JP3825577B2 - Battery temperature rise monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for monitoring a temperature rise of each unit cell during charge / discharge in an assembled battery formed by connecting a plurality of unit cells in series or in parallel.
[0002]
[Prior art]
Conventionally, an element (PTC element) having a positive temperature coefficient is attached to each of a plurality of single cells constituting an assembled battery, and these PTC elements are connected in series with each other, and the total resistance of these PTC elements is An apparatus for detecting a large temperature rise during charging / discharging by measuring is proposed (Japanese Patent Laid-Open No. 10-270094).
In this device, when a large temperature rise exceeding a predetermined value occurs in any single cell, the resistance value of the PTC element attached to the single cell increases rapidly, and all of the plurality of PTC elements are thereby Since the measured value of resistance increases, the occurrence of a large temperature rise can be detected with this.
[0003]
[Problems to be solved by the invention]
However, even if it can be detected that a large temperature rise has occurred in any single cell by the conventional temperature rise detection device, it cannot be specified which cell has a large temperature rise.
For example, as shown in FIG. 6 (a), in an assembled battery consisting of five single cells, the remaining charge capacity (charged) as shown in the figure due to variations in battery characteristics and differences in heat dissipation during the process of repeated charge / discharge cycles. Variations in depth may occur. When charging is started in the state where the remaining discharge capacity varies in this way, as shown in FIG. 5B, the batteries ("Battery 1" and "Battery 5") having a large remaining discharge capacity at the start of charging, as shown in FIG. ) Is first fully charged, and the temperature of the battery rises. As a result, the resistance value of the PTC element attached to the battery increases, and charging is terminated.
[0004]
However, as shown in FIG. 6B, the battery ("Battery 3") having a small remaining discharge capacity at the start of charging is terminated without being fully charged.
Therefore, when the charge / discharge cycle is repeated, the remaining discharge capacity of the specific battery gradually increases, and the battery capacity of the assembled battery as a whole decreases.
[0005]
Therefore, an object of the present invention is to specify a battery when a large temperature rise occurs in any of a plurality of unit cells constituting the assembled battery, and disconnect the battery from the charge / discharge system as necessary. It is an object of the present invention to provide a battery temperature rise monitoring device capable of performing the above.
[0006]
[Means for solving the problems]
The battery temperature rise monitoring device according to the present invention is a device for monitoring the temperature rise of each unit cell during charging / discharging in an assembled battery formed by connecting a plurality of unit cells in series or in parallel. An element having a negative temperature coefficient (hereinafter referred to as an NTC element) is attached to the battery, and these elements are connected to a plurality of parallel lines (51, 51) connecting two series lines (41) (42). ) (52) (53) (54) (55), respectively, and connected in parallel to each other, one series line (42) , in each series line section extending between adjacent parallel lines, A resistor is interposed, and the two series lines (41) and (42) are connected to a resistance detection circuit (7).
As the NTC element, for example, a critical temperature thermistor (CTR) can be adopted.
[0007]
In charge / discharge monitoring using the battery temperature rise monitoring device of the present invention, current is supplied from the resistance detection circuit (7) to each NTC element, and two series lines (41 ) (42) is detected. However, in the state where the temperature of all the single cells is low, the resistance value of all the NTC elements is very large, and the current flowing through each NTC element is weak.
Here, when a temperature rise exceeding a predetermined value occurs in one unit cell, the resistance of the NTC element attached to the unit cell rapidly decreases, and the parallel line in which the NTC element is interposed Therefore, a large amount of current flows through the series line section on the upstream side of the parallel line.
As a result, the resistance value between the two serial lines (41) and (42) is the resistance value of the series line section upstream of the parallel line and the NTC interposed in the parallel line upstream of the parallel line. It is generally determined according to the resistance value of the element.
[0008]
That is, as the temperature rises more in the upstream battery near the resistance detection circuit (7), the resistance value between the two series lines (41) and (42) becomes smaller. The resistance value between the two series lines (41) and (42) becomes larger as it is generated in the battery farther from (7) and further downstream.
Therefore, by detecting the resistance value between the two serial lines (41) and (42), that is, the resistances at both ends of a plurality of NTC elements connected in parallel, it is possible to identify a single cell in which a large temperature rise has occurred. .
[0009]
In addition, since one of the series lines (42) includes a resistor in each series line section extending between adjacent parallel lines, two series lines (41) are caused by the temperature rise of the unit cell. The resistance value between (42) changes more greatly.
Therefore, a battery in which a temperature rise exceeding a predetermined value has occurred can be detected with high sensitivity.
[0010]
Further, in a specific configuration, the battery pack includes a charging line (60) for supplying power from the charger (6) to the assembled battery, and disconnects the individual cells from the charging line (60) individually. It has a circuit.
According to this specific configuration, all the cells can be charged to a fully charged state by continuing charging while disconnecting from the charging line (60) in order from the battery in which a large temperature increase has occurred.
[0011]
【The invention's effect】
According to the battery temperature rise monitoring device of the present invention, when a large temperature rise occurs in any of the plurality of single cells constituting the assembled battery, the battery is specified, and if necessary, the battery The battery can be disconnected from the charge / discharge system.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
As shown in FIG. 1, five single cells (11), (12), (13), (14), and (15) made of a secondary battery such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery are connected in series. The assembled battery (1) is configured by being connected to the battery charger (6), and the charger (6) is connected to the assembled battery (1) via the charging line (60). The operation of the charger (6) is controlled by a charge control circuit (8).
[0013]
The battery temperature rise monitoring device according to the present invention monitors the temperature rise during charging of the assembled battery (1), and each cell (11) (12) (13) (14) (15) As the NTC element, critical temperature thermistors (21) (22) (23) (24) (25) are affixed to the surface of these, and these thermistors are connected between the two series lines (41) (42). Are connected to each other in parallel through five parallel lines (51), (52), (53), (54), and (55).
[0014]
The two series lines (41) and (42) are connected to a pair of resistance detection terminals A and B provided in the resistance detection circuit (7), and the temperature is determined based on the resistance value between the terminals A and B. A rising instruction signal is generated and supplied to the charge control circuit (8). In response to this, the charge control circuit (8) supplies a charge stop command to the charger (6).
[0015]
Also, one series line (42) has a resistor (31) (31) in each series line section extending between the connection points with each parallel line (51) (52) (53) (54) (55). 32) (33) (34) (35) intervene.
Here, each of the critical temperature thermistors (21), (22), (23), (24), and (25) has resistance values Rl (L) to R5 (L) at a low temperature (for example, 70 ° C. or less), and at a high temperature (for example, 80 Between the resistance values R1 (H) to R5 (H) of not less than [° C.] and the resistance values R11 to R15 of the resistors (31) (32) (33) (34) (35) The relationship is established.
[0016]
[Expression 1]
Rl (L) to R5 (L) >> R11 to R15 >> R1 (H) to R5 (H)
For example, Rl (L) to R5 (L) are set to several thousand Ω, R11 to R15 are set to several hundred Ω, and R1 (H) to R5 (H) are set to tens of Ω.
[0017]
In the above temperature rise monitoring device, a constant voltage is applied between the two series lines (41) and (41) by the resistance detection circuit (7), and the magnitude of the current flowing through the series lines (41) and (42) is increased. Based on this, the resistance value between the serial lines (41) and (42) is detected.
FIG. 3 shows an equivalent circuit for the resistance value of the temperature rise monitoring device. As is clear from the equivalent circuit, the critical temperature thermistor attached to the unit cell due to the temperature increase of one unit cell. When the resistance values (R1 to R5) are lowered, the combined resistance values of the plurality of resistance elements are changed in accordance with the connection relationship between the thermistor and the resistance values R11 to R15 of the resistors.
[0018]
After starting the charging of the battery pack (1) by the charger (6) shown in FIG. 1, the temperature rise exceeding a predetermined value is observed in any single battery (11) (12) (13) (14) (15). In the state where it does not occur, the resistance value of each critical temperature thermistor (21) (22) (23) (24) (25) is as high as several thousand Ω, and the resistance value between the series lines (41) (42) is The parallel resistance values of the critical temperature thermistors (21), (22), (23), (24), and (25) become dominant, and are approximately equal to the resistance value of one critical temperature thermistor.
Therefore, the current flowing through each parallel line (51) (52) (53) (54) (55) is extremely weak.
[0019]
After that, when a certain unit cell, for example, the third unit cell (13) reaches a fully charged state and a large temperature rise exceeding a predetermined value occurs in the unit cell, it is attached to the unit cell. The resistance value R3 of the critical temperature thermistor (23) suddenly decreases from several thousand Ω to several tens of Ω, and a large amount of current flows into the parallel line (53) in which the critical temperature thermistor (23) is interposed. This current flows through the resistors (31), (32) and (33) interposed in the series line section on the upstream side of the parallel line (53).
As a result, the resistance value between the series lines (41) and (42) is dominated by the series resistance values (R11 + R12 + R13) of these three resistors (31), (32), and (33), and before the temperature rise occurs. The value is smaller than the resistance value.
[0020]
Here, the number of the dominant resistors decreases as the unit cell in which a large temperature rise occurs is located on the upstream side closer to the resistance detection circuit (7). In addition, the number of dominant resistors increases as the unit cell in which a large temperature rise occurs is located further downstream from the resistance detection circuit (7).
Therefore, any single cell (11) (12) (13) is detected by detecting the resistance value between the serial lines (41) and (42) by the resistance detection circuit (7) and determining the magnitude of the resistance value. (14) It is possible to detect whether a large temperature rise has occurred in (15).
[0021]
In the circuit shown in FIG. 1, when the occurrence of a large temperature rise is detected, a temperature rise instruction signal is supplied from the resistance detection circuit (7) to the charge control circuit (8), and as a result, the charge control circuit (8). Is sent to the charger (6), and the charging operation of the charger (6) is interrupted.
Then, after the battery having a large temperature rise is disconnected from the charging line (60), charging is started again. In this way, all the cells (11), (12), (13), (14), and (15) are charged to the fully charged state.
[0022]
FIG. 4 is equipped with a disconnection circuit for disconnecting the individual cells (11) (12) (13) (14) (15) from the charging line (60). In FIG. 4, the critical temperature thermistor, the series line, the parallel line, and the resistor to be attached to each of the single cells (11), (12), (13), (14), and (15) are not shown.
In the circuit, five bypass lines (66), (67), (68), (69) bypassing each cell (11) (12) (13) (14) (15) with respect to the charging line (60). ) (70) are connected, and five changeover switches (61) (62) (63) (64) (65) for switching the charging path to each bypass line are interposed.
At the start of charging, all change-over switches (61) (62) (63) (64) (65) are connected to the a terminal, and all the cells (11) (12) (13) (14) (15 ) To form a charging system.
[0023]
In the above temperature rise monitoring device, when it is detected by the resistance detection circuit (7) that a large temperature rise has occurred in any of the single cells (11) (12) (13) (14) (15), A temperature increase instruction signal indicating the effect is supplied to the charge control circuit (8), and further, a temperature increase battery display signal indicating a single cell in which a large temperature increase has occurred is supplied to the temperature increase battery indicator (9). Which cell has a large temperature rise is displayed.
Therefore, in accordance with the display of the temperature rise battery indicator (9), a changeover switch located on the input side of the cell is connected to the b terminal in order to disconnect the cell having a large temperature rise from the charging line (60). To continue charging the remaining cells.
As a result, all the cells (11), (12), (13), (14), and (15) are charged to the fully charged state.
[0024]
FIG. 5 shows changes in battery capacity during charging / discharging using the above-described temperature rise monitoring device according to the present invention, and changes in battery capacity during charging / discharging using a conventional temperature rise detection device (Japanese Patent Laid-Open No. 10-270094). Is a comparison.
In the temperature rise monitoring device of the present invention, the assembled battery shown in FIGS. 1 and 4 is configured using a single type 1 nickel-cadmium battery as a single battery, and a critical temperature composed of vanadium dioxide VO ₂ as an NTC element. A thermistor is used.
[0025]
Further, the charging system shown in FIG. 4 was configured for charging, and at the time of discharging, an electronic load device was connected instead of the charger (6), and discharging was performed at a constant current.
The charge / discharge conditions are as follows.
Charging: 20A, ambient temperature 60 ° C
Discharge: 20A, final voltage 5V, ambient temperature 60 ° C
[0026]
In the charging using the temperature rise monitoring device of the present invention, as described above, the single cells whose temperature has risen are sequentially disconnected from the charging system, and all the single cells are fully charged.
On the other hand, in the charge using the conventional temperature rising detection device, the charge was performed in the same manner as the present invention except that the charge was terminated when the series resistance values of the plurality of PTC elements increased rapidly. .
[0027]
As is apparent from FIG. 5, in charging using the temperature rise monitoring device of the present invention, a substantially constant battery capacity is obtained regardless of the increase in the number of charge / discharge cycles, whereas the conventional temperature rise In the charging using the detection device, the battery capacity decreases as the number of charge / discharge cycles increases, and this is not enough for the entire assembled battery due to the variation in the charging depth of each unit cell as described above. It is for becoming.
[0028]
In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, as shown in FIG. 2, it is possible to omit a resistor to be interposed in the series line (42). In this case, by increasing the sensitivity of the resistance detection circuit (7), it is possible to specify which cell has risen in temperature. Further, even when the sensitivity of the resistance detection circuit (7) is low, it is possible to detect that a temperature rise has occurred in any single cell in the assembled battery. The generated current can be used for relay disconnection and safety device operation.
The NTC element is not limited to a critical temperature thermistor, and various known elements can be employed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a temperature rise monitoring apparatus according to the present invention.
FIG. 2 is a block diagram showing another configuration of the temperature rise monitoring apparatus according to the present invention.
FIG. 3 is a diagram showing an equivalent circuit relating to resistance of the temperature rise monitoring device shown in FIG. 1;
FIG. 4 is a block diagram showing a configuration of a temperature rise monitoring device in which each cell is equipped with a system disconnection circuit.
FIG. 5 is a graph showing the relationship between the number of charge / discharge cycles and the battery capacity.
FIG. 6 is a graph illustrating a decrease in battery capacity due to variation in remaining discharge capacity in a conventional charging method.
[Explanation of symbols]
(1) Battery pack
(11)-(15) Cell
(21)-(25) Critical temperature thermistor
(31)-(35) Resistor
(41) (42) Series line
(51)-(55) Parallel line
(6) Battery charger
(7) Resistance detection circuit
(8) Charge control circuit
(9) Temperature rise battery indicator
(60) Charging line
(61) to (65) selector switch
(66)-(70) Bypass line

Claims (3)

In an assembled battery formed by connecting a plurality of single cells in series or in parallel, the device monitors the temperature rise of each single cell during charging or discharging, and each single cell has a negative temperature coefficient. Elements are attached, and these elements are respectively interposed in a plurality of parallel lines (51) (52) (53) (54) (55) connecting the two series lines (41) (42). to are connected in parallel with each other, the one of the series lines (42), in each of the series line segment extending between adjacent parallel lines, resistors interposed, said two series lines (41) (42 ) Is connected to the resistance detection circuit (7), and by detecting the resistance value between the two series lines (41) and (42), it is possible to identify the unit cell in which the temperature rise has occurred. Temperature rise monitoring device. The temperature rise monitoring device according to claim 1, wherein the element having a negative temperature coefficient is a critical temperature thermistor. Together comprising charging line (60) for supplying power from the assembled battery to the charger (6), the claims and includes a disconnect circuit for disconnecting the respective cells individually from the charging line (60) The temperature rise monitoring apparatus according to claim 1 or 2 .

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