JP2020124041A - Battery pack unit and cell balance adjustment method - Google Patents

Abstract

PURPOSE: To provide a battery pack unit and a cell balance adjustment method capable of performing maintenance suppressing a reduction of battery life.CONSTITUTION: A battery pack unit according to the present invention has a battery pack including a battery cell group made of first to n-th (n is an integer equal to or more than 2) battery cells connected in series, a discharge processing portion outputting a discharge control signal which is a signal instructing to discharge the battery cell group until total voltage becomes lower than balance voltage when the total voltage which is cell voltage synthesized that is each voltage of the first to the n-th battery cells of the battery cell group is larger than predetermined balance voltage, and a charge processing portion outputting a charge control signal which is a signal instructing to charge by applying the balance voltage to the battery pack until a difference between the cell voltages of the first to the n-th battery cells becomes smaller than an allowable difference after the total voltage becomes lower than the balance voltage by discharge of the battery cell group by the discharge processing portion.SELECTED DRAWING: Figure 2

Description

The present invention relates to a battery pack unit including a plurality of battery cells and a cell balance adjusting method for equalizing the voltages of the battery cells.

Currently, a battery pack unit including a plurality of battery packs connected in series has been commercialized as a power source for a motor mounted in an electric vehicle, a hybrid vehicle, an electrically assisted bicycle, or the like. Each battery pack has a structure in which rechargeable secondary batteries such as a lead storage battery, a nickel hydrogen battery, and a lithium ion battery are connected in series.

By the way, it is known that the performance of a secondary battery deteriorates when it is used for a long time or left as it is, and the progress of the deterioration is not uniform. Therefore, the deterioration state of a plurality of battery packs connected in series becomes non-uniform after long-term use. Therefore, if a plurality of battery packs in such a state are charged, some battery packs may be fully charged and other battery packs may be over-discharged or over-charged, resulting in being unusable. was there. In addition, when charging one battery pack, some cells in the battery pack are in a fully charged state and other cells are in an overdischarged or overcharged state, and the battery pack becomes unusable. There was a risk of becoming.

Therefore, a reproduction processing method has been proposed in which a plurality of battery modules (corresponding to a battery pack) in such a state are restored to the states at the time of shipping (for example, refer to Patent Document 1).

In the regeneration process, the discharge voltage of each battery module is temporarily adjusted to be equal to or lower than the discharge completion voltage value by forcibly discharging the plurality of battery modules until the respective discharge voltages become equal to or lower than a predetermined discharge completion voltage value. After that, the battery is fully charged by charging.

Re-table 2017/046900

By the way, in the maintenance of the battery by the above-described regeneration process, the voltage of each battery module can be temporarily adjusted to a predetermined voltage value or less by discharging the plurality of battery modules. However, when there is a large variation in the voltage of each battery module immediately before performing the discharge, a great difference also occurs in the voltage of each battery module after the end of the discharge. Therefore, if each battery module is charged to reach the fully charged state after the end of the discharge, some battery modules may be overcharged or overdischarged, which may lead to a decrease in battery life. was there.

Therefore, an object of the present invention is to provide a battery pack unit and a cell balance adjusting method capable of performing maintenance while suppressing a decrease in battery life, for example.

A battery pack unit according to the present invention includes a battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series, and first to first battery cell groups. Instructing to discharge the battery cell group until the total voltage falls below the balance voltage when the total voltage obtained by combining the cell voltages that are the respective voltages of the nth battery cells is larger than a predetermined balance voltage. A discharge processing unit that outputs a discharge control signal that is a signal to perform, and after the total voltage falls below the balance voltage due to discharge of the battery cell group by the discharge processing unit, the first to nth battery cells A charging processing unit that outputs a charging control signal that is a signal instructing to charge the battery pack by applying the balance voltage until the difference between the cell voltages becomes smaller than a tolerance.

Moreover, the cell balance adjusting method according to the present invention is directed to each of the battery cells of the battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series. A cell balance adjusting method for adjusting a voltage, wherein the total cell voltage that is a voltage of each of the first to nth battery cells of the battery cell group is combined until the total voltage falls below the balance voltage. And a discharging step of discharging the total voltage below the balance voltage, and a charging step of charging the battery pack by applying the balance voltage until the difference between the cell voltages becomes smaller than a tolerance. With.

In short, in the above-described battery pack unit and cell balance adjusting method, the following discharge processing and charging processing are sequentially performed as the maintenance of the battery pack unit, so that the cell voltage of each battery cell of the battery cell group composed of a plurality of battery cells is calculated. Adjust the cell balance to make it uniform.

That is, first, the battery cell group is forcibly discharged until the total voltage obtained by combining the cell voltages of the plurality of battery cells falls below a predetermined balance voltage (discharge processing). Then, the battery cell group is continuously charged with the above-described balance voltage until the difference between the cell voltages of the battery cells included in the battery cell group becomes smaller than the tolerance (charging process).

