JP5783051B2 - Secondary battery and secondary battery remaining capacity calculation device - Google Patents

Description

  The present invention relates to a secondary battery that is mounted on, for example, a vehicle and functions as a driving source, and an apparatus that calculates the remaining capacity of the secondary battery.

  Degradation of the secondary battery will be promoted if it falls into an overdischarge state where the remaining capacity (SOC: state of charge) of the secondary battery decreases beyond the appropriate range, or an overcharge state that increases beyond the appropriate range. . Therefore, it is necessary to perform charge / discharge control so that the SOC is within an appropriate range. For that purpose, it is necessary to calculate the SOC with high accuracy. Then, since there is a correlation between the terminal voltage of the secondary battery when not charging / discharging and the SOC (see the characteristic line Lm in FIG. 2A), the voltage of the secondary battery is detected, and the detected value is The SOC can be calculated.

  By the way, when falling into the above-described overcharge state, there is a concern that the secondary battery may generate abnormal heat and be thermally damaged. In response to this concern, for example, secondary batteries that are advantageous against thermal damage have been developed in recent years, such as lithium batteries in which a lithium metal phosphate having an olivine structure is included in the positive electrode (see Patent Documents 1 and 2). .

  However, the secondary battery advantageous for heat damage in this manner has a small change in voltage with respect to the change in SOC within the appropriate range of SOC. In the example of the characteristic line Lm described above, the inclination within the appropriate range (m1 <SOC <m3) is smaller than the inclination outside the appropriate range. Therefore, when calculating the SOC from the voltage detection value in the appropriate range, there arises a problem that the SOC cannot be calculated with high accuracy.

  With respect to this problem, in Patent Document 2, when a plurality of main battery cells are connected in series to form a secondary battery, only one voltage detection battery cell (detection battery cell) is used. Connected in series. Then, by configuring the detection battery cell with an electrode made of a material different from the electrode of the main battery cell, the inclination of the characteristic line Lx (see FIG. 2A) of the detection battery cell is inclined to the characteristic line Lm of the main battery cell. It is set to be larger.

  According to this, the SOC (s) of the detection battery cell can be calculated with high accuracy from the voltage detection value of the detection battery cell. Then, the SOC (m) can be calculated from the correspondence relationship between the SOC (s) and the SOC (m) of the main battery cell, and as a result, the SOC of the entire secondary battery can be calculated. Therefore, the SOC of the secondary battery can be calculated with high accuracy based on the characteristic line Lx having a large inclination in the appropriate range of the secondary battery mainly composed of a plurality of main battery cells.

JP 2009-296699 A JP 2007-220658 A

  However, in the secondary battery according to Patent Document 2, since it is necessary to prepare two types of battery cells (main battery cell and detection battery cell) having different electrode materials, the productivity of the secondary battery is extremely deteriorated.

  The present invention has been made to solve the above-described problems, and its purpose is to provide a secondary battery capable of calculating the remaining capacity with high accuracy while suppressing deterioration in productivity, and the remaining capacity of the secondary battery. It is to provide a calculation device.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

In the first invention, the secondary battery is configured by connecting a voltage detection battery in series to a plurality of main battery cells connected in series, and the electrode of the voltage detection battery is the electrode of the main battery cell. And the capacity of the voltage detection battery is made larger than the capacity of the main battery cell.

  By the way, in the central portion of the above-described appropriate range (m1 <SOC <m3), it is not necessary to calculate the SOC with high accuracy because it does not immediately fall outside the appropriate range. On the other hand, in the low SOC region portion, there is a concern that an overdischarge state may occur, so that it is highly necessary to calculate the SOC with high accuracy.

  In the above-described invention focusing on this point, the voltage detection battery is made of the same material as that of the main battery cell, and the capacity of the voltage detection battery is made larger than the capacity of the main battery cell. According to this, the characteristic line Ls (see FIG. 2B) representing the correlation between the voltage of the voltage detection battery and the SOC is the characteristic line Lm (see FIG. 2A) of the main battery cell of the same material. The shape is enlarged in the SOC axis direction. Therefore, among the characteristic lines Ls of the voltage detection battery, the slopes of the regions s1 to s2 (see FIG. 2B) corresponding to the low SOC region portions m1 to m2 (see FIG. 2A) of the main battery cells are In the characteristic line Lm of the main battery cell, it becomes larger than the inclination of the low SOC region portions m1 to m2.

  Therefore, for the regions s1 to s2, the remaining capacity (SOC (s)) of the voltage detection battery can be calculated with high accuracy from the voltage detection value of the voltage detection battery. Then, the SOC (m) can be calculated from the correspondence between the SOC (s) and the remaining capacity (SOC (m)) of the main battery cell, and as a result, the remaining capacity of the entire secondary battery can be calculated. Therefore, the remaining capacity of the secondary battery can be calculated with high accuracy based on the characteristic line Ls having a large slope for the low SOC region portions m1 to m2 of the secondary battery mainly composed of a plurality of main battery cells.

  As described above, according to the above-described invention, the remaining capacity of the secondary battery is reduced for the low SOC region portions m1 to m2 where high-accuracy calculation is required while the voltage detection battery is composed of electrodes made of the same material as the main battery cell. It can be calculated with high accuracy. Therefore, the remaining capacity can be calculated with high accuracy while suppressing the deterioration of the productivity of the secondary battery.

In the second invention, the voltage detection battery is configured by connecting a plurality of detection battery cells in parallel, and the capacity of the detection battery cell is the same as the capacity of the main battery cell. (See FIG. 3).

  According to the above invention, since the detection battery cell and the main battery cell have the same capacity, the voltage detection battery can be configured using the same battery cell as the main battery cell. Therefore, the productivity improvement of the secondary battery can be promoted. Incidentally, the above phrase “the capacity of the detection battery cell is the same as the capacity of the main battery cell” is not strictly limited to the same capacity, but the capacity variation in design (for example, design (Plus or minus 5% of capacity) is permitted.

In a third aspect of the invention, the voltage detection battery includes one detection battery cell, and the capacity of the detection battery cell is larger than the capacity of the main battery cell ( (See FIG. 1).

  According to the said invention, compared with the case where the battery for voltage detection is comprised by connecting a some detection battery cell in parallel, the number reduction of a detection battery cell can be aimed at.

The fourth invention is characterized by being applied to an in-vehicle secondary battery that can be charged with electric power generated by an internal combustion engine mounted on a vehicle and that can be charged from an external power source of the vehicle.

  In this type of plug-in hybrid vehicle (PHV vehicle), in the middle and high SOC range, the internal combustion engine is stopped (EV traveling) with the electric motor stopped. Then, when the remaining capacity of the secondary battery decreases and becomes a low SOC region, both the internal combustion engine and the electric motor are operated while charging the secondary battery by appropriately operating the internal combustion engine so that the remaining capacity does not fall below the appropriate range. (HV running).

  On the other hand, in a hybrid vehicle (HV vehicle) that cannot be charged from an external power source, since the capacity of the secondary battery is smaller than that of a PHV vehicle, the lower limit SOC of the appropriate range is generally set to a high value. Therefore, there is a low demand for calculating the remaining capacity with high accuracy specialized for the low SOC region.

  As described above, in the PHV vehicle, since there is a high demand for calculating the remaining capacity with high accuracy specialized for the low SOC region, the above-described effect that the remaining capacity can be calculated with high accuracy for the low SOC region parts m1 to m2 is achieved. This is effective in the above-described invention applied to a vehicle.

In a fifth aspect of the invention, when the remaining capacity of the in-vehicle secondary battery is equal to or greater than a predetermined amount, the vehicle travels with an electric motor while the internal combustion engine is stopped, and the in-vehicle secondary battery. When the remaining capacity of the vehicle is less than a predetermined amount, the internal combustion engine is appropriately operated to charge the in-vehicle secondary battery, and is controlled to be switched to a hybrid travel mode in which the internal combustion engine or the electric motor travels. When the remaining capacity at the point where the slope of the characteristic line representing the relationship between the voltage of the voltage detecting battery and the remaining capacity of the voltage detecting battery is less than a predetermined value is referred to as a detected capacity threshold, The capacity of the voltage detection battery is set so that the remaining capacity of the main battery cell corresponding to the threshold value is equal to or greater than the predetermined amount.

  In the example of FIG. 2, the remaining capacity s2 at the point indicated by the symbol P in the characteristic line Ls of the detection battery cell (voltage detection battery) is “the remaining capacity (detection at which the slope of the characteristic line Ls is less than a predetermined value). Capacity threshold) ”. As shown in the drawing, the SOC (s) of the voltage detection battery can be calculated with high accuracy in the SOC region of the characteristic line Ls less than the detection capacity threshold s2, and cannot be calculated with high accuracy in the region of the threshold s2 or more.

  In the hybrid driving mode of the PHV vehicle, control is performed to appropriately charge and charge the internal combustion engine so that the secondary battery is not overdischarged. Therefore, the electric driving mode (EV driving mode) in which such charging is not performed. Compared to sometimes, there is a high demand for calculating the remaining capacity with high accuracy in the hybrid travel mode (HV travel mode).

  In the above invention in view of these points, the remaining capacity of the main battery cell corresponding to the detected capacity threshold value s2 is set to a value equal to or greater than the determination threshold value (predetermined amount) for switching control between the EV traveling mode and the HV traveling mode. Therefore, the remaining capacity can be calculated with high accuracy using the SOC region of the characteristic line Ls that is less than the detected capacity threshold value s2 in the HV traveling mode in which the demand for calculating the remaining capacity with high accuracy is high.

  However, if the remaining capacity is excessively higher than the determination threshold value, the slope of the region below s2 in the characteristic line Ls illustrated in FIG. Impedes improvement. In view of this point, it is desirable to match the remaining capacity s2 to the determination threshold. In short, in the above-described invention, the remaining capacity s2 at the point indicated by the symbol P may be in the EV travel region. However, it is desirable to locate the boundary remaining capacity s2 between the EV traveling area and the HV traveling area from the viewpoint of improving calculation accuracy.

In a sixth aspect of the invention, the positive electrode of the main battery cell includes at least a lithium metal phosphate having an olivine structure.

  Here, in the case of a secondary battery having an olivine structure as a positive electrode, the risk of abnormal heat generation due to overcharging and thermal damage is low as compared with other structures. However, in the secondary battery described in Patent Document 2 using two types of battery cells having different electrode materials, the olivine structure is adopted as one of the main battery cell and the voltage detection battery (detection battery cell). Therefore, an electrode other than the olivine structure must be employed, and an olivine structure that is resistant to thermal damage cannot be employed for both battery cells. On the other hand, in the above invention, the voltage detection battery is made of the same material as the main battery cell, and the olivine structure is adopted for the positive electrode of the main battery cell, so that both the main battery cell and the voltage detection battery are heated. An olivine structure that is resistant to damage is adopted, and a secondary battery that is resistant to thermal damage can be realized.

  Moreover, in the case of the main battery cell comprised with such a material, although the strength to the heat damage mentioned above improves, as a contradiction, the characteristic line Lm in the appropriate range of the main battery cell (refer FIG. 2 (a)) ) Becomes smaller, the problem is that the remaining capacity cannot be calculated with high accuracy from the voltage of the main battery cell. Therefore, according to the above-described invention applied to the main battery cell of the material in which the problem becomes remarkable in this way, the above-described effect that the remaining capacity can be calculated with high accuracy is preferably exhibited.

In the seventh aspect of the present invention, a remaining capacity calculating device for calculating the remaining capacity of any Kano secondary battery of the sixth invention, a voltage sensor for detecting a voltage of said voltage detecting cell, the voltage sensor And calculating means for calculating the remaining capacity of the main battery cell based on the voltage detected by.

In short, as illustrated in FIG. 1, in the first to sixth inventions , the secondary battery 30 is the subject of the invention, whereas in the above invention, the remaining capacity provided with the voltage sensor 50 and the calculation means (battery ECU 40). The calculation device is the subject of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the secondary battery concerning 1st Embodiment of this invention, and the PHV vehicle by which the secondary battery is mounted. The figure which shows the SOC-V characteristic of the detection battery cell and main battery cell which are shown in FIG. Schematic which shows the secondary battery concerning 2nd Embodiment of this invention, and the PHV vehicle by which the secondary battery is mounted.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
FIG. 1 is a schematic diagram showing a PHV vehicle equipped with a secondary battery according to the present embodiment. The PHV vehicle includes an internal combustion engine 10 and an electric motor (MG20) as a travel drive source, and an electric motor 20. And a secondary battery 30 for supplying electric power. The MG 20 is a motor generator that also functions as a generator. For example, the MG 20 generates regenerative power when the vehicle decelerates. Alternatively, power is generated by the driving force of the internal combustion engine 10.

  Secondary battery 30 and MG 20 are connected via a power converter (inverter 21 and DCDC converter 22). Specifically, the electric power of the secondary battery 30 is boosted by the DCDC converter 22, and the boosted power is energized and controlled by the inverter 21 to each phase winding of the MG 20, thereby driving the motor of the MG 20. Further, the generated power of the MG 20 is rectified by the inverter 21, and the rectified power is stepped down by the DCDC converter 22 to charge the secondary battery 30.

  The charger 23 is a means for stepping down the power supplied from a plug of an external power source (not shown) and supplying it to the secondary battery 30. Thereby, the secondary battery 30 can be charged from an external power source when the vehicle operation is stopped. The battery ECU 40 (calculation means) calculates the remaining capacity of the secondary battery 30 by a method described in detail later, and controls the operation of the charger 23 based on the calculated remaining capacity and the like. Specifically, the operation of the charger 23 is controlled so that the remaining capacity of the secondary battery 30 does not exceed the upper limit of the optimum range and overcharge occurs.

  The hybrid ECU 41 obtains the remaining capacity value from the battery ECU 40. Then, during operation of the vehicle, the DCDC converter 22 and the inverter are based on the acquired remaining capacity value so that the secondary battery 30 is charged and discharged with the MG 20 so that the remaining capacity of the secondary battery 30 is in the optimum range. 21 is controlled.

  The engine ECU 42 calculates the output required for the internal combustion engine 10 based on the accelerator operation amount by the driver and the rotational speed of the internal combustion engine 10, and controls the operation of the internal combustion engine 10 according to the required output. In addition, the internal combustion engine 10 appropriately performs a power generation operation so that the remaining capacity does not exceed the lower limit of the optimum range to cause overdischarge. In short, during vehicle operation, the engine ECU 42, the hybrid ECU 41, and the battery ECU 40 perform switching control between an EV traveling mode and an HV traveling mode described below.

  That is, when the remaining capacity of the secondary battery 30 is equal to or greater than a predetermined amount, the operation of the internal combustion engine 10, the inverter 21 and the DCDC converter 22 is performed in the EV travel mode in which the motor travels by the MG 20 while the internal combustion engine 10 is stopped. Control. Therefore, in the EV traveling mode, the regenerative electric power generated by the MG 20 is charged in the secondary battery 30, but the MG 20 is not generated and charged by the driving force of the internal combustion engine 10.

  On the other hand, when the remaining capacity of the secondary battery 30 is less than the predetermined amount, the operation of the internal combustion engine 10, the inverter 21, and the DCDC converter 22 is controlled in the HV traveling mode. Specifically, at least one of the internal combustion engine 10 and the MG 20 is driven while the internal combustion engine 10 is appropriately operated to charge the secondary battery 30 so that the remaining capacity does not exceed the lower limit of the optimum range and the battery is charged. Run as.

  Next, the structure of the secondary battery 30 will be described.

  The secondary battery 30 is configured by connecting a plurality of main battery cells 31 in series and connecting one detection battery cell 32 in series to the main battery cells 31. The electrode materials of the plurality of main battery cells 31 and the detection battery cells 32 are the same.

For example, a material containing a lithium metal phosphate having an olivine structure is used for the positive electrodes of these battery cells 31 and 32. Specific examples of the lithium metal phosphate include LiMPO ₄ , and specific examples of M contained therein include Fe, Mn, Co, and Ni. In addition, you may use M mixed so that at least 1 of these Fe, Mn, Co, and Ni may be included.

  Further, a carbon-based material (for example, graphite-based) is used for the negative electrodes of these battery cells 31 and 32. By using the carbon-based material, the capacity of the battery cells 31 and 32 can be easily increased. Whichever material is used, the same material is used for the positive electrodes of the plurality of main battery cells 31 and the detection battery cells 32, and the same material is also used for the negative electrodes.

  However, the capacity of each of the main battery cells 31 is 20 Ah (capacity that allows a current of 20 A to continue to flow for 1 hour), whereas the capacity of the detection battery cell 32 is 60 Ah. Thus, the capacity of the detection battery cell 32 is set larger than the capacity 20 Ah of the main battery cell 31.

  A solid line Lm in FIG. 2A represents an SOC-V characteristic line for the main battery cell 31 (capacity 20 Ah) using a positive electrode using lithium metal phosphate having an olivine structure and a negative electrode using a carbon-based material. Show. The SOC-V characteristic line indicates a correlation between the terminal voltage of the battery cell and the SOC when charging / discharging is not performed. As shown in the figure, when the main battery cell 31 is made of an olivine-based material, the slope of the characteristic line Lm in the appropriate SOC range can be made extremely small (flat). Therefore, it is possible to discharge with a stable output regardless of the change in the value of the remaining capacity.

  A solid line Ls in FIG. 2B indicates an SOC-V characteristic line for the detection battery cell 32 (capacity 60 Ah) having the same material and triple the capacity as the main battery cell 31. As shown in the figure, the characteristic line Ls of the detection battery cell 32 expands the characteristic line Lm of the main battery cell 31 in the SOC axis direction (left and right direction in FIG. 2) by the capacity increase (three times in the example of FIG. 2). The shape becomes.

  The characteristic line Lm is controlled in the above-described HV traveling mode in the range of m1 to m2, and is controlled in the EV traveling mode in the range of m2 to m3. In addition, m1-m3 is the appropriate range of the main battery cell 31, and it is controlled so that SOC is always maintained in the range of m1-m2 at the time of HV driving mode.

  Returning to the description of FIG. 1, the voltage between the positive and negative electrodes of the detection battery cell 32 is detected by the voltage sensor 50. For example, information on the characteristic line Ls of the detection battery cell 32 and information on the characteristic line Lm of the main battery cell 31 are stored in the battery ECU 40 in advance, and the battery ECU 40 detects the characteristic line Ls of the detection battery cell 32 and the voltage sensor 50. Based on the detected voltage value, the remaining capacity SOC (s) of the detected battery cell 32 at the present time is calculated.

  The two characteristic lines Ls and Lm are associated with each other, and in the example of FIG. 2, a value three times the remaining capacity SOC (s) of the detection battery cell 32 is equal to the remaining capacity SOC (m ). Therefore, if the SOC (s) value calculated as described above based on the detected voltage value is 5%, the current SOC (m) can be calculated to be 15%. In short, when the SOC (m) is in the HV traveling region, the SOC (m) is calculated based on the detected voltage value of the detection battery cell 32.

  When the vehicle is in the EV travel region, SOC (m) may be calculated based on the detected voltage value in the same manner, or the current flowing through the secondary battery 30 is detected and the integrated value of the detected current value is calculated. You may calculate by other methods, such as calculating SOC (m) based on it. Further, the “remaining capacity calculation device” is configured by the battery ECU 40 and the voltage sensor 50 when calculating the SOC (m) as described above.

  The association between the two characteristic lines Ls and Lm may be set based on the capacity of the detection battery cell 32 and the capacity of the main battery cell 31. For example, the SOC axis of the characteristic line Ls may be associated with a scale obtained by enlarging the characteristic line Lm in the SOC axis direction in accordance with the ratio of both capacities.

  Here, the remaining capacity s2 at the point where the slope of the characteristic line Ls of the detection battery cell 32 is less than a predetermined value (the point indicated by the symbol P in the example of FIG. 2) corresponds to the detection capacity threshold value. According to the association described above, the remaining capacity s2 (detected capacity threshold) of the characteristic line Ls corresponds to the remaining capacity m2 of the characteristic line Lm, and this remaining capacity m2 is determined to switch between the EV traveling mode and the HV traveling mode. This corresponds to the remaining capacity (predetermined amount) used for.

  According to the present embodiment described in detail above, the detection battery cell 32 is made of the same material as the main battery cell 31, and the capacity of the detection battery cell 32 (maximum chargeable capacity) is set to the capacity of the main battery cell 31 (chargeable). Larger than the maximum capacity). Therefore, the slope of the regions s1 to s2 of the characteristic line Ls associated with the low SOC region portions m1 to m2 of the main battery cell 31 is low in the low SOC region portions m1 to m2 of the characteristic line Lm of the main battery cell 31. It becomes larger than the slope of.

  Therefore, for the regions s1 to s2, the SOC (s) can be calculated with high accuracy from the voltage detection value of the detection battery cell 32. Then, the SOC (m) can be calculated from the association between the two characteristic lines Ls and Lm, and the remaining capacity of the secondary battery 30 can be calculated. That is, for the low SOC region portions m1 to m2, it is possible to calculate the remaining capacity of the secondary battery with high accuracy based on the characteristic line Ls having a large inclination by using the detection battery cell 32 of the same material as the main battery cell 31. it can. Therefore, the remaining capacity can be calculated with high accuracy while suppressing the deterioration of the productivity of the secondary battery.

  Incidentally, in the high SOC region (region of m3 or more shown in FIG. 2A) in which overcharge is a concern, the slope of the characteristic line Lm is steep as in the region of m1 or less. Therefore, even if the remaining capacity of the secondary battery 30 is calculated based on the terminal voltage of the secondary battery 30 or the voltage of the main battery cell 31, it can be calculated with high accuracy. Therefore, it is possible to easily control the SOC so as not to overcharge.

(Second Embodiment)
In the first embodiment, the secondary battery 30 is configured by connecting one detection battery cell 32 in series to a plurality of main battery cells 31, whereas in the present embodiment shown in FIG. The detection battery cells 32b (three in the example of FIG. 3) are connected in parallel to form a voltage detection battery 32A, and the voltage detection battery 32A is connected in series to a plurality of main battery cells 31 to form a secondary battery 30. Is configured. In the case of the first embodiment, it can be said that one detection battery cell 32 constitutes a voltage detection battery.

  Also in the present embodiment, the electrode materials of the main battery cell 31 and the detection battery cell 32b are the same as in the first embodiment. However, in the first embodiment, the capacity of the detection battery cell 32 is larger than that of the main battery cell 31, whereas in this embodiment, the capacity of the detection battery cell 32b is the same as that of the main battery cell 31. .

  In short, in this embodiment, it can be said that the detection battery cell 32 in the first embodiment is replaced with a voltage detection battery 32A. That is, the SOC-V characteristic line of the voltage detection battery 32A is the same as the characteristic line Ls of the detection battery cell 32 shown in FIG.

  As described above, according to the present embodiment, since the detection battery cell 32b and the main battery cell 31 have the same capacity, the voltage detection battery 32A can be configured using the same battery cell as the main battery cell 31. . Therefore, the productivity improvement of the secondary battery 30 can be promoted.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, the present invention is applied to the secondary battery 30 mounted on the PHV vehicle, but the present invention is applied to the secondary battery mounted on the HV vehicle that cannot be charged from the external power source. Also good.

  In the example shown in FIG. 2, the remaining capacity s2 at the point P where the slope of the characteristic line Ls is less than a predetermined value is referred to as a detected capacity threshold, and the remaining capacity m2 on the characteristic line Lm associated with the detected capacity threshold is the main. In the case of calling the capacity threshold, the capacity of the detection battery cell 32 is set so that the remaining capacity (predetermined amount) used for determination of switching between the EV travel mode and the HV travel mode matches the main capacity threshold. On the other hand, the main capacity threshold value may deviate from the predetermined amount. However, for the entire HV travel region, the main capacity threshold is set to the predetermined amount so that the remaining capacity can be calculated using a portion of the characteristic line Ls that is lower in SOC than the detected capacity threshold (a portion having a steep slope). It is desirable that it is shifted to the higher SOC side.

  30 ... secondary battery, 31 ... main battery cell, 32A ... battery for voltage detection, 32, 32b ... detection battery cell, 40 ... battery ECU (calculation means (remaining capacity calculation device)), 50 ... voltage sensor (remaining capacity calculation) Device), P ... the point at which the slope of the characteristic line Ls becomes less than a predetermined value, s2 ... the detected capacity threshold, m2 ... the remaining capacity of the main battery cell corresponding to the detected capacity threshold.

Claims (7)

A plurality of main battery cells connected in series are configured by connecting voltage detection batteries in series,
The voltage detection battery is provided with a voltage sensor for detecting a voltage,
A secondary battery in which a remaining capacity of the main battery cell is calculated by a remaining capacity calculation device based on a voltage detected by the voltage sensor;
A secondary battery characterized in that the electrode of the voltage detection battery is made of the same material as the electrode of the main battery cell, and the capacity of the voltage detection battery is larger than the capacity of the main battery cell. The voltage detection battery is configured by connecting a plurality of detection battery cells in parallel,
The secondary battery according to claim 1, wherein the capacity of the detection battery cell is the same as the capacity of the main battery cell. The voltage detection battery is configured to have one detection battery cell,
The secondary battery according to claim 1, wherein a capacity of the detection battery cell is larger than a capacity of the main battery cell.   4. The method according to claim 1, wherein the second battery is applied to an in-vehicle secondary battery that can be charged with electric power generated by an internal combustion engine mounted on a vehicle and can be charged from an external power source of the vehicle. The secondary battery as described in one. The vehicle is
When the remaining capacity of the in-vehicle secondary battery is a predetermined amount or more, an electric travel mode in which the internal combustion engine is caused to travel by an electric motor while being stopped, and
When the remaining capacity of the in-vehicle secondary battery is less than a predetermined amount, the hybrid driving mode in which the internal combustion engine or the electric motor is driven while appropriately driving the internal combustion engine and charging the in-vehicle secondary battery; Is controlled to switch to
The characteristic line representing the relationship between the voltage of the voltage detection battery and the remaining capacity of the voltage detection battery, and the characteristic line representing the relationship between the voltage of the main battery cell and the remaining capacity of the main battery cell, The voltage detection battery and the main battery cell are associated with each other based on the capacity, and in the lower capacity region portion than the predetermined capacity used in the hybrid travel mode, the slope of the characteristic line of the voltage detection battery is cormorant I ing larger than the gradient of the characteristic line of the main cell, secondary battery according to claim 4, characterized in that setting the capacitance of the voltage detection cell.   The secondary battery according to claim 1, wherein the positive electrode of the main battery cell includes at least a lithium metal phosphate having an olivine structure. A remaining capacity calculation device for calculating the remaining capacity of the secondary battery according to any one of claims 1 to 6,
A voltage sensor for detecting a voltage of the voltage detection battery;
Calculation means for calculating a remaining capacity of the main battery cell based on the voltage detected by the voltage sensor;
An apparatus for calculating a remaining capacity of a secondary battery, comprising: