A complete system, specifically for a vehicle, including a lithium-ion battery and a battery management system to control fast charging
The battery management system uses a continuous function to adjust charging current based on internal temperature and initial state of charge, addressing inconsistent charging times and lithium deposition in lithium-ion batteries, ensuring consistent performance and user convenience.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- AUTOMOTIVE CELLS CO SE
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing fast charging protocols for lithium-ion batteries result in inconsistent charging times and lithium deposition, leading to user inconvenience and battery degradation, especially when the initial state of charge is just above or below a certain threshold.
A battery management system calculates a corrected state of charge parameter using a continuous function that considers the internal temperature and initial state of charge, ensuring consistent charging times and minimizing lithium deposition by adjusting the charging current based on a single 'map' without discontinuities.
This approach ensures consistent charging times and reduces lithium deposition, enhancing battery usability and user experience by eliminating the need for multiple charging protocols based on initial state of charge thresholds.
Smart Images
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Abstract
Description
Title of the invention: An assembly, particularly for a vehicle, comprising a lithium-ion battery and a battery management system for controlling fast charging
[0001] DOMAIN
[0002] The present invention relates to an assembly, particularly for vehicles, comprising a lithium-ion battery and a battery management system.
[0003] The invention also relates to a vehicle comprising such an assembly, as well as a corresponding method for charging the battery. EARLIER ART
[0004] The term "battery" usually refers to a plurality of electrochemical cells electrically connected to each other. According to a particular example of a battery, the plurality of electrochemical cells is arranged in the form of one or more module(s), each module comprising several electrochemical cells electrically connected to each other and mechanically assembled.
[0005] An electrochemical cell typically comprises, in particular, a plurality of positive electrodes intertwined with negative electrodes and separators, called a "stack" when they are cut into pieces, or a "jelly roll" when they are continuously wound together. The positive electrodes are connected to each other and to a positive terminal of the cell, and the negative electrodes are connected to each other and to a negative terminal of the cell.
[0006] The battery is intended to supply an electric current when in use, to be inactive during a rest period, or to be charged by receiving a current or power from a charging system for a charging period.
[0007] The negative electrodes contain, for example, graphite, or a mixture of graphite and silicon, which are capable of releasing lithium ions Li+ and electrons during discharge, and doing the opposite during the charging period.
[0008] During battery operation, lithium plating can occur on the surface of the negative electrodes, constituting a battery degradation mechanism with a negative impact on performance. To prevent this lithium plating, a known technique consists of designing the negative electrodes so that they overlap the positive electrodes, and ensuring that no negative electrode is shorter than a neighboring positive electrode.
[0009] In order to reduce charging time, a specific fast charging protocol is designed for high-power charging stations. To control fast charging, a "map" is often used. The "map" is a set of data providing, for example, a maximum input current based on the battery's internal temperature and its state of charge (or alternatively, its open-circuit or operating voltage). During battery charging, the state of charge increases, the internal temperature changes, and the charging current is frequently readjusted to a value prescribed by the "map." By considering the state of charge, temperature, and charging current as coordinates of a point, the point moves across the "map" over time during charging.
[0010] Alternatively, instead of a "map", an equivalent function or algorithm may be used, which are based on the internal temperature and the state of the load (or the open-circuit voltage).
[0011] Using a single card does not optimize charging time in all cases, for example, when starting charging with a completely discharged battery or when starting charging with a 20% state of charge, while avoiding lithium deposition in all cases. To reduce charging time, it is known to use two separate "cards":
[0012] - a first "map" if the initial state of charge of the battery (before charging) is below a given limit, for example 20% (as a percentage of a maximum or nominal battery charge), and
[0013] - a second "card" if the initial state of charge is greater than or equal to the limit data.
[0014] Figure 1 is a graph showing two curves, Cl and C2, corresponding to two "maps." Each of these curves, Cl and C2, gives a charging current I as a function of the battery's state of charge (SOC). In this example, if the initial state of charge is 20%, the charge follows curve Cl from point A to the right. If the initial state of charge is 19%, the charge follows curve C2 from point B to the right.
[0015] This method results in fast charging occurring quite differently depending on whether the battery's initial state of charge is just above or just below the limit. For example, depending on whether the state of charge is 19% or 20%, fast charging takes approximately 30 minutes longer on curve C2 compared to curve C1, which can be confusing, or even unpleasant, for the user. Indeed, the user may have to wait an extra 30 minutes for a full charge even though the battery was initially only 1% discharged (19% instead of 20%).
[0016] An object of the invention is therefore to solve or improve the above problems, in particular to provide a lithium-ion battery assembly and a battery management system in which lithium deposition does not occur or is reduced, while preserving battery usability during charging. Summary of the invention
[0017] To this end, the invention relates to an assembly, particularly for a vehicle, comprising:
[0018] - a lithium-ion battery intended to supply current during use, and to be at rest, or to be charged by receiving a current or power from a charging system for a charging time, and
[0019] - a battery management system adapted to control the current or power during the charging time, the battery management system being configured to calculate a first parameter representing the current or power using at least a second parameter representing an internal temperature of the battery, and a third parameter SOC' belonging to a predefined definition interval,
[0020] in which the battery management system is configured to calculate the third parameter SOC' from a fourth parameter SOC representing a state of charge of the battery and a fifth parameter SOC0 representing an initial state of charge of the battery, with SOC' = F(SOC, SOC0), where F(SOC, SOC0) is a continuous function with respect to the fifth parameter SOC0 and F(SOC, SOC0) belongs to the definition interval.
[0021] According to particular embodiments, the assembly comprises one or more of the following features, taken alone or in all technically possible combinations:
[0022] - the battery management system is configured so that, regardless of the values of the fourth parameter SOC and the fifth parameter SOC0, the difference SOC' - SOC has a constant sign, and is preferably positive or zero;
[0023] - the battery management system is configured so that, if SOC0 belongs to the interval of definition, then SOC' = SOC;
[0024] - the interval of definition is [LIM1;LIM2], LIM1 and LIM2 being two values predefined, the battery management system being configured so that, if SOC0 belongs to another predefined interval adjacent to the definition interval, then:
[0025] . SOC' = SOC + D(SOCo), if SOC + D(SOC0) is within the interval of definition,
[0026] . SOC' = LIM1 if SOC + D(SOC0) < LIM1,
[0027] . SOC' = LIM2 if SOC + D(SOC0) > LIM2,
[0028] D being a shift function depending on the fifth parameter SOC0, and being independent of the fourth parameter SOC;
[0029] - the other interval has an upper bound equal to LIM1, the management system of battery being configured so that, if SOC0 belongs to the other interval, then
[0030] SOC' = Min(SOC + LIM1 - SOC0 ; LIM2), «Min» being the «minimum» function;
[0031] - LIM1 is between 10% and 30%, preferably between 15% and 25%, of a state of nominal or maximum battery charge;
[0032] - LIM2 is equal to 100% of a nominal or maximum state of charge of the battery; and
[0033] - the battery comprises a plurality of electrically connected positive electrodes a positive terminal of the battery, a plurality of negative electrodes electrically connected to a negative terminal of the battery and intertwined with the positive electrodes, and layers of electrolyte to form at least one stack extending along a stacking direction, the negative electrodes having a larger dimension than the positive electrodes perpendicular to the stacking direction.
[0034] The invention also relates to a vehicle comprising an assembly as described above.
[0035] The invention also relates to a charging method comprising the following steps:
[0036] - obtaining an assembly or vehicle as described above,
[0037] - control, by the battery management system, of the current or power during charging time,
[0038] - calculation, by the battery management system, of the third parameter SOC' from of the fourth parameter SOC representing a state of charge of the battery and of the fