JP6724693B2 - Battery short circuit determination system - Google Patents

Description

The present invention relates to a battery short circuit determination system, and more particularly to a determination system capable of determining a slight short circuit that recovers to a normal state after a temporary short circuit occurs.

A battery module, which is a DC power supply, is installed in a vehicle that uses a rotating electric machine as a drive source, such as an electric vehicle or a hybrid vehicle. In the battery module, a plurality of battery cells (unit cells) are stacked and connected.

The battery cell includes a positive electrode plate, a negative electrode plate, and insulating paper (separator) separating the two. When metal or the like is deposited on at least one of the positive electrode plate and the negative electrode plate, the deposit may penetrate through the insulating paper to cause a short circuit. For example, in the case of a lithium ion battery, it is known that metallic lithium is deposited on the negative electrode plate in a dendrite shape. When this deposit penetrates the insulating paper, a short circuit occurs.

One of the causes for the deposit to break through the insulating paper is the relative movement between the negative electrode plate on which the deposit is formed and the insulating paper. For example, when the battery cells expand due to so-called high-rate deterioration accompanying charging/discharging with a large current, and during the contraction process of the battery cells when charging/discharging is stopped (the process of eliminating high-rate deterioration), the negative electrode plate and the insulating paper move relative to each other. In the process, the deposit penetrates the insulating paper, reaches the positive electrode plate, and causes a short circuit.

When a short circuit occurs, the internal resistance drops and the voltage across the terminals drops sharply. Therefore, it is possible to determine the presence/absence of a short circuit in the battery cell by capturing the sudden decrease in the voltage between the terminals.

For example, in Patent Document 1, when the inter-terminal voltage of the battery being charged/discharged is lower than a predetermined voltage allowable value, predetermined voltage drop information is stored. Further, the deterioration degree of the storage battery is estimated based on the amount of change in the terminal voltage during the charge/discharge stop period, and when the deterioration degree exceeds the deterioration allowable value, predetermined deterioration excess information is stored. When both the voltage drop information and the deterioration excess information are stored, it is determined that the battery has a short circuit.

Further, in Patent Document 2, a voltage change of the battery is measured, and if the amount of change is below a reference value, it is preliminarily determined that the battery has a short circuit. After that, when the temperature change amount of the battery exceeds the reference value, a final determination is made that the battery has a short circuit.

JP, 2011-112453, A JP 2012-52857 A

By the way, when the voltage of the battery cell is measured while charging/discharging is stopped (energization interruption period), the voltage is measured intermittently (for example, every one hour) from the viewpoint of suppressing the power consumption of the voltage measurement system. Here, in the waiting time (interval) between the voltage measurement and the next voltage measurement, if a small short-circuit, that is, a so-called minute short circuit occurs, the short-circuit state is recovered by the time of the next voltage measurement, and It may be difficult to detect.

For example, when the deposit on the negative electrode plate penetrates the insulating paper to reach the positive electrode plate and short-circuits, current concentrates on the deposit. When the deposit is small, the deposit is burnt out due to current concentration, the short circuit is eliminated, and the normal state is restored. If a short circuit occurs after the voltage measurement and the normal state is restored by the next voltage measurement, the minute short circuit cannot be detected.

Therefore, an object of the present invention is to provide a battery short-circuit determination system capable of detecting a micro short-circuit with higher accuracy than before while suppressing power consumption.

The present invention relates to a battery short-circuit determination system for determining whether or not each of the battery cells of a main battery in which a plurality of battery cells are stacked is short-circuited. The system includes a voltage sensor, a short circuit determination unit, a timer switch, and an interval setting unit. The voltage sensor measures the voltage of the battery cell. The short circuit determination unit is intermittently activated during the energization cutoff period of the main battery, and determines the presence or absence of a short circuit in the battery cell based on the voltage of the battery cell. The timer switch has a first start-up interval set as an initial value of a start-up interval for starting the short-circuit determination unit. The interval setting unit, during the energization cutoff period after charging, which has transitioned to the energization cutoff period after charging the main battery, from the voltage value of the battery cell at the time of a predetermined start-up, the voltage of the battery cell at the immediately preceding start-up. When a state in which the voltage value difference obtained by subtracting the value is lower than a predetermined voltage threshold value occurs a plurality of times, or when the voltage value difference is a positive value, the activation interval by the timer switch is set to the first activation. The second activation interval shorter than the interval is set.