Therefore, according to the battery pack unit and the cell balance adjustment described above, the cell voltages are compared with each other as compared with the case where the cell voltage of each of the plurality of battery cells included in the battery pack is equalized only by the discharge process performed on the battery pack. The difference between can be reduced. This reduces the number of battery cells that are in an overcharged state and the duration of the overcharged state at the time of charging to reach the fully charged state of the battery pack, which is performed after the cell balance adjustment is completed. Therefore, it is possible to suppress a decrease in battery life.

Further, the battery pack unit according to the present invention includes a battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series, and a first battery cell group of the battery cell group. Discharging for discharging the battery cell group until the total voltage becomes lower than the balance voltage when the total voltage obtained by combining the cell voltages of the first to nth battery cells is larger than a predetermined balance voltage. When the total voltage becomes lower than the balance voltage due to the processing unit and the discharge of the battery cell group by the discharge processing unit, the balance of the battery pack is maintained until the difference between the cell voltages becomes smaller than a tolerance. And a charge processing unit that outputs a charge control signal that is a signal instructing to apply a voltage to charge the battery.

According to such a battery pack unit, when the above-described discharge process and charge process are sequentially performed, in this discharge process, the discharge processing unit included in itself discharges the electronic cell group. Therefore, it is not necessary to use an electronic load device or the like for discharging the electronic cell group at the time of maintenance work of the battery pack unit, so that maintenance can be performed with an inexpensive system configuration.

Further, still another battery pack unit according to the present invention includes first to first battery cell groups each including a first to nth (n is an integer of 2 or more) battery cells connected in series. The voltage generated by each of the r (where r is an integer of 2 or more) battery pack and the first to rth battery packs is output as a total voltage, and the first to rth batteries are also output. An external power supply terminal for receiving a voltage for charging the pack, and if the total voltage is higher than a predetermined balance voltage, the first to rth battery packs are included until the total voltage falls below the balance voltage. After a discharge processing unit that outputs a discharge control signal that is a signal instructing to discharge all the battery cell groups, the total voltage is below the balance voltage due to discharge of the battery cell groups by the discharge processing unit. , Until the difference between the cell voltages in all the battery cells included in the first to r-th battery packs becomes smaller than a tolerance, charging the balance voltage by applying the balance voltage to the external power supply terminals. And a charge processing unit that outputs a charge control signal that is an instruction signal.

In short, in such a battery pack unit, at the time of maintenance of itself, by performing the following discharge process and charge process in order, cell balance adjustment for equalizing the cell voltage of each battery cell included in a plurality of battery packs is performed. To do.

That is, first, the plurality of battery packs are forcibly discharged until the total voltage obtained by combining the cell voltages of the battery cells included in the plurality of battery packs falls below a predetermined balance voltage (discharge processing). Then, continuously, the plurality of battery packs are charged with the above-described balance voltage via the external power supply terminal until the difference between the cell voltages of the battery cells included in the plurality of battery packs becomes smaller than the tolerance (charging process). ..

According to this battery pack unit, it is possible to reduce the difference in cell voltage between the battery cells included in each battery pack, as compared with the case where the voltage is made uniform for each battery pack only by the discharging process performed on the plurality of battery packs. .. As a result, the number of battery cells that are in an overcharged state and the period during which the overcharged state continues during charging to reach the fully charged state for each battery pack, which is performed after the cell balance adjustment is completed. Since it can be reduced, it is possible to suppress a decrease in battery life.

It is a block diagram showing a configuration of a battery pack unit 100 according to the present invention. It is a circuit diagram which extracts CU1 out of cell controllers CU1 to CUr and shows its internal configuration. 3 is a block diagram showing an example of a system configuration constructed when performing maintenance on the battery pack unit 100. FIG. It is a flow chart which shows the procedure of the maintenance processing which CPU20 performs. It is a flow chart which shows an example of the procedure of cell balance adjustment processing. It is a figure which shows an example of the discharge characteristic of a battery cell. It is a figure showing an example of the state of each cell voltage of battery cells B1-Bn contained in each battery pack just before implementation of balance adjustment processing. It is a figure showing an example of the state of each cell voltage of battery cells B1-Bn contained in each battery pack immediately after the end of discharge. It is a figure showing an example of the state of each cell voltage of battery cells B1-Bn contained in each battery pack when the difference of Vmax and Vmin becomes smaller than VAL. FIG. 6 is a block diagram showing another example of a system configuration constructed when performing maintenance of the battery pack unit 100. It is a flowchart which shows another example of the procedure of a cell balance adjustment process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a battery pack unit 100 according to the present invention.

The battery pack unit 100 includes battery packs BC1 to BCr (r is an integer of 2 or more) connected in series, external power supply terminals T0 and T1, cell controllers CU1 to CUr, and a battery protection unit BMU.

Each of the battery packs BC1 to BCr includes battery cells B1 to Bn (n is an integer of 2 or more) that generate DC voltage (hereinafter, referred to as cell voltage) and are connected in series. ing. The battery cells B1 to Bn are rechargeable secondary batteries such as lead storage batteries, nickel hydrogen batteries, or lithium ion batteries.

In each of the battery packs BC1 to BCr, the positive electrode terminal of the battery cell B1 included therein is a positive power supply terminal, and the negative electrode terminal of the battery cell Bn is a negative power supply terminal. Each battery pack outputs a voltage obtained by combining the voltages generated by the battery cells B1 to Bn included in the battery pack as a battery pack voltage via the power supply terminal on the positive electrode side and the power supply terminal on the negative electrode side. To do.

Further, as shown in FIG. 1, the power source terminal on the positive side of BC1 of the battery packs BC1 to BCr is connected to the external power source terminal T0, and the power source terminal on the negative side of BC1r is connected to the external power source terminal T1. ing.

With the above configuration, the battery pack unit 100 outputs a voltage obtained by combining the battery pack voltages generated by the battery packs BC1 to BCr as the battery voltage via the external power supply terminals T0 and T1. The battery pack unit 100 is shipped, for example, in a charged state such that the voltage value of the battery voltage becomes a specified rated voltage value.

As shown in FIG. 1, cell controllers CU1 to CUr are associated with and connected to the battery packs BC1 to BCr, respectively. For example, the positive and negative terminals of the battery cells B1 to Bn included in the battery pack BC1 are connected to the cell controller CU1, and the positive and negative terminals of the battery cells B1 to Bn included in the battery pack BC2 and The negative electrode terminal is connected to the cell controller CU2. That is, the cell controller CU(k) (k is an integer of 1 to r) is connected to the positive electrode terminal and the negative electrode terminal of each of the battery cells B1 to Bn included in the battery pack BC(k).

The cell controllers CU1 to CUr individually determine the voltage (referred to as cell voltage) of each of the battery cells B1 to Bn included in each of the battery packs BC1 to BCr, the current flowing through each, the temperature of the battery pack BC(k), and the like. Measurement is performed, and measurement information indicating the measurement result is generated. Further, the cell controllers CU1 to CUr supply the above-mentioned measurement information to the battery protection unit BMU or force any battery cell among the battery cells B1 to Bn according to various control signals from the battery protection unit BMU. Discharge processing is performed to electrically discharge.

FIG. 2 is a block diagram showing a part of the internal configuration of CU1 extracted from the cell controllers CU1 to CUr.

In FIG. 2, the voltage sensors CS1 to CSn individually measure the cell voltages generated in the battery cells B1 to Bn, and output cell voltage signals V1 to Vn representing the measured cell voltage for each battery cell to the battery protection. Supply to department BMU.

The discharge switches SW1 to SWn and the resistors R1 to Rn are discharge circuits that selectively discharge each of the battery cells B1 to Bn according to the discharge control signals P1 to Pn supplied from the battery protection unit BMU. The discharge switches SW1 to Wn are switch elements including, for example, MOS (Metal Oxide Semiconductor) type or bipolar type transistors.

That is, the discharge switch SW(t) (t is an integer of 1 to n) is turned off when the discharge control signal P(t) indicates, for example, a logic level 0 indicating the discharge stop, and the discharge control signal P( When t) indicates, for example, a logic level 1 that instructs execution of discharge, the state is ON. When the discharge switch SW(t) is turned on, the positive electrode terminal and the negative electrode terminal of the battery cell B(t) are electrically connected via the resistor R(t), and the battery cell B(t) is discharged. At this time, the discharge current flows into the resistor R(t) and is consumed, so that the battery capacity of the battery cell B(t) is reduced. On the other hand, while the discharge switch SW(t) is in the off state, one end of the resistor R(t) is opened, so that the above-mentioned discharge does not occur.

The battery protection unit BMU performs a battery protection process for avoiding the battery packs BC1 to BCr from being overcharged or overdischarged. That is, the battery protection unit BMU monitors the state of overcharge or overdischarge of the battery packs BC1 to BCr based on the above measurement information acquired from the cell controllers CU1 to CUr. Then, the battery protection unit BMU performs various controls on the cell controllers CU1 to CUr based on the monitoring result to prevent the battery packs BC1 to BCr from being overcharged or overdischarged.

Further, when the battery protection unit BMU receives the maintenance execution signal MEX urging the battery maintenance process, the battery protection unit BMU performs the maintenance process described below and outputs the charge control signal CGS or the discharge control signal DCS in the process.

The battery protection unit BMU includes a ROM (Read Only Memory) 10 in which a program representing the procedure of the battery protection processing and the maintenance processing described above is stored, and a CPU 20 that executes the program stored in the ROM 10.

The maintenance operation of the battery pack unit 100 performed in a factory or the like that undertakes maintenance of the battery pack unit 100 when, for example, the cumulative usage period of the battery pack unit 100 approaches the recommended period or the battery duration becomes short explain.

FIG. 3 is a block diagram showing a system configuration constructed to maintain the battery pack unit 100.

As shown in FIG. 3, the electronic load device 200 and the power supply device 300 are connected to the external power supply terminals T0 and T1 of the battery pack unit 100 to be maintained.

When receiving the discharge control signal DCS output from the battery pack unit 100, the electronic load device 200 forces the battery packs BC1 to BCr included in the battery pack unit 100 via the external power supply terminals T0 and T1. To discharge.

When receiving the charge control signal CDS output from the battery pack unit 100, the power supply device 300 applies the charging voltage indicated by the charge control signal CDS to the external power supply terminals T0 and T1 of the battery pack unit 100. Then, the battery packs BC1 to BCr are charged.

In the system configuration shown in FIG. 3, when battery pack unit 100 receives maintenance execution signal MEX, CPU 20 executes the maintenance process shown in FIG. 4 according to the program stored in ROM 10.

That is, first, the CPU 20 executes a cell balance adjustment process for equalizing the cell voltages of the battery cells B1 to Bm included in the battery packs BC1 to BCr, respectively (step S100).

FIG. 5 is a flowchart showing the procedure of the cell balance adjustment processing.

In FIG. 5, the CPU 20 supplies to the cell controllers CU1 to CUr the discharge control signals P1 to Pn instructing to set all the discharge switches SW1 to SWn included in the cell controllers CU1 to CUr to the off state. (Step S11).

Next, the CPU 20 takes in the cell voltage signals V1 to Vn from the cell controllers CU1 to CUr (step S12).

Next, the CPU 20 calculates, as the total voltage Vsum, a voltage obtained by combining the cell voltages of the battery cells included in the battery packs BC1 to BCr based on the cell voltage signals V1 to Vn fetched from the cell controllers CU1 to CUr. Yes (step S13). The total voltage Vsum corresponds to the battery voltage output from the external power supply terminals T0 and T1 of the battery pack unit 100 described above.

Next, the CPU 20 determines whether the total voltage Vsum is lower than the balance voltage BV described below (step S14).

The balance voltage BV is a fixed voltage that is a target when equalizing the cell voltages of all the battery cells, and represents the transition of the discharge voltage with respect to the battery capacity of the battery cells, for example, based on the discharge characteristics as shown in FIG. Ask like.

That is, first, based on the discharge characteristics, a voltage lower than the discharge voltage corresponding to the battery capacity at a change point at which the rate of decrease of the discharge voltage that decreases as the battery capacity decreases greatly, that is, a so-called end-of-discharge voltage, The basic balance voltage FV per unit is set.

For example, according to the discharge characteristics when the battery cell is a lithium-ion battery as shown in FIG. 6, when the battery capacity is about 10% at the time of full charge, the decrease rate of the discharge voltage with respect to the decrease of the battery capacity is sharp. Is increasing. Therefore, in the example shown in FIG. 6, the discharge voltage at the end of discharge, which is a voltage at which the battery capacity is lower than the discharge voltage V0 at 10% when fully charged, is determined as the basic balance voltage FV per battery cell. Then, a voltage obtained by multiplying the basic balance voltage FV by (n·r), which is the number of series stages of battery cells of the battery packs BC1 to BCr, is set as the balance voltage BV.

When it is determined in step S14 that the total voltage Vsum is not lower than the balance voltage BV, the CPU 20 supplies the electronic load device 200 with the discharge control signal DCS for forcibly discharging the battery packs BC1 to BCr (step S15). At this time, the electronic load device 200 discharges all the battery cells included in the battery packs BC1 to BCr according to the discharge control signal DCS.

After execution of step S15, the CPU 20 returns to the execution of step S14 described above, and executes the above-described operation again.

During this time, when it is determined in step S14 that the total voltage Vsum is lower than the balance voltage BV, the CPU 20 supplies the electronic load device 200 with the discharge control signal DCS instructing to stop the discharge (step S16). As a result, the electronic load device 200 stops the forced discharge of all the battery cells included in the battery packs BC1 to BCr.

By executing steps S14 to S16, CPU 20 outputs discharge control signal DCS instructing to discharge all the battery cells included in battery packs BC1 to BCr until total voltage Vsum falls below balance voltage BV. Then, the electronic load device 200 forcibly discharges all the battery cells included in the battery packs BC1 to BCr according to the discharge control signal DCS. As a result, the cell voltage of each battery cell gradually decreases as time passes, and the total voltage Vsum also decreases accordingly, and the voltage value falls below the balance voltage BV.

After execution of step S16, the CPU 20 supplies the power supply device 300 with the charge control signal CGS instructing to charge the battery packs BC1 to BCr with the balanced voltage BV (step S17). The power supply device 300 generates the balance voltage BV according to the charge control signal CGS and applies the balance voltage BV to the external power supply terminals T0 and T1 of the battery pack unit 100 to charge the battery packs BC1 to BCr. ..

Next, the CPU 20 takes in the cell voltage signals V1 to Vn from each of the cell controllers CU1 to CUr (step S18). Then, based on the acquired cell voltage signal group, the CPU 20 sets the maximum cell voltage to the cell voltage Vmax and the minimum cell voltage to the cell voltage among the cell voltages of all the battery cells included in the battery packs BC1 to BCr. The voltage Vmin is detected (step S19).

Next, the CPU 20 determines whether or not the difference between the cell voltage Vmax and the cell voltage Vmin is smaller than a predetermined allowable voltage difference VAL (step S20). That is, by executing step S20, the CPU 20 causes each cell voltage to the extent that the difference between the maximum cell voltage Vmax and the minimum cell voltage Vmin among the cell voltages of all the battery cells becomes smaller than the allowable voltage difference VAL. It is determined whether or not the voltage values of are uniform.

When it is determined in step S20 that the difference between the cell voltage Vmax and the cell voltage Vmin is not smaller than VAL, the CPU 20 sets all discharge switches corresponding to each of the battery cells other than the battery cell that generated the cell voltage Vmin. Discharge control signals P1 to Pn instructing to turn on are supplied to the cell controllers CU1 to CUr (step S21). As a result, among the discharge switches SW1 to SWn included in each cell controller, the discharge switch designated by the discharge control signals P1 to Pn to be turned on is turned on, and the battery cell connected to the discharge switch is forced. Be discharged.

After execution of step S21, the CPU 20 returns to the execution of step S18, and executes the operations of steps S18 to S21 described above again.

By executing steps S17 to S21 described above, the CPU 20 performs the following process after the total voltage Vsum falls below the balance voltage BV by the above-described discharge process (S14 to S16).

That is, the CPU 20 instructs to charge the battery packs BC1 to BCr by applying the balance voltage BV until the difference between Vmax and Vmin, that is, the difference between the cell voltages of all the battery cells becomes smaller than the allowable voltage difference VAL. The charging control signal CGS is output. In response to the charge control signal CGS, the power supply device 300 generates the balance voltage BV and applies it to the battery packs BC1 to BCr via the external power supply terminals T0 and T1 to charge the battery packs BC1 to BCr. To do.

During this time, when it is determined in step S20 that the difference between the cell voltage Vmax and the cell voltage Vmin is smaller than the allowable voltage difference VAL, the CPU 20 exits the cell balance adjustment processing S100 and performs the next charging processing (step S200). To execute.

In the charging process, the CPU 20 takes in the cell voltage signals V1 to Vn from each of the cell controllers CU1 to CUr, and calculates the total voltage Vsum based on the taken-in cell voltage signal group as in step S13. Then, the CPU 20 performs charge control that instructs to apply the charge voltage to the external power supply terminals T0 and T1 of the battery pack unit 100 until the voltage value of the total voltage Vsum becomes equal to the rated voltage value of the battery pack unit 100. The signal CGS is supplied to the power supply device 200.

Here, when the voltage value of the total voltage Vsum becomes equal to the rated voltage value, the COU 20 determines that the battery packs BC1 to BCr are in a fully charged state, and ends the maintenance process shown in FIG.

Below, in the system configuration shown in FIG. 3, the cell voltage equalization achieved by executing the cell balance adjustment processing shown in FIG. 5 will be described.

FIG. 7 is a diagram showing an example of the states of the cell voltages of the battery cells B1 to Bn included in the battery packs BC1 to BCr just before the execution of the balance adjustment process. In the example shown in FIG. 7, the cell voltages of the battery cells vary, and the total voltage Vsum obtained by combining the cell voltages of all the battery cells included in the battery packs BC1 to BCr is the balance voltage BV. It is assumed that it is larger than (=FV·n·r).

Therefore, when the battery pack unit 100 receives the maintenance execution signal MEX, first, all the battery cells included in the battery packs BC1 to BCr are forcibly discharged until the total voltage Vsum becomes lower than the balance voltage BV. (S14, S15). Then, when the total voltage Vsum becomes smaller than the balance voltage BV, this discharge is stopped (S16).

FIG. 8 is a diagram showing an example of the states of the cell voltages of the battery cells B1 to Bn included in the battery packs BC1 to BCr just after the discharge is stopped.

That is, due to the above-described forced discharge (S14, S15), as shown in FIG. 8, the cell voltage of each of the battery cells B1 to Bn included in each battery pack BC is reduced to near the basic balance voltage FV.

Then, after the forced discharge is stopped (S16), the balance voltage BV is applied to the external power supply terminals T0 and T1 of the battery pack unit, and the battery packs BC1 to BCr are charged by the balance voltage BV (S17). ..

Further, during the charging, until the difference between the maximum cell voltage Vmax and the minimum cell voltage Vmin among the cell voltages of all the battery cells included in the battery packs BC1 to BCr becomes smaller than the allowable voltage difference VAL. , The battery cells other than the battery cell generating the minimum cell voltage Vmin are forcibly discharged (S20 to S21).

For example, in the example shown in FIG. 8, the cell voltages of the battery cell B2 included in the battery pack BC1 and the battery cell B1 included in the battery pack BCr are the minimum. Therefore, the battery cell B2 included in the battery pack BC1 and the battery cell B1 included in the battery pack BCr are charged, and the respective cell voltages gradually increase. On the other hand, the battery cells B2 included in the battery pack BC1 and the discharge cells other than the battery cell B1 included in the battery pack BCr are connected to the discharge circuits (SW1 to SWn, R1 to R1) respectively connected thereto. Rn) causes individual discharge and each cell voltage gradually decreases.

As a result, the difference between the cell voltage Vmax and the cell voltage Vmin becomes small, and the cell voltages of all the battery cells included in the battery packs BC1 to BCr are made uniform.

FIG. 9 shows the state of the cell voltage of each of the battery cells B1 to Bn included in each of the battery packs BC1 to BCr when the difference between the cell voltage Vmax and the cell voltage Vmin becomes smaller than the allowable voltage difference VAL. It is a figure showing an example.

Thus, according to the cell balance adjustment shown in FIG. 5, even if there is a relatively large voltage difference between the battery pack voltages of the battery packs, the cell voltage of each battery cell included in each battery pack is The voltage is equalized so that the difference between the voltages becomes smaller than the allowable voltage difference.

Therefore, by performing the cell balance adjustment on the battery pack unit 100, the battery cells included in each battery pack can be compared with the case where the voltage is made uniform for each battery pack only by the discharging process performed on the plurality of battery packs. The difference between the cell voltages can be reduced. As a result, the number of battery cells that are in an overcharged state and the period during which the overcharged state continues during charging to reach the fully charged state for each battery pack, which is performed after the cell balance adjustment is completed. Since it can be reduced, it is possible to suppress a decrease in battery life.

In the embodiment shown in FIG. 1, the cell controllers CU1 to CUr and the battery protection unit BMU included in the battery pack unit 100 perform the discharging process in steps S11 to S16 and the charging process in steps S17 to S20 shown in FIG. , Are being implemented.

In short, the battery pack unit 100 includes first to r-th battery cells each including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells (B1 to Bn) connected in series. In addition to the battery pack (BC1 to BCr) (r is an integer of 2 or more), the following external power supply terminals, a discharge processing unit, and a charging processing unit may be included.

That is, the external power supply terminals (T0, T1) output the combined voltage of the voltages generated by the first to r-th battery packs (BC1 to BCr) as the total voltage (Vsum), and the first to first It is provided to receive a voltage for charging the rth battery pack.

When the total voltage (Vsum) is higher than a predetermined balance voltage (BV), the discharge processing units (CS1 to CSn, BMU) store the first to rth battery packs until the total voltage falls below the balance voltage. It outputs a discharge control signal (DCS) instructing to discharge all the included battery cell groups.

The charge processing units (CS1 to CSn, BMU) are arranged so that the total voltage drops below the balance voltage due to the discharge of the battery cell group by the discharge processing unit, and then the cell voltages of all the battery cells included in the first to r-th battery packs are different from each other. Until the difference between the two becomes smaller than the allowable difference (VAL), a charge control signal (CGS) is output to instruct to apply the balance voltage to the external power supply terminals (T0, T1) for charging.

Further, in the above embodiment, the battery pack unit 100 has been described by taking the one including a plurality of battery packs (BC1 to BCr) as an example, but at least one battery pack may be included.

In short, the battery pack unit 100 includes a battery pack (BC) including a battery cell group (B1 to Bn) including first to nth (n is an integer of 2 or more) battery cells connected in series. In addition, it may include any of the following discharge processing unit and charge processing unit.

That is, the discharge processing units (CS1 to CSn, BMU) have a predetermined total balance voltage (Vsum) obtained by combining the cell voltages (V1 to Vn) that are the voltages of the first to nth battery cells. When it is larger than BV), a discharge control signal (DCS) that instructs to discharge the battery cell group (B1 to Bn) until the total voltage falls below the balance voltage is output.

The charge processing units (CS1 to CSn, BMU) are charged as follows after the total voltage (Vsum) falls below the balance voltage (BV) due to the discharge of the battery cell group (B1 to Bn) by the above-described discharge processing unit. The control signal (CGS) is output. That is, the charge processing unit applies the balance voltage (BV) to the battery pack until the difference between the cell voltages of the first to nth battery cells (B1 to Bn) becomes smaller than the tolerance (VAL). A signal for instructing charging is output as a charge control signal (CGS).

