Snapshot balancing method of battery and system therefor

Abstract

The present document relates to a method for selectively performing balancing for a specific battery type by recording charging / discharging information of a battery in a snapshot manner as if a picture is taken, and a system therefor. The method comprises: applying an initial cycle in which charging and discharging of a battery are repeated a predetermined number of times, wherein during the initial cycle, at least one of a charging current amount or a charging voltage is recorded when the battery is charged, and at least one of a discharge current amount or a discharge voltage is recorded when the battery is discharged; and comparing at least one of the charging current amount or the charging voltage with at least one of the discharging current amount or the discharging voltage to distinguish the cell types of the battery; and performing balancing using a power consumption element on a battery cell of a specific cell type among the cell types of the battery.

Description

Snapshot balancing method for batteries and system therefor

[0001] The following description relates to battery balancing, and more specifically, to a method and system for selectively performing balancing on a specific battery type by recording battery charge / discharge information in a snapshot manner, as if taking a photograph.

[0002] Secondary batteries, unlike primary batteries, which are non-rechargeable, are rechargeable and dischargeable. These secondary batteries are used in a variety of fields, including portable devices like cell phones and laptops, as well as electric vehicles and energy storage systems (ESS).

[0003] Among these secondary batteries, lithium secondary batteries, which are currently the most popular, have a larger capacity than nickel-cadmium batteries or nickel-hydrogen batteries, and their utilization is increasing due to their high energy density per unit weight.

[0004] However, these lithium secondary batteries have the disadvantage of being vulnerable to fire safety, and thus, research on aqueous batteries that can replace / supplement them is actively being conducted.

[0005]

[0006] Meanwhile, batteries contain multiple cells, and managing the variation between these cells is a critical element in overall system control. For example, in an ESS battery containing 1,000 cells, the OCV (Open Circuit Voltage) variation across the cells must remain within a certain range for normal control.

[0007] Figure 1 is a drawing to explain the concept of changes in OCV and measured voltage during charging and discharging of a battery.

[0008] As illustrated in 110 of FIG. 1, when charging is performed from a theoretical point of SoC (State of Charge) 0% to a theoretical point of SoC 100%, a measured voltage higher than the OCV is observed, and conversely, when discharging is performed, a measured voltage lower than the OCV is observed. This is because various forms of ohmic loss occur as described below, and the difference between the measured voltage and the OCV can be expressed as an IR drop / rise.

[0009] Typically, battery charging is terminated when the voltage reaches the theoretical SoC 100% point (approximately 1.65 V in the case of Figure 1).

[0010] Under these assumptions, for example, if one cell has a high OCV and the other cells have the same OVC, that one cell may satisfy the overvoltage condition first, causing charging to stop, or the overall average may reach the charge termination condition before the average of the remaining cells, reducing the capacity of the battery. Conversely, a cell with a lower OCV than the average may cause the overall battery capacity to decrease.

[0011] In particular, as shown in the graph 110 of Fig. 1, the two ends of the SOC are inflection points in the OCV-SOC curve, so the deviation may gradually widen. Therefore, in the case of a general battery, it is common to define the SOC or state of charge based on the linear section, rather than the inflection point section at the two ends, as shown in 120 of Fig. 1, as the operation window.

[0012]

[0013] As described above, when the voltage of a specific cell of a battery is higher than that of other cells, it is common to perform balancing to lower the voltage of that cell to solve problems such as a decrease in the capacity of the entire battery.

[0014] However, the inventors of the present invention have discovered that cell balancing based on such measured voltage may actually worsen the overall battery performance. Accordingly, there is a need for a method and system for more efficiently performing cell balancing by distinguishing battery types.

[0015] In order to solve the above-described problem, one aspect of the present invention proposes a method and a system therefor for selectively performing balancing for a specific battery type by recording battery charge / discharge information in a snapshot manner, as if taking a photograph.

[0016] Specifically, in one embodiment of the present invention, by analyzing the cause of a specific cell voltage of a battery being high, the battery type is divided into a first type having high cell internal resistance, a second type having small cell storage capacity, and a third type having low SDR (Self-Discharge Rate) or high current efficiency, and a method and system therefor for performing balancing limited to a third type battery cell are proposed.

[0017] In addition, in one embodiment of the present invention, it is proposed to determine a balancing amount based on the degree to which SDR is low or current efficiency is high, and if balancing is performed using a BMS (Battery Management System), to control the duty ratio of the BMS based on the determined balancing amount.

[0018] In addition, in various embodiments of the present invention, the timing for performing the snapshot as described above is provided by differentiating it according to the type of charge / discharge cycle and the degree of SDR stabilization.

[0019] The problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0020] In one aspect of the present invention for solving the above-described problem, a method for performing cell balancing of a battery is proposed, comprising: applying an initial cycle in which charging and discharging of the battery are repeated a predetermined number of times; recording at least one of a charging current and a charging voltage when charging the battery based on the initial cycle; recording at least one of a discharging current and a discharging voltage when discharging the battery; comparing at least one of the charging current and the charging voltage with at least one of the discharging current and the discharging voltage to distinguish a cell type of the battery; and performing balancing using a power consumption device on a battery cell of a specific cell type among the cell types of the battery.

[0021] In the above-described method, the inventor proposes to refer to recording at least one of the charging current and the charging voltage, and recording at least one of the discharging current and the discharging voltage as a snapshot for snapshot balancing, and the present invention can be described more clearly through this term.

[0022] Accordingly, in another aspect of the present invention, a snapshot balancing method is proposed, which comprises: performing a snapshot, which includes recording at least one of a charging current amount and a charging voltage when charging the battery, and recording at least one of a discharging current amount and a discharging voltage when discharging the battery; and performing balancing to lower the voltage for a specific battery cell having a low Self-Discharge Rate (SDR) or high current efficiency based on the recording according to the snapshot.

[0023] If balancing is applied by distinguishing the types of battery cells, the cell types of the battery may include a first type having high internal cell resistance, a second type having low cell storage capacity, and a third type having low SDR (Self-Discharge Rate) or high current efficiency.

[0024] At this time, it is desirable to perform balancing using the power consumption element in a limited manner on the third type of battery cell among the cell types of the battery.

[0025] Specifically, distinguishing the cell types of the battery may be done by estimating an OCV (Open Circuit Voltage) using at least one of the charging current and charging voltage and at least one of the discharging current and discharging voltage; and distinguishing the second type of battery cell from the third type of battery cell based on whether the OCV differs from other cells during charging or discharging.

[0026] At this time, the OCV of the second type of battery cell may be different from that of other cells at the end of charging, but the OCV may be maintained the same as that of other cells at the end of discharging, and the OCV of the third type of battery cell may be higher than that of other cells both at the end of charging and at the end of discharging.

[0027] Meanwhile, the first type of battery cell can correspond to a battery cell having a larger IR drop or IR rise than other cells when switching between charge and discharge.

[0028] In addition, it may further include estimating a balancing amount based on at least one of a degree to which the SDR of the third type cell is lower than the first reference value or a degree to which the current efficiency of the third type cell is higher than the second reference value, and in this case, it is preferable to perform balancing on the third type cell based on the estimated balancing amount.

[0029] If the power consumption device is a BMS (Battery Management System), performing balancing on the third type cell may include adjusting a duty ratio for operating the BMS based on the estimated balancing amount.

[0030] The above initial cycle is preferably performed at the installation location of the battery, after the battery is shipped in a fully charged state, and during the storage and delivery period of the shipped permanent battery, the SDR of the battery is stabilized.

[0031] Additionally, it is preferable that the snapshot be performed in an area where the SoC (State of Charge) of the battery is 50% or more.

[0032] Additionally, it may include additionally performing the snapshot in a random cycle in which charging and discharging of the battery are performed at an arbitrary level after the end of the initial cycle, in which case it is preferable that the snapshot in the random cycle is performed at a point in time when charging and discharging are switched.

[0033] In the above-described embodiments, when the power consumption device is used as a BMS, it is preferable that the BMS is a type of BMS that performs balancing by consuming the energy of a specific cell of the battery as heat energy.

[0034] The above battery may include a VIB (Vanadium Ion Battery).

[0035] Meanwhile, in another aspect of the present invention, a cell balancing system is proposed, comprising: a charger for applying an initial cycle of repeating charging and discharging a predetermined number of times to a battery including a plurality of cells; a power consuming device configured to perform a balancing operation of lowering the voltage of a specific cell among the plurality of cells; and a processor connected to the charger and the power consuming device, recording at least one of a charging current and a charging voltage when the charger is charging, recording at least one of a discharging current and a discharging voltage when the charger is discharging, comparing at least one of the charging current and the charging voltage with at least one of the discharging current and the discharging voltage to distinguish a cell type of the battery, and controlling balancing to be performed using the power consuming device on a battery cell of a specific cell type among the cell types of the battery.

[0036] In addition, in another aspect of the present invention, a system for performing snapshot balancing of a battery, using the term of the above-described snapshot balancing, is proposed, comprising: a charger for performing charging and discharging of a battery including a plurality of cells; and a processor configured to perform a snapshot, including recording at least one of a charging current amount and a charging voltage when charging the charger and recording at least one of a discharging current amount and a discharging voltage when discharging the charger, and performing balancing to lower the voltage for a specific battery cell having a low Self-Discharge Rate (SDR) or high current efficiency based on the recording according to the snapshot.

[0037] According to the embodiments of the present invention as described above, battery charge / discharge information is recorded in a snapshot manner as if taking a photograph, and balancing is selectively performed for a specific battery type, thereby reducing energy loss and preventing performance degradation due to incorrect balancing.

[0038] In addition, in one embodiment of the present invention, by determining and applying a balancing amount based on the degree to which SDR is low or current efficiency is high, the performance of the entire system can be improved through more precise cell balancing.

[0039] In addition, in various embodiments of the present invention, the timing of performing the snapshot as described above can be differentiated according to the type of charge / discharge cycle and the degree of SDR stabilization, and differential balancing can be applied according to the exact battery state.

[0040] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0041] Figure 1 is a drawing to explain the concept of changes in OCV and measured voltage during charging and discharging of a battery.

[0042] Figure 2 is a drawing for explaining VRFB.

[0043] FIG. 3 is a drawing for explaining VIB as a water-based battery according to one embodiment of the present invention.

[0044] FIG. 4 is a drawing for explaining the configuration of a transition section of a VIB according to one embodiment of the present invention.

[0045] Figure 5 is a diagram for explaining the relationship between the capacity of a battery and the number of ions in an aqueous battery.

[0046] FIG. 6 is a diagram for explaining a method of performing balancing by distinguishing battery types through snapshots according to one embodiment of the present invention.

[0047] FIG. 7 is a diagram for explaining a first type of high cell internal resistance among the causes of high cell voltages according to one embodiment of the present invention.

[0048] FIG. 8 is a drawing for explaining a second type of cause of high cell voltage and small chargeable capacity according to one embodiment of the present invention.

[0049] FIG. 9 is a diagram for explaining a third type of cause of high cell voltage, which is a small SDR or high current efficiency, according to one embodiment of the present invention.

[0050] FIG. 10 is a drawing for explaining a method of performing balancing only for a third type cell according to one embodiment of the present invention.

[0051] FIG. 11 is a drawing for explaining a method for distinguishing cell types of a battery according to one embodiment of the present invention.

[0052] FIG. 12 is a diagram illustrating a method for performing snapshot balancing according to another embodiment of the present invention.

[0053] FIG. 13 is a drawing for explaining the concept of cell balancing using BMS according to one embodiment of the present invention.

[0054] FIG. 14 is a drawing for explaining a method of performing balancing by controlling the duty ratio of a BMS according to one embodiment of the present invention.

[0055] FIG. 15 is a drawing for explaining SDR reduction characteristics according to one embodiment of the present invention.

[0056] Figure 16 is a drawing to explain the concept of a cell type that is difficult to solve by balancing.

[0057] FIG. 17 is a diagram illustrating a method according to one embodiment of the present invention for resolving the constraints described in FIGS. 15 and 16.

[0058] FIG. 18 is a diagram for explaining the timing of performing a snapshot according to one embodiment of the present invention.

[0059] Figure 19 is a graph showing the change in SoH according to the repetition of cycles in LIB.

[0060] FIG. 20 is a block diagram illustrating a system for performing snapshot balancing on a battery according to one embodiment of the present invention.

[0061] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description have been omitted to clearly explain the present invention, and similar parts have been designated with similar reference numerals throughout the specification.

[0062] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0063]

[0064] As described above, in one aspect of the present invention, a method and a system therefor for selectively performing balancing for a specific battery type by recording battery charge / discharge information in a snapshot manner, as if taking a photograph, are proposed.

[0065] This method can be applied to various batteries, but for convenience of explanation, the following description assumes the use of VRFB and VIB developed by the applicant.

[0066] Figure 2 is a drawing for explaining VRFB.

[0067] As illustrated in FIG. 2, the VRFB may include a stack (1) of vanadium-based battery cells, a positive electrode electrolyte tank (2), a negative electrode electrolyte tank (3), and a pump (4) as its basic components.

[0068] The stack (1) has a structure in which unit cells (6) are stacked as shown on the right, and the unit cells (6) may have a structure in which electrodes (9) are formed on both sides with a separator (8) in between, and a current collector (7) is arranged surrounding the electrodes (9).

[0069] In this structure, the structure that generates current is explained. First, the electrolyte (S110) in the electrolyte tank (3) is used to generate a flow of electrolyte (S120) using a pump (4), and this flow of electrolyte moves (S140) to the battery stack (1) through a pipe (S130).

[0070] A battery that generates current by returning the electrolyte to the tank after a vanadium redox reaction occurs within the battery stack (1) can be viewed as a VRFB.

[0071] However, in the case of the VRFB described above, there are problems such as energy consumption of the pump (4), imbalance of ions in the tank (2, 3), occurrence of electrode resistance due to uneven flow of electrolyte, and problems with planted pipelines, which result in reduced energy efficiency.

[0072] FIG. 3 is a drawing for explaining VIB as a water-based battery according to one embodiment of the present invention.

[0073] Referring to FIG. 3, the structurally most significant difference from the VRFB described in FIG. 2 is the absence of a pump (3). Instead, in some embodiments, the VIB (200A) is configured such that the first and second electrolytes can be ion-relocated within the positive electrolyte receptacle (106A) of the first half-cell (204A) and the negative electrolyte receptacle (106B) of the second half-cell (204B), respectively. Various structural modifications are possible, and the ion-relocation is possible because of: an osmotic pressure difference between the two receptacles (106A, 106B); a density change in one or both of the first and second electrolytes; diffusion or migration of one or both of the first and second electrolytes; first and second redox half reactions; and / or expansion or contraction of one or both of the first and second electrolytes due to temperature.

[0074] The inventors have recognized that sufficient stability and power supply and energy output for the VIB can be provided if the cross-sectional thickness of the positive and negative electrolyte receiving portions (106A, 106B) does not exceed a specific value, for example, 20 cm, 15 cm, 10 cm, 5 cm, 2 cm, 1 cm, or a range defined by these values.

[0075] A VIB implemented in this manner can offer various technical and commercial advantages. For example, it can minimize or eliminate failures or reliability issues arising from passages such as pipe / tube joints between the battery cells and the receiving compartment (tank), as well as malfunctions / malfunctions of pumps used to circulate the electrolyte, thereby reducing the need for repairs, safety issues, and operating costs associated with the operation of the VIB (200A). Furthermore, since there is no need for a pump to circulate the electrolyte between the battery cells and the receiving compartment (tank), overall efficiency can be improved.

[0076] The present inventors have discovered that the use of a VIB (200A) can increase power or energy density by 2 to 50 times, depending on its size, by eliminating the electrolyte circulation between the battery cells and the electrolyte tank required in the VRFB described above with reference to FIG. 2. As described above, power or energy density refers to the power or energy density output relative to the total volume of the energy storage device. Therefore, in the case of a VIB, power or energy density refers to the ratio of the total capacity of the VIB to the power or energy output. In addition, since separate equipment such as a tank, pump, and circulation pipe required for the electrolyte circulation system is not necessary, the space occupied by the energy storage device can also be significantly reduced.

[0077] Additionally, the overall system complexity can be significantly reduced, thereby eliminating constraints on the commercial application of VRFBs. For example, unlike the VRFB of FIG. 2, the VIB (200A) can be manufactured in a pack form, similar to lithium-ion batteries, making it suitable for automated processes and mass production. Furthermore, the VRFB of FIG. 2 does not require the design and construction of chemical plants, such as piping and pumps.

[0078] The following describes the general operating principles and characteristics of a redox battery, using a VIB based on vanadium-based redox pairs as an example. However, embodiments of the present invention are not limited thereto, and it will be appreciated that the principles described below are applicable to other types of redox batteries utilizing other types of redox pairs.

[0079]

[0080] As described above, a liquid electrode can be accommodated in the positive electrolyte receiving portion (106A) and the negative electrolyte receiving portion (106B). A separator (112; membrane) is arranged between these electrolyte receiving portions (106A and 106B), and as described below, it can be seen that protons move between the separators (112) to maintain electrical balance between the electrolytes.

[0081] The liquid electrode contains ions in which a redox (i.e., oxidation-reduction) reaction occurs. The first liquid electrode is an electrolyte in which an anode redox couple is dissolved. The anode redox couple can be implemented with a material including at least one of transition metals such as titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), or zinc (Zn), bromine (Br), and cesium (Cs), and the electrolyte of the present embodiments includes vanadium (V) and V. 2+ / V 3+ The redox couple is dissolved.

[0082] The first liquid electrode may be an acidic aqueous solution that conducts current through ionization, preferably containing sulfuric acid.

[0083] In this embodiment, the first liquid electrode can be manufactured by dissolving VOSO4 (vanadylsulfate), V2O5 (vanadium pentoxide) or other suitable substances in an H2SO4 aqueous solution.

[0084] The first liquid electrode causes the first half-reaction. The first half-reaction is as shown in [Chemical Formula 1] below, where the right arrow (→) indicates the direction of the discharge reaction and the left arrow (←) indicates the direction of the charge reaction.

[0085] [Chemical Formula 1]

[0086] V 2+ ←→V 3+ + e-

[0087] In the relationship described above, vanadium divalent ions are oxidized to vanadium trivalent ions during discharge, and vanadium trivalent ions are reduced to vanadium divalent ions during charge.

[0088] Meanwhile, the second liquid electrode is an electrolyte in which the cathode redox couple is dissolved, and in the present embodiments, V 4+ / V 5+ Redox couples may exist.

[0089] The second liquid electrode causes the second half-reaction. The second half-reaction is as shown in [Chemical Formula 2] below, where the right arrow (→) indicates the direction of the discharge reaction and the left arrow (←) indicates the direction of the charge reaction.

[0090] [Chemical Formula 2]

[0091] V 5+ + e - ←→V 4+

[0092] At this time, during discharge, vanadium pentavalent ions are reduced to vanadium tetravalent ions, and during charge, vanadium tetravalent ions are oxidized to vanadium pentavalent ions.

[0093]

[0094] FIG. 4 is a drawing for explaining the configuration of a transition section of a VIB according to one embodiment of the present invention.

[0095] The inventors of the present invention have confirmed that water molecules move from the positive electrode to the negative electrode during the charge / discharge process of vanadium-based batteries. This is due to differences in the hydrophilicity of each vanadium ion.

[0096] The sizes of the hydrates of divalent, trivalent, tetravalent, and pentavalent vanadium ions are 8.24, 8.14, 8.18, and 8.34 Å, respectively. The sizes of divalent and trivalent are relatively smaller than those of tetravalent and pentavalent vanadium ions, which means that the ions at the cathode attract water better (higher hydrophilicity) than the ions at the anode. As the initial vanadium concentration increases, more water molecules move to the cathode.

[0097] As shown in 410 of Figure 4, the form of vanadium hydration shows that divalent ions are hydrated with a greater number of water molecules, which indicates that divalent ions are in a form that attracts water well.

[0098] The VRFB described above with reference to FIG. 2 may be relatively less sensitive to changes in liquid volume because it has a separate electrolyte storage tank. That is, since the VRFB is not a closed volume, the pressure does not increase relatively much even when water moves to the cathode, and thus has the characteristic of not impeding the movement of water.

[0099] Meanwhile, the VIB described above with reference to FIG. 3, unlike this, has the characteristic of being a closed volume, so that changes in the amount of the negative electrolyte due to the osmotic pressure change the pressure within the battery, which can lead to fatal consequences such as damage to the separator (membrane) and electrolyte leakage. To compensate for this, the inventor of the present invention solved this problem through a transition portion (TV; 430) that directly connects the positive and negative electrodes, as illustrated at 420 in FIG. 4.

[0100] The transition portion (430) immediately reacts to the movement of water from the anode to the cathode and transports the same amount of cathode electrolyte toward the anode. At this time, assuming that the cathode electrolyte is uniform within the cell, vanadium ions within the electrolyte tend to be transported from the cathode to the anode. That is, since water, which is a solvent, moves from the anode to the cathode, and the electrolyte containing vanadium ions moves from the cathode to the anode, the vanadium concentration (and sulfate ion concentration) of the cathode electrolyte gradually increases.

[0101] The size of the transition portion (430) is related to the amount of water transferred per cycle (transition portion volume > change in liquid volume), thereby minimizing the decrease in electrolyte efficiency. Nevertheless, in a fully charged state, the concentration difference between the positive and negative electrodes is large, so some of the negative vanadium ions and positive vanadium ions meet, resulting in self-discharge.

[0102] The inventors have confirmed that when the ion concentration at the anode is increased relative to that at the cathode, osmotic pressure reaches equilibrium. This is because the osmotic pressure resulting from the greater number of solutes at the anode offsets the osmotic pressure resulting from the hydration of the divalent ions. Furthermore, this phenomenon is influenced by the concentration of the overall electrolyte, and it has been confirmed that as the concentration increases, the difference in concentration between the anode and cathode must become greater for osmotic pressure equilibrium to be achieved.

[0103]

[0104] Figure 5 is a diagram for explaining the relationship between the capacity of a battery and the number of ions in an aqueous battery.

[0105] As shown in the chemical formulas 1 and 2 above, the chemical reaction of the battery's charge / discharge process can be viewed as one electron moving between the first liquid electrode and the second liquid electrode. In other words, the number of electrons and the number of charged ions can be viewed as being the same.

[0106] Therefore, theoretically, when one electron enters one electrolyte during charging, one electron should come out during discharging, and in the charge / discharge graph illustrated in FIG. 5, the area of ​​the region indicated by the dotted line with the reference numeral 410 should be equal to the sum of the area of ​​the region indicated by the dotted line with the reference numeral 420 and the area of ​​the region indicated by the dotted line with the reference numeral 430.

[0107] However, the actual voltage is measured to be higher during charging and lower during discharging, as shown by the solid line in Fig. 5. This can be attributed to the fact that various forms of ohmic loss occur in the area indicated by the reference numeral 430.

[0108] That is, energy loss may occur because charging at higher pressure and discharging at lower pressure (V=IR).

[0109] As described above, the difference in the area of ​​the area expressed by OCV and the area of ​​the area measured by the actual voltage may occur for the following reasons.

[0110]

[0111] * Membrane crossover

[0112] * SDR

[0113] * Electrolyte movement due to the transition (TV)

[0114]

[0115] As mentioned above, when electrons are not used for the desired reaction, losses occur, and the extent of this loss can be referred to as Coulomb efficiency (CE). In other words, current efficiency can be viewed as an expression of the extent to which undesired reactions occur.

[0116]

[0117]

[0118] The charge-discharge cycle in Figure 5 is depicted as having symmetrical charge and discharge times. However, in reality, the time required for discharging is slightly shorter than the time required for charging. The reason why the charge time is slightly longer than the discharge time in a constant-current cycle can be expressed mathematically as follows.

[0119] [Mathematical Formula 1]

[0120] Charging current X current efficiency = Discharging current

[0121]

[0122] Snapshot balancing based on cell type distinction

[0123] Considering the characteristics such as SDR, current efficiency, battery capacity and ion movement during charge and discharge as described above, one embodiment of the present invention proposes a method of performing cell balancing by distinguishing battery types.

[0124] FIG. 6 is a diagram for explaining a method of performing balancing by distinguishing battery types through snapshots according to one embodiment of the present invention.

[0125] In this embodiment, first, an initial cycle can be applied in which the charging and discharging of the battery is repeated a predetermined number of times (S510). At this time, while applying the initial cycle, it is proposed to record at least one of the charging current and the charging voltage when charging the battery, and to record at least one of the discharging current and the discharging voltage when discharging the battery. In this embodiment, the recording of such information is referred to as a 'snapshot' in the sense that it secures voltage / current information during charging / discharging as if taking a photograph (S520).

[0126] In this embodiment, by comparing one or more of the charging current and charging voltage obtained through such a snapshot with one or more of the discharging current and discharging voltage, the cell type of the battery is distinguished (S530).

[0127] In addition, it is proposed to perform cell balancing (S540) on battery cells of a specific cell type among the cell types of the battery classified in this way, thereby preventing cell balancing from having a negative effect on the overall battery performance as in the prior art, and increasing power efficiency.

[0128] In the above-described method, the cell types of the battery may include a first type having a high internal cell resistance, a second type having a small cell storage capacity, and a third type having a low SDR or high current efficiency, and each type is described in detail below.

[0129]

[0130] FIG. 7 is a diagram for explaining a first type of high cell internal resistance among the causes of high cell voltages according to one embodiment of the present invention.

[0131] Among the multiple cells included in a battery, there may be cells with a higher internal resistance than other cells due to various reasons, such as a problem with the current collector resistance, a problem with the ion permeability of the separator (membrane), or a problem with the solid electrode resistance. In Figure 7, a cell with a higher internal resistance than other cells is depicted as an "abnormal cell" in comparison with a "normal cell."

[0132] In the case of such an ideal cell, when current flows, the voltage appears to be higher than that of other cells when charging due to the difference in IR drop / rise (610), as shown in the graph at reference numeral 610 of FIG. 7. However, the actual amount of current charged is the same as that of other cells (assuming that factors affecting the amount of current, such as current efficiency, SDR, and degree of electrolyte mixing, are the same).

[0133] Drawing reference numeral 620 of FIG. 7 illustrates a case (640) where balancing is applied to such an abnormal cell to force it to match the voltage of other cells. In this case, the amount of current charged to the abnormal cell is reduced compared to other cells, which may result in a lower OCV of the abnormal cell (650). If this balancing continues, the difference in the amount of charging current between the abnormal cell and other cells may become increasingly large.

[0134] Accordingly, in one embodiment of the present invention, it is proposed to control not to perform balancing on a first type cell, which has a higher internal resistance than other cells as described above and thus has a higher voltage measured than other cells when charged, even if the measured voltage is higher than other cells.

[0135] As can be seen in the graph illustrated at reference numeral 610 in FIG. 7, this type 1 cell has a large IR drop / rise (630) due to its higher internal resistance than other cells during charge / discharge, but is identical to other cells in terms of OCV, and therefore does not affect the overall battery performance even without special balancing. In addition, energy efficiency can be increased by eliminating the power that is forcibly consumed through balancing.

[0136] FIG. 8 is a drawing for explaining a second type of cause of high cell voltage and small chargeable capacity according to one embodiment of the present invention.

[0137] Among the multiple cells included in a battery, there may be cases where the chargeable capacity of a cell is lower than that of other cells due to various reasons, such as differences in the amount of electrolyte injected or the presence of unreacted electrolyte. In Figure 8, such cells with lower chargeable capacities are depicted as "abnormal cells" in comparison with "normal cells."

[0138] Since SoC is the ratio of the currently charged capacity to the total chargeable capacity, as shown in the graph illustrated in reference numeral 710 of FIG. 8, even when charged the same amount, such an abnormal cell can be observed to have a high SoC, which can be seen as a higher OCV than other cells.

[0139] However, as indicated in the graph of drawing symbol 710 of Fig. 8, the actual current amount charged is the same for the abnormal cell and the normal cell. (It is assumed that factors affecting the current amount, such as current efficiency, self-discharge rate, and electrolyte mixing degree, are the same.)

[0140] Drawing reference numeral 720 of Fig. 8 illustrates a case (730) where balancing is performed on such an abnormal cell to forcibly adjust the voltage. When balancing is performed on such an abnormal cell to forcibly adjust the current, the amount of current charged decreases compared to other cells, and a deviation may gradually occur.

[0141] Accordingly, in one embodiment of the present invention, it is proposed to control so as not to apply balancing even to a second type cell having a small cell storage capacity as described above. That is, even if a second type cell having an insufficient cell storage capacity is measured to have a higher voltage than other cells, as illustrated in reference numeral 710 of FIG. 8, it will ultimately have the same voltage after discharge, so that there may be no degradation in the performance of the entire battery even if balancing is not performed on the cell. In addition, cell balancing can reduce unnecessary power consumption, thereby increasing energy efficiency.

[0142] FIG. 9 is a diagram for explaining a third type of cause of high cell voltage, which is a small SDR or high current efficiency, according to one embodiment of the present invention.

[0143] Among the multiple cells included in a battery, there may be cells with lower SDR or higher current efficiency (CE) than other cells due to various reasons, such as performance variations in the separator (membrane) or variations in the mixing ratio due to transition region (TV) tolerance. Figure 9 illustrates cells with lower SDR or higher current efficiency as "abnormal cells" in comparison with "normal cells."

[0144] As shown in the graph at reference numeral 810 of FIG. 9, these abnormal cells actually store more current than other cells during charging due to their lower loss. Therefore, as charging and discharging are repeated, the stored energy in these cells gradually increases compared to other cells, potentially leading to a deviation.

[0145] The graph depicted in drawing reference numeral 820 of FIG. 9 illustrates a case where balancing forces current consumption equal to the difference in loss amount. In this case, it indicates that the charging / discharging operation is performed similarly to other cells.

[0146] Therefore, in one embodiment of the present invention, it is assumed that cell balancing is effective for the third type cell, and it is proposed to apply cell balancing to a limited extent to the third type cell among the first to third type cells described above.

[0147] However, the above-described distinctions between the first to third types of cells may overlap with each other within a single battery. That is, a specific battery may contain both the first to third types of cells, and the proportions of each type of cell may differ.

[0148] Therefore, in this document, it is assumed that the 'cell type classification' includes the concept of classification that takes into account the ratio of each cell type contained in a specific battery to determine whether / to what extent subsequent cell balancing operations are applied.

[0149] In addition, the distinction between the first to third type cells described above is explained as a concept for distinguishing cells that exhibit contrasting characteristics, under the assumption that other cells in the battery are normal cells, as described in FIGS. 7 to 9.

[0150]

[0151] FIG. 10 is a drawing for explaining a method of performing balancing only for a third type cell according to one embodiment of the present invention.

[0152] The snapshot balancing proposed in this embodiment proposes to distinguish cell types (S910) based on information acquired through a snapshot (S520) as described above with respect to FIG. 6. Specifically, the cell types can be classified into a first type cell (S920a) in which the voltage is observed to be higher than other cells due to high internal resistance as described above in FIG. 7, a second type cell (S920b) in which the voltage is observed to be higher than other cells due to small cell storage capacity as described above in FIG. 8, and a third type cell (S920c) in which the voltage is observed to be higher than other cells due to low SDR or high current efficiency as described above in FIG. 9.

[0153] In this embodiment, for the reasons described above, it is proposed to consume the current of the third type cell (S920c) only through cell balancing (S930), and among the methods for performing balancing in this way, balancing using a BMS (Battery Management System) can also be performed as described later.

[0154] Of course, the distinction between the first to third type cells as described above can correspond to the distinction according to the ratio of each type of cell in the battery, and in one embodiment of the present invention, it can be applied in a way that cell balancing (S930) is performed on a battery having a high proportion of third type cells in a specific battery.

[0155] Additionally, if cell balancing (S930) can be performed on a cell-by-cell basis within a specific battery, then sensor balancing (S930) may be performed on a limited basis on the third type cells (S920c) as described above.

[0156] FIG. 11 is a drawing for explaining a method for distinguishing cell types of a battery according to one embodiment of the present invention.

[0157] First, the OCV can be estimated using the voltage / current recorded through the snapshots described above (S1010). Based on this OCV, it can be determined whether the OCV differs from other cells during charging or discharging (S1020).

[0158] If the cell is a second type cell (S920b), as described above with respect to Fig. 8, even if the OCV differs from other cells at the end of charging, it exhibits a characteristic in which the OCV remains the same as other cells at the end of discharging. On the other hand, if the cell is a third type cell (S920c), as described above with respect to Fig. 9, the OCV of the cell is higher than other cells at both the end of charging and the end of discharging.

[0159] Therefore, in this embodiment, it is proposed to distinguish between the second type cell and the third type cell based on the presence of such OCV difference, and to perform cell balancing only for the third type cell (S930).

[0160] Meanwhile, the first type cell (920a) described above is a battery cell having a larger IR drop or IR rise than other cells when switching between charge and discharge, and can be distinguished by measuring the IR drop / rise (S1030).

[0161]

[0162] Snapshot balancing according to SDR / CE level

[0163] Snapshot balancing according to the cell type classification described above is a type in which a specific abnormal cell is measured to have a higher voltage than other normal cells, and a method of performing cell balancing limited to the third type cells having low SDR or high CE as described above by distinguishing three cell types was introduced. At this time, balancing for the third type cells can be performed based on a balancing amount determined according to the degree of low SDR / high CE.

[0164] Meanwhile, in another embodiment of the present invention, a method is proposed to apply cell balancing based on the degree to which SDR is low and CE is high, without specifically considering the degree to which a specific cell has a higher voltage than other cells as described above.

[0165] FIG. 12 is a diagram illustrating a method for performing snapshot balancing according to another embodiment of the present invention.

[0166] The snapshot balancing method according to the present embodiment is performed in the same manner as performing a snapshot (S1110), which includes first recording at least one of a charging current amount and a charging voltage when charging a battery, and then recording at least one of a discharging current amount and a discharging voltage when discharging the battery.

[0167] Thereafter, based on the record according to the snapshot, balancing is performed (S1140) to lower the voltage for a specific battery cell (S1120) having a low SDR or high current efficiency. That is, unlike the snapshot balancing based on the cell type classification described above, it is proposed to perform cell balancing on a specific cell based on the classification of a specific cell having a low SDR or a high CE.

[0168] Specifically, it is proposed to estimate a balancing amount based on at least one of the degree to which the SDR of a specific cell is lower than a first reference value or the degree to which the current efficiency is higher than a second reference value (S1130), and to perform balancing on the cell based on the thus estimated balancing amount (S1140). At this time, the 1 / 2 reference value used may be set differently depending on the temperature.

[0169] FIG. 13 is a drawing for explaining the concept of cell balancing using BMS according to one embodiment of the present invention.

[0170] Typically, for battery series systems, balancing can be achieved by placing a BMS to compensate for performance differences between batteries by diverting some of the current flowing to a specific battery cell and consuming energy.

[0171] BMS used for this cell balancing include active BMS that returns the bypassed energy back to the battery and utilizes it as energy, and passive BMS that converts the bypassed energy into heat energy and dissipates it.

[0172] In one embodiment of the present invention, it is proposed to use a passive BMS among the types of BMS described above to reduce system complexity, and when such a passive BMS is used, there is an advantageous aspect in applying it to an ESS (including electric vehicle batteries) with a large number of batteries.

[0173] Because BMSs tend to consume energy, the voltage of corresponding cells tends to drop during operation. In other words, a typical BMS operates on cells with higher voltages. Operation during charging and discharging can differ, and this can be determined by the strategies of each BMS manufacturer.

[0174] Conventional lithium-ion battery (LIB) BMSs usually operate passively only for cells whose voltage is above a certain standard when fully charged.

[0175] Figure 13 is a simplified circuit diagram illustrating a case where a passive BMS is used among the active / passive BMSs described above. As shown in Figure 13, if only the BMS portion of the circuit is separated, it can be seen that current flows in only one direction, regardless of charging or discharging.

[0176] According to Kirchhoff's law, current can be viewed as flowing, influenced by the current voltage of the battery and the resistance of the power-consuming element. Since the battery voltage does not become negative during charging or discharging, the current direction can be viewed as the same, as shown in Fig. 13. That is, the current in the BMS always flows in one direction, and when balancing is performed, as shown in Fig. 13, a portion of the current flowing into the battery is bypassed, and it can be viewed as an element that consumes power through the power-consuming element.

[0177] Therefore, if balancing is performed using a BMS on a cell type for which balancing is not suitable as described above, energy loss may occur.

[0178] FIG. 14 is a drawing for explaining a method of performing balancing by controlling the duty ratio of a BMS according to one embodiment of the present invention.

[0179] As described above with respect to FIG. 12, the amount of balancing can be determined based on at least one of the degree to which the SDR per cell of the battery is lower than the first reference value or the degree to which the current efficiency is higher than the second reference value, and the present embodiment proposes to adjust the duty ratio of the BMS accordingly.

[0180] That is, as illustrated in Fig. 14, the cycle for turning on the BMS corresponding to a specific cell with low SDR or high current efficiency can be controlled based on the aforementioned balancing amount. In addition, it is also possible to perform a similar form of PWM (Pulse Width Modulation) control.

[0181]

[0182] Conditions for applying snapshot balancing

[0183] Snapshot balancing as described above must take into account the following characteristics:

[0184] Most batteries tend to have unstable SDR and capacity in the early cycles, and snapshots that do not take this SDR and capacity instability into account can lead to problems such as incorrect cell type classification and incorrect balancing amount estimation.

[0185] FIG. 15 is a drawing for explaining SDR reduction characteristics according to one embodiment of the present invention.

[0186] In relation to the SDR issue described above, the inventors of the present invention have confirmed that SDR decreases during a process of maintaining a high voltage for a certain period of time during the charging stage prior to battery storage. Reference numeral 1510 of Fig. 15 illustrates a graph of SDR reduction according to CV (Constant Voltage) charging time. As shown in reference numeral 1510, it can be confirmed that SDR saturation gradually occurs as the CV charging time increases.

[0187] Additionally, it can be confirmed that the higher the CV voltage, the faster the saturation state is reached. For example, a faster SDR decline trend can be observed when a CV voltage of 1.5 V is applied compared to when a CV voltage of 1.4 V is applied.

[0188] Meanwhile, drawing reference numeral 1520 of FIG. 15 illustrates a graph of SDR reduction according to idle time. As shown in drawing reference numeral 1520, it can be confirmed that SDR saturation is gradually achieved as the idle time increases.

[0189] However, both methods illustrated in FIG. 15 require a significant amount of time to stabilize the SDR, potentially reducing the operational efficiency of the aqueous battery. One embodiment of the present invention proposes a method for securing CV charging time and a method for securing idle time, utilizing a method for securing idle time, but securing this idle time as the time taken for the aqueous battery to be stored and / or delivered to the installation site after manufacturing. Accordingly, snapshot balancing is proposed as a method for performing initial cycles while the SDR is stable.

[0190]

[0191] Figure 16 is a drawing to explain the concept of a cell type that is difficult to solve by balancing.

[0192] Among the multiple cells included in a battery, there may be cells with a higher SDR or lower current efficiency than other cells due to various reasons, such as variations in the performance of the separator (membrane) or variations in the mixing ratio due to the transition region (TV) tolerance. Figure 16 depicts such a specific cell as an abnormal cell, comparing it with a normal cell and the changes in measured voltage / OCV.

[0193] As illustrated in Figure 16, abnormal cells have lower voltages than normal cells, which can lead to performance degradation due to deviations occurring without an opportunity for balancing. One embodiment of the present invention proposes managing such cells so that they are deemed defective from a quality control perspective and can be replaced.

[0194]

[0195] FIG. 17 is a diagram illustrating a method according to one embodiment of the present invention for resolving the constraints described in FIGS. 15 and 16.

[0196] In the method according to the present embodiment, a battery cell block is first manufactured (S1710). Here, the term "cell block" is assumed to refer to a form in which multiple cells are stacked. The VIB described above can be viewed as a concept corresponding to a monoblock. However, the aqueous battery according to the present embodiment may be of various types other than VIB, and is not limited thereto.

[0197] Each cell can assume a structure in which multiple layers are stacked, where the 'layers' can correspond to the separator, solid electrode, current collector, etc. in the VRFB and VIB described above with reference to FIGS. 2 and 3.

[0198] Thereafter, the method according to the present embodiment can perform quality control by repeating charging and discharging on the manufactured cell block a predetermined number of times (S1520). In this quality control step (S1520), as described above with respect to FIG. 16, it is proposed to classify abnormal cells with high SDR / low current efficiency that cannot be resolved by cell balancing as type 4 cells (S1530) and replace such cells.

[0199] Meanwhile, the method according to the present embodiment proposes that cell blocks that have passed the above-described quality control criteria be shipped at a state of charge exceeding a predetermined standard (S1540). Preferably, this state of charge exceeding the predetermined standard may correspond to a fully charged state of the cell block, but may also be interpreted as ensuring the maximum possible state of charge based on the state of the charger and / or cell block that can be performed in the quality control step (S1520).

[0200] Thereafter, the method according to the present embodiment proposes to install the cell block at the installation location (S1550) in a state in which the SDR of the cell block is stabilized during the storage and / or delivery period of the shipped cell block. That is, as described above with reference to the drawing reference numeral 1520 of FIG. 15, it is proposed to secure the SDR saturation state of the water-based battery at the time of installation by securing the idle period through the storage and / or delivery period of the shipped cell block.

[0201] For batteries that have achieved SDR stabilization during storage and / or shipping, more accurate cell type differentiation is possible when an initial balancing cycle is applied to perform snapshots (S1560).

[0202] Afterwards, the cell types are distinguished as in the above-described embodiment (S1570), the first to third type cell blocks are distinguished as described above (S1580a to S1580c), and BMS-based balancing can be performed in a limited manner for the third type cell blocks (S1590).

[0203]

[0204] FIG. 18 is a diagram for explaining the timing of performing a snapshot according to one embodiment of the present invention.

[0205] The snapshot according to the above-described embodiments suggests performing snapshots (voltage recording) in the buffer range in normal situations, and in the case of VIB, it is desirable to perform snapshots around an average of about 1.55 V.

[0206] Even if snapshots are performed before the charge reaches full capacity, we recommend performing snapshots at 50% or higher of the SoC, if possible. In the case of aqueous batteries, ion placement tends to be a probabilistic problem at low SoCs, leading to significant deviations.

[0207] In a preferred embodiment of the present invention, it is proposed that the snapshot record be performed at the point in time when charging is terminated during a charge / discharge cycle.

[0208] Meanwhile, as illustrated in FIG. 18, when the initial full cycle test (1810) is completed during actual battery use, it is highly likely that the battery will operate in a random cycle (1820). Therefore, there is a need to perform snapshots even in situations other than the full-charge point, and one embodiment of the present invention proposes performing snapshots at the charge-discharge transition point (1830) in such a random cycle.

[0209] Assuming that the internal resistance of the cell does not change during charging and discharging, the OCV can be estimated as follows.

[0210] [Equation 2]

[0211] OCV = V 충전종료 - {I 충전 / (I 충전 +I 방전 )X ΔV IR drop

[0212] Additionally, if there is a rest time (1840) as shown in FIG. 18, a snapshot may be possible depending on the SoC.

[0213]

[0214] Snapshot balancing according to the embodiments described above has the advantage of increasing energy efficiency by reducing power consumption in power-consuming devices such as BMS by not balancing cells that do not require balancing.

[0215] Additionally, it is possible to efficiently detect abnormal cells and determine the degree of deviation, and implement a balancing method that allows for adjustment of the amount of balancing based on the degree of deviation. Furthermore, once the balancing amount is determined, the balancing operation can be performed continuously during charging or discharging.

[0216] Accordingly, balancing operations can be performed for a longer period of time compared to BMSs that operate instantaneously based on voltage measurement. In other words, it is possible to achieve a large balancing effect even with a small allowable current.

[0217] However, snapshot balancing, as described above, can be seen as an advantageous approach when applied to VIBs, where capacity remains nearly 100%. Lithium-based batteries, however, require additional variables because their capacity fluctuates due to the State of Health (SoH), making control difficult.

[0218] Figure 19 is a graph showing the change in SoH according to the repetition of cycles in LIB.

[0219] Among the various methods for estimating SoH, the method of analyzing the capacity difference versus the voltage difference (dQ / dV) is being used.

[0220] Figure 19 shows that as the cycle is repeated for LIB, the dQ / dV curve moves to the right with respect to voltage, and the maximum value gradually decreases.

[0221] The reason why the maximum value decreases as the deterioration progresses is that as the deterioration progresses in DQ / DV, the DV value at the same DQ point increases, so the overall DQ / DV value decreases.

[0222] Also, the reason why the curve moves to the right as the deterioration increases is because the internal resistance increases with deterioration, so when DQ / DV is the same, the DV value increases. In other words, when charging the same amount of capacity, the amount of change in voltage increases, which means that the amount of change increases when viewed based on the voltage on the x-axis, and accordingly, the graph appears to move to the right.

[0223] Considering the SoH characteristics of such LIBs, the capacity of the battery decreases and the internal resistance increases depending on the state of SoH, so there is a disadvantage in that the control becomes complicated by additional consideration of SoH at the time of performing the snapshot.

[0224] Therefore, in one embodiment of the present invention, it is proposed to apply the above-described snapshot balancing to a water-based battery, preferably a VIB as described above in FIG. 4.

[0225]

[0226] FIG. 20 is a block diagram illustrating a system for performing snapshot balancing on a battery according to one embodiment of the present invention.

[0227] First, the battery (2010) on which snapshot balancing is performed according to the present embodiment includes a plurality of cells, and is preferably a battery with a small capacity change according to SoH, such as VIB.

[0228] Additionally, the snapshot balancing system according to the present embodiment includes a charger (2020) and can apply an initial cycle of repeating charging and discharging a predetermined number of times to the battery (2010) as described above with respect to FIG. 18, or a random cycle performed after the initial cycle.

[0229] In addition, the snapshot balancing system according to the present embodiment includes a power consumption device (2030) configured to apply balancing to each cell of the battery (2010), and as an example, a BMS can be used as the power consumption device (2030) as described above with reference to FIG. 13.

[0230] Additionally, the snapshot balancing system according to the present embodiment may include a processor (2040) configured to be connected to the charger (2020), power consumption device (2030), and battery (2010) as described above.

[0231] The processor (2040) may be configured to distinguish cell types and apply balancing to specific cell types in a limited manner based on information acquired through snapshots as described above with respect to FIG. 10.

[0232] In addition, the processor (2040) may be configured to determine the amount of balancing based on the degree of low SDR and high current efficiency, regardless of the cell type, as described above with respect to FIG. 11, and perform balancing using the power consumption element (2030) accordingly.

[0233]

[0234] The detailed description of the preferred embodiments of the present invention disclosed above has been provided to enable those skilled in the art to implement and practice the present invention. While the above description has been made with reference to preferred embodiments of the present invention, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the scope of the present invention. For example, those skilled in the art can utilize the individual components described in the above-described embodiments in combination with each other.

[0235] Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0236] Snapshot balancing according to embodiments of the present invention as described above can be utilized not only for VIB but also for various batteries to be developed in the future with improved SoH performance.

Claims

1. A method for performing cell balancing of a battery, Apply an initial cycle of repeating charging and discharging of the above battery a predetermined number of times. Based on the above initial cycle, When charging the above battery, record at least one of the charging current and the charging voltage; When discharging the above battery, at least one of the discharge current and discharge voltage is recorded; Comprising distinguishing the cell type of the battery by comparing at least one of the charging current and charging voltage with at least one of the discharging current and discharging voltage; and A method for balancing cells of a battery, comprising performing balancing using a power consumption element on a battery cell of a specific cell type among the cell types of the above battery.

2. In paragraph 1, The cell type of the above battery is, A method for balancing cells of a battery, comprising a first type having high internal cell resistance, a second type having small cell storage capacity, and a third type having low Self-Discharge Rate (SDR) or high current efficiency.

3. In paragraph 2, A method for cell balancing of a battery, which performs balancing in a limited manner using the power consumption element on a battery cell of the third type among the cell types of the battery.

4. In paragraph 2, Distinguishing the cell types of the above batteries is: Estimating the OCV (Open Circuit Voltage) using at least one of the above charging current and charging voltage and at least one of the above discharging current and discharging voltage; A method for balancing cells in a battery, wherein the second type of battery cell and the third type of battery cell are distinguished based on whether the OCV differs from other cells during charging or discharging.

5. In paragraph 4, A method for balancing cells of a battery, wherein the OCV of the second type of battery cell is maintained to be the same as that of the other cells when discharge is terminated, even if the OCV of the second type of battery cell is different from that of the other cells when charge is terminated.

6. In paragraph 4, A method for balancing cells of a battery, wherein the OCV of the third type of battery cell is higher than that of other cells both at the end of charging and at the end of discharging.

7. In paragraph 2, A method for balancing cells in a battery, wherein the first type of battery cell is a battery cell having a larger IR drop or IR rise than other cells during the transition between charge and discharge.

8. In paragraph 3, It additionally includes estimating a balancing amount based on at least one of the degree to which the SDR of the third type cell is lower than the first reference value or the degree to which the current efficiency of the third type cell is higher than the second reference value. Balancing is performed on the above third type cells, A method for balancing cells of a battery, performed based on the estimated above balancing amount.

9. In paragraph 8, The above power consumption device includes a BMS (Battery Management System), Balancing is performed on the above third type cells, A method for balancing cells in a battery, comprising adjusting a duty ratio for operating the BMS based on the estimated balancing amount.

10. In paragraph 1, The above initial cycle is, A method for cell balancing of a battery, wherein the battery is shipped in a fully charged state, and during the storage and delivery period of the shipped permanent battery, the SDR of the battery is stabilized, and is performed at the installation location of the battery.

11. In paragraph 1, Record at least one of the above charging current and charging voltage; Recording one or more of the above discharge current and discharge voltage, A method of balancing cells in a battery corresponding to snapshots for snapshot balancing.

12. In paragraph 11, A method for cell balancing of a battery, wherein the above snapshot is performed in an area where the SoC (State of Charge) of the battery is 50% or more.

13. In paragraph 11, A method for balancing cells of a battery, comprising additionally performing said snapshots in random cycles in which charging and discharging of said battery are performed at any level after completion of said initial cycle.

14. In paragraph 13, A method for balancing cells in a battery, wherein the snapshot is performed at the transition point between charge and discharge in the above random cycle.

15. In paragraph 1, The above power consumption components include a BMS, A method for balancing cells in a battery, wherein the BMS is a type of BMS that performs balancing by consuming the energy of a specific cell of the battery as heat energy.

16. In paragraph 1, The above battery is a method for balancing cells of a battery including a VIB (Vanadium Ion Battery).

17. In a system for performing cell balancing of a battery, A charger for applying an initial cycle of repeating charging and discharging a predetermined number of times to a battery containing multiple cells; A power consuming device configured to perform a balancing operation for lowering the voltage of a specific cell among the plurality of cells; and Connected to the above charger and the above power consumption device, A cell balancing system comprising a processor that records at least one of a charging current and a charging voltage when the charger is charging, records at least one of a discharging current and a discharging voltage when the charger is discharging, compares at least one of the charging current and the charging voltage with at least one of the discharging current and the discharging voltage to distinguish the cell type of the battery, and controls balancing to be performed using the power consumption device on a battery cell of a specific cell type among the cell types of the battery.

18. In paragraph 17, The above power consuming device is a cell balancing system including a BMS (Battery Management System).

19. In paragraph 17, The above processor, The cell type of the above battery, A cell balancing system configured to distinguish between one of the following cell types: a first type having high internal cell resistance, a second type having small cell storage capacity, and a third type having low Self-Discharge Rate (SDR) or high current efficiency.

20. In paragraph 19, The above processor, A cell balancing system configured to perform limited balancing using the BMS on battery cells of the third type among the cell types of the above battery.

21. In paragraph 19, The above processor, Estimating a balancing amount based on at least one of a degree to which the SDR of the third type cell is lower than the first reference value or a degree to which the current efficiency of the third type cell is higher than the second reference value; A cell balancing system configured to control the power consuming elements based on the estimated balancing amount.

22. In paragraph 21, The above power consumption device includes a BMS (Battery Management System), A cell balancing system, wherein the processor is configured to adjust a duty ratio for operating the BMS based on the estimated balancing amount.

23. In paragraph 22, The above BMS is a cell balancing system, a type of BMS that performs balancing by consuming the energy of a specific cell of the battery as heat energy.

24. In paragraph 17, The above battery includes a VIB (Vanadium Ion Battery), The above VIB is, First electrode and second electrode using aqueous electrolyte; a separator between the first electrode and the second electrode; and A cell balancing system comprising a transition unit for moving the aqueous electrolyte of the first electrode to the second electrode.

25. A method for performing snapshot balancing of a battery, Performing a snapshot, which includes recording at least one of a charging current amount and a charging voltage when charging the battery, and recording at least one of a discharging current amount and a discharging voltage when discharging the battery; and A snapshot balancing method, comprising: performing voltage-lowering balancing on a specific battery cell having a low Self-Discharge Rate (SDR) or high current efficiency based on a record according to the snapshot.

26. In paragraph 25, It additionally includes estimating a balancing amount based on at least one of the degree to which the SDR of the specific battery cell is lower than a first reference value or the degree to which the current efficiency of the specific battery cell is higher than a second reference value, Performing the above balancing is: A snapshot balancing method performed based on the estimated above balancing amount.

27. In paragraph 25, Performing the above balancing is: A snapshot balancing method comprising controlling current from said specific battery cell to bypass and pass through a power consuming device.

28. In paragraph 26, Performing the above balancing is: A snapshot balancing method comprising adjusting a duty ratio for operating a BMS (Battery Management System) connected to the specific battery cell based on the estimated balancing amount.

29. In a system that performs snapshot balancing of batteries, A charger for performing charging and discharging on a battery comprising multiple cells; and When charging the charger, a snapshot is performed including recording at least one of the charging current and the charging voltage, and when discharging the charger, at least one of the discharging current and the discharging voltage is recorded. A snapshot balancing system, comprising a processor configured to perform voltage-lowering balancing for a specific battery cell having a low Self-Discharge Rate (SDR) or high current efficiency based on records according to the snapshot.

30. In paragraph 29, The above processor, A snapshot balancing system configured to estimate a balancing amount based on at least one of a degree to which the SDR of the specific battery cell is lower than a first reference value or a degree to which the current efficiency of the specific battery cell is higher than a second reference value, and to perform balancing on the specific battery cell based on the estimated balancing amount.

31. In paragraph 29, In addition, power consumption components are included, A snapshot balancing system, wherein the processor controls current from a specific battery cell to bypass and pass through the power consuming device when performing balancing on the battery cell.

32. In paragraph 30, In addition, it includes a plurality of BMS (Battery Management Systems) connected to the above plurality of cells, The above processor, A snapshot balancing system that adjusts the duty ratio of operating the BMS connected to the specific battery cell among the plurality of BMSs based on the estimated balancing amount.

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