JP2016077115A - Battery control device, battery system and battery control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for balance processing by increasing an electric current running through a resistor.SOLUTION: The battery control device is configured to keep charging rates of battery cells constant by connecting a switching element and a resistor in series and turning on the switching element of discharge circuits provided at each of a plurality of battery cells to discharge each of the battery cells, and changes a variable duty ratio which is a duty ratio of the switching element on the basis of a total of calorific values by the resistors and the discharge circuits and the allowable total of calorific values.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery control device, a battery system, and a battery control method.

  A battery system (for example, refer to Patent Document 1 below) performs a discharging process for supplying electric power from a battery to an external load, and also performs a charging process for charging the battery. The battery system has, for example, a battery composed of battery cells connected in series, and when the battery is charged, the battery cell having a high voltage is discharged by a discharge circuit in which a resistor and a switching element are connected in series. Thereby, the balance process which arranges this battery cell to a battery cell with a low voltage is performed. Further, in the above battery system, when n discharge circuits are provided for n battery cells, discharge is simultaneously performed by resistors of a maximum of (n-1) discharge circuits, so (n-1) pieces. For example, the upper limit value of the current flowing through the resistor of one discharge circuit is an allowable total calorific value so that the calorific value when discharged by the resistor of the discharge circuit does not exceed the allowable total calorific value ( It is set based on the value divided by n-1).

JP 2010-142039 A

  Here, when n discharge circuits are provided for n battery cells, a maximum of (n-1) discharge circuits discharge, but not all discharge circuits necessarily discharge. Absent. Depending on variations in the voltage distribution of the battery cells, it may be possible that only a small number of discharge circuits, fewer than n-1, discharge. In such a case, in the prior art, despite the small number of battery cells that need to be discharged, that is, despite the small number of resistors in the discharge circuit that need to be discharged by passing a current, An upper limit value of current is set based on a value obtained by dividing the total calorific value allowable for each discharge circuit by (n−1). For this reason, the current flowing through the resistor is suppressed to an unnecessarily small amount despite the fact that there is a surplus in the amount of heat that can be tolerated, so the time required for the balancing process to align the voltages of the battery cells is reduced. I couldn't.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to reduce the time required for the balance process by increasing the current flowing through the resistor.

  In order to achieve the above object, according to the present invention, as a first solution means for a battery control device, the switching element of a discharge circuit formed by connecting a switching element and a resistor in series and provided in each of a plurality of battery cells. Is a battery control device that causes each of the battery cells to be discharged by turning on the battery cell to make the charging rate of the battery cells uniform, and the total amount of heat generated by the resistors of the discharge circuit is allowed. A means is employed in which the variable duty ratio, which is the duty ratio of the switching element, is changed based on the total heat generation amount.

  In the present invention, as a second solving means related to the battery control device, in the first solving means, one battery cell whose voltage is an upper limit value is added to the discharge circuit, and the duty ratio of the switching element is set to 100%. The calorific value when discharged is set equal to the total calorific value, and the variable duty ratio is a voltage detection value of each battery cell that causes the discharge circuit to discharge the square of the upper limit value of the voltage of the battery cell. A method is adopted in which the sum is the sum of the squares of 2 and divided.

  In the present invention, as a third solving means relating to the battery control device, an intermediate value between the maximum value and the minimum value of the voltage detection values in each of the plurality of battery cells is calculated in the first or second solving means. The discharge circuit provided in the battery cell exceeding the intermediate value is discharged, and the discharge circuit provided in the battery cell lower than the intermediate value is not discharged.

  In the present invention, as a solving means related to the battery system, a plurality of discharge circuits each including a switching element, and each of the switching elements included in each of the plurality of discharge circuits are connected, and the switching element is in an ON state. A battery module comprising a plurality of battery cells for discharging and a battery cell for discharging by decreasing the duty ratio of the on-state and off-state of the switching element if the number of battery cells for discharging increases In this case, a means of controlling the on state and the off state of the switching element so as to increase the magnitude of the duty ratio is adopted.

  In the present invention, as a means for solving the battery control method, the switching element and the resistor are connected in series, and each of the battery cells is turned on by turning on the switching element of the discharge circuit provided in each of the plurality of battery cells. The discharge rate of the battery cells is equalized, the charging rate of the battery cells is made uniform, and the variable duty which is the duty ratio of the switching element based on the total amount of heat generated by the resistors of the discharge circuit and the allowable total heat generation amount Use a means to change the ratio.

  According to the present invention, the switching element and the resistor are connected in series, and the switching element of the discharge circuit provided in each of the plurality of battery cells is turned on so that each battery cell is discharged. A battery control device that equalizes the charging rate of the discharge circuit, by changing the variable duty ratio, which is the duty ratio of the switching element, based on the total amount of heat generated by the resistors of the discharge circuit and the allowable total heat generation amount, Or, in other words, if the number of battery cells to be discharged increases, the duty ratio between the on state and the off state of the switching element is decreased, and the number of battery cells to be discharged is decreased. Then, the on-state and off-state of the switching element are controlled so as to increase the magnitude of the duty ratio, so that the resistor flows. Current increased, it is possible to shorten the time required for the balancing process.

It is a schematic block diagram of the battery system which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the battery system which concerns on one Embodiment of this invention. The timing chart which shows the variable duty ratio (a) when there are many battery cells discharged by the discharge circuit in one Embodiment of this invention, and the variable duty ratio (b) when there are few battery cells discharged by a discharge circuit. It is.

Embodiments of the present invention will be described below with reference to the drawings.
The battery system A according to the present embodiment is mounted on various electric devices such as forklifts, and is charged with the battery modules L1 to Ln when connected to the charger J and charged, and the battery modules L1 to L1 when power is consumed. A discharge treatment of Ln is performed. The charger J is detachable from the battery system A.

  As shown in FIG. 1, the battery system A includes a connection terminal T, battery modules L1 to Ln, control boards K1 to Kn, and a host control device Uc.

The connection terminal T is a terminal that is electrically connected to the charger J when the charger J is attached to the battery system A.
The battery modules L1 to Ln are n battery modules and are connected in series. Moreover, the positive electrode of the battery module L1 disposed at one end among the battery modules L1 to Ln connected in series is connected to the connection terminal T. In addition, since each battery module L1-Ln is the same structure, only battery module L1 is demonstrated and description is abbreviate | omitted about battery module L2-Ln.

  The battery module L1 is composed of battery cells C1 to Cm. Battery cells C1 to Cm are storage batteries (secondary batteries) such as m lithium ion batteries, and are connected in series to constitute a battery module L1.

  The control boards K1 to Kn are provided in the battery modules L1 to Ln, and include discharge circuits H1 to Hm, voltage sensors D1 to Dm, and a microcomputer M (battery control device) as shown in FIG. Since the control boards K1 to Kn have the same configuration, only the control board K1 will be described, and the description of the control boards K2 to Kn will be omitted.

  The discharge circuits H1 to Hm are provided in the battery cells C1 to Cm, and discharge the battery cells C1 to Cm based on a control signal input from the microcomputer M. As shown in FIG. 1, such discharge circuits H <b> 1 to Hm include discharge switching elements AS <b> 1 to ASm and resistors R <b> 1 to Rm. Since each of the discharge circuits H1 to Hm has the same configuration, only the discharge switching element AS1 and the resistor R1 of the discharge circuit H1 will be described, and the description of the discharge circuits H2 to Hm will be omitted.

  The discharging switching element AS1 is, for example, a bipolar transistor, and has a base terminal connected to the microcomputer M, an emitter terminal connected to the positive electrode of the battery cell C1, and a collector terminal connected to one end of the resistor R1.

  The discharge switching element AS1 is turned on when a control signal having a high voltage value is input from the microcomputer M to the base terminal, and discharges the power of the battery cell C1 to the resistor R1. On the other hand, when a control signal having a high voltage value is not input to the base terminal, the discharging switching element AS1 is turned off and stops discharging from the battery cell C1 to the resistor R1.

  In addition to the bipolar transistor, the discharge switching element AS1 may be, for example, an FET transistor (Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor).

  One end of the resistor R1 is connected to the collector terminal of the discharging switching element AS1, and the other end is connected to the negative electrode of the battery cell C1. When the discharge switching element AS1 is turned on, the resistor R1 receives electric power from the battery cell C1 and converts the electric power into heat energy, that is, generates heat.

  The voltage sensors D1 to Dn are provided in the battery cells C1 to Cn, detect the voltages of the battery cells C1 to Cn, and output a detection signal indicating the detected voltage detection value to the microcomputer M.

  The microcomputer M is an IC chip composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an interface circuit that transmits and receives various signals to / from each electrically connected part. is there. The microcomputer M controls the entire operation of the control board K1 by performing various arithmetic processes based on various arithmetic control programs stored in the ROM and communicating with each unit. Although details will be described later, the microcomputer M shortens the time required for the balancing process for equalizing the charging rates of the battery cells C1 to Cm by increasing the current flowing through the resistors R1 to Rm during charging. In the present invention, if the number of the battery cells to be discharged increases, the microcomputer M (control device) decreases the duty ratio of the on-state and the off-state of the switching element, and the battery cells to be discharged are discharged. If the number decreases, the ON state and the OFF state of the switching element are controlled so that the magnitude of the duty ratio is increased.

  The host controller Uc includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and performs various arithmetic processes based on various arithmetic control programs stored in the ROM. At the same time, the overall operation of the battery system A is controlled based on the calculation processing result. For example, the host control device Uc outputs a balance processing execution instruction to the microcomputer M when the battery modules L1 to Ln are charged.

Next, the operation of the battery system A configured as described above will be described with reference to FIG.
For example, when the battery system A is mounted on a forklift, when the charging rate of each of the battery modules L1 to Ln is reduced, the charger J is attached by the worker in charge. Here, the battery system A performs the following characteristic operations in order to shorten the time required for the balance process when the battery modules L1 to Ln are charged.

  First, in the battery system A, the host controller Uc balances the microcomputers M of the control boards K1 to Kn after the charger J is connected to the connection terminal T and the battery modules L1 to Ln are charged. A process execution instruction is output to the microcomputer M. For example, in the control board K1, the microcomputer M executes the balance process when the execution instruction of the balance process is input from the host control device Uc.

  That is, the microcomputer M turns on the discharge switching elements AS1 to ASm of the discharge circuits H1 to Hm provided in the high voltage ones of the battery cells C1 to Cm in order to align the high voltage ones with the low ones. As a result, a high voltage is discharged.

Here, the microcomputer M has a variable duty ratio that is a duty ratio of the discharge switching elements AS1 to ASm based on the total amount of heat generated by the resistors R1 to Rm of the discharge circuits H1 to Hm and the allowable total heat generation. The balance process is executed so as to change. Specifically, when the detection signal is input from the voltage sensors D1 to Dn, the microcomputer M determines the maximum value Vmax and the minimum value Vmin of the voltage detection value from the voltage detection value in each of the battery cells C1 to Cm indicated by the detection signal. And an intermediate value Vmid between the maximum value Vmax and the minimum value Vmin is calculated (step S1). That is, the microcomputer M calculates the intermediate value Vmid according to the following equation (1).
Vmid = (Vmax + Vmin) ÷ 2 (1)

  The microcomputer M causes the discharge circuits H1 to Hm provided in the battery cells C1 to Cm exceeding the intermediate value Vmid to discharge, and does not cause the discharge circuits H1 to Hm provided to the battery cells C1 to Cm below the intermediate value Vmid to discharge. Is determined (step S2). That is, the microcomputer M compares the intermediate value Vmid with the voltage detection values V1 to Vm of the battery cells C1 to Cm, and if the intermediate value Vmid is exceeded (that is, the voltage detection value ≧ Vmid), the intermediate value In the case where the discharge circuits H1 to Hm provided in the battery cells C1 to Cm exceeding 1 are discharged and below the intermediate value (that is, the voltage detection value <Vmid), the battery cells C1 to Cm below the intermediate value are provided. It is determined that the discharge circuits H1 to Hm are not discharged. In this way, the microcomputer M determines the battery cells C1 to Cm to be discharged by the discharge circuits H1 to Hm.

  Subsequently, the microcomputer M calculates a variable duty ratio d that can shorten the time required for the balance process most (step S3). In calculating the variable duty ratio d, the total heat generation amount Pmax allowed in the control board K1 is, for example, that one battery cell C1 whose voltage is the upper limit value VLim is connected to the discharge circuit H1 of the discharge switching element AS1. Assume that the heat generation amount is set equal to the amount of heat generated when discharging with a duty ratio of 100%.

That is, the allowable total heat generation amount Pmax is a value obtained by the following equation (2).
Pmax = (VLim ^ 2) / R × 1 (2)
In the equation (2), R represents the resistance value of the resistor R1 of the discharge circuit H1. Also, the resistors R2 to Rm other than the resistor R1 have the same resistance value R as that of the resistor R1. Furthermore, “1” in equation (2) indicates a duty ratio of 100%.

  In the process of step S3, the microcomputer M equalizes the total heat generation amount Pmax allowed in the control board K1 and the heat generation amounts P1 to Pm of the resistors R1 to Rm in order to shorten the time required for the balance processing. A variable duty ratio d is calculated. That is, the microcomputer M substitutes the above equation (2) into the following equation (3), and then calculates the equation (4) and equation (5), thereby making it possible to reduce the time required for the balance process to the shortest. The ratio d can be calculated.

  Note that the heat generation amount P1 of the resistor R1 is obtained by multiplying the square of the voltage detection value V1 of the battery cell C by the variable duty ratio d and further dividing by the resistance value R of the resistor R1 (P1 = (V1 ^ 2) × d ÷ R). Moreover, it calculates with the method similar to the emitted-heat amount P1 also about the emitted-heat amount P2-Pm of each resistor R2-Rm.

Pmax = P1 + P2 + P3 + ... + Pm (3)
(VLim ^ 2) / R = (V1 ^ 2 + V2 ^ 2 + V3 ^ 2 + ... + Vm ^ 2) * d ÷ R (4)
d = (VLim ^ 2) / (V1 ^ 2 + V2 ^ 2 + V3 ^ 2 + ... + Vm ^ 2) (5)

  Then, the microcomputer M controls the discharge switching elements AS1 to ASm of the discharge circuits H1 to Hm based on the calculated variable duty ratio d (step S4). That is, the microcomputer M changes the duty ratio of the discharge switching elements AS1 to ASm while turning on the discharge switching elements AS1 to ASm of the discharge circuits H1 to Hm provided in the battery cells C1 to Cm exceeding the intermediate value Vmid. Set the duty ratio. At this time, charging from the charger J is stopped.

  As shown in FIG. 3 (a), the variable duty ratio is small when there are many battery cells to be discharged, and is large when there are few battery cells to be discharged as shown in FIG. 3 (b). . That is, in the present invention, if the number of battery cells to be discharged increases by the microcomputer M (control device), the size of the duty ratio between the ON state and the OFF state of the switching element is decreased, and the number of battery cells to be discharged. The ON state and the OFF state of the switching element are controlled so as to increase the magnitude of the duty ratio if the value decreases. As a result, when the number of battery cells to be discharged is small, the current to be discharged is increased and can be discharged in a short time, so that the time required for the balance process can be reduced. On the other hand, the microcomputer M turns off the discharge switching elements AS1 to ASm of the discharge circuits H1 to Hm provided in the battery cells C1 to Cm below the intermediate value Vmid.

  According to the present embodiment as described above, the discharge switching elements AS1 to ASm and the resistors R1 to Rm are connected in series and the discharge switching of the discharge circuits H1 to Hm provided in each of the plurality of battery cells C1 to Cm. The elements AS1 to ASm are turned on so that the battery cells C1 to Cm are discharged, the charge rates of the battery cells C1 to Cm are aligned, and the amount of heat generated by the resistors R1 to Rm of the discharge circuits H1 to Hm. By changing the variable duty ratio, which is the duty ratio of the discharge switching elements AS1 to ASm, based on the total sum and the allowable total heat generation amount, the current flowing through the resistors R1 to Rm is increased, and the balance process is performed. Reduce the time required.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) The present embodiment may be mounted on an electric device other than a forklift.

(2) In the present embodiment, the discharge circuits H1 to Hm provided in the battery cells C1 to Cm higher than the intermediate value Vmid between the maximum value Vmax and the minimum value Vmin are discharged, but the present invention is not limited to this. For example, the discharge circuits H1 to Hm provided in the battery cells C1 to Cm higher than a preset threshold value may be discharged.

(3) In the present embodiment, charging from the charger J is stopped, and in this state, the discharge circuits H1 to Hm provided in the battery cells C1 to Cm are discharged, but the present invention is not limited to this. You may make it discharge to discharge circuit H1-Hm provided in battery cell C1-Cm in the state which continued charging from the charger J. FIG. As a result, the battery cells C1 to Cm discharged by the discharge circuits H1 to Hm stop increasing in voltage, and the battery cells C1 to Cm that are not discharged by the discharge circuits H1 to Hm increase in voltage. The voltage of ~ Cm can be made uniform.

A battery system J charger L1 to Ln battery module K1 to Kn control board Uc host controller C1 to Cm battery cell H1 to Hm discharge circuit D1 to Dm voltage sensor M microcomputer AS1 to ASm discharge switching element R1 to Rm resistor

Claims (5)

A switching element and a resistor are connected in series, and each of the battery cells is discharged by turning on the switching element of a discharge circuit provided in each of the plurality of battery cells. A battery control device for aligning
A battery control device that changes a variable duty ratio, which is a duty ratio of the switching element, based on a total amount of heat generated by the resistors of the discharge circuit and an allowable total amount of heat generated. The calorific value and the total calorific value are set to be equal when one battery cell whose voltage is the upper limit value is discharged to the discharge circuit with the duty ratio of the switching element being 100%,
The variable duty ratio is a value obtained by dividing the square of the upper limit value of the voltage of the battery cell by the sum of the square of the detected voltage value of each battery cell to be discharged by the discharge circuit. Item 2. The battery control device according to Item 1.   An intermediate value between a maximum value and a minimum value of a voltage detection value in each of the plurality of battery cells is calculated, discharged to the discharge circuit provided in the battery cell exceeding the intermediate value, and to a battery cell below the intermediate value The battery control device according to claim 1, wherein the discharge circuit is not discharged. A plurality of discharge circuits each including a switching element;
A battery module comprising a plurality of battery cells connected to each of the switching elements included in each of the plurality of discharge circuits, and discharging when the switching elements are in an on state;
If the number of battery cells to be discharged is increased, the duty ratio of the on-state and the off-state of the switching element is decreased, and if the number of battery cells to be discharged is decreased, the duty ratio is decreased. A control device for controlling an on state and an off state of the switching element so as to increase;
A battery system.   A switching element and a resistor are connected in series, and each of the battery cells is discharged by turning on the switching element of a discharge circuit provided in each of the plurality of battery cells. And a variable duty ratio, which is a duty ratio of the switching element, is changed based on a total amount of heat generated by the resistors of the discharge circuit and an allowable total amount of heat generated.

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