According to the present invention, the interval of voltage measurement and short-circuit presence/absence determination is shortened when a phenomenon in which the occurrence of a minute short circuit is suspected, that is, a phenomenon in a recovery process in which the occurrence of a minute short circuit is recovered to a normal state is captured. In this way, by limiting the period in which voltage measurement is performed at short intervals to a specific period, it is possible to suppress power consumption compared to the case where voltage measurement is always performed at short intervals. Further, by shortening the voltage measurement interval, it is possible to detect the voltage at the time of occurrence of the short circuit or immediately after that, and it is possible to detect the short circuit with high accuracy.

It is a figure which illustrates the battery short circuit determination system which concerns on this embodiment, and the structure of the vehicle which mounts this. It is a figure which illustrates the functional block of a control part. It is a figure which illustrates a short circuit judgment flow. It is a figure which illustrates the selection flow of the after-charge/after-discharge interval setting part. It is a figure which illustrates the interval setting flow after charge. It is a figure which illustrates the process of a short circuit detection in the after-charge energization cutoff period. It is a figure which shows another example of the process of short circuit detection in the electricity supply cutoff period after charge. It is a figure which illustrates the interval setting flow after discharge. It is a figure which illustrates the process of short circuit detection in the electricity supply cutoff period after discharge. It is a figure which shows another example of the process of short circuit detection in the after-discharge energization cutoff period.

FIG. 1 illustrates a configuration of a battery short circuit determination system according to the present embodiment and a vehicle equipped with the system. Note that, for simplification of the illustration, in FIG. 1, a configuration having a low relevance to the short circuit determination system according to the present embodiment is omitted as appropriate. The arrow lines represent signal lines.

In the vehicle shown in FIG. 1, electric power is supplied from the main battery 10 to the loads such as the rotary electric machines MG1 and MG2 that are drive sources. Specifically, the DC power output from the main battery 10 is boosted by the step-up/down DC/DC converter 12. The boosted DC power is orthogonally converted by the inverter 14. The converted AC power is supplied to at least one of the rotary electric machines MG1 and MG2. Since the power transmission path from the rotary electric machines MG1 and MG2 to the wheels 16 is known, the description thereof is omitted here.

Further, a branch electric path is provided which is branched from an electric path connecting the main battery 10 and the step-up/down DC/DC converter 12 and is connected to the step-down DC/DC converter 18. The high-voltage power of the main battery 10 is stepped down by the step-down DC/DC converter 18 and supplied to the sub-battery 20, the control unit 22, the voltage sensor unit 24, and other auxiliary equipment.

A system main relay SMR is provided between the main battery 10, the step-up/down DC/DC converter 12, and the step-down DC/DC converter 18. When the system main relay SMR is in the connected state, the main battery 10 is connected to the high-voltage system loads such as the rotary electric machines MG1 and MG2 and the low-voltage system loads such as the control unit 22 and the auxiliary machines. Become. For example, when the driver turns on a start switch (not shown), the system main relay SMR is switched from the disconnected state to the connected state. Further, when the driver turns off the start switch, the system main relay SMR is switched from the connected state to the disconnected state.

Further, the vehicle shown in FIG. 1 is capable of charging the main battery 10 (external charging) from an external AC power source 26 like a so-called plug-in hybrid vehicle or an electric vehicle. For external charging, the connector 28 (plug) of the AC power supply 26 is connected to the connector 30 (inlet) provided on the vehicle. After connecting the connectors 28 and 30, the AC power supplied from the AC power supply 26 is subjected to AC/DC conversion and boosting by the charger 34, and the DC power after the conversion and boosting is supplied to the main battery 10.

A charging relay CHR is provided between the main battery 10 and the charger 34. When the charging relay CHR is in the connected state, the AC power source 26 and the main battery 10 are in the connected state. For example, when the connectors 28 and 30 are connected after the driver turns off a start switch (not shown), the charging relay CHR enters the connected state. Moreover, when the main battery 10 is charged to the target SOC, the charging relay CHR is turned off.

In this way, the energization/de-energization state of the main battery 10 is switched by the system main relay SMR and the charging relay CHR. That is, if at least one of the system main relay SMR and the charging relay CHR is in the connected state, the main battery 10 is in the energized state. On the other hand, if both the system main relay SMR and the charging relay CHR are cut off, the main battery 10 is turned off.

The main battery 10 is configured to include a stacked body in which a plurality of battery cells 32 of secondary batteries are stacked. In the example shown in FIG. 1, a plurality of battery packs 33 including a plurality of battery cells 32 connected in parallel are connected in series.

The battery cell 32 is composed of, for example, a lithium ion battery. Since the detailed structure of the lithium-ion battery is known, it will be briefly described here. A lithium ion battery includes a positive electrode plate made of a material such as lithium cobalt oxide, a negative electrode plate made of a material such as graphite, and an insulating paper separating the two. A layer obtained by bundling the positive electrode plate, the insulating paper (separator), and the negative electrode plate is housed in a metal case in a wound state, for example.

When metal or the like is deposited on at least one of the positive electrode plate and the negative electrode plate of the battery cell 32, the deposit may penetrate through the insulating paper to cause a short circuit. For example, in the case of a lithium-ion battery, it is known that metallic lithium is deposited in the form of dendrites on the negative electrode plate when the amount of reaction between the graphite forming the negative electrode plate and lithium exceeds a predetermined amount. When the deposit and the insulating paper move relative to each other, the deposit may break through the insulating paper and cause a short circuit.

Relative movement between the deposit (and the negative electrode plate on which it is deposited) and the insulating paper occurs as the battery cell 32 expands/contracts. For example, it occurs when the battery cell 32 expands due to the occurrence of high rate deterioration and when the battery cell 32 contracts due to the elimination of the high rate deterioration. In the high rate deterioration, the negative electrode plate and the insulating paper relatively move when the battery cell 32 is charged and discharged with a large current.

During high-current charging/discharging (high-rate charging/discharging), the distribution of ions and concentration in the electrode plate and in the electrolyte is uneven. At this time, the internal resistance increases and heat is generated at a portion where the lithium ion concentration is relatively low. The battery cell 32 expands due to this heat generation. In addition, at a location where the concentration of lithium ions is relatively high, the amount of lithium ions stored in the electrode plate (active material) increases, and the electrode plate expands accordingly.

As described above, the high rate deterioration occurs due to the uneven distribution of ions and concentration distribution inside the electrode plate and in the electrolytic solution, and therefore is eliminated when the uneven distribution is uniformed. That is, the high rate deterioration is eliminated by leaving the battery cell 32 in the power-off state. During this standing period, the expanded battery cell 32 contracts, which causes relative movement between the negative electrode plate and the insulating paper. For example, the pressure from the outside to the inside presses the negative electrode plate against the insulating paper, and in the process, the deposit may break through the insulating paper and cause a short circuit.

When a short circuit occurs, the internal resistance of the battery cell 32 lowers, and the voltage across the terminals drops sharply (suddenly drops). Therefore, it is possible to determine the presence/absence of a short circuit in the battery cell 32 by capturing the sudden decrease in the voltage between the terminals.

However, when this short circuit is a small scale, that is, a minute short circuit in which the precipitate is small, the current is concentrated, the precipitate burns out, the short circuit disappears, and the normal state is restored. When the voltage measurement is performed intermittently, a short circuit may occur after the specified voltage measurement and then recover to the normal state by the next voltage measurement.In such a case, a short circuit may occur. Can no longer be detected.

As will be described later, in the short circuit determination system according to the present embodiment, the presence or absence of a short circuit in the battery cell 32 is intermittently determined during the energization cutoff period of the main battery 10 in which the battery cell 32 may contract. In the present embodiment, with respect to the interval for determining the presence or absence of this short circuit, in the present embodiment, a phenomenon in which the occurrence of a slight short circuit is suspected is detected, and the interval for voltage detection is shortened accordingly.

As shown in FIGS. 6 and 9, the behavior of the voltage change of the battery cell 32 during the energization interruption period is different between the high rate deterioration due to the large current discharge and the high rate deterioration due to the large current charge. For example, as shown in FIG. 6, when high rate deterioration occurs due to charging with a large current, the terminal voltage of the battery cell 32 gradually decreases during the energization cutoff period (post-charge energization cutoff period). On the other hand, as shown in FIG. 9, when the high rate deterioration occurs due to the large current discharge, the terminal voltage of the battery cell 32 gradually increases during the energization cutoff period (post-discharge energization cutoff period).

In response to such a difference in the behavior of the voltage between terminals, in the present embodiment, the flow for determining whether or not the interval of voltage detection can be shortened is used in the case where the high-rate deterioration caused by the large current discharge occurs and the case where the large current charge occurs. Different from when high rate deterioration occurs.

<Short circuit judgment system>
The short circuit determination system according to this embodiment includes a sub battery 20, a voltage sensor unit 24, a control unit 22, and a timer switch 40.

The sub-battery 20 is a so-called auxiliary battery, and is composed of, for example, a lead storage battery. As described above, when the system main relay SMR is in the connected state, the sub battery 20 is charged from the main battery 10 via the step-down DC/DC converter 18. Further, when the system main relay SMR and the charging relay CHR are in the cut-off state and the main battery 10 enters the energization cut-off period, the sub-battery 20 supplies electric power to the auxiliary machines. Specifically, electric power is supplied to the control unit 22, the voltage sensor unit 24, the timer switch 40, and auxiliary equipment such as a clock.

The voltage sensor unit 24 measures the voltage (inter-terminal voltage) of each battery cell 32 of the main battery 10. The measured voltage value of each battery cell 32 is sent to the control unit 22. The voltage sensor unit 24 is intermittently activated in order to suppress the power consumption during the power interruption period of the main battery 10. For example, in response to the activation command from the timer switch 40, the sensor switch 46 is switched from the disconnected state to the connected state, whereby the electric power of the sub battery 20 is supplied to the voltage sensor unit 24.

The control unit 22 is composed of, for example, a computer, and includes a CPU 36, which is an arithmetic circuit, and a storage unit 38. The storage unit 38 includes a volatile memory such as SRAM and a non-volatile memory such as ROM and hard disk. The storage unit 38 stores a program for executing a short circuit determination flow, an interval setting unit selection flow, and a post-charge/post-discharge flow interval setting flow, which will be described later.

The control unit 22 controls various devices in the vehicle. For example, the rotation speeds and torques of the rotary electric machines MG1 and MG2 are controlled through on/off control of switching elements (not shown) of the step-up/down DC/DC converter 12 and the inverter 14. Further, the step-down operation is controlled through on/off control of a switching element (not shown) of the step-down DC/DC converter 18.

Further, the control unit 22 switches the system main relay SMR to the disconnection state or the connection state according to the ON operation and the OFF operation of the start switch (not shown). Further, at the time of external charging (plug-in charging), the charging relay CHR is switched between the disconnected state and the connected state according to the charging timer setting, the SOC of the main battery 10, and the like.

The control unit 22 also receives detection values from various sensors mounted on the vehicle. Specifically, the current value I and the temperature T of the main battery 10 are received from the current sensor 42 and the temperature sensor 44, respectively. Further, the voltage value V of each battery cell 32 is received from the voltage sensor unit 24. The control unit 22 detects whether or not the battery cell 32 is short-circuited based on the voltage value V of each battery cell 32 acquired from the voltage sensor unit 24. That is, the control unit 22 also functions as a detection unit that detects the presence or absence of a short circuit in the battery cell 32.

Specifically, by executing the programs of the short circuit determination flow, the interval setting unit selection flow, and the post-charge/post-discharge interval setting flow stored in the storage unit 38 of the control unit 22, the control unit 22 can: It has a plurality of functional units as shown in FIG. That is, the control unit 22 includes a short circuit determination unit 50, an interval setting flow determination unit 52, a post-charge interval setting unit 54, and a post-discharge interval setting unit 56. The operation of each of these functional units will be described later.

The timer switch 40 determines an activation interval (interval) of the voltage sensor unit 24, the short circuit determination unit 50, the post-charge interval setting unit 54, and the post-discharge interval setting unit 56 during the energization cutoff period of the main battery 10. As will be described later, at the start of the energization cutoff period, Δta (first activation interval) is set as the initial value of the interval Δt. Further, the post-charge interval setting unit 54 and the post-discharge interval setting unit 56 change this interval Δt to Δtb (second activation interval) shorter than Δta.

FIG. 3 exemplifies a determination flow of the presence or absence of a short circuit by the short circuit determination unit 50. This determination flow may be executed independently for each battery cell 32 of the main battery 10.

The short circuit determination unit 50 is intermittently activated and determines the presence or absence of a short circuit each time. Specifically, when the short-circuit determination unit 50 receives a cutoff command (relay-off command) to both the system main relay SMR and the charging relay CHR, or receives a start command from the timer switch 40 thereafter, it is shown in FIG. Run the flow.

When the relay off command is received, the various parameters set in the short circuit determination unit 50 are initialized. For example, n=1 in the flow of FIG.

The short circuit determination unit 50 causes the voltage sensor unit 24 to detect the terminal voltage Vn of the battery cell 32 (S10). Subsequently shorting determination unit 50, the suffix n of the terminal voltage V _n determines whether two or more (S12). When the suffix n is less than 2, the process directly skips to step S20. When the suffix n is 2 or more, the short circuit determination unit 50 obtains a voltage value difference ΔV _n by subtracting the terminal voltage V _n-1 at the time of startup from the terminal voltage V _n detected this time (S14). ).

After obtaining the voltage value difference [Delta] V _n, shorted determination unit 50, the voltage value difference [Delta] V _n is equal to or less than a predetermined voltage threshold value Vth (S16). The voltage threshold Vth is set to a predetermined negative value, for example. For example, as seen at times t7 and t8 in FIG. 6, when a short circuit occurs, the inter-terminal voltage sharply decreases. Therefore, the voltage value difference ΔV ₇ obtained by subtracting the voltage value V ₇ immediately before the occurrence of the short circuit from the voltage value V _{8 at} the time t8 immediately after the occurrence of the short circuit, just before that, has a negative value. When this voltage value difference ΔV ₇ is more negative than the voltage threshold value Vth, that is, when the voltage drop is large, the short circuit determination unit 50 determines that there is a short circuit in the battery cell 32 that is the determination target (S18).

The voltage threshold value Vth is determined based on the voltage between the terminals of the battery cell 32 at the time of normal (no short circuit) and at the time of short circuit. For example, a value obtained by multiplying a difference value obtained by subtracting the terminal voltage at the time of full charge (upper limit SOC) from the terminal voltage at the time of short circuit by a predetermined ratio (for example, an arbitrary ratio of 50% or more and 70% or less) is the voltage threshold Vth. And

In step S18, the short circuit determination unit 50 transmits a predetermined short circuit occurrence notification to a driver's terminal or the like through a display device such as a display in the vehicle or a telematics system (not shown). Further, the short circuit determination flow proceeds to step S20, and the suffix n is incremented. After that, the short circuit determination unit 50 outputs a count command to the timer switch 40 (S22), and causes the timer switch 40 to start counting the interval period. After outputting the count command, the short circuit determination unit 50 shifts to a sleep (sleep) state.

The interval setting flow determination unit 52, the post-charge interval setting unit 54, and the post-discharge interval setting unit 56 set an interval (starting interval) by the timer switch 40. The interval setting flow determination unit 52 determines which setting unit and flow, the post-charge interval setting unit 54 or the post-discharge interval setting unit 56, is used to set the interval.

FIG. 4 illustrates a determination flow by the interval setting flow determination unit 52 (hereinafter referred to as a flow determination unit). The flow is executed at the transition from the energization period (charge/discharge period) of the main battery 10 to the energization cutoff period (charge/discharge stop period). When the flow determination unit 52 receives a cutoff command (relay-off command) to both the system main relay SMR and the charging relay CHR, the flow determination unit 52 sets Δta (first activation interval) in the timer switch 40 as an initial value of the interval Δt. (See Figure 2).

In the flow determining unit 52, the detected value of the battery current Ib by the current sensor 42 is continuously sent and stored from the energization period of the main battery 10. For example, starting from the time when the system main relay SMR switches from the disconnected state to the connected state (for example, the start operation time of the start switch), and thereafter, switching from the connected state to the disconnected state (for example, the time operation of the start switch off). The battery current Ib of is stored in the flow determination unit 52. Alternatively, the battery current Ib from the time when the charging relay CHR switches from the disconnected state to the connected state (external charging start time) to the subsequent switching from the connected state to the disconnected state (external charging end time) to the flow determination unit 52. Remembered.

In this flow, it is determined whether the high rate deterioration that has occurred in the battery cell 32 is due to a large current discharge or a large current charge. That is, it is determined whether the energization cutoff period has shifted after charging (post-charge energization cutoff period) or after discharging (post-discharge energization cutoff period). Based on this determination, it is determined whether the flow after discharging or the flow after charging is used as the interval setting flow.

The flow determination unit 52 calculates the integrated value of high rate charging. That is, the charging current integrated value ΣIch in which the battery current Ib is less than the predetermined current threshold value Ihr- is obtained (S30). In addition, as a sign of the battery current Ib, the discharge current is represented by positive (+) and the charge current is represented by negative (-).

Next, the flow determination unit 52 obtains an integrated value of high rate discharge. That is, the discharge current integrated value ΣIdc at which the battery current Ib exceeds the predetermined current threshold value Ihr+ is obtained (S32).

Further, the flow determination unit 52 compares the charging current integrated value ΣIch and the discharge current integrated value ΣIdc in absolute value (S34). When the charging current integrated value ΣIch (absolute value) is relatively large, the flow determination unit 52 outputs a determination command to the post-charge interval setting unit 54 (S36). When the discharge current integrated value ΣIdc (absolute value) is relatively large, the flow determination unit 52 outputs a determination command to the post-discharge interval setting unit 56 (S38).

Note that in the flow of FIG. 4, only the battery current Ib is used as the determination reference, but the present invention is not limited to this form. For example, expansion of the battery cell 32 is also caused by heating from peripheral devices. For example, the charger 34 may generate heat and be transferred to the main battery 10. Therefore, the battery temperature obtained by the temperature sensor 44 may be added to the criterion.

FIG. 5 illustrates a post-charge interval setting flow by the post-charge interval setting unit 54. The flow is executed at the time when the determination command is received from the flow determination unit 52 and at the time when the activation command is received by the timer switch 40 thereafter. In addition, when the determination command of the flow determination unit 52 is not received, even if the activation command is received from the timer switch 40, it is set (AND setting) so that the flow of FIG. 5 is not executed.

When the determination command is received from the flow determination unit 52, various parameters set in the post-charge interval setting unit 54 are initialized. For example, in the flow of FIG. 5, n=1 and k=0.

The post-charge interval setting unit 54 causes the voltage sensor unit 24 to detect the terminal voltage Vn of the battery cell 32 (S40). Then after charging interval setting unit 54, the suffix n of the terminal voltage V _n it determines whether two or more (S42). When the suffix n is less than 2, the process directly skips to step S56. When the suffix n is 2 or more, the post-charge interval setting unit 54 obtains the voltage value difference ΔV _n by subtracting the terminal voltage V _n-1 at the time of the activation immediately before that from the terminal voltage V _n detected this time. (S44).

Subsequently, the post-charge interval setting unit 54 determines whether or not a slight short circuit has occurred in the battery cell 32, in other words, whether or not a phenomenon associated with the occurrence of the slight short circuit has occurred. That is, the post-charge interval setting unit 54 determines whether the voltage value difference ΔV _n is less than the predetermined voltage threshold Va (S46). The voltage threshold Va is set to a predetermined negative value, for example.

As shown in FIG. 6, when a slight short circuit occurs in the process of eliminating the high rate deterioration, the inter-terminal voltage sharply drops and then recovers. In this embodiment, the voltage measurement interval is shortened when the inter-terminal voltage in the recovery process is captured.

In the process of eliminating the high rate deterioration after charging with a large current, the terminal voltage of the battery cell 32 gradually decreases. Therefore, in the normal state (the past value is subtracted from the current value), the voltage value difference ΔV _n is always ΔV _n <0. The voltage threshold Va is set to a value between the voltage difference that can occur in this normal state and the voltage difference when a slight short circuit occurs.

For example, a value obtained by multiplying a difference value obtained by subtracting the terminal voltage at the time of full charge (upper limit SOC) from the terminal voltage at the time of short circuit by a predetermined ratio is set as the voltage threshold Va. Here, if the voltage threshold value Va is set closer to the time of the short circuit, the recovery process of the slight short circuit becomes difficult to detect by that much. In other words, the timing of falling below the voltage threshold Va is limited to a short period immediately after the occurrence of the slight short circuit. On the other hand, if the voltage threshold value Va is set near the normal time, there is a possibility that it may be erroneously detected that a slight short circuit has occurred during the normal time.

Therefore, in the present embodiment, for example, the predetermined ratio is set to 10% or more and 20% or less, and the recovery process of the micro short circuit can be detected for a long period from the time when the micro short circuit occurs. Further, in order to suppress erroneous detection of a slight short circuit, the state where the voltage value difference ΔV _n is less than the voltage threshold Va is counted, and when the voltage value difference ΔV _n is less than the voltage threshold Va over a plurality of times. In addition, the interval of voltage measurement (that is, short circuit determination) is shortened.

Note that, as shown in FIG. 6, in the process of eliminating the high rate deterioration after the high current charging, the voltage decrease curve gradually becomes gentle. In other words, the rate of decrease in the voltage between the terminals of the battery cell 32 decreases with time. Therefore, the voltage threshold value Va may be decreased with the passage of time. For example, the voltage threshold Va may be a function Va(t) with the start time of the energization interruption period being time 0.

The post-charge interval setting unit 54 increments the counter k when it is determined in step S46 that the voltage value difference ΔV _n is less than the voltage threshold Va (S48). Furthermore, the post-charge interval setting unit 54 determines whether the counter k exceeds a predetermined counter threshold value kth (S50). If it exceeds, the interval Δt of the timer switch 40 is set and changed to Δtb (second startup interval) shorter than the initial value Δta (first startup interval) (S54). For example, in FIG. 6, with kth=1, the interval is changed to Δtb at the second time t4 when the voltage value difference ΔV _n becomes less than the voltage threshold Va. If the counter k is equal to or smaller than the predetermined counter threshold value kth in step S50, the process skips to step S56.

The interval Δtb may be a period shorter than Δta, and for example, an arbitrary time of 0 or more and less than Δta can be set. For example, if Δtb=0, voltage measurement (and short circuit determination) can be continuously performed.

When the voltage value difference ΔV _n is greater than or _equal to the voltage threshold Va in step S46, the post-charge interval setting unit 54 determines whether or not a slight short circuit has occurred in the battery cell 32, in other words, accompanies the occurrence of the slight short circuit. A second judgment is made to judge whether or not the phenomenon has occurred. That is, the post-charge interval setting unit 54 determines whether or not the voltage value difference ΔV _n is positive (ΔV _n >0) (S52).

As described above, in the process of eliminating the high rate deterioration after the high current charging, the terminal voltage of the battery cell 32 gradually decreases. Therefore, in the normal state (the past value is subtracted from the current value), the voltage value difference ΔV _n is always ΔV _n <0. From this, it is highly possible that a slight short circuit has occurred when ΔV _n >0. For example, as shown at time t2 and time t3 in FIG. 7, it can be estimated that ΔV _n >0 as a result of subtracting the previous terminal voltage in the recovery process of the slight short circuit from the current terminal voltage in the normal state.

When the voltage value difference ΔV _n is positive (ΔV _n >0), the post-charge interval setting unit 54 sets the interval Δt of the timer switch 40 to Δtb (second interval) shorter than the initial value Δta (first activation interval). Setting is changed to (starting interval) (S54). When the voltage value difference ΔV _n is 0 or less, the process proceeds to step S56.

In step S56, the suffix n of the voltage measurement number is incremented. After that, the post-charge interval setting unit 54 outputs a count command to the timer switch 40 (S58), and causes the timer switch 40 to start counting the interval period. After outputting the count command, the post-charge interval setting unit 54 shifts to a sleep (sleep) state.

FIG. 8 illustrates a post-discharge interval setting flow by the post-discharge interval setting unit 56. The flow is executed at the time when the determination command is received from the flow determination unit 52 and at the time when the activation command is received by the timer switch 40 thereafter. When the determination command of the flow determination unit 52 is not received, even if the activation command is received from the timer switch 40, it is set (AND setting) so that the flow of FIG. 8 is not executed.

When the determination command is received from the flow determination unit 52, various parameters set in the post-discharge interval setting unit 56 are initialized. For example, n=1 and k=0 in the flow of FIG.

The post-discharge interval setting unit 56 causes the voltage sensor unit 24 to detect the terminal voltage Vn of the battery cell 32 (S60). Then after discharge interval setting unit 56, the suffix n of the terminal voltage V _n determines whether two or more (S62). When the suffix n is less than 2, the process directly skips to step S76. When the suffix n is 2 or more, the post-discharge interval setting unit 56 obtains a voltage value difference ΔV _n by subtracting the terminal voltage V _n-1 at the time of the immediately preceding start from the terminal voltage V _n detected this time. (S64).

Then, the after-discharge interval setting unit 56 determines whether or not the battery cell 32 is in the process of recovering from the slight short circuit. That is, the post-discharge interval setting unit 56 determines whether the voltage value difference ΔV _n exceeds the predetermined voltage threshold Vb (S66). The voltage threshold Vb is set to a predetermined positive value, for example.

As shown in FIG. 9, in the process of eliminating the high rate deterioration after the large current discharge, the terminal voltage of the battery cell 32 gradually increases. When the voltage value difference ΔV _n is large enough to exceed the ratio of the gradual increase, it is suspected that a short circuit has occurred in the battery cell 32, in other words, a phenomenon associated with the occurrence of the short circuit has occurred. Presumed.

The voltage threshold Vb is set to, for example, a value obtained by multiplying a difference value obtained by subtracting the terminal voltage at the time of full charge (upper limit SOC) from the terminal voltage at the time of a short circuit by a predetermined ratio. Here, if the voltage threshold value Vb is set closer to the time of the short circuit in the same manner as the voltage threshold value Va in the post-charge interval setting flow, it becomes difficult to detect the recovery process of the slight short circuit accordingly. That is, the timing of exceeding the voltage threshold Vb is limited to a short period immediately after the occurrence of the slight short circuit. On the other hand, if the voltage threshold value Vb is set near the normal time, there is a possibility that it is erroneously detected that a slight short circuit has occurred during the normal time.

Therefore, in the present embodiment, for example, the predetermined ratio is set to 10% or more and 20% or less so that the recovery process of the minute short circuit can be detected for a long period of time. Further, in order to suppress erroneous detection of a slight short circuit, the state in which the voltage value difference ΔV _n exceeds the voltage threshold value Vb is counted, and when the voltage value difference ΔV _n exceeds the voltage threshold value Vb over a plurality of times. , The interval of voltage measurement (that is, short circuit determination) is shortened.

Note that, as shown in FIG. 9, in the process of eliminating the high rate deterioration after the large current discharge, the increase rate of the terminal voltage of the battery cell 32 decreases with time. Therefore, the voltage threshold value Vb may be decreased with time. For example, the voltage threshold value Vb may be a function Vb(t) with the start time of the energization interruption period being time 0.

When it is determined in step S66 that the voltage value difference ΔV _n exceeds the voltage threshold value Vb, the post-discharge interval setting unit 56 increments the counter k (S68). Further, the after-discharge interval setting unit 56 determines whether or not the counter k exceeds a predetermined counter threshold value kth (S70). If it exceeds, the interval Δt of the timer switch 40 is changed to Δtb (second activation interval) shorter than the initial value Δta (first activation interval) (S74). For example, in FIG. 9, with kth=1, the interval is changed to Δtb at time t6 when the voltage value difference ΔV _n exceeds the voltage threshold value Vb for the second time. If the counter k is equal to or less than the predetermined counter threshold value kth in step S70, the process skips to step S76.

When the voltage value difference ΔV _n is less than or _equal to the voltage threshold Vb in step S66, the post-discharge interval setting unit 56 makes a second determination to determine that the process is a recovery process from a slight short circuit. That is, the post-discharge interval setting unit 56 determines whether or not the voltage value difference ΔV _n is negative (ΔV _n <0) (S72).

As described above, in the process of eliminating the high rate deterioration after the large current discharge, the terminal voltage of the battery cell 32 gradually increases. Therefore, in the normal state (the past value is subtracted from the current value), the voltage value difference ΔV _n is always ΔV _n >0. From this, when ΔV _n <0, there is a high possibility that a slight short circuit has occurred. For example, as shown at time t3 and time t4 in FIG. 10, when ΔV _n <0 is obtained as a result of subtracting the normal terminal voltage (time t3) from the terminal voltage (time t4) in the recovery process of the slight short circuit. Can be estimated.

The post-discharge interval setting unit 56 sets the interval Δt of the timer switch 40 to Δtb (second start interval) shorter than the initial value Δta (first activation interval) when the voltage value difference ΔV _n is negative (ΔV _n <0). The setting is changed to (starting interval) (S74). When the voltage value difference ΔV _n is 0 or more, the process proceeds to step S76.

In step S76, the suffix n of the voltage measurement number is incremented. After that, the after-discharge interval setting unit 56 outputs a count command to the timer switch 40 (S78), and causes the timer switch 40 to start counting the interval period. After outputting the count command, the post-discharge interval setting unit 56 shifts to a sleep (sleep) state.

10 main battery, 20 sub battery, 22 control unit, 24 voltage sensor unit, 32 battery cell, 33 battery pack, 40 timer switch, 50 short circuit determination unit, 52 interval setting flow determination unit, 54 post-charge interval setting unit, 56 discharge Rear interval setting section, CHR charging relay, SMR system main relay.

Claims (1)

A main battery having a plurality of battery cells stacked, for determining whether each of the battery cells is short-circuited, a battery short-circuit determination system,
A voltage sensor for measuring the voltage of the battery cell,
A short-circuit determination unit that is intermittently activated during a power interruption period of the main battery, and determines whether or not the battery cell is short-circuited based on the voltage of the battery cell,
A timer switch in which a first activation interval is set as an initial value of the activation interval for activating the short-circuit determination unit;
A voltage obtained by subtracting the voltage value of the battery cell at the immediately preceding startup from the voltage value of the battery cell at a predetermined startup during the after-charge energization cutoff period after the main battery has been charged and then transitioned to the energization cutoff period. When a state in which the value difference falls below a predetermined voltage threshold occurs a plurality of times, or when the voltage value difference is a positive value, the activation interval by the timer switch is set to be shorter than the first activation interval. Interval setting part to set to the starting interval of 2,
A short circuit determination system for a battery, comprising: