JP3633412B2 - Battery pack control device and battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery control device and a battery pack, and more particularly to an assembled battery control device that controls an assembled battery in which a plurality of secondary batteries are connected in series, and a battery pack including the control device and the assembled battery. .
[0002]
[Prior art]
For example, in an electric vehicle or the like, an assembled battery in which a plurality of secondary batteries (single batteries) are connected in series corresponding to a required capacity is used. Since such an assembled battery uses a plurality of secondary batteries, it is important to ensure reliability. That is, when any of the secondary batteries constituting the assembled battery has its function lowered due to overcharge or overdischarge, the function of the assembled battery as a whole is also lowered. In addition, each secondary battery constituting the assembled battery has variations at the time of manufacture, and when a secondary battery is used as the assembled battery, the charge acceptance and discharge capacity are different due to non-uniform temperature distribution etc. Come.
[0003]
For this reason, the discharge capacity from a discharge depth of 0% (full charge) varies in each secondary battery, and the discharge capacity as an assembled battery decreases. That is, at the time of discharging, the secondary battery having a small discharge capacity ends discharging quickly and becomes overdischarged, and the secondary battery that has become overdischarged becomes the load of other secondary batteries, and all the secondary batteries Before the depth of discharge reaches 100%, the voltage drops, and the assembled battery ends discharging. Conversely, when charging, the secondary battery that did not reach the discharge depth of 100% at the time of discharge first reaches the discharge depth of 0%, the voltage rises and the charging ends, but the secondary battery that is overdischarged at the time of discharge. Since the charging ends without reaching the discharge depth of 0%, the difference in the discharge capacity of each secondary battery widens. Therefore, if charging / discharging is repeated, the overcharged secondary battery is always insufficiently charged, so that the variation becomes large and the discharge capacity of the assembled battery as a whole decreases.
[0004]
In the assembled battery in which a plurality of secondary batteries are connected in series in this way, there are variations between the secondary batteries, and the problem that the discharge capacity is reduced as a whole assembled battery and the particular secondary battery is particularly deteriorated. In addition, there is a case where heat is generated due to overcharge or overdischarge.
[0005]
In order to deal with the above problem, there is a voltage detection means for detecting the battery voltage for each secondary battery constituting the assembled battery, and charging is terminated when the detected voltage reaches the charge end voltage. . In addition, for each secondary battery constituting the assembled battery, a voltage detection means and a bypass circuit for bypassing the secondary battery to flow the charging current are provided in parallel, and the detected voltage becomes the charge end voltage. Some batteries have a secondary battery bypass circuit that bypasses the charging current.
[0006]
[Problems to be solved by the invention]
However, in the former case, if there is a secondary battery that has reached the end-of-charge voltage among a plurality of secondary batteries constituting the assembled battery, charging is stopped, so there is no risk of overcharging. This variation cannot be eliminated. In the latter case, the charging current is bypassed only by the battery voltage. However, in reality, there is a variation in the internal resistance between the secondary batteries. Even if it is small, the terminal voltage increases depending on the internal resistance and reaches the end-of-charge voltage, so that a high charge state cannot be obtained for a battery having a low internal resistance. This causes variations in the charged state of the secondary battery having a large internal resistance, and inhibits each secondary battery from being fully and uniformly charged, in other words, preventing the entire assembled battery from being fully charged.
[0007]
In order to charge a battery in which variations occur between the batteries as described above, Japanese Patent Application Laid-Open No. 6-165399 discloses a charging technique for batteries connected in series. According to this technology, there is a voltage detection means for detecting the voltage of each secondary battery connected in series, and when the charge stop voltage is reached, a bypass circuit that bypasses the secondary battery is formed by a switch, The other secondary battery is charged.
[0008]
However, in the technique of the above publication, since charging is stopped at every point when the charging stop voltage is reached, the time for stopping charging differs among batteries connected in series. In addition, since a battery having a high internal resistance quickly reaches the charge stop voltage, charging may stop before the battery is fully charged.
[0009]
In view of the above-described case, the present invention provides an assembled battery control device and a battery pack that can charge each secondary battery equally and sufficiently regardless of variations in internal resistance of the secondary batteries constituting the assembled battery. Is an issue.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present onset Ming, the battery pack controller for controlling an assembled battery obtained by connecting a plurality of secondary batteries in series, to detect the internal resistance of each of the plurality of secondary batteries Internal resistance detection means, state detection means for detecting the charge / discharge state of the assembled battery, and a plurality of secondary batteries connected in parallel via a switch, and connected in series with a plurality of resistance values A battery voltage balance circuit that includes a resistor and a switch connected in parallel to each of the plurality of resistors, and bypasses a charging current flowing through the secondary battery by turning the switch on or off, and the state detection unit. Based on the detected charge / discharge state of the assembled battery and the internal resistance value of each of the secondary batteries detected by the internal resistance detecting means, the battery voltages of the secondary batteries are made equal. The power Control means for determining ON / OFF conditions of the switch of the voltage balance circuit, and the control means is a difference in internal resistance value of each of the secondary batteries detected by the internal resistance detection means during charging / discharging suspension. The on / off condition of the switch is determined from the battery voltage balance circuit, and the battery voltage of each of the secondary batteries is equal at the next charging according to the on / off condition of the switch determined by the control means when charging / discharging is stopped. Thus, the charging current flowing in the secondary battery is bypassed.
[0011]
In the present invention, each of the plurality of secondary batteries is connected in parallel through a switch, and has a plurality of series-connected resistors having different resistance values, and a switch connected in parallel to each of the plurality of resistors. And a battery voltage balance circuit that bypasses the charging current flowing through the secondary battery by turning the switch on or off. The state detection means detects the charge / discharge state of the assembled battery. The control means balances the battery voltage so that the battery voltage of each secondary battery becomes equal from the difference in the internal resistance value of each secondary battery detected by the internal resistance detection means during the charging / discharging pause detected by this state detection means. The battery voltage balance circuit determines that the battery voltage of each of the secondary batteries is equal at the next charging according to the switch on / off condition determined during charging / discharging suspension by the control means. The charging current flowing in the secondary battery is bypassed . According to the present invention , even if there is a variation in the internal resistance of each secondary battery during charging / discharging suspension , the charging current of the secondary battery is bypassed during charging according to this variation, so that each secondary battery is fully charged. Can be charged, and the discharge capacity of the assembled battery as a whole can be kept high , and the battery voltage balance circuit can be finely adjusted according to the internal resistance of each secondary battery. The battery voltage uniformity can be ensured at a high level .
[0012]
In the present invention, in order to equalize the battery voltage of each secondary battery and eliminate the variation in battery voltage, the battery further includes a battery voltage detection means for detecting each battery voltage of the secondary battery, and the control means is used for the next charging. When the difference between the battery voltages of the secondary batteries is equal to or greater than a predetermined set value, the battery voltage balance circuit may be allowed to bypass the charge / discharge current flowing through the secondary battery. In addition, the battery voltage detecting means for detecting the battery voltage of each of the secondary batteries is further provided, and the control means includes the battery voltage of each of the secondary batteries at the previous charging time and each of the secondary batteries at the next charging time. When the voltage change amount expressed as a difference from the voltage is equal to or larger than a predetermined set value, the battery voltage balance circuit may be allowed to bypass the charge / discharge current flowing through the secondary battery.
[0013]
The Also, the battery voltage balance circuit, if to implement separated on a control board, since the other circuit battery voltage balance circuit and weak current which a large current flows through are separated, the battery pack due to noise It is possible to prevent malfunction of the control device.
[0014]
If the battery pack is provided with the assembled battery control device and the assembled battery of the above aspect, the reliability of the secondary battery is not deteriorated, the discharge capacity of the assembled battery as a whole is reduced, the malfunction is not caused by noise, and the like. A high battery pack can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a battery pack to which the present invention can be applied will be described with reference to the drawings.
[0016]
(Constitution)
As shown in FIG. 1, in the battery pack 10 of this embodiment, a plurality of lithium ion batteries (hereinafter referred to as single cells) 51, 52,..., 5m as secondary batteries are connected in series. The battery pack 5 includes a battery pack 5 and a battery pack controller that controls the battery pack 5.
[0017]
The battery pack control device includes a microcomputer (hereinafter referred to as a microcomputer) 1. The microcomputer 1 is a CPU that performs arithmetic processing, a program that is executed by the CPU, a ROM that stores predetermined values that represent preset differences, which will be described later, a RAM that serves as a work area for the CPU, and an input / output signal port to the outside. It includes an input / output interface and the like.
[0018]
The assembled battery control device is inserted between the plus side of the unit cell 51 and the plus terminal of the assembled battery 5, detects the charging, discharging, or resting state of the assembled battery 5 and changes the state of the assembled battery 5 to the microcomputer 1. The charging / discharging discrimination | determination part 2 output to is provided. The charge / discharge discriminating unit 2 detects the direction of the current flowing through the assembled battery 5 using, for example, a shunt (shunt) resistance, and the like. When the assembled battery 5 is in a charged state, the default value is 1; When in a discharging state, the default value -1 is output to the microcomputer 1 respectively.
[0019]
Further, the battery pack control device includes balance circuits 31, 32,..., 3m that are connected in parallel to the single cells 51, 52,. Yes. As shown in FIG. 2, the balance circuit 31 includes FETs Q <b> 1 to Q <b> 5 that can be turned on / off by a signal from the microcomputer 1 and four bypass resistors whose resistance values are R, 2R, 4R, and 8R, respectively. Each bypass resistor except for the FET Q1 is inserted between the source and drain of the FETs Q2 to Q5. The balance circuit 32,..., 3m has the same circuit configuration as the balance circuit 31.
[0020]
As shown in FIG. 1, the battery pack control device is connected to each single cell 51, 52,..., 5 m and detects the voltage of each single cell and outputs it to the microcomputer 1. 4 is provided. The battery voltage detection unit 4 includes a plurality of differential amplifier circuits having operational amplifiers and resistors. Further, the battery pack control device includes an internal resistance detection unit 6 that is connected to each of the single cells 51, 52,..., 5m and outputs the internal resistance of each single cell to the microcomputer 1. The internal resistance detector 6 generates an alternating current by, for example, an inverter, energizes the alternating current for each unit cell 51, 52,..., 5m, and detects a voltage value and a current value at that time. The circuit can calculate the internal resistance from these values and output it to the microcomputer 1. The positive terminal of the battery pack 10 shown in FIG. 1 and the negative terminal connected to the negative side of the unit cell 5m are connected to a charger or a load.
[0021]
As shown in FIG. 3, the assembled battery control device is mounted on the control board 7. The control board 7 has a balance circuit mounting portion 7A on which the balance circuits 31, 32,..., 3m are mounted and a large current flows, and a predetermined distance from the balance circuit mounting portion 7A. -The microcomputer 1 other than 3 m, the charge / discharge discriminator 2, the battery voltage detector 4, and the internal resistance detector 6 are mounted and wired separately to the detection / control circuit mounting portion 7B through which a minute signal current flows. . Further, the bypass connector 8 that collects leads connected to the balance circuits 31, 32,..., 3m, and the detection / control leads connected to the single cells 51, 52,. The connector 9 is separated on the control board 7.
[0022]
(Operation)
Next, the operation of the battery pack 10 of this embodiment will be described with reference to a flowchart. When the microcomputer 1 is turned on, the CPU of the microcomputer 1 initializes the RAM work area according to a program stored in the ROM, reads a predetermined value stored in the ROM, and performs an initial process for transferring to the RAM. The execution of the battery control processing routine is started.
[0023]
As shown in FIG. 4, in this assembled battery control processing routine, first, in step ST1, the default value from the charge / discharge determination unit 2 is fetched and stored in the RAM, and the assembled battery 5 is loaded from the default value fetched in the next step ST2. It is determined whether or not it is in a dormant state. If the determination is affirmative, a suspension processing subroutine, which will be described later, is executed in step ST4. If the determination is negative, whether or not the assembled battery 5 is in a charged state is determined in the next step ST3. When the determination at step ST3 is affirmative, a charge processing subroutine described later is executed at the next step ST5, and when the determination at step ST3 is negative, the single cells 51, 52,. Another process such as monitoring so that 5 m is not overdischarged is executed. When the process in step ST4, ST5 or ST6 ends, the process returns to step ST1 and the above assembled battery control process routine is repeated.
[0024]
As shown in FIG. 5, in the suspension processing subroutine, first, in step ST41, it is determined whether or not the assembled battery 5 is in a discharge suspension state from the previous default value and the current default value stored in step ST1, and when negative determination is made. Advances to step ST45, and when an affirmative determination is made, in step ST42, the internal resistance of each of the cells 51, 52,... In addition, in this internal resistance value taking-in, the balance circuits 31, 32,..., 3m and the battery voltage detection unit 4 are inserted in parallel to the single cells 51, 52,. Therefore, prior to the detection of the internal resistance of the internal resistance detector 6, the FET Q1 shown in FIG. 2 is turned off, and the switch element such as an FET (not shown) in the battery voltage detector 4 is also turned off. Next, in step 43, it is determined whether or not the captured internal resistance value has a difference greater than a preset difference. If the determination is negative, the process proceeds to step ST45. If the determination is affirmative, the bypass current is determined in the next step ST44. Is stored in the RAM.
[0025]
More specifically, the processing in these steps ST43 and ST44 will be described. As shown in FIG. 7, for example, when an assembled battery in which three unit cells A, B and C are connected in series is discharged, The internal resistance becomes high at the end of discharge. Therefore, the cell A is charged in accordance with the set bypass current in advance by setting a bypass current at the next charging (see ST57 in FIG. 6), so that the battery voltage does not rise quickly during charging due to the internal resistance difference. To. Therefore, in step ST43, for example, when the difference in internal resistance of the single battery A is 5 mΩ or more larger than that of the other single battery B or C, the bypass current for the next charge is set.
[0026]
The bypass current is set by the internal resistance difference and the charging current. For example, if the charging current is 1 A and the internal resistance difference is 5 mΩ, the voltage difference due to the internal resistance difference is 1 A × 5 mΩ = 5 mV. In step ST44, it is predicted that the voltage increase of 5 mV is suppressed, and the bypass resistor set information of the balance circuit 3 corresponding to the unit cell to be corrected is stored in the RAM. As shown in FIG. 2, since the bypass resistance value can take various values by switching the switch composed of FETs according to the output signal from the microcomputer, the balance circuits 31, 32,..., 3m The current value of the bypass current that can be adjusted with can also take various values.
[0027]
In step ST45 of FIG. 5, the voltage values of the individual cells 51, 52,..., 5m output from the battery voltage detector 4 are captured, and in the next step ST46, the individual cells 51, 52,. It is determined whether or not there is a difference greater than or equal to a preset difference between the voltage values. When a negative determination is made, the pause processing subroutine is terminated and the process returns to step ST1. When an affirmative determination is made, in the next step ST47, The bypass resistor of the balance circuit 3 is set, and the cells having a high open-circuit voltage value are discharged until the voltage values of the respective cells 51, 52,... Return to ST1.
[0028]
As shown in FIG. 6, in the charging process subroutine, first, in step ST51, the voltage values of the individual cells 51, 52,..., 5m output from the battery voltage detection unit 4 are captured and stored in the RAM. Next, it is determined whether or not there is a difference greater than a preset difference between the battery voltage values captured in step ST52. If the determination is affirmative, the process proceeds to step ST57. If the determination is negative, the next step ST53 is performed. The voltage change amount is calculated at. In this voltage change amount calculation, the difference between the battery voltage value stored in the previous RAM and the battery voltage value stored in the current RAM is calculated. Next, in step ST54, it is determined whether or not there is a significant difference in the battery voltage change amount by determining whether or not the difference calculated in step ST53 is greater than or equal to a preset difference. The process proceeds to ST57, and in the case of negative determination, in step ST55, the set information of the bypass resistor of the balance circuit 3 stored in the RAM in step ST44 is read, and whether or not bypass by the balance circuit 3 is necessary is bypassed in the next step 56 Judgment from resistance set information. The determination at this step ST56 can be made from, for example, on (eg, 1) / off (eg, 0) information of the FET Q1. If the determination in step ST56 is negative, the charging process subroutine is terminated and the process returns to step ST1. If the determination is positive, in step ST57, a part of the charging current is bypassed by the balance circuit 3 and the battery voltage difference caused by the internal resistance is determined. All the cells are completely charged fully, the charging process subroutine is terminated, and the process returns to step ST1.
[0029]
(Action etc.)
According to the battery pack 10 of the present embodiment, the balance circuit 3 causes the voltage difference between the single cells 51, 52,..., 5m and the voltage change amount difference to be greater than or equal to a preset difference during charging. Since part of the charging current of the unit cell to be adjusted is bypassed (ST51 to ST54, ST57), the cell voltages of the unit cells 51, 52,... Therefore, the single cells 51, 52,..., 5m constituting the assembled battery can be fully charged. In FIG. 8, two unit cells C and D are connected in series and charged using the battery pack control device of this embodiment (Example) (see FIG. 8B), and not (Comparative Example). ) And (see FIG. 8A). The difference between the voltage difference and the voltage change amount was 40 mV and 8 mV, respectively. As is clear by comparing FIGS. 8A and 8B, the battery voltage (cell voltage) between the single cells C and D of the example is equalized by using the assembled battery control device of this embodiment. A voltage difference is maintained between the battery voltages of the cells C and D of the comparative example. This is because, as shown in FIG. 8B, there is a voltage difference of 40 mV or more and / or a battery voltage change amount difference of 8 mV or more between the unit cells C and D of the embodiment. The inserted balance circuit 3 operates and a bypass current I1 flows through the balance circuit 3. As a result, the charging current of the battery C becomes (I-I1) and decreases from the charging current I flowing through the cell D, so that the battery voltage V1 of the cell C gradually becomes equal to the battery voltage V2 of the cell D and fully charged. This is because it matches before.
[0030]
Moreover, according to the battery pack 10, when the voltage difference between the single cells 51, 52,... Are equal (ST45 to ST47), it is possible to prevent the load from concentrating on a specific unit cell to generate heat or deteriorate.
[0031]
Furthermore, according to the battery pack 10, the bypass resistance that sets the bypass current value when the internal resistance value of the single cells 51, 52,... (ST42 to ST44), and the current value set at the next charging is bypassed by a part of the charging current by the balance circuit 3 (ST55 to ST57), so that the single cells 51, 52,. -5 m can be charged evenly until it is fully charged, and the discharge capacity of the assembled battery 5 can be kept high.
[0032]
According to the battery pack 10, the control circuit board 7 is divided into the balance circuit mounting portion 7A and the detection / control circuit mounting portion 7B to divide the signal circuit and the power circuit. Since a power line through which the current flows and a signal line (detection / control lead) for voltage detection and the like are separated from each other so as not to create a common impedance, it is possible to prevent malfunction.
[0033]
In the present embodiment, only one example of the battery pack to which the present invention is applied is shown. However, the present invention is not limited to the present example, and various aspects can be adopted in the above-described claims. Don't wait for the argument.
[0034]
【The invention's effect】
As described above, according to this onset bright, even if there are variations in the internal resistance of the secondary battery during charge and discharge quiescent, so to bypass charging current of the secondary battery during charging in accordance with this variation, Each secondary battery can be charged until it is fully charged, the discharge capacity of the assembled battery as a whole can be maintained high, and the battery voltage balance circuit is finely adjusted according to the internal resistance of each secondary battery. Therefore, it is possible to obtain the effect that the uniformity of the battery voltage between the secondary batteries can be secured at a high level .
[0035]
Further, according to the second aspect, even if there is a variation in the internal resistance of each secondary battery at the end of the discharge, the charging current of the secondary battery is bypassed during charging according to this variation. The battery can be charged until it is fully charged, and the effect that the discharge capacity of the assembled battery as a whole can be maintained high can be obtained.
[0036]
Furthermore, according to the third aspect, the open battery voltage can be made equal even when there is a variation in the open battery voltage during the discharge pause due to the difference in internal resistance and charging current of each secondary battery. It is possible to obtain an effect that the secondary battery can be prevented from becoming a load, heat generation and deterioration.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a battery pack according to an embodiment to which the present invention is applicable.
FIG. 2 is a circuit diagram of a balance circuit of the battery pack according to the embodiment.
FIG. 3 is a mounting diagram schematically showing a control board of the battery pack of the embodiment.
FIG. 4 is a flowchart showing an assembled battery control processing routine of the battery pack according to the embodiment.
FIG. 5 is a flowchart showing details of a suspension processing subroutine of step ST4 of the assembled battery control processing routine.
FIG. 6 is a flowchart showing details of a charging processing subroutine of step ST5 of the assembled battery control processing routine.
FIG. 7 is a graph showing the internal resistance value of each battery when three unit cells are connected in series.
FIG. 8 is a graph showing the relationship between the cell voltage and the charging current with respect to the charging time when two single cells are connected in series, and (A) is a test result of a comparative battery pack having no balance circuit. , (B) are test results of the battery pack of the example having a balance circuit.
[Explanation of symbols]
1 Microcomputer ( control means )
2 Charging / discharging discrimination unit (state detection means)
31 ... 3m balance circuit (battery voltage balance circuit)
4 Battery voltage detector (battery voltage detection means)
5 batteries 51 ... 5m single battery (secondary battery)
6 Internal resistance detector (internal resistance detector)
7 Control board 7A Balance circuit mounting part 10 Battery pack

Claims (6)

In an assembled battery control device for controlling an assembled battery in which a plurality of secondary batteries are connected in series,
Internal resistance detecting means for detecting internal resistance of each of the plurality of secondary batteries;
State detecting means for detecting a charge / discharge state of the assembled battery;
Each of the plurality of secondary batteries is connected in parallel via a switch, and has a plurality of series-connected resistors having different resistance values, and a switch connected in parallel to each of the plurality of resistors, A battery voltage balance circuit that bypasses the charging current flowing through the secondary battery with the switch turned on or off ; and
Based on the charge / discharge state of the assembled battery detected by the state detection means and the internal resistance value of each of the secondary batteries detected by the internal resistance detection means, the battery voltage of each of the secondary batteries Control means for determining the on / off condition of the switch of the battery voltage balance circuit so that
The control means determines an on / off condition of the switch from a difference in internal resistance value of each of the secondary batteries detected by the internal resistance detection means during charge / discharge suspension, and the battery voltage balance circuit Is characterized in that the charging current flowing through the secondary battery is bypassed so that the battery voltage of each of the secondary batteries becomes equal at the next charging according to the on / off condition of the switch determined by the control means when charging / discharging is stopped. An assembled battery control device. Battery voltage detection means for detecting the battery voltage of each of the secondary batteries is further provided, and the control means is configured such that a difference between the battery voltages of the secondary batteries at the next charging is equal to or greater than a predetermined set value. 2. The assembled battery control circuit according to claim 1, wherein the battery voltage balance circuit is allowed to bypass a charge / discharge current flowing through the secondary battery. 3. Battery voltage detection means for detecting the battery voltage of each of the secondary batteries is further provided, and the control means includes the battery voltage of each of the secondary batteries at the previous charging time and the voltage of the secondary battery at the next charging time. When the amount of voltage change expressed as a difference from each battery voltage is equal to or greater than a predetermined set value, the battery voltage balance circuit is allowed to bypass a charge / discharge current flowing through the secondary battery. The assembled battery control circuit according to claim 1. 4. The assembled battery control circuit according to claim 1, wherein the control circuit includes a memory that stores an on / off condition of the switch. 5. The battery voltage balance circuit, the battery pack controlling apparatus according to any one of claims 1 to 4, characterized in that it is mounted to be separated on a control board. A battery pack comprising the assembled battery control device and the assembled battery according to any one of claims 1 to 6.

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