JPWO2019081084A5 - - Google Patents

Description

The present invention uses serial charge and serial discharge currents flowing through all batteries to charge and discharge an energy reservoir with at least one cell block consisting of multiple battery cells connected in series with each other. The method relates to a method in which at least some of the battery cells may have different capacities.

In an energy storage (battery) consisting of multiple rechargeable battery cells connected in series with each other, in particular, each individual cell is neither overcharged nor undercharged when charging the energy storage, all. It is important for the life of the energy storage that the battery cells of the battery are in the same charged state as much as possible. This is especially true for energy stores composed of a plurality of lithium ion batteries, lithium polymer batteries and / or lithium iron phosphate batteries connected in series with each other.

Therefore, usually such energy storages use a charge control device to continuously monitor the charge status of individual battery cells, and on the other hand, average them when the charge status of individual battery cells is different. It is connected to a device, often called a battery management system. In that case, the averaging of the state of charge of the battery cells, which is also called balancing, can be performed by passive or active balancing. Moreover, in known battery management systems, charge averaging begins only when at least one of the battery cells is fully charged, resulting in a relatively time-consuming entire charging process for one cell block. It takes.

In passive balancing, excess energy is converted to heat through resistance in the battery cell that first achieves the end-of-charge voltage, and is therefore lost during the charging process.

In contrast, in active balancing, the energy extracted from a battery cell whose cell voltage is too high is not converted into thermal energy and is used to charge another battery cell in the energy storage. However, even in active balancing, charge averaging begins only when at least one of the battery cells in the cell block reaches the charge end voltage of that battery cell.

From Patent Document 1, a method of charging an energy storage device including a cell block composed of a plurality of battery cells connected in series with each other is well known, in which a battery is charged by a serial charging current flowing through all the battery cells. It has been proposed to carry out cell charging and overcharge the selected battery cell as specified by an additional selective charging process. Subsequently, the charge state of the selected battery cell is adapted to the charge state of the other battery cells. Advantageously, cell blocks are used for selective charging of selected battery cells. Overcharging of such individual battery cells is certainly possible with lead or nickel cadmium batteries, whereas it is not possible with lithium ion batteries, lithium polymer batteries and / or lithium iron phosphate batteries. , They break quickly.

According to Patent Document 2, a method for charging an energy storage device including a plurality of battery cells connected in series with each other is well known, in which a corresponding auxiliary charging controller in which each battery cell is connected to an AC voltage network is known. Charged separately by, then charge averaging between the individual battery cells is performed using its auxiliary charging controller.

Finally, Patent Document 3 discloses a method of charging an energy storage device including a plurality of battery cells connected in series with each other, in which all battery cells are used to accelerate the charging process. In addition to the flowing serial charge current, an auxiliary charge current is supplied to each battery cell measured to be below a predetermined charge state. In that method, a separate DC power source is advantageously used for selective charging of the selected battery cell.

In these well-known methods described above, the battery cell voltage at any given time is measured in order to determine the state of charge of the battery cell at any given time, and then the battery cell voltage value is exceeded or exceeds a predetermined battery cell voltage value. If it falls below that, in some cases, charge averaging between battery cells with different charge states will start. However, in that case, the cell voltage remains extremely constant during the current charging process of the battery cell, and as a result, it is difficult to estimate the current state of charge of the battery cell from the cell voltage. Problem occurs. Only shortly before reaching the current charge or discharge final voltage will there be a relatively large drop or drop in the battery cell voltage at any given time that can be used in the appropriate control process for charge averaging.

European Patent Registration No. 1941594 German Patent Publication No. 102010017439 German Patent Publication No. 10212020544

The object of the present invention specifically, allows for more reliable and faster charging and discharging of energy storage, as compared to well-known methods, especially when the individual battery cells of the cell block have different capacities. It is to provide a method of charging and discharging an energy storage. Further, it is possible to present the state of charge and the state of discharge at each time of the charge process and the discharge process of each battery cell.

In the present invention, the present invention is solved by the feature of claim 1 with respect to the charging of the energy storage, and by the feature of claim 2 with respect to the discharge of the energy storage. Dependent claims disclose further particularly advantageous embodiments of the invention.

Charging of individual battery cells is controlled by cell voltage measurements, and only when at least one of the battery cells is fully charged, the average charge between the individual battery cells based on the measured cell voltage. Unlike the well-known method in which the conversion is carried out, the present invention measures the capacity CN of N battery cells in one cell block at regular time intervals with the measured capacity for each battery cell. It is proposed to determine the charging current of the battery cell based on a predetermined C _coefficient ( maximum charging current IN; ratio of _max to capacity CN). Then, during the charging time t (t ≦ 1 / C) given by the C coefficient, N battery cells are simultaneously charged by these charging currents. In this case, the battery cells 3 to 7 having the maximum charge currents _{IN; max} of the plurality of battery cells 3 to 7 corresponding to the serial charge currents _Io are charged only by the serial charge currents _Io . The maximum charging current IN of the plurality of battery cells 3 to 7 _{; the battery cells 3 to 7 having a max} larger than the serial charging current I _o are the serial charging current I _o and the plurality of auxiliary charging / discharging devices 9 to 13. It is simultaneously charged by a plurality of auxiliary charging currents _IN that can be taken out from the cell block 20 via the cell block 20 . At this time, _IN = IN _{; max} −I _o is established. The maximum charging currents IN of the plurality of battery cells 3 to 7 _{; the battery cells 3 to 7 having a max} smaller than the serial charging current Io _are charged by the serial charging currents Io, and at the same time, the maximum charging currents are charged _. IN; a current exceeding max I _o - _IN ; _max is supplied as an auxiliary discharge current to the cell block 20 via the corresponding auxiliary charge / discharge device.

For example, if all of the calculated maximum charge currents (IN; max) are greater than the available serial charge currents (Io) due to the low available voltage of the energy source, then the values of the plurality of charge currents will be. The plurality of battery cells are simultaneously charged by the plurality of charging currents having the same ratio as the calculated maximum charging current ( _{IN; max} ).

With respect to the discharge of the energy storage, the above can be said accordingly. Only the direction of the current is reversed, that is, in this case, the charging current becomes the discharge current, the auxiliary charging current becomes the auxiliary discharge current, and the auxiliary discharge current becomes the auxiliary charging current.

When the method according to the present invention is used, all the battery cells are charged or discharged in the same state with respect to the effective capacity at that time. Therefore, at each time point, it is possible to present the current state of charge of each battery cell of the cell block with respect to the fully charged or discharged state of the cell block.

In this method, the maximum charge time and maximum discharge time are obtained from the relational expression tmax = 1 / C, are the same for all battery cells, and are clearly shorter than the maximum charge time and maximum discharge time according to the well-known method. It is possible to do. If this charging time and discharging time are observed, overcharging and undercharging of individual battery cells will not occur.

It is possible to omit additional active or passive balancing, as all battery cells will be in the same state of charge for each current effective capacity after the maximum charge time, regardless of their current capacity. can.

In the first advantageous embodiment of the present invention, the battery cell having the minimum capacity is charged by its maximum charging current, and the other battery cells are added to the serial charging current, respectively, with the capacity of each battery cell. It is specified that the serial charging current is selected so that it is charged by the maximum auxiliary charging current obtained from the difference between the capacities of the battery cell having the smallest capacity.

In the second embodiment, it is specified that the serial charging current is selected so that the serial charging current matches the maximum charging current of the average capacity calculated from all the battery cells. Then, during the charging process, in a battery cell having a capacity smaller than this average capacity, a part of the serial charging current is supplied to the cell block again via the auxiliary charging / discharging device assigned to the battery cell. Will be done. On the other hand, a battery cell having a capacity larger than this average capacity is charged simultaneously by the serial charging current and the auxiliary charging current.

In the third embodiment , the serial charging current is selected so that the battery cell having the maximum capacity is charged by the maximum charging current of the battery cell, and at least a part of the other battery cells is serially charged. A current component charged by the current and exceeding the maximum charging current of the battery cell is supplied to the cell block again via the auxiliary charging / discharging device assigned to the battery cell.

In the discharge of the energy storage, only the direction of the current changes again with respect to the above three embodiments, that is, the charging current becomes the discharge current, the auxiliary charging current becomes the auxiliary discharge current, and the auxiliary discharge current becomes the auxiliary charging current. Is stipulated to be.

These capacity measurements are advantageous in series-connected battery cells so that the energy storage can be charged and discharged as specified without time-consuming interruptions to determine battery capacity. , It is automatically carried out at predetermined time intervals.

Therefore, in the first advantageous embodiment, the battery cells are first charged by the serial charge current until delivered to their charge end voltage, at which time the battery cell's excess that first reaches the charge end voltage. Charging is prevented by supplying the excess current component to the cell block again via the auxiliary charging / discharging device assigned to the battery cell. Then, the battery cell is then charged by a predetermined serial charging current until the final discharge voltage of the battery cell having the largest capacity is reached. To prevent undercharging of a battery cell that reaches the final discharge voltage before the battery cell with the largest capacity, the battery cell is assigned to the auxiliary after reaching the final discharge voltage. Current is supplied from the cell block via the charging / discharging device.

Then, from the time transition of the discharge current between the charged state of the battery cell and the arrival of the final discharge voltage of each battery cell, the capacity of the battery cell (capacity CN = discharge current Io'× discharge time t). Is obtained, and this capacity is then used for further optimal charging and discharging processes of the cell block.

Of course, to calculate the capacity, the time transition of the charging process can be used, or the average value between the capacity values calculated when the battery is discharged and charged can be used.

In the second advantageous embodiment, it is considered that in a series-connected battery cell, the charge termination voltage of the entire cell block is usually smaller than the sum of the charge termination voltages of the individual battery cells.

Therefore, when measuring capacity, first the cell block is charged to its end-of-charge voltage, then each of the individual battery cells is charged with the corresponding auxiliary charge / discharge device. It is further charged until the end voltage is reached.

Then, the capacity of the battery cell can be obtained again from the time transition of the discharge current between the charged state of the battery cell and the arrival of the final discharge voltage of each battery cell. In this case, first, the entire cell block is discharged to a discharge depth (DoD) of 80% by the series discharge current (ie, the cell block still has 20% remaining capacity). Then, again, each of the individual battery cells is discharged to each final discharge voltage via the auxiliary charge / discharge device assigned to it.

Even in this case, in order to measure the capacity of the battery cell, the time transition of the charging process at that time can be used, or the average value between the capacity values calculated when the battery cell is charged and discharged can be used. ..

Further details and advantages of the present invention will be revealed from the examples described below based on the block connection diagram.

Block connection diagram of the device for charging and discharging the energy storage according to the present invention.

In the drawing, for example, bidirectional AC / DC conversion by equipment that generates renewable energy (solar cell equipment, wind power generation equipment, biogas equipment, etc.) while playing a role of supplying energy to the power supply network of the building. A device for charging and discharging the energy storage designated by reference numeral 2 which can be charged and discharged via the machine 100 is illustrated by reference numeral 1.

In the illustrated embodiment, the energy storage 2 has a cell block 20 with five rechargeable battery cells 3-7 connected in series with each other, by a controllable main charge / discharge device 8. It can be charged and discharged.

Further, each battery cell 3 to 7 is connected to the cell block 20 via a controllable auxiliary charge / discharge device 9 to 13 assigned to the battery cell 3 to 7. These auxiliary charge / discharge devices 9 to 13 are advantageously controllable bidirectional DC / DC converters.

In order to manage the charge state and the discharge state of the individual battery cells 3 to 7, both the auxiliary charge / discharge device 9 to 13 and the main charge / discharge device 8 are connected via the data wiring 15 corresponding to the battery cell. The management / control device 14 is deployed.

Hereinafter, the charging process of the energy storage 2 of the apparatus 1 according to the present invention will be described in detail.

First, the capacity CNs of the individual battery cells 3 to 7 are measured and stored in the memory of the management / control device 14 (for example, the capacities C3, C5, C6 of the battery cells 3, 5 and 6 are about 2Ah. , The capacity C4 of the battery cell 4 is about 2.5 Ah, and the capacity C7 of the battery cell 7 is about 3 Ah).

Then, if the individual battery cells 3 to 7 are subsequently charged with a charging current of, for example, 1C (where the C _coefficient is the ratio of the maximum charging current IN to the capacity _{CN; max} ), it is managed. The control device 14 has a maximum charge current IN for each battery cell 3-7; max (in the case of the above capacities, these currents are IN; max = C × CN, and 2A for battery cells 3, 5 and 6). Yes, in battery cells 4 and 7, 2.5A and 3A are obtained, respectively) and store these values in the corresponding memory as well.

Here, when a management device (not shown) detects, for example, that the energy of the equipment that generates the renewable energy is larger than the energy required from the power supply network, at least a part of the excess energy is AC / DC. It is delivered to the main charge / discharge device 8 of the device 1 according to the present invention via the converter 100. The present device 1 generates a serial charging current Io of a predetermined strength based on the serial charging current Io.

Here, in order to charge all the battery cells 3 to 7 at the same time by the maximum charge current IN; max assigned to them, the management / control device 14 sets the maximum charge current IN based on the selected serial charge current Io. ; Max serves to charge the battery cells 3 to 7 having the same serial charging current Io only with the serial charging current Io. On the other hand, the battery cells 3 to 7 having a maximum charge current IN; max larger than the serial charge current Io are charged by the serial charge current Io, and at the same time, the auxiliary charge / discharge devices 9 to 13 corresponding to the battery cells are charged. Is charged by the auxiliary charging current IN which can be taken out from the cell block 20 using the above, and IN = IN; max-Io holds in this regard. Finally, the battery cells 3 to 7 having a maximum charge current IN; max smaller than the serial charge current Io are charged by the first charge current Io, and at the same time, a current Io-IN; max exceeding the maximum charge current IN; max. Is supplied to the cell block 20 as a discharge current.

That is, for example, the serial charging current Io is selected so that the battery cells 3, 5 and 6 having the largest capacity (2Ah in the above example, respectively) are charged by their maximum charging current (Imax = 2A). If (ie, Io is 2A), the other battery cells 4 and 7 add to the serial charging current Io and have the capacity and minimum capacity of each battery cell 4, 7 (in this case). , Charged by the maximum auxiliary charging current (0.5A or 1A) from the auxiliary charging / discharging devices 10 and 13 assigned to those battery cells, which is obtained from the difference from the capacity of the battery cells 3, 5 and 6), respectively. Will be done.

By monitoring the final charge voltage of the battery cells 3 to 7, the management / control device 14 can charge the battery cells 3 to 7 with the maximum charge current (tmax = 1 / C = 60 in the above example). Monitor minutes) to prevent overcharging of each battery cell.

For example, if all of the calculated maximum charge currents (IN; max) are greater than the available serial charge currents (Io) due to the low available voltage of the energy source, then the values of the plurality of charge currents will be. The plurality of battery cells are simultaneously charged by the plurality of charging currents having the same ratio as the calculated maximum charging current ( _{IN; max} ). That is, in the above example, when the serial charging current Io is only 1A, the battery cells 3, 5 and 6 are charged at 1A, the battery cell 4 is charged at 1.25A, and the battery cell 7 is charged at 1.5A. It will be charged.

In order to automatically calculate the capacity of the battery cells 3 to 7 at predetermined time intervals (for example, after 100 charge / discharge cycles) in the battery cells 3 to 7 connected in series, first, the cell block 20 is used. It is charged to its end-of-charge voltage, and then each of the individual battery cells 3 to 7 is further charged to its respective final charge voltage using the auxiliary charge / discharge devices 9 to 13 assigned to it.

Then, after charging all the battery cells 3 to 7, the device 1 is used to discharge the battery cells 3 to 7 as specified. In this case, first, the entire cell block 20 is discharged to a discharge depth (DoD) of 80% by the serial discharge current Io'given from the main charge / discharge device 8. Next, each of the individual batteries 3 to 7 is discharged to the respective final discharge voltage via the auxiliary charge / discharge devices 9 to 13 assigned to the individual batteries 3 to 7.

Then, the capacity CN of the battery cell is calculated from the transition of the serial discharge current Io'measured between the start of discharge of all the battery cells 3 to 7 and the arrival of the final discharge voltage of each battery cell. Can be done.

However, to measure the capacity of the battery cell, the time transition of each charging process can be used, or the average value between the capacity values calculated during charging and discharging of the battery cell can be used.

As a matter of course, the present invention is not limited to the examples described here.

Therefore, for example, first, the battery cells 3 to 7 are charged by using the serial charging current Io generated by the main charge / discharge device 8 until all the battery cells 3 to 7 reach their charge end voltages. It is also possible to calculate the capacity of. In this case, in order to prevent overcharging of the battery cell having a lower final charging voltage than the battery cell having the maximum capacity (battery cell 7 in the above example), the excess current is allocated to each battery cell. It is supplied to the cell block 20 via the auxiliary charging / discharging devices 9 to 13.

Then, after charging all the battery cells 3 to 7, the device 1 is used to discharge the battery cells 3 to 7 as specified. Therefore, the battery cells 3 to 7 are discharged by the serial discharge current Io'given by the main charge / discharge device 8, specifically, during the time until the final discharge voltage of the battery cell having the largest capacity is reached. Will be done. In order to prevent the battery cell that reaches the final discharge voltage before the battery cell having the largest capacity from being undercharged, the battery cell is assigned to the battery cell after reaching the final discharge voltage. Auxiliary charging current is supplied from the cell block 20 by using the auxiliary charging / discharging device.

Then, the capacity CN of the battery cell is calculated from the transition of the serial discharge current Io'measured between the start of discharge of all the battery cells 3 to 7 and the arrival of the final discharge voltage of each battery cell. Can be done.

Furthermore, it is not necessary to calculate the capacities of all battery cells in one charge / discharge cycle. Rather, it may be advantageous to determine the capacity of the battery cells in sequence in a plurality of charge / discharge cycles.

Further, as a matter of course, the serial charge current or serial discharge current does not necessarily have to be selected so that the current matches the maximum charge current or maximum discharge current of the battery cell having the smallest capacity. Rather, the serial charge or serial discharge current may be selected , for example to match the maximum charge or maximum discharge current of the battery cell with the average capacity or the battery cell with the largest capacity.

Finally, the energy storage can also consist of multiple cell blocks, including a series battery storage.

1 This device 2 Energy storage 20 Cell block 3 to 7 Battery cell, cell 8 Main charge / discharge equipment 9 to 13 Auxiliary charge / discharge equipment 14 Management / control equipment 15 Data wiring Io Serial charge current Io'Serial discharge current

Claims (9)

At least some of the plurality of battery cells (3-7 ₎ may have different capacities (CN), and the serial charging current (Io) energizes all the battery cells (3-7). ) Is a method for charging an energy storage (2) including at least one cell block (20) composed of the plurality of battery cells (3 to 7) connected in series with each other. The method is
a) The feature that the capacity ( _CN ) of each of the battery cells (3 to 7) is measured at predetermined time intervals and stored in the memory of the management / control device (14).
b) Then , in consideration of a predetermined C _coefficient (maximum charging current IN; ratio of _max to the capacity _CN ), the maximum charging current ( _{IN; max} ) inherent to each said capacity (CN). ) Is the characteristic calculated by the management / control device (14).
c) Then , within a predetermined period t ≦ 1 / C coefficient , the plurality of battery cells (3 to 7) are assigned a maximum charge current ( _IN; ) to these battery cells (3 to 7). It has the feature of being charged at the same time by _max ),
Only the serial charging current (I _o ) is the only battery cell (3 to 7) whose maximum charging current ( _{IN; max} ) of the plurality of battery cells (3 to 7) matches the serial charging current ( I _o ). Charged by
The battery cells (3 to 7) in which the maximum charging current ( _{IN; max} ) of the plurality of battery cells (3 to 7) is larger than the serial charging current (I _o ) are the serial charging current (I _o ) . , It is simultaneously charged by a plurality of auxiliary charging currents ( _IN ) that can be taken out from the cell block (20) via a plurality of auxiliary charging / discharging devices (9 to 13), and at this time , _IN = _IN . _{; Max} - _Io is established ,
The battery cells (3 to 7) having a maximum charging current ( _{IN; max} ) smaller than the serial charging current (I _o ) of the plurality of battery cells (3 to 7) have the serial charging current (I _o ). Therefore , at the same time as being charged, a current ( _IO -IN _{; max} ) exceeding the maximum charging current (IN _{; max} ) serves as an auxiliary discharge current, and the cell block (20) passes through the corresponding auxiliary charge / discharge device. Supplied or supplied to
When all the calculated maximum charging currents ( _{IN; max} ) are larger than the serial charging currents ( _Io ) that can be provided , the values of the plurality of charging currents are the calculated maximum charging currents (IN; max). The method in which a plurality of battery cells (3 to 7) are simultaneously charged by the plurality of charging currents having the same ratio as _{IN; max} ) . At least some of the plurality of battery cells (3-7 ₎ may have different capacities (CN), and the serial charging current (Io) energizes all the battery cells (3-7). ^′ ) Is a method for discharging and charging an energy storage device (2) including at least one cell block (20) composed of the plurality of battery cells (3 to 7) connected in series with each other . And the method is
a) The feature that the capacity ( _CN ) of each of the battery cells (3 to 7) is measured at predetermined time intervals and stored in the memory of the management / control device (14).
b) Then , in consideration of a predetermined C _coefficient (maximum charging current IN; ratio of _max to the capacity _CN ), the maximum charging current ( _{IN; max} ) inherent to each said capacity (CN). ) Is the characteristic calculated by the management / control device (14).
c) Then , within a predetermined period t ≦ 1 / C coefficient , the plurality of the battery cells (3 to 7) are assigned to the battery cells (3 to 7) the maximum discharge current ( _IN; It has the characteristic of being discharged at the same time by _max ).
The battery cells (3 to 7) in which the maximum discharge current ( _{IN; max} ) of the plurality of battery cells (3 to 7) matches the serial discharge current (I _o ^′ ) are the serial charge current (I _o ). Discharged only by
The battery cells (3 to 7) in which the maximum discharge current ( _{IN; max} ) of the plurality of battery cells (3 to 7) is larger than the serial discharge current (I _o ^′ ) are the serial discharge current (I _o ^′ ). ) And a plurality of auxiliary discharge currents ( _IN ^′ ) that can be taken out from the cell block (20) via the plurality of _auxiliary charge / discharge devices (9 to 13). ^′ = IN _{; max} −I _o ^′ is established ,
The battery cells (3 to 7) in which the maximum discharge current ( _{IN; max} ) of the plurality of battery cells (3 to 7) is smaller than the serial discharge current (I _o ^′ ) are the serial discharge current (I _o ^′ ). ) , And at the same time, a current (I _o ^′ -IN _{; max} ) exceeding the maximum discharge current is used as an auxiliary charge current via the corresponding auxiliary charge / discharge device (9-13). The method supplied to 20). The serial charging current ( _Io ) is selected so that the battery cell (3-7) with the smallest capacity is charged by the maximum charging current of the battery cell .
Each of the other battery cells (3-7) is the maximum obtained from the difference between the capacity of each battery cell and the capacity of the battery cell having the minimum capacity, in addition to the serial charging current ( _Io ). The method according to claim 1, wherein the battery is charged by an auxiliary charging current. The serial charging current is selected so that the serial charging current matches the maximum charging current of the battery cells (3-7) having the average capacity calculated from all the battery cells (3-7).
During the charging process, in battery cells (3-7) having a capacity smaller than the average capacity , a part of the serial charging current ( _Io ) is supplied to the cell block again .
The battery cells (3 to 7) having a capacity larger than the average capacity are characterized in that they are simultaneously charged by the first charging current and the auxiliary charging current that can be taken out from the entire battery. The method according to claim 1 . The serial charging current ( _Io ) is selected so that the battery cell (3-7) having the maximum capacity is charged by the maximum charging current of the battery cell.
At least a part of the other battery cells (3 to 7) is charged by the serial charging current ( _Io ), and a current component exceeding the maximum charging current of the battery cell is supplied to the cell block (20). The method according to claim 1, wherein the method is characterized by the above. With a plurality of battery cells (3 to 7) connected in series, the capacity of each battery cell (3 to 7) in one cell block (20) is automatically measured . The method according to any one of claims 1 to 5, which is characterized . For the time being , the entire cell block (20) is charged by the serial charging current ( _Io ) until the charging end voltage of the cell block is reached, and subsequently , each of the cell blocks (20) is individually charged. The battery cells (3 to 7) are further charged using the auxiliary charging / discharging device (9 to 13) assigned to the battery cells until the final charging voltage of the battery cells is reached .
The cell block (20) is then discharged to a discharge depth of 80% by the serial discharge current (I _o '), and each individual battery cell (3-7) is subsequently transferred to the battery cell . Using the assigned auxiliary charge / discharge device (9 to 13), the battery cells are discharged to the final discharge voltage of each battery cell .
Finally, a claim characterized in that the capacities of these battery cells are calculated from the discharge current of the cell block integrated over the time and the discharge current of the individual battery cells integrated over the time. Item 6. The method according to Item 6. First , all plurality of battery cells (3-7) are charged by the serial charging current ( _Io ) until the charging end voltage of those battery cells is reached .
The battery cell (3 to 3) having the maximum capacity is supplied by the excess current via the auxiliary charging / discharging device (9 to 13) of the cell block (20) assigned to the plurality of battery cells, respectively. Overcharging of battery cells (3-7) with a lower final charge voltage than 7) is avoided.
Subsequently , the plurality of battery cells (3 to 7) are discharged by a predetermined serial discharge current (I _o ') until the final discharge voltage of the battery cell (3 to 7) having the maximum capacity is reached. ,
Prior to the battery cells having the maximum capacity (3-7) , the auxiliary charging current is applied to the cells to avoid undercharging of the battery cells (3-7) that reach the final discharge voltage of those battery cells. It is supplied from the blocks (20) to the plurality of cell blocks (20) via auxiliary charging / discharging devices (9 to 13) assigned to those battery cells (3 to 7).
Next , the serial discharge current (I _o ') from the state in which all the battery cells (3 to 7) were charged until the respective battery cells (3 to 7) reached the final discharge voltage was measured. The method according to claim 6 , wherein the capacities of the plurality of battery cells are calculated from the time transition. In order to calculate the capacity of the plurality of battery cells, the time transition of each charging process is also used, and the capacity value measured when the corresponding battery is charged and the capacity value measured when the corresponding battery is discharged. The method of claim 7 or 8 , wherein the average value between is used as the capacity of the respective battery cell.