JP4503499B2 - Battery voltage detector - Google Patents

Description

  The present invention relates to an assembled battery voltage detection device that detects the voltage of an assembled battery composed of a plurality of battery modules connected in series.

  For example, in a hybrid vehicle, an electric vehicle, a fuel cell vehicle, etc., an assembled battery consisting of a secondary battery and a fuel cell is composed of a number of battery modules connected in series with each other, and each battery module connects a predetermined number of single cells in series. Configured. In addition, here, the definition of the battery module is taken broadly, and the battery module is composed of a single unit cell that is not modularized (the assembled battery is composed of a plurality of unit cells that are not modularized). Is also included. Conventionally, there are the following prior arts 1 and 2 as prior arts as devices for detecting the voltage of an assembled battery.

  In Prior Art 1, the voltages of two battery modules adjacent to each other are simultaneously read into two flying capacitors, the output side switches are sequentially turned on to multiplex the storage voltage of the flying capacitors, and the voltage is detected and A / D After conversion, the output side switch is simultaneously turned on to discharge the charges of the two flying capacitors.

Prior Art 2 divides a plurality of battery modules constituting an assembled battery into two groups, controls the switch, reads the voltage of the battery module into one flying capacitor provided for each group, and simultaneously It describes that detection processing, amplification processing, absolute value processing, and A / D conversion processing of the storage voltage of the flying capacitor are sequentially performed.
JP 2002-289263 A JP2003-14792A

  A battery module (including a single cell) has a reduced voltage when the charge rate (SOC) is reduced by discharging. Therefore, in order to accurately detect the voltage when the voltage of the battery module is lowered, it is necessary to widen the voltage detection range. For example, it is assumed that the detection accuracy when the battery detection range of the battery module is 10 to 20V is ± 0.5V. At this time, if the voltage detection range is set to 0 to 20 V, the detection accuracy deteriorates to ± 1 V if the number of quantization bits is the same. On the other hand, in order to maintain detection accuracy, for example, it is necessary to provide a plurality of sets of operational amplifiers and A / D converters, which causes a problem that the circuit becomes complicated and the cost increases.

  In the prior arts 1 and 2, the voltage of each battery module is A / D converted by an A / D converter. However, when the voltage detection range is widened, the detection accuracy deteriorates or the detection accuracy is maintained. If this is attempted, there is a problem that the circuit scale of the operational amplifier and the A / D converter increases and the cost increases. That is, it is impossible to ensure the voltage detection accuracy and to widen the detection range without complicating the circuit configuration.

  The present invention has been made in view of the above problems, and provides an assembled battery voltage detection device capable of ensuring voltage detection accuracy and widening the detectable voltage without complicating the circuit configuration. The purpose is to do.

  According to the first aspect of the present invention, there is provided an assembled battery voltage detecting device for detecting a voltage of an assembled battery in which a plurality of battery modules are connected in series, the battery modules being connected to positive and negative electrodes at both ends of each battery module. A plurality of first and second switch means; and one or more capacitors having a positive electrode connected to the plurality of first switch means and a negative electrode connected to the plurality of second switch means; When the voltage between the switch driving means for controlling on / off of the plurality of first and second switch means based on the switch control signal and the positive and negative electrodes of the capacitor is within a certain range. A voltage detection unit that outputs a voltage value corresponding to the voltage and outputs a predetermined value when the voltage is lower than the predetermined range; and a plurality of voltages when the voltage output by the voltage detection unit is the predetermined value. Pieces are straight Provided is an assembled battery voltage detection device comprising voltage detection control means for outputting the switch control signal so that a voltage between electrodes at both ends of the connected battery module is held by each capacitor. Is done.

  According to a second aspect of the present invention, in the first aspect of the invention, the voltage detection control means is configured such that the number of the battery modules connected in series when the voltage output from the voltage detection means is the predetermined value. Output a switch control signal so that the increased voltage is held in the capacitor, and when each voltage output from the voltage detecting means is within the certain range, a total voltage calculating means for calculating a sum of the voltages An assembled battery voltage detecting device is provided.

  According to a third aspect of the present invention, in the second aspect of the present invention, each of the capacitors has a power-of-two battery module connected through the plurality of first and second switch means, and the voltage detection control. The switch is configured so that, when the voltage output from the voltage detection unit is the predetermined value, the voltage obtained by increasing the number of the battery modules connected in series to twice the current number is held in the capacitors. The assembled battery voltage detection device according to claim 2, which outputs a control signal.

  According to the assembled battery voltage detecting device according to claim 1, when the voltage detecting means for detecting a voltage in a certain range with a certain accuracy is used and the voltage output from the voltage detecting means is a predetermined value, a plurality of them are connected in series. Since the voltage detection control means for outputting the switch control signal is provided so that the voltage between the electrodes at both ends of the battery module is held by the capacitor, the circuit configuration is not complicated, and the voltage detection accuracy is ensured. The detectable voltage can be widened.

  According to the assembled battery voltage detection device of claim 2, the voltage detection control means is configured such that when the voltage output from the voltage detection means is a predetermined value, the voltage obtained by increasing the number of battery modules connected in series is applied to the capacitor. Since the switch control signal is output so as to be held, it is possible to ensure the voltage detection accuracy and further widen the detectable voltage.

  According to the assembled battery voltage detection apparatus of claim 3, each capacitor is connected to a power module of power of 2 through the plurality of first and second switch means, and the voltage detection control means includes the voltage detection means. When the output voltage is a predetermined value, a voltage in which the number of battery modules connected in series is increased to twice the current number is detected. Therefore, the sum of the detected voltages becomes the voltage of the assembled battery. The battery voltage can be calculated from the sum.

  FIG. 1 is a partial schematic configuration diagram of a hybrid vehicle equipped with an assembled battery voltage detection device according to an embodiment of the present invention. FIG. 2 is a configuration diagram of the assembled battery voltage detection device 10. As shown in FIG. 1, the hybrid vehicle includes an assembled battery 2, a power drive unit (PDU) 4, a motor 6, an engine 8, and an assembled battery voltage detection device 10. As shown in FIG. 2, the assembled battery 2 includes a battery module 50 # ij (i = 1 to 1) composed of a plurality of secondary batteries (for example, nickel-hydrogen (Ni-MH) or lithium ion secondary batteries). n, j = 1 to m) are connected in series, and a high voltage is output to the PDU 4 and charged from the PDU 4. Thus, the state of the assembled battery 2, that is, the battery module 50 #ij (i = 1 to n, The voltage of j = 1 to m) changes every moment due to the driving / regeneration of the motor 6. The battery module 50 # ij includes the case of one unit cell that is not modularized.

  Battery module 50 # ij is divided into n groups. Each group has m battery modules (also called the number of channels). The voltage of the battery modules belonging to the same group is held by the same capacitor. For example, it means that the voltage of the battery module 50 # ij (j = 1 to m) belonging to the group Gri is held in the capacitor 70 # i provided for the group Gri. Note that the number of groups n is determined from the viewpoint of detecting the voltage at high speed (the higher the n, the higher the speed) and the cost. The number m of battery modules belonging to each group is preferably a power of 2 as will be described later.

  The PDU 4 includes, for example, an inverter including an SW module that is bridge-connected using a plurality of IGBTs and diodes connected in parallel. When the motor 6 is driven, the DC power supplied from the assembled battery 2 is converted into three-phase AC power by PWM control of the SW of the SW module based on the torque command value from the ECU 12 and supplied to the motor 6. . Further, during regeneration of the motor 6, the three-phase AC power supplied from the motor 6 is converted into a DC voltage, and the assembled battery 2 is charged. The motor 6 is directly connected to the output shaft of the engine 8 and functions as an electric motor and a generator that transmit and regenerate driving force to a transmission (not shown).

  The assembled battery voltage detection device 14 includes an assembled battery voltage detection peripheral circuit 10 and an ECU 12. As shown in FIG. 2, the assembled battery voltage detection peripheral circuit 10 includes switching means such as a photo MOS relay 52, a capacitor 54, switching means such as a photo MOS relay 56, a differential amplifier 58, an A / A A D converter 60 and a SW driver 62 are included.

  The photo MOS relay 52 includes a plurality of photo MOS relays 60 # ijH and 60 # ijL provided for each battery module 50 # ij (i = 1 to n, j = 1 to m). Photo MOS relay (first switch means) 60 # ijH has an input side connected to an input terminal to which a positive electrode of battery module 50 # ij is connected, and an output side connected to a positive electrode of capacitor 70 # i. Photo MOS relay (second switch means) 60 # ijL has an input side connected to an input terminal to which a negative electrode of battery module 50 # ij is connected, and an output side connected to a negative electrode of capacitor 70 # i.

  The capacitor 54 includes a plurality of capacitors 70 # i (i = 1 to n) provided for each group Gri (i = 1 to n). Capacitor 70 # i has a positive electrode connected to photoMOS relay 60 # ijH (j = 1 to m) and photoMOS relay 80 # iH, and a negative electrode connected to photoMOS relay 60 # ijL (j = 1 to m) and Connected to the input side of photo MOS relay 80 # iL. Photo MOS relay 80 # iH (i = 1 to n) has an input side connected to the positive electrode of capacitor 80 # iH and an output side connected to the input side of differential amplifier 58. The photo MOS relay 80 # iL (i = 1 to n) has an input side connected to the negative electrode of the flying capacitor 80 # iH and an output side grounded.

  The differential amplifier 58 passes the differential voltage between the input voltage input from the capacitor 70 # i (i = 1 to n) and the reference voltage Vref through the photo MOS relay 80 # iH (i = 1 to n) with a predetermined gain. The signal is amplified and output to the A / D converter 60, and includes, for example, three operational amplifiers 90, 92, and 94.

  The operational amplifier 90 is an operational amplifier that amplifies the input voltage from the capacitor 70 # i (i = 1 to n) with a constant gain. The operational amplifier 92 is an operational amplifier that amplifies the reference voltage Vref with the same gain as the operational amplifier 90. The operational amplifier 94 is an operational amplifier that amplifies the differential voltage between the operational amplifiers 90 and 92 with a constant gain.

  The reference voltage Vref corresponds to the lower limit of the voltage within the certain range for detecting a voltage within a certain range with a certain detection accuracy and outputting a predetermined value for a voltage lower than that, for example, 10V When an input voltage of ˜20V is detected with an accuracy of ± 0.5V and a predetermined value of 9V is output for a voltage of 9V or less, the reference voltage Vref is 9V.

  The A / D converter 60 quantizes the output voltage of the differential amplifier 58 with a certain detection accuracy and converts it into a digital signal. At this time, since the output voltage of the differential amplifier 58 is obtained by amplifying the differential voltage between the input voltage and the reference voltage Vref, a constant accuracy is maintained for a voltage within a certain range. A voltage lower than the voltage is fixed to a predetermined value. For example, in the range of 10V to 20V, it is detected with an accuracy of ± 0.5V, but a voltage of 9V or less is detected as 9V. When the SW driver 62 receives the SW control signal from the ECU 12, the SW driver 62 controls on / off of the photo MOS relays 52 and 56 based on the SW control signal.

  The ECU 12 is a CPU that constitutes a part of the assembled battery voltage detection device 14. The ECU 12 performs PWM control of the PDU 4 when the motor 6 is driven and regenerated, and has the following functions related to the assembled battery voltage detection. FIG. 3 is a functional block diagram relating to the assembled battery voltage detection realized by the ECU 12. As shown in FIG. 3, the assembled battery voltage detection device 14 includes a buffer memory 100, a voltage detection control unit 102, a SW control unit 104, a total voltage calculation unit 106, and a battery abnormality detection unit 108.

  The buffer memory 100 is a memory for storing a voltage output from the A / D converter 60, and a memory 150 # ij (i = i) for the battery module 50 # ij (i = 1 to n, j = 1 to m). 1 to n, j = 1 to m). The buffer 100 stores voltages from the top in the order of detection. The voltage value stored in the memory 150 # ij is denoted as VHB ((i−1) × n + j). The voltage detection control means 102 performs the following process.

  (1) Voltage detection start, for example, when the ignition switch is turned on, 1 is substituted for N, and M = 1 battery module 50 # ij (i = 1 to 1), which is the smallest divisor of the number of channels m SW control so as to sequentially detect the voltage across both ends of n, j = 1 to m) connected in series, that is, the voltage of each battery module 50 # ij (i = 1 to n, j = 1 to m). The means 104 is instructed. In this way, the control for sequentially detecting each battery module 50 # ij (i = 1 to n, j = 1 to m) is referred to as control 1.

  (2) The voltage VHB (k) (k = 1 to n * m / M) is read from the head of the buffer memory 100, and the voltage VHB (k) (k = 1 to n * m / M) is smaller than a certain range. For example, if it is 9V or less, (N + 1) is substituted for N, and the Nth divisor M (the next largest divisor of m after the current Nth smallest m divisor) The SW control means 104 is instructed to detect the voltage across the two battery modules 50 # ij connected in series. The reason why M is a divisor of the number of channels m is to detect the voltage of the assembled battery 2 based on the sum of voltages at both ends of the M battery modules 50 # ij connected in series. Note that if the number m of the battery modules 50 # ij (j = 1 to m) is a power of 2, M is twice the current M.

  For example, when a range from 10V to 20V is detected and 9V or less is detected as 9V, if V = 2 (M = 2 and VHB (k) (k = 1 to n * m / 2) is 9V or less, each battery The voltage of the module is determined to be 5V (= 10/2) or less. At this time, if it becomes clear that M = 2 and 10V or less, the voltage of each battery module is 10V / 2 = 5V or less. Therefore, M = 4, that is, the voltage for four battery modules is detected. Even if 4 * 5V = 20V can be detected, and m is a power of 2, m is divisible by 4. Therefore, by setting M = 4, all battery modules 50 # ij (i = 1 to 1) n, j = 1 to m) is detected, and the total voltage of the assembled battery 2 can be detected.

  (3) The voltage VHB (k) (k = 1 to n * m / N) is read from the buffer memory 100, and the voltage VHB (k) (k = 1 to n * m / N) is an upper limit value, for example, 20V. If there is, (N−1) is substituted for N, and the Nth divisor M (the next smaller divisor of m next to the Nth smallest m divisor) from the smaller m is the battery module 50. It instructs the SW control means 104 to detect the voltage across both ends of #ij connected in series. If the number m of the battery modules 50 # ij (j = 1 to m) is a power of 2, M is ½ times the current M.

  (4) Through the processes (1), (2), and (3), all the voltages VHB (k) (k = 1 to n * m / M) read from the buffer 100 are within a certain range (10V to 20V). Is output to the total voltage calculation means 106 and the battery abnormality detection means 108.

  The SW control unit 104 sequentially detects the voltages at both ends of the M battery modules 50 # ij (i = 1 to n, j = 1 to m) instructed by the voltage detection control unit 102 in series. The SW control signal is output to the SW driver 62.

  The total voltage calculation means 106 reads the voltage VHB (k) (k = 1 to n * m / M) from the buffer 100 based on M output from the voltage detection control means 102, and adds all these voltages. And outputs the added total voltage VES. The battery abnormality detection means 108 reads the voltage VHB (k) (k = 1 to n * m / M) from the buffer 100 based on M output from the voltage detection control means 102, and the maximum voltage value VHB (MAX) ) And the minimum voltage value VHB (MIN), (VHB (MAX) / M−VHB (MIN) / M)) is calculated, and this value is substituted into VER. When VER exceeds a predetermined value, a battery error is output.

  4 to 6 are diagrams showing the battery voltage detection order. In FIG. 4, the assembled battery 2 is composed of six battery modules 50 # ij (i = 1 to 2, j = 1 to 3) and is divided into two groups Gr1 and Gr2, and each group Gri (i = 1, 2). ) Shows a case where three battery modules 50 # ij (j = 1, 2, 3) belong.

  The voltage of the battery module 50 # ij (i = 1 to 2, j = 1 to 3) is represented by VHBk (k = (i−1) * 3 + j). The photo MOS relays 60 # ijH and 60 # ijL of the battery module 50 # ij are represented by the symbol iHj (i = 1, 2, j = 1 to 3), and the capacitor 70 # i (i = 1, 2) for Gri PMi (i = 1, 2) and the photo MOS relay 60 # ijL are represented by a symbol iL (i = 1, 2).

  As shown in FIG. 6, the photo MOS relays are turned on in the order of 1H1, 2H1, 1H2, 2H2, 1H3, and 2H3, and 1L and 2L are alternately turned on. As shown in FIG. , VHB3 and VHB6 are detected in this order. Then, corresponding digital values are written in order from the top of the buffer 100. That is, when M = 1, for each j, the voltage of the battery module 50 # ij is detected in ascending order of i, then the voltage is detected in ascending order of j, and written in order from the top of the buffer 100.

  Next, the detection order of the battery voltage when M> 1 will be described. FIG. 7 is a diagram showing the battery detection order when eight battery modules are divided into four groups (n = 4, m = 4). iHj (i = 1 to 4, j = 1, 2) indicates the photo MOS relays 60 # ijH and 60 # ijL, and indicates that the hatched photo MOS relays are turned on.

  When M = 2, as shown in (1) in FIG. 7A, the photo MOS relays 60 # 11H (1H1H) and 60 # 12L (1H2L) of the group Gr1 are turned on and the battery module 50 # 11 is turned on. , 50 # 12 in series connection voltage, as shown in (2), group Gr2 photo MOS relays 60 # 21H, 60 # 22L are turned on and battery modules 50 # 21, 50 # 22 in series connection voltage, As shown in (3), the photo MOS relays 60 # 31H and 60 # 32L of the group Gr3 are turned on and the voltage of the battery modules 50 # 31 and 50 # 32 connected in series, as shown in (4), the group Gr4 Photo MOS relays 60 # 41H and 60 # 42L are turned on, and the series connection voltages of the battery modules 50 # 41 and 50 # 42 are sequentially detected. (1) corresponds to FIG.

  FIGS. 8 and 9 are diagrams showing the battery voltage detection order when eight battery modules are divided into two groups Gr1 and Gr2 (n = 2, m = 4). When M = 2, as shown in (1) in FIG. 8A, the photo MOS relays 60 # 11H and 60 # 12L of the group Gr1 are turned on and the battery modules 50 # 11 and 50 # 12 are connected in series. Connection voltage, as shown in (2), the photo MOS relays 60 # 21H and 60 # 22L of the group Gr2 are turned on, the series connection voltages of the battery modules 50 # 21 and 50 # 22, and the photo MOS relay of the group Gr1 60 # 13H and 60 # 14L are turned on and the voltage of the battery modules 50 # 13 and 50 # 14 connected in series, and the photo MOS relays 60 # 23H and 60 # 24L of the group Gr2 are turned on and the battery modules 50 # 23 and 50 are turned on. The voltage of # 24 connected in series is sequentially detected. (1) corresponds to FIG.

  In the case of M = 4, as shown in (1) in FIG. 9, the photo MOS relays 60 # 11H and 60 # 14L of the group Gr1 are turned on and the battery modules 50 # 11 and 50 # 14 are connected in series. As shown in (2), the photo MOS relays 60 # 21H and 60 # 24L of the group Gr2 are turned on, and the series connection voltages of the battery modules 50 # 21 and 50 # 24 are sequentially detected. (1) corresponds to FIG.

  Thus, when M> 1, voltages are detected in the order of the groups Gr1, Gr2,..., Grn, Gr1, Gr2,. The control sequence of the photo MOS relays 52 and 56 for voltage detection is the same as in the case of M = 1.

  FIG. 10 is a flowchart illustrating a battery voltage detection method according to an embodiment of the present invention. In step S2, an initial value 1 is substituted for N. The substitution of the initial value is performed, for example, when the ignition switch is turned on in a hybrid vehicle. In step S2, a SW control signal for performing control (M) is created. Control (M) means that M is the number of battery modules 50 #ij (j = 1 to m) belonging to the group Gri and the Nth divisor from the smaller number m of the battery modules 50 # ij (j = 1 to m). This means that the voltage at both ends is detected according to the sequence described above. When N = 1, M = 1.

  In step S4, a SW control signal for performing control (M) is transmitted to the SW driver 62. The SW driver 62 controls ON / OFF of the corresponding photoMOS relays of the photoMOS relays 52 and 56 in order to perform control (M) based on the SW control signal.

  In step S8, the detection voltage VHB (k) (k = 1 to n * m / M) by the control (M) is sequentially written from the top of the buffer 100. In step S10, it is determined whether or not the detected voltage VHB (k) (k = 1 to n * m / M) is an upper limit value, for example, 20V or more. If a positive determination is made, the process proceeds to step S12. If a negative determination is made, the process proceeds to step S14.

  In step S12, (N-1) is substituted for N, and the process returns to step S4. In step S14, it is determined whether or not the voltage VHB (k) (k = 1 to n * m / M) is smaller than a certain range, for example, 9V or less. If a positive determination is made, the process proceeds to step S16. If a negative determination is made, the process proceeds to step S18. In step S16, (N + 1) is substituted for N, and the process returns to step S4.

  In step S18, the voltage VHB (k) (k = 1 to n * m / M) is read from the buffer 100, and all of these are added (VHB (1) + VHB (2) +. + VHB (n * m / M) ), The addition result is substituted into the total voltage VES. At this time, since M is a divisor of m, VES is the voltage of the assembled battery 2. In step S20, the minimum value VHB (MIN) is subtracted from the maximum value VHB (MAX) of the voltage VHB (k) (k = 1 to n * m / M) and divided by M ((VHB (MAX) −VHB (MIN)). )) / M). The result is substituted into VER.

  When VER exceeds a predetermined value, it is determined that the battery module is abnormal and output. Returning to step S4, the above-described steps S4 to S20 are repeatedly executed at a constant cycle. Since the next voltage detection is not performed from N = 1 but at N at the end of the previous voltage detection, the voltage detection is completed at high speed.

  Note that step S12 for decreasing N is performed when the assembled battery 2 is charged by regeneration of the motor 6 to increase the voltage, and step S16 for increasing N is performed when the assembled battery 2 is left standing for a long time and discharged. For example, the battery 2 is discharged to drive the motor 6.

  According to this embodiment described above, there are the following effects. Since the battery module 50 # ij (i = 1 to n, j = 1 to m) is divided into n groups, high-speed voltage detection and circuit configuration become complicated by setting n to an optimum value. Both can be satisfied.

  FIG. 11 is an explanatory diagram of another effect. As shown to Fig.11 (a), when voltage a1, a2 of each battery module 50 # ij (i = 1-n, j = 1-m) is the range of 10-20V, as shown to a3, a4 , It can be detected with a detection accuracy of ± 0.5V within a detection range of 10-20V. Moreover, as shown in FIG.11 (b), when voltage b1, b2 of each battery module 50 # ij (i = 1-n, j = 1-m) is 10V or less, for example in the range of 5V-10V, As shown in b3, it can be detected with a detection accuracy of ± 0.5 V with a voltage in the detection range of 10 to 20 V obtained by adding the voltages b1 and b2 of the two battery modules. Thus, by increasing the detectable width, it is possible to detect the assembled battery voltage with high accuracy while suppressing the complexity of the circuit configuration of the operational amplifier and the A / D converter.

  Since the battery module includes one unit cell as described above, in this case, as in the case of the battery module, when the voltage of each unit cell is not within a certain range, a plurality of units connected in series are connected. The voltage at both ends of the unit cell is measured, and the voltage of the assembled battery is measured by the sum of the voltages.

1 is a schematic configuration diagram of a hybrid vehicle equipped with an assembled battery voltage detection device according to an embodiment of the present invention. It is a figure which shows the peripheral circuit of the assembled battery voltage detection apparatus by embodiment of this invention. It is a functional block diagram of the main control of an assembled battery voltage detection apparatus. It is a figure which shows battery voltage detection order. It is a figure which shows battery voltage detection order. It is a figure which shows battery voltage detection order. It is a figure which shows the battery voltage detection order in the case of m = 2 and M = 2. It is a figure which shows the battery voltage detection order in the case of m = 4 and M = 2. It is a figure which shows the battery voltage detection order in the case of m = 4 and M = 4. It is a flowchart which shows a battery voltage detection method. It is a figure for demonstrating the effect of this invention.

Explanation of symbols

2 assembled battery 50 # ij (i = 1 to n, j = 1 to m) battery module 52 photo MOS relay 54 flying capacitor 56 photo MOS relay 58 differential amplifier 60 A / D converter 62 SW driver 102 voltage detection control means 104 SW control means 106 Total voltage calculation means

Claims (3)

An assembled battery voltage detection device for detecting a voltage of an assembled battery in which a plurality of battery modules are connected in series,
A plurality of first and second switch means connected to a positive electrode and a negative electrode at both ends of each battery module;
One or more capacitors having a positive electrode connected to the plurality of first switch means and a negative electrode connected to the plurality of second switch means;
Switch driving means for controlling on / off of the plurality of first and second switch means based on a switch control signal;
Voltage detection means for outputting a voltage value corresponding to the voltage when the voltage between the positive and negative electrodes of the capacitor is within a certain range, and outputting a predetermined value when the voltage is lower than the certain range When,
When the voltage output from the voltage detection means is the predetermined value, the switch control signal is output so that a voltage between electrodes at both ends of the battery modules connected in series is held in the capacitors. Voltage detection control means;
An assembled battery voltage detection device comprising:   The voltage detection control means outputs the switch control signal so that when the voltage output from the voltage detection means is the predetermined value, the voltage in which the number of battery modules connected in series is increased is held in the capacitor. 2. The assembled battery voltage detection device according to claim 1, further comprising: total voltage calculation means for calculating a total sum of the voltages when each voltage outputted and outputted from the voltage detection means is within the predetermined range. .   Each of the capacitors has a power-of-two battery module connected through the plurality of first and second switch means, and the voltage detection control means is configured such that the voltage output from the voltage detection means is the predetermined value. 3. The assembled battery voltage detection device according to claim 2, wherein the switch control signal is output so that a voltage obtained by increasing the number of the battery modules connected in series to twice the current number is held in each capacitor.

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