one of a parasitic diode (49B) through which current flows only in a direction for charging the battery pack (30) and a parasitic diode (50B) through which current flows only in a direction for discharging, and which is connected in parallel with the shutter (47), wherein in the bypass path (46), a2 nd field coil (51) which switches the shutter (47) on by magnetic flux by flowing current of a predetermined current value is connected in series with the parasitic diode (49B) and the parasitic diode (50B).)

1. A protection device for an electric storage element, comprising:

a switch provided in a current path connecting the electric storage element and an electric device;

a control unit that switches the shutter to a shut-off state when it is predicted that the power storage element is abnormal; and

a bypass path having at least one of a rectifying element through which a current flows only in a direction of charging the electric storage element and a rectifying element through which a current flows only in a direction of discharging the electric storage element, and connected in parallel to the switch,

in the bypass path, an exciting coil that switches the shutter to an energized state by a magnetic flux by flowing a current of a predetermined current value is connected in series with the rectifying element.

2. The protection device of claim 1,

in the bypass path, a1 st parallel circuit and a2 nd parallel circuit are provided in series, the 1 st parallel circuit being a circuit in which the rectifying element and the 1 st switch through which current flows only in a direction of charging the electric storage element are connected in parallel, the 2 nd parallel circuit being a circuit in which the rectifying element and the 2 nd switch through which current flows only in a direction of discharging the electric storage element are connected in parallel,

when it is predicted that the power storage element is overcharged, the control unit sets the 1 st switch to an energized state and sets the 2 nd switch to a cut-off state.

3. The protection device of claim 1,

in the bypass path, a1 st parallel circuit and a2 nd parallel circuit are provided in series, the 1 st parallel circuit being a circuit in which the rectifying element and the 1 st switch through which current flows only in a direction of charging the electric storage element are connected in parallel, the 2 nd parallel circuit being a circuit in which the rectifying element and the 2 nd switch through which current flows only in a direction of discharging the electric storage element are connected in parallel,

the control unit turns off the 1 st switch and turns on the 2 nd switch when it is predicted that the power storage element is overdischarged.

4. The protection device of claim 3,

the 2 nd switch is a normally open non-latching switch,

in the bypass path, a latch type auxiliary switch is provided in parallel with the 2 nd switch,

the control unit switches the auxiliary switch to the energized state when the 2 nd switch is switched to the energized state.

Technical Field

Relates to a technique for protecting an electric storage element.

Background

A technique is known that allows charging or discharging while protecting an electric storage element from abnormality such as overcharge or overdischarge (for example, see patent document 1). The power storage device described in patent document 1 includes: a plurality of switches provided between the electric device and the power storage element and connected in parallel with each other; and a rectifying element connected in series with any one of the switches. In this power storage device, when it is determined that the power storage element is not normal, the control unit sends a close command signal to a switch connected to the rectifier element, thereby bringing the switch into a closed state (energized state) and bringing the other switches into an open state (cut-off state).

According to this power storage device, for example, when the rectifier element is an element through which a current flows only in a direction in which the power storage element is charged, the power storage element can be charged while being protected from over-discharge. On the other hand, when the rectifying element is an element through which current flows only in a direction in which the power storage element is discharged, it is possible to supply electric power to the electric device while protecting the power storage element from overcharge.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2014-217169

Disclosure of Invention

Problems to be solved by the invention

The power storage device described in patent document 1 described above causes the switch to be in the closed state by software-based control such as transmission of a close command signal from the control unit to the switch. However, when the switch is closed by software control, the current consumption may increase.

Disclosed is a technology which, when switching to an energized state is to be performed after a switch such as a switch is switched to an off state in order to protect an electric storage element from an abnormality such as overcharge or overdischarge, can quickly switch to the energized state and suppress current consumption for switching.

Means for solving the problems

A protection device for an electric storage element includes: a switch provided in a current path connecting the electric storage element and an electric device; a control unit that switches the shutter to a shut-off state when it is predicted that the power storage element is abnormal; and a bypass path that has at least one of a rectifier element that flows a current only in a direction of charging the power storage element and a rectifier element that flows a current only in a direction of discharging the power storage element, and that is connected in parallel with the switch, wherein an excitation coil that is connected in series with the rectifier element and that switches the switch to an energized state by a magnetic flux when a current of a predetermined current value flows through the excitation coil is connected in series with the rectifier element.

Effects of the invention

When the switch is switched to the on state after the switch is switched to the off state in order to protect the power storage element from abnormality such as overcharge and overdischarge, the switch is quickly switched to the on state and the consumption current for switching is suppressed.

Drawings

Fig. 1 is a schematic diagram illustrating an automobile and a battery according to embodiment 1.

Fig. 2 is a perspective view of the battery.

Fig. 3 is an exploded perspective view of the battery.

Fig. 4 is a circuit diagram of the battery (in the case where no abnormality is predicted).

Fig. 5 is a circuit diagram of the secondary battery (in case of overcharge predicted: the shutter is opened).

Fig. 6 is a circuit diagram of the battery (case where overcharge is predicted: shutter on).

Fig. 7 is a circuit diagram of the secondary battery (in the case where overdischarge is predicted: the shutter is open).

Fig. 8 is a circuit diagram of the battery (in the case where overdischarge is predicted: the shutter is turned on).

Detailed Description

(outline of the present embodiment)

A protection device for an electric storage element may include: a switch provided in a current path connecting the electric storage element and an electric device; a control unit that switches the shutter to a shut-off state when it is predicted that the power storage element is abnormal; and a bypass path that has at least one of a rectifier element that flows a current only in a direction of charging the power storage element and a rectifier element that flows a current only in a direction of discharging the power storage element, and that is connected in parallel with the switch, wherein an excitation coil is connected in series with the rectifier element, and the excitation coil switches the switch to an energized state by a magnetic flux when a current of a predetermined current value flows.

The rectifier device is configured such that, when an overcurrent flows only in a direction of charging the power storage device, the switch is switched to the off state when overdischarge is predicted, thereby protecting the power storage device from the influence of overdischarge. When the charging device is connected in this state, a charging current flows from the charging device to the power storage element via the rectifier element, thereby allowing charging.

On the other hand, when a current flows only in a direction in which the power storage element is discharged, the rectifier element switches the switch to the off state when overcharge is predicted, thereby protecting the power storage element from overcharge. When the electrical load is connected in this state, a discharge current flows from the power storage element to the electrical load via the rectifier element, thereby allowing discharge.

When a large current flows through the rectifier element, the rectifier element may be damaged. In this case, it is also conceivable to prevent the breakdown by using a rectifier device having a large maximum allowable current, but in general, a rectifier device having a large maximum allowable current is relatively expensive and has a large size. Therefore, when the current value of the current flowing through the rectifying element reaches a predetermined current value, the switch is switched to the energized state in order to prevent the rectifying element from being damaged.

In this case, it is conceivable that the current flowing through the rectifier element is periodically measured, and when a predetermined current value is reached, the switch is switched to the energized state. It is conceivable to switch the shutter to the energized state by software-based control. However, in order to quickly switch the switch to the energized state when the current value reaches a predetermined current value, the current must be measured in a short cycle, and the current consumption increases.

When a current of a predetermined current value flows through the rectifier element, the switch is switched to the energized state by the exciting coil, and therefore, when the current value reaches the predetermined current value (in other words, when the switch is to be switched to the energized state), the switch can be quickly switched to the energized state. Since measurement of current for switching the shutter to the energized state is not required, current consumption can be suppressed as compared with the case where current is measured in a short cycle.

Since the switch is switched to the conduction state by hardware, not by software control, the switch is switched to the disconnection state to protect the electric storage element from abnormality such as overcharge or overdischarge, and then is switched to the conduction state, the switch can be quickly switched to the conduction state and the consumption current for switching can be suppressed.

In the bypass path, a1 st parallel circuit and a2 nd parallel circuit may be provided in series, the 1 st parallel circuit being a circuit in which the rectifying element and the 1 st switch through which current flows only in a direction of charging the power storage element are connected in parallel, the 2 nd parallel circuit being a circuit in which the rectifying element and the 2 nd switch through which current flows only in a direction of discharging the power storage element are connected in parallel, and the control unit may set the 1 st switch to an energized state and the 2 nd switch to a cut-off state when overcharge of the power storage element is predicted.

It is possible to supply electric power to the electrical load while protecting the power storage element from overcharge.

In the bypass path, a1 st parallel circuit and a2 nd parallel circuit may be provided in series, the 1 st parallel circuit being a circuit in which the rectifier element and the 1 st switch through which current flows only in a direction of charging the power storage element are connected in parallel, the 2 nd parallel circuit being a circuit in which the rectifier element and the 2 nd switch through which current flows only in a direction of discharging the power storage element are connected in parallel, and the control unit may turn off the 1 st switch and turn on the 2 nd switch when overdischarge of the power storage element is predicted.

The power storage element can be charged while being protected from over-discharge.

The 2 nd switch may be a normally open non-latching switch, a latching auxiliary switch may be provided in the bypass path in parallel with the 2 nd switch, and the control unit may switch the auxiliary switch to the energized state when the 2 nd switch is switched to the energized state.

When overdischarge is predicted, the remaining battery capacity is reduced, and therefore, if the 2 nd switch is brought into an energized state, if this state continues for a long time, the power of the power storage element may become insufficient and the 2 nd switch may be brought into an off state. When the 2 nd switch is turned off, the power storage element cannot be charged. In contrast, since the auxiliary switch is of a latch type, electric power for maintaining the energized state is not required, and the energized state can be maintained even if the electric power of the power storage element becomes insufficient. Therefore, even when the 2 nd switch is turned off, the power storage element can be charged via the auxiliary switch.

The present invention can be implemented in various forms such as a protection device for an electric storage element, a protection method for an electric storage element, a computer program for realizing the functions of these devices or methods, and a recording medium on which the computer program is recorded.

< embodiment 1>

Embodiment 1 is described with reference to fig. 1 to 8. In the following description, referring to fig. 2 and 3, the vertical direction of battery case 21 when battery case 21 is placed horizontally without being inclined with respect to the installation surface is referred to as the Y direction, the direction along the longitudinal direction of battery case 21 is referred to as the X direction, and the depth direction of battery case 21 is referred to as the Z direction.

(1) Structure of accumulator

As shown in fig. 1, a battery 20 is mounted in an automobile 1 such as an electric automobile or a hybrid automobile, and supplies electric power to an electric load 3 (see fig. 4) such as a power source operated by electric power.

As shown in fig. 2, battery 20 has a block-shaped battery case 21. As shown in fig. 3, a battery pack 30 in which a plurality of battery cells 31 are connected in series, a control board 28, and the like are housed in a battery case 21. The battery pack 30 is an example of an electric storage device. Battery case 21 includes: a box-shaped case main body 23 opened at the upper side, a positioning member 24 for positioning the plurality of battery cells 31, an intermediate lid 25 attached to the upper portion of the case main body 23, and an upper lid 26 attached to the upper portion of the intermediate lid 25.

A plurality of cell chambers 23A that individually accommodate the respective battery cells 31 in the case main body 23 are arranged in the X direction. The positioning member 24 is provided with a plurality of bus bars 27 on the upper surface, and the positioning member 24 is provided above a plurality of battery cells 31 provided in the case main body 23, so that the plurality of battery cells 31 are positioned and connected in series by the plurality of bus bars 27.

The middle cap 25 has a substantially rectangular shape in plan view, and has a step in the Y direction. The middle cover 25 is provided at both ends in the X direction with a positive electrode terminal 22P and a negative electrode terminal 22N to which harness terminals, not shown, are connected. The middle cover 25 internally accommodates the control substrate 28, and the middle cover 25 is assembled to the case main body 23, so that the battery pack 30 and the control substrate 28 are connected.

(2) Electrical structure of accumulator

The electrical structure of battery 20 will be described with reference to fig. 4. The Battery 20 includes a Battery pack 30 and a Battery Management device 40 (BMS: Battery Management System). BMS40 is an example of a protection device for an electric storage element.

As described above, the battery pack 30 connects a plurality of battery cells 31 in series. Each battery cell 31 is a rechargeable battery, and specifically, for example, is an iron phosphate lithium ion battery using an iron phosphate material for a positive electrode and graphite for a negative electrode. The battery pack 30 is provided in a current path 41 connecting the positive terminal 22P and the negative terminal 22N, and is selectively connected to the charging device 3 provided inside or outside the automobile 1 and the electrical load 3 provided inside the automobile 1 via the positive terminal 22P and the negative terminal 22N. The charging device 3 and the electrical load 3 are examples of electrical equipment.

BMS40 includes control unit 42, current sensor 43, voltage sensor 44, analog-to-digital converter 45 (hereinafter referred to as ADC45), relay L1, and bypass path 46.

The control unit 42 operates based on the electric power supplied from the battery pack 30. The controller 42 includes a central processing unit 42A (hereinafter, referred to as a CPU42A), a ROM42B, a RAM42C, and the like. Various control programs are stored in the ROM 42B. The CPU42A executes a control program stored in the ROM42B, thereby executing processing for estimating the SOC (State Of Charge) Of the battery pack 30, processing for protecting the battery pack 30 from abnormality such as overcharge and overdischarge, and the like. The SOC is also called a state of charge, a charging rate, and represents an amount of charge with respect to an electric capacity by a ratio.

The current sensor 43 is provided in the current path 41 in series with the battery pack 30. The current sensor 43 measures a current value I [ a ] of a charging current flowing from the charging device 3 to the battery pack 30 at the time of charging and a discharging current flowing from the battery pack 30 to the electrical load 3 at the time of discharging, and outputs an analog measurement signal SG1 corresponding to the measured current value I to the ADC 45. In the following description, the charging current and the discharging current are referred to as charging/discharging current without distinction.

The voltage sensor 44 is connected to both ends of each battery cell 31 of the battery pack 30. The voltage sensor 44 detects a voltage value V [ V ] that is a terminal voltage of the battery cell 31, and outputs an analog measurement signal SG2 corresponding to the detected voltage value V to the ADC 45. The ADC45 converts the measurement signals SG1 and SG2 output from the current sensor 43 and the voltage sensor 44 from analog signals to digital signals, and outputs digital data indicating the current value I and the voltage value V to the control unit 42.

The relay L1 and the battery pack 30 are provided in series in the current path 41. The relay L1 includes a latch-type shutter 47 and the 1 st excitation coil 48 that switches the shutter 47 off (a cut-off state and an open state) by magnetic flux. The relay L1 is not limited to switching the shutter 47 to be open by the magnetic flux.

The bypass path 46 is provided in the current path 41 in parallel with the relay L1. The bypass path 46 includes a charging FET49, a discharging FET50, a2 nd exciting coil 51, and an auxiliary relay L2. The charging FET49 is an example of the 1 st parallel circuit. The discharge FET50 is an example of the 2 nd parallel circuit. The 2 nd exciting coil 51 is an example of an exciting coil. The auxiliary relay L2 is an example of an auxiliary switch.

The charging FET49 and the discharging FET50 are provided in series in the bypass path 46. The charging FET49 includes: the semiconductor switch 49A and the parasitic diode 49B are provided in parallel with the semiconductor switch 49A and flow current only in a direction of charging the battery pack 30. The semiconductor switch 49A is a normally open non-latch switch, and is turned on (energized state, closed state) only during the period when power is supplied. The parasitic diode 49B is an example of a rectifier element through which current flows only in a direction of charging the power storage element. The semiconductor switch 49A is an example of the 1 st switch.

The discharge FET50 includes: the semiconductor switch 50A and the parasitic diode 50B are provided in parallel with the semiconductor switch 50A and allow a current to flow only in a direction in which the battery pack 30 is discharged. The semiconductor switch 50A is also a normally open non-latch type switch, and is turned on only during the period when power is supplied. The parasitic diode 50B is an example of a rectifying element through which current flows only in a direction of discharging the power storage element. The semiconductor switch 50A is an example of the 2 nd switch.

The 2 nd exciting coil 51 is provided in series with the charging FET49 and the discharging FET50 in the bypass path 46. The 2 nd field coil 51 is disposed in the vicinity of the shutter 47, and switches the shutter 47 on by magnetic flux when a current of a predetermined current value flows. The predetermined current value is a current value of a magnitude at which the parasitic diodes 49B and 50B are not broken.

The current may be supplied to the 2 nd exciting coil 51 through a path not shown, or the current may be supplied to the 2 nd exciting coil 51 to switch the shutter 47 on.

The auxiliary relay L2 is a latch-type relay, and is provided in the bypass path 46 in parallel with the discharge FET 50.

(3) Estimation of SOC

As described above, control unit 42 estimates the SOC of battery pack 30. As a method of estimating SOC, a current integration method will be described as an example. The current integration method is a method of measuring an amount of electric power output and input from and to a battery by constantly measuring a charge/discharge current of the battery, and estimating an SOC by adding and subtracting the amount of electric power from an initial capacity. The current integration method has an advantage that the SOC can be estimated even when the battery is in use, but since the charge/discharge power amount is always integrated by measuring the current, measurement errors of the current sensor 43 are accumulated and become inaccurate in some cases.

The SOC estimated by the current accumulation method may be reset based on an Open Circuit Voltage (OCV) of the battery (hereinafter, referred to as OCV reset). This is a method of measuring a battery voltage (OCV) when no current flows in the battery using a correlation relationship with relatively good accuracy between the OCV and the SOC when no current flows in the battery, obtaining the SOC corresponding to the measured OCV with reference to a correlation relationship between the OCV and the SOC stored in advance, and correcting the SOC estimated by a current integration method. When the OCV is reset, the accumulation of errors in the current integration method is cut off, and therefore the estimation accuracy of the SOC can be improved.

(4) Protection of battery pack

The control unit 42 determines the state of the battery pack 30 based on the estimated SOC, and protects the battery pack 30 from an abnormality when an abnormality such as overcharge or overdischarge is predicted.

(4-1) prediction of abnormality of Battery pack

For example, overcharge is performed when the SOC is 90% or more, and overdischarge is performed when the SOC is 10% or less. In this case, control unit 42 determines that overcharge is imminent when SOC increases to 85%. That is, overcharge is predicted by the control unit 42. When the SOC decreases to 15%, control unit 42 determines that overdischarge is imminent. That is, overdischarge is predicted by the control unit 42.

The above values are examples, and the values that are the reference values for overcharge and overdischarge, or the values that are the reference values for determining that overcharge and overdischarge are approaching are not limited to the above values.

(4-2) operation in case where abnormality is not predicted

As shown in fig. 4, when abnormality such as overcharge or overdischarge is not predicted, that is, when the battery pack 30 is normal, the control unit 42 turns on the shutter 47 and turns off the semiconductor switch 49A, the semiconductor switch 50A, and the auxiliary relay L2.

(4-3) operation in case of prediction of overcharge

As shown in fig. 5, when overcharge of the battery pack 30 is predicted, the control unit 42 performs the following operation to protect the battery pack 30 from overcharge.

(a1) The 1 st field coil 48 is energized to switch the shutter 47 off.

(a2) The semiconductor switch 49A of the charging FET49 is switched on.

By performing the above-described operation (a1), it is possible to prevent the charging current from flowing from the charging device 3 to the battery pack 30 via the current path 41. Since the semiconductor switch 50A of the discharging FET50 is kept off, the charging current can be prevented from flowing from the charging device 3 to the battery pack 30 via the bypass path 46. Thereby, the battery pack 30 can be protected from overcharge.

By performing the above-described operation (a2), when the electrical load 3 is connected to the battery 20 while protecting the battery pack 30 from overcharge, a discharge current flows from the battery pack 30 to the electrical load 3 via the semiconductor switch 49A of the charging FET49 and the parasitic diode 50B of the discharging FET 50. Therefore, even in a state where the battery pack 30 is protected from overcharge, a power failure (interruption of power supply) in which power is not supplied to the electrical load 3 can be prevented.

As shown in fig. 6, when the discharge current I1 flows from the battery pack 30 to the electrical load 3 via the semiconductor switch 49A and the parasitic diode 50B, the 2 nd exciting coil 51 switches the shutter 47 on when the discharge current I1 gradually increases to reach the predetermined current value. This prevents the parasitic diode 50B from being broken by a large current flowing through the parasitic diode 50B.

(4-4) operation in case of predicting overdischarge

As shown in fig. 7, when it is predicted that the battery pack 30 is overdischarged, the control unit 42 performs the following operation in order to protect the battery pack 30 from the overdischarge.

(b1) The 1 st field coil 48 is energized to switch the shutter 47 off.

(b2) The semiconductor switch 50A of the discharge FET50 is switched on.

(b3) The auxiliary relay L2 is switched on.

By performing the above-described operation (b1), it is possible to prevent the discharge current from flowing from the assembled battery 30 to the electrical load 3 via the current path 41. Since the semiconductor switch 49A of the charging FET49 is kept off, it is also possible to prevent a discharge current from flowing from the battery pack 30 to the electrical load 3 via the bypass path 46. Thereby, the battery pack 30 can be protected from over-discharge.

By performing the above-described operation (B2), when the charging device 3 is connected to the battery 20 while protecting the battery pack 30 from the over-discharge, the charging current flows from the charging device 3 to the battery pack 30 via the semiconductor switch 50A of the discharge FET50 and the parasitic diode 49B of the charge FET 49. Therefore, even in a state where the battery pack 30 is protected from over-discharge, the battery pack 30 can be charged.

As shown in fig. 8, when the charging current I2 flows from the charging device 3 to the battery pack 30 via the semiconductor switch 50A and the parasitic diode 49B, the 2 nd exciting coil 51 switches the shutter 47 on when the charging current I2 gradually increases to reach the predetermined current value. This prevents the parasitic diode 49B of the charging FET49 from being broken by a large current flowing through the parasitic diode 49B.

As shown in fig. 7, since the control unit 42 is also operated (b3), the auxiliary relay L2 is switched on. When overdischarge is predicted, the remaining battery capacity decreases, and therefore, if the semiconductor switch 50A of the discharge FET50 is switched on by the operation of (b2), if this state continues for a long time, the electric power of the battery pack 30 may become insufficient and the semiconductor switch 50A may be switched off in the middle of the time. When the semiconductor switch 50A is turned off, the battery pack 30 cannot be charged.

In contrast, since the auxiliary relay L2 is of a latch type, electric power for maintaining the on state is not required, and the on state can be maintained even if the electric power of the battery pack 30 becomes insufficient. Therefore, even when the semiconductor switch 50A is turned off, the battery pack 30 can be charged via the auxiliary relay L2.

(5) Effects of the embodiments

According to BMS40 of embodiment 1 described above, when the current value of the current flowing through bypass path 46 reaches a predetermined current value, switch 47 is switched on by second excitation coil 51. This enables the switch 47 to be quickly switched on when the current value reaches a predetermined current value (in other words, when the switch 47 should be switched on). Since the BMS40 does not require measurement of a current for switching the shutter 47 on, current consumption can be suppressed compared to a case where the current is measured in a short cycle. According to BMS40, since switch 47 is switched on by hardware rather than by software control, when switch 47 should be switched on, it is possible to quickly switch on and suppress current consumption.

When the shutter 47 is switched to on by software control, there is a concern that the operation may become unstable due to a software failure. In BMS40, since switching to on is performed by hardware, switch 47 can be switched to on stably.

According to BMS40, it is possible to supply electric power to electrical load 3 while protecting battery pack 30 from overcharging.

According to the BMS40, the battery pack 30 can be charged while protecting the battery pack 30 from over-discharge.

According to the BMS40, the auxiliary relay L2 is switched on when the semiconductor switch 50A of the discharging FET50 is switched on, so even if the power of the battery pack 30 becomes insufficient and the semiconductor switch 50A is switched off, the battery pack 30 can be charged via the auxiliary relay L2.

< other embodiment >

The technology disclosed in the present specification is not limited to the embodiments described above and illustrated in the drawings, and includes various embodiments as follows, for example.

(1) In the above-described embodiment, the battery pack 30 was described as an example of the electric storage element, but the electric storage element may be configured by one battery cell 31, may be configured by connecting a plurality of battery cells 31 in series, or may be configured by connecting a plurality of battery cells 31 in parallel.

(2) In the above-described embodiment, the iron phosphate-based lithium ion battery was described as an example of the electric storage element, but the electric storage element is not limited to the iron phosphate-based lithium ion battery, and may be another secondary battery such as a manganese-based lithium ion battery, a titanium-based lithium ion battery containing titanium in the negative electrode, or a lead battery. Further, the electric storage element is not limited to the secondary battery, and may be a capacitor.

(3) In the above embodiment, the case where the charging FET49 (1 st parallel circuit) and the discharging FET50 (2 nd parallel circuit) are provided in the bypass path 46 was described as an example, but only one of the rectifier element through which the current flows only in the direction of charging the power storage element and the rectifier element through which the current flows only in the direction of discharging the power storage element may be provided.

(4) In the above embodiment, the charging FET49 was described as the 1 st parallel circuit, but the 1 st parallel circuit may be provided with a rectifier element and a1 st switch in parallel, and may not be an FET. In this case, the 1 st switch is not necessarily a semiconductor switch, and may be a mechanical relay, for example. The same applies to the 2 nd parallel circuit.

(5) In the above embodiment, the case where the auxiliary relay L2 is provided in the bypass path 46 was described as an example, but the auxiliary relay L2 may not be provided.

(6) In the above-described embodiment, the control unit 42 having the single CPU42A has been described as an example of the control unit 42, but the configuration of the control unit 42 is not limited to this. For example, the control unit 42 may be configured to include a plurality of CPUs, a hardware Circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or both a hardware Circuit and a CPU.

(7) The above-described embodiment may be applied to a secondary battery (backup battery) of a vehicle. The auxiliary battery (backup battery) is a battery that assists the main battery, and is used to keep the supply of power to the vehicle from being interrupted when the main battery is disconnected (OFF, power loss) for some reason. The auxiliary battery is maintained at full charge (SOC above a given value). When the present invention is applied to the sub-battery, the shutter can be turned OFF (OFF) without monitoring the sub-battery to prevent overcharging. When the main battery is turned OFF (OFF, power is lost), the switch is automatically turned ON (ON), and thus the supply of power to the vehicle can be uninterrupted.

(8) The above embodiment may be applied to an auxiliary battery of a vehicle. The auxiliary battery is used as a 12V power supply for driving an ECU and lighting of a Hybrid Electric Vehicle (HEV). When the power supply (alternator) of the vehicle fails, the shutter is automatically turned ON (ON), and thus the power supply to the vehicle can be uninterrupted.

Description of the symbols

3: electrical equipment, 30: battery pack, 40: battery management device (an example of a protection device for power storage element), 41: current path, 42: control unit, 46: bypass path, 47: shutter, 49: charging FET (example of 1 st parallel circuit), 49A: semiconductor switch (example of 1 st switch), 49B: parasitic diode (an example of a rectifying element through which current flows only in a direction of charging the power storage element), 50: discharge FET (an example of the 2 nd parallel circuit), 50A: semiconductor switch (example of 2 nd switch), 50B: parasitic diode (an example of a rectifying element through which current flows only in a direction of discharging the electric storage element), 51: 2-th field coil (an example of a field coil), L2: an auxiliary relay (an example of an auxiliary shutter).