Therefore, compared with the case where the cell voltage of each of the plurality of battery cells included in the battery pack is equalized only by the discharge process performed on the battery pack by performing the cell balance adjustment shown in FIG. 5 on the battery pack unit 100. Thus, the difference between cell voltages can be reduced. This reduces the number of battery cells that are in an overcharged state and the duration of the overcharged state at the time of charging to reach the fully charged state of the battery pack, which is performed after the cell balance adjustment is completed. Therefore, it is possible to suppress a decrease in battery life.

In addition, in the cell balance adjustment shown in FIG. 5, as shown in FIGS. 8 and 9, each of the battery cells B1 to Bn included in each battery pack is targeted with the basic balance voltage FV that is a voltage at the end of discharge of the battery cell as a target. The cell voltages of are aligned. Here, in the final stage of discharge when the battery capacity of the battery cell is about 10% or less, as compared with the case where the battery capacity exceeds about 10%, as shown in FIG. The amount of decrease is large. As a result, in the final stage of discharge, the difference in discharge voltage corresponding to the difference in battery capacity between the battery cells becomes larger than that before the final stage of discharge.

Therefore, by using the basic balance voltage FV, which is the voltage at the end of discharge, as the target voltage for aligning the cell voltages, the cell voltages of the battery cells B1 to Bn included in the battery packs can be accurately equalized. Is possible.

In the above embodiment, as shown in FIG. 3, the electronic load device 200 is connected to the battery pack unit 100 to be maintained, and all the battery cells included in the battery packs BC1 to BCr are connected by the electronic load device 200. They are discharged all at once (S15).

However, the simultaneous discharge of all the battery cells may be performed not by the electronic load device 200 but by the discharge circuits (R1 to Rn, SW1 to SWn) included in each of the cell controllers CU1 to CUr.

FIG. 10 is a block diagram showing another example of the system configuration constructed when the battery pack unit 100 is maintained in view of the above point.

In the system configuration shown in FIG. 10, the electronic load device 200 is not used, and only the power supply device 300 for charging is connected to the external power supply terminals T0 and T1 of the battery pack unit 100.

FIG. 11 is a flow chart showing the procedure of the cell balance adjustment processing executed in step S100 shown in FIG. 4 when the system configuration shown in FIG. 10 is adopted for the maintenance of the battery pack unit 100.

Note that in the flowchart shown in FIG. 11, the operations of other steps S11 to S14 and S17 to S21 are shown in FIG. 5 except that steps S150 and S160 are adopted instead of steps S15 and S16 shown in FIG. It is the same as the one. Therefore, only the operations of steps S150 and S160 will be described below.

Step S150 is executed when CPU 20 determines in step S14 shown in FIG. 11 that balance voltage BV is not higher than total voltage Vsum. In step S150, the CPU 20 supplies the discharge control signals P1 to Pr for setting all the discharge switches SW1 to SWn included in the cell controllers CU1 to CUr to the ON state to the cell controllers CU1 to CUr. After the execution of step S150, the CPU 20 returns to the execution of step S14 and executes the above-described operation again.

During this time, when it is determined in step S14 that the balance voltage BV is higher than the total voltage Vsum, the CPU 20 executes step S160. In step S160, the CPU 20 supplies the discharge control signals P1 to Pr for setting all the discharge switches SW1 to SWn included in the cell controllers CU1 to CUr to the off state to the cell controllers CU1 to CUr. After executing step S160, the CPU 20 moves to execution of step S17 described above.

That is, by executing steps S14, S150, and S160, when the total voltage Vsum is higher than the balance voltage BV, the CPU 20 discharges all the battery cells included in the battery packs BC1 to BCr until the Vsum becomes lower than BV. .. That is, at this time, the discharge circuits (R1 to Rn, SW1 to SWn) included in each of the cell controllers CU1 to CUr forcibly discharge all the battery cells included in the battery packs BC1 to BCr. ..

In short, when performing the cell balance adjustment process as shown in FIG. 11, the battery pack unit 100 includes a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series. In addition to the battery pack (BC) including (B1 to Bn), the following discharge processing unit and charge processing unit may be included.

That is, the discharge processing unit (CS1 to CSn, SW1 to SWn, R1 to Rn, BMU) is a total voltage (Vsum) obtained by combining the cell voltages (V1 to Vn) that are the voltages of the first to nth battery cells. Is greater than a predetermined balance voltage (BV), the battery cell groups (B1 to Bn) are discharged until the total voltage falls below the balance voltage.

When the total voltage (Vsum) is lower than the balance voltage (BV) due to the discharge of the battery cell group (B1 to Bn) by the discharge processing unit, the charge processing unit (CS1 to CSn, BMU) determines the difference between the cell voltages. Until the difference becomes smaller than the tolerance (VAL), the charging control signal (CGS) is output to instruct to apply the balance voltage (BV) to the battery pack for charging.

According to such a configuration, when the cell balance adjustment is performed, the cell voltage of each of the battery cells B1 to Bn included in each battery pack BC is basically balanced without using the electronic load device 200, as shown in FIG. It is possible to reduce the voltage to the vicinity of the voltage FV.

100 battery pack unit 200 electronic load device 300 power supply device B1 to Bn battery cells BC1 to BCr battery pack BMU battery protection unit CU1 to CUr cell controller
SW1 to SWn discharge switch

Moreover, the cell balance adjusting method according to the present invention is directed to each of the battery cells of the battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series. A cell balance adjusting method for adjusting a voltage, wherein the total voltage obtained by combining cell voltages, which are voltages of the first to nth battery cells of the battery cell group, falls below a predetermined balance voltage. A discharging step of discharging the battery cell group, and after the total voltage falls below the balance voltage, the battery pack is charged by applying the balance voltage until the difference between the cell voltages becomes smaller than a tolerance. And a charging step.

Claims (9)

A battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series;
When the total voltage obtained by combining the cell voltages that are the voltages of the first to nth battery cells of the battery cell group is greater than a predetermined balance voltage, the battery until the total voltage falls below the balance voltage. A discharge processing unit that outputs a discharge control signal that is a signal instructing to discharge the cell group,
After the total voltage falls below the balance voltage due to the discharge of the battery cell group by the discharge processing unit, until the difference between the cell voltages of the first to nth battery cells becomes smaller than a tolerance, A battery pack unit, comprising: a charge processing unit that outputs a charge control signal that is a signal instructing to charge the battery pack by applying the balance voltage. The discharge processing unit,
By the discharge circuit capable of individually discharging the first to nth battery cells, the difference between the maximum cell voltage and the minimum cell voltage is from the time when the total voltage is lower than the balance voltage. The battery cells other than the battery cell that generates the minimum cell voltage among the first to nth battery cells are discharged until the difference becomes smaller than the allowable voltage difference. Alternatively, the battery pack unit described in 2. The charge processing unit,
A signal instructing to charge the battery pack until the voltage value of the total voltage becomes equal to the rated voltage value when the difference between the maximum cell voltage and the minimum cell voltage becomes smaller than the tolerance. The battery pack unit according to claim 2, wherein is output as the charge control signal. The balance voltage is a discharge voltage corresponding to the battery capacity at a change point where the rate of decrease of the discharge voltage that decreases as the battery capacity decreases in the discharge characteristics that represents the transition of the discharge voltage with respect to the battery capacity in the battery cell. The battery pack unit according to any one of claims 1 to 3, wherein the battery pack unit has a voltage value obtained by multiplying a predetermined lower voltage by n times. The battery pack unit according to any one of claims 1 to 3, wherein the predetermined voltage is a discharge voltage of the battery cell at a final stage of discharge of the battery cell. The battery cell is a lithium-ion battery,
The battery pack unit according to claim 4, wherein the predetermined voltage is a discharge voltage corresponding to a battery capacity of 10% or less of a fully charged capacity of the battery cell. A cell balance adjusting method for adjusting a voltage of each of the battery cells of a battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series,
A discharging step of discharging the battery cell group until the total voltage obtained by combining the cell voltages that are the respective voltages of the first to nth battery cells of the battery cell group falls below the balance voltage;
After the total voltage is below the balance voltage, a charging step of applying the balance voltage to the battery pack for charging until the difference between the cell voltages becomes smaller than a tolerance,
A method of adjusting cell balance, comprising: A battery pack including a battery cell group including first to n-th (n is an integer of 2 or more) battery cells connected in series;
When the total voltage obtained by combining the cell voltages that are the voltages of the first to nth battery cells of the battery cell group is greater than a predetermined balance voltage, the battery until the total voltage falls below the balance voltage. A discharge processing unit for discharging the cell group,
When the total voltage is lower than the balance voltage due to the discharge of the battery cell group by the discharge processing unit, the balance voltage is applied to the battery pack until the difference between the cell voltages becomes smaller than a tolerance. And a charging processing unit that outputs a charging control signal that is a signal instructing to charge the battery,
A battery pack unit comprising: First to r-th (r is an integer of 2 or more) battery packs each including a battery cell group consisting of first to n-th (n is an integer of 2 or more) battery cells connected in series;
An external power supply terminal for receiving a voltage for charging the first to r-th battery packs, as well as outputting a voltage obtained by combining the voltages generated by the first to r-th battery packs as a total voltage,
When the total voltage is higher than a predetermined balance voltage, a signal instructing to discharge all the battery cell groups included in the first to rth battery packs until the total voltage falls below the balance voltage. A discharge processing unit that outputs a discharge control signal that is
After the total voltage has dropped below the balance voltage due to the discharge of the battery cell group by the discharge processing unit, the difference between the cell voltages in all the battery cells included in the first to rth battery packs is allowed. A charging processing unit that outputs a charging control signal that is a signal instructing charging by applying the balance voltage to the external power supply terminal until it becomes smaller than a difference,
A battery pack unit comprising:

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