JP6498558B2 - Secondary battery status detector - Google Patents

Description

  The present invention relates to a secondary battery state detection device that detects the state of the battery, such as the degree of battery deterioration and internal resistance.

  For example, in various vehicles such as an electric vehicle (EV) that travels using an electric motor and a hybrid vehicle (HEV) that travels using both an engine and an electric motor, a lithium ion rechargeable battery is used as a power source for the electric motor. And rechargeable batteries such as nickel metal hydride batteries.

  It is known that such secondary batteries are deteriorated by repeating charging and discharging, and the chargeable capacity (current capacity, power capacity, etc.) gradually decreases. In an electric vehicle using a secondary battery, the storageable capacity is obtained by detecting the degree of deterioration of the secondary battery, and the distance that can be traveled by the secondary battery and the life of the secondary battery are calculated. doing.

  One index indicating the degree of deterioration of the secondary battery is SOH (State of Health), which is the ratio of the current chargeable capacity to the initial chargeable capacity. This SOH is known to have a correlation with the internal resistance of the secondary battery, and the SOH can be detected based on the internal resistance by obtaining the internal resistance of the secondary battery.

  As an apparatus for detecting the internal resistance of the secondary battery, for example, an apparatus described in Patent Document 1 has been proposed. The secondary battery state detection device of Patent Document 1 includes two capacitors, holds the battery voltages of the two states of the secondary battery, for example, the discharge state and the discharge stop state, and holds the capacitor by an amplifier. By amplifying the difference in the battery voltage, the internal resistance and SOH are obtained with high accuracy.

  In the secondary battery state detection device shown in Patent Document 1 described above, the amplifier can output only the voltage difference between the bipolar voltages of the secondary battery in the two states. For this reason, it is necessary to provide a circuit (first ADC) for detecting the bipolar voltage of the secondary battery separately from the circuit (second ADC) for detecting the differential voltage output from the amplifier, which is a problem in terms of cost.

JP 2014-219511 A

  Then, this invention makes it a subject to provide the secondary battery state detection apparatus which can detect the state and bipolar voltage of a secondary battery cheaply.

  The invention according to claim 1, which has been made in order to solve the above-described problem, is a secondary battery state detection device that detects a state of a secondary battery, and selects a pair of capacitors and one of the pair of capacitors. A first switch for connecting the monopolar plate to the secondary battery, and connected to both electrodes of the secondary battery, and either one of the two electrodes of the secondary battery is used as the first switch. A second switch for connecting, the first switch and the second switch to control one pole of the secondary battery when the secondary battery is in the first state; First switch control means for connecting one pole of the secondary battery to only the other of the pair of capacitors when the secondary battery is in a second state after being connected to at least one of the first and second capacitors; Controlling the switch and the second switch A second switch control means for connecting one pole of the secondary battery to at least one of the pair of capacitors and then connecting the other pole of the secondary battery to only the other of the pair of capacitors; and the pair of capacitors A differential amplifier circuit that outputs a differential voltage of a unipolar voltage, a battery state detection unit that detects a state of the secondary battery based on the differential voltage during control by the first switch control unit, and the second And a bipolar voltage detecting means for detecting a bipolar voltage of the secondary battery based on the differential voltage during the control by the switch control means.

  According to a second aspect of the present invention, the second switch control means controls the first switch and the second switch to connect one pole of the secondary battery to both of the pair of capacitors. 2. The secondary battery state detection device according to claim 1, wherein the other electrode of the secondary battery is connected to only the other of the pair of capacitors.

  According to a third aspect of the present invention, a plurality of the secondary batteries are connected in series with each other, and the second switch is provided in each of the plurality of secondary batteries, A resistor provided between the second switch and the second switch is controlled to connect both ends of the resistor to both electrodes of the secondary battery having a high bipolar voltage. The secondary battery state detection device according to claim 1, further comprising equalization means for discharging the battery.

  As described above, according to the first aspect of the present invention, the differential amplifier circuit can be shared by the secondary battery state detecting means and the bipolar voltage detecting means, and the cost can be reduced.

  According to the second aspect of the present invention, the other of the pair of capacitors can be quickly set to the same voltage as the other electrode of the secondary battery.

  According to the invention described in claim 3, since the equalization can be performed by using the second switch, the cost can be further reduced.

It is a circuit diagram which shows one Embodiment of the secondary battery state detection apparatus of this invention. It is a flowchart which shows the procedure of the battery state detection process of MCU shown in FIG. It is a flowchart which shows the procedure of the bipolar voltage detection process of MCU shown in FIG.

  Hereinafter, the secondary battery state detection device of the present invention will be described with reference to FIG. The secondary battery state detection device 1 of the present embodiment is mounted on an electric vehicle, for example, and detects the states of a plurality of secondary batteries Ce included in the electric vehicle. The plurality of secondary batteries Ce are connected to each other in series.

  As shown in FIG. 1, the secondary battery state detection device 1 includes a pair of capacitors Co1 and Co2, a first switch unit 2, a second switch unit 3, a charging unit 4, and a first switch control. Means 5, second switch control means, battery state detection means, bipolar voltage detection means MCU 5, differential amplifier circuit 6, and AD converter 7 (AD converter 7 for supplying the output of differential amplifier circuit 6 to MCU 5) Hereinafter abbreviated as ADC7) and a resistor R.

  In the present embodiment, a plurality of capacitors Co1 are provided corresponding to the plurality of secondary batteries Ce, respectively. The capacitor Co1 has one electrode plate connected to the non-inverting input of the differential amplifier circuit 6, and the other electrode plate connected to the ground (reference potential). In the present embodiment, a plurality of capacitors Co2 are provided corresponding to a plurality of secondary batteries. The capacitor Co2 has one electrode plate connected to the inverting input of the differential amplifier circuit 6, and the other electrode plate connected to the ground.

  In the present embodiment, a plurality of first switch units 2 are provided corresponding to the plurality of secondary batteries Ce. The first switch unit 2 includes first switches SW11 and SW12 for selecting any one of the pair of capacitors Co1 and Co2 and connecting the unipolar plate to the corresponding secondary battery Ce. Yes.

  One end of the first switch SW11 is connected to a unipolar plate of the capacitor Co1. One end of the first switch SW12 is connected to a monopolar plate of the capacitor Co2. The other ends of the first switches SW11 and SW12 are commonly connected to each other.

  In the present embodiment, a plurality of second switch units 3 are provided corresponding to the plurality of secondary batteries Ce. The second switch unit 3 is connected to both electrodes of the corresponding secondary battery Ce, and second switches SW21 and SW22 for connecting either one of the electrodes of the secondary battery Ce to the first switches SW11 and SW12. It is composed of The second switches SW21 and SW22 have one end connected to both electrodes of the corresponding secondary battery Ce, the other end connected in common, and the other end connected to the common connection of the first switches SW11 and SW12. Yes.

  According to the above configuration, when the first switch SW11 is turned on, the capacitor Co1 is selected, and when the second switch SW21 is turned on, the positive electrode (one pole) of the secondary battery Ce is connected to the one-pole plate of the capacitor Co1. can do. Further, if the second switch SW22 is turned on when the first switch SW11 is turned on, the negative electrode (other electrode) of the secondary battery Ce can be connected to the one-pole plate of the capacitor Co1.

  Further, when the first switch SW12 is turned on, the capacitor Co2 is selected, and when the second switch SW21 is turned on, the positive electrode of the secondary battery Ce can be connected to one pole of the capacitor Co2. Further, when the second switch SW22 is turned on when the first switch SW12 is turned on, the negative electrode of the secondary battery Ce can be connected to one pole of the capacitor Co2.

  The charging unit 4 is provided so that a predetermined charging current Ic can flow when charging a plurality of secondary batteries Ce. The charging unit 4 is connected to the MCU 5 to be described later, and in accordance with a control signal from the MCU 5, the charging current Ic is supplied to the plurality of secondary batteries Ce to charge, and the charging current Ic is supplied to the secondary battery Ce. To stop charging.

  The MCU 5 is composed of a microcomputer having a known CPU, ROM, RAM and the like. The MCU 5 controls the on / off control of the first switch unit 2 and the second switch unit 3 and the charging unit 4.

  When the MCU 5 receives the state detection command from the electronic control unit, the MCU 5 controls the first switch unit 2 and the second switch unit 3 so that the plurality of secondary batteries Ce are in the first state. After the positive electrode of the battery Ce is connected to the monopolar plate of the capacitor Co1, the positive electrodes of the plurality of secondary batteries Ce are connected to the monopolar plate of the capacitor Co2 when the secondary battery Ce is in the second state. Here, the first state and the second state indicate states in which currents flowing in the secondary battery Ce are different from each other. In the present embodiment, the charging state in which the charging current Ic flows in the secondary battery Ce is the first state, and the charging stop state in which no current flows in the secondary battery Ce is the second state.

  When the MCU 5 receives the bipolar voltage detection command from the electronic control unit, the MCU 5 controls the first switch unit 2 and the second switch unit 3 so that the positive electrodes of the plurality of secondary batteries Ce are the one poles of both the capacitors Co1 and Co2. After connecting to the plate, the negative electrode of the secondary battery Ce is connected to the unipolar plate only of the capacitor Co2.

  In the present embodiment, a plurality of differential amplifier circuits 6 are provided corresponding to the plurality of secondary batteries Ce. The differential amplifier circuit 6 amplifies the difference between the unipolar plate voltages of the capacitors Co1 and Co2 input to the non-inverting input and the inverting input, respectively, and outputs the amplified voltage as a differential voltage.

  In addition, the MCU 5 receives the state detection command and takes in the differential voltage output from the differential amplifier circuit 6 when controlling the first and second switch units 2 and 3, thereby obtaining a plurality of secondary batteries Ce. Each internal resistance is detected, and each state of the plurality of secondary batteries Ce is detected.

  Further, when the MUC 5 receives the bipolar detection command and controls the first and second switch units 2 and 3, the MUC 5 uses the differential voltage output from the differential amplifier circuit 6 as the bipolar voltage of the plurality of secondary batteries Ce. Capture as.

  The resistor R is a current limiting resistor provided between the two electrodes of the secondary battery Ce and the second switches SW21 to SW22.

  Next, the operation of the secondary battery state detection device 1 configured as described above will be described below with reference to FIGS. FIG. 2 is a flowchart showing the procedure of the secondary battery state detection process of the MCU 5 shown in FIG. FIG. 3 is a flowchart showing a procedure of bipolar voltage detection processing of the MCU 5 shown in FIG.

  When the MCU 5 receives the state detection command from the electronic control device mounted on the vehicle, the MCU 5 starts the battery state detection process shown in FIG. First, the MCU 5 turns on the first switches SW11 and SW12 and the second switch SW21, and connects the positive electrode of the secondary battery Ce to one electrode plate of both the capacitors Co1 and Co2 (step S1).

  Next, the MCU 5 transmits a charging start control signal to the charging unit 4 (step S2). The charging unit 4 starts charging the secondary batteries Ce1 to Ce4 with the charging current Ic according to the control signal.

  Next, the MCU 5 turns off the first switch SW12 to disconnect the connection between the one-electrode plate of the capacitor Co2 and the positive electrode of the secondary battery Ce, and to the positive electrode of the secondary battery Ce only on the one-electrode plate of the capacitor Co1. Are connected (step S3). Thereby, the positive electrode potential of the secondary battery Ce in the charged state is held in the capacitor Co1.

  After that, when a sufficient time t1 has passed so that the voltage of the capacitor Co1 reaches the positive electrode potential of the secondary battery Ce (Y in step S4), the MUC5 turns off the first switch SW11 and turns off the capacitor Co1 and the secondary. The connection with the battery Ce is disconnected (step S5). Thereafter, a charging stop control signal is transmitted to the charging unit 4 (step S6). The charging unit 4 stops charging the secondary battery Ce according to the control signal.

  Next, the MCU 5 turns on the first switch SW12 and connects the positive electrode of the secondary battery Ce to the one-electrode plate of the capacitor Co2 (step S7). Thereby, the positive electrode potential of the secondary battery Ce in the charge stop state is held in the capacitor Co2.

  Thereafter, when the time t1 elapses (Y in step S8), the MUC 5 turns off the first switch SW12 and the second switch S21 to disconnect the connection between the capacitor Co2 and the secondary battery Ce (step S9).

  Thereafter, the MCU 5 takes in the differential voltage output from each differential amplifier circuit 6 to obtain the internal resistance of each secondary battery Ce (step S10), and ends the battery state detection process.

  On the other hand, when receiving the bipolar voltage detection command from the electronic control device mounted on the vehicle, the MCU 5 starts the bipolar voltage detection process shown in FIG. First, the MCU 5 turns on the second switch SW22 and the first switches SW11 and SW12, and connects the negative electrode of the secondary battery Ce to the unipolar plate of both the capacitors Co1 and Co2 (step S11). Thereby, the negative electrode potential of the secondary battery Ce is held in the capacitors Co1 and Co2.

  Next, when a sufficient time t1 has elapsed (Y in step S12), the MCU 5 turns off the second switch S22 and the first switch SW12, turns on the second switch S21, and sets one pole of the capacitor Co1. The positive electrode of the secondary battery Ce is connected to the plate (step S13). Thereby, the positive electrode potential of the secondary battery Ce is held in the capacitor Co1.

  Thereafter, when a sufficient time t1 has elapsed (Y in step S14), the MCU 5 turns off the second switches SW21 and SW22 and disconnects the connection between the secondary battery Ce and the capacitors Co1 and Co2 (step S15).

  Thereafter, the MCU 5 takes in the differential voltage output from each differential amplifier circuit 6 as the bipolar voltage of the secondary battery Ce (step S16), and ends the bipolar voltage detection process.

  According to the embodiment described above, the differential amplifier circuit 6 and the ADC 7 are connected to the battery state detection process for detecting the state (internal resistance) of the secondary battery Ce and the bipolar voltage detection process for detecting the bipolar voltage of the secondary battery Ce. Can be shared, and cost reduction can be achieved.

  According to the embodiment described above, the MCU 5 controls the first switch unit 2 and the second switch unit 3 in the bipolar voltage detection process, and connects the negative electrode of the secondary battery Ce to both the capacitors Co1 and Co2. After that, the positive electrode of the secondary battery Ce is connected only to the capacitor Co1. As a result, the capacitor Co1 is at the same potential as the negative electrode of the secondary battery Ce before being connected to the positive electrode of the secondary battery Ce, and charges are accumulated to some extent. It becomes the same as the positive electrode potential of the secondary battery Ce.

  Further, according to the above-described embodiment, the second switches SW21 and SW22 are provided at both poles of the secondary battery Ce, and the resistor R is provided between the secondary battery Ce and the second switches SW21 and SW22. ing. Accordingly, when the second switches SW21 and SW22 are turned on, the resistor R is connected to both electrodes of the secondary battery Ce, and the secondary battery Ce can be discharged by the resistor R. Therefore, the second switch unit 3 may be controlled so that the MCU 5 functions as an equalizing unit to equalize the secondary batteries Ce.

  Specifically, after detecting the bipolar voltages of the plurality of secondary batteries Ce by the bipolar voltage detection process, the MCU 5 controls the second switch unit 3 to resist both poles of the secondary battery Ce having a high bipolar voltage. R is connected and discharged to achieve equalization. Thereby, since the equalization can be performed by diverting the second switch unit 3, the cost can be further reduced.

  In the above-described embodiment, the positive electrode potential of the secondary battery Ce in the charged state (first state) and the charge stopped state (second state) is held in the capacitors Co1 and Co2, and the difference voltage is obtained. However, it is not limited to this. What is necessary is just to hold | maintain the positive electrode potential of the secondary battery Ce of two different states to capacitor | condenser Co1, Co2, for example, making the capacitor | condenser Co1, Co2 hold the positive electrode potential of the secondary battery Ce of a charge state and a discharge state. Also good. The positive electrode potential of the secondary battery Ce in a charged state when a large charging current is flowing and a charged state when a small charging current is flowing may be held in the capacitors Co1 and Co2. The capacitors Co1 and Co2 may hold the positive electrode potential of the secondary battery Ce in a discharge state when a current is flowing and in a discharge state when a small discharge current is flowing.

  Further, according to the above-described embodiment, the first switch unit 2, the capacitors Co1 and Co2, the differential amplifier circuit 6, and the ADC 7 are provided in correspondence with the plurality of secondary batteries Ce. Not a thing. For each of the plurality of secondary batteries Ce, one first switch unit 2, capacitors Co1, Co2, differential amplifier circuit 6, and ADC 7 are provided, and the plurality of secondary batteries Ce are sequentially connected to the capacitors Co1, Co2. You may do it.

  Further, according to the above-described embodiment, in the bipolar voltage detection process, after the negative electrode of the secondary battery Ce is connected to both the capacitors Co1 and Co2, the positive electrode of the secondary battery Ce is connected only to the capacitor Co1. This is not the only one. After connecting the negative electrode of the secondary battery Ce only to the capacitor Co2, the positive electrode of the secondary battery Ce may be connected to the capacitor Co1.

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Secondary battery state detection apparatus 5 MCU (1st switch control means, 2nd switch control means, battery state detection means, bipolar voltage detection means, equalization means)
6 differential amplifier circuit Ce secondary battery Co1 capacitor Co2 capacitor R resistor SW11, SW12 first switch SW21, SW22 second switch

Claims (3)

A secondary battery state detection device for detecting a state of a secondary battery,
A pair of capacitors;
A first switch for selecting one of the pair of capacitors and connecting the unipolar plate to the secondary battery;
A second switch connected to both electrodes of the secondary battery, and connecting either one of the electrodes of the secondary battery to the first switch;
After controlling the first switch and the second switch to connect one pole of the secondary battery to at least one of the pair of capacitors when the secondary battery is in the first state, First switch control means for connecting one pole of the secondary battery to only the other of the pair of capacitors when the secondary battery is in the second state;
After controlling the first switch and the second switch to connect one electrode of the secondary battery to at least one of the pair of capacitors, the other electrode of the secondary battery is connected to the other of the pair of capacitors. A second switch control means connected only to,
A differential amplifier circuit that outputs a differential voltage of a unipolar voltage of the pair of capacitors;
Battery state detection means for detecting the state of the secondary battery based on the differential voltage during control by the first switch control means;
A bipolar voltage detecting means for detecting a bipolar voltage of the secondary battery based on the differential voltage during the control by the second switch control means;
A secondary battery state detection device comprising: The second switch control means controls the first switch and the second switch so that one pole of the secondary battery is connected to both of the pair of capacitors, and then the other of the secondary battery. The secondary battery state detection device according to claim 1, wherein a pole is connected only to the other of the pair of capacitors. A plurality of the secondary batteries are connected in series with each other,
The second switch is provided in each of the plurality of secondary batteries,
A resistor provided between both electrodes of the plurality of secondary batteries and the second switch;
And further comprising an equalizing means for controlling the second switch to connect both ends of the resistor to both electrodes of the secondary battery having a high bipolar voltage, and to discharge the connected secondary battery. The secondary battery state detection device according to claim 1 or 2, characterized in that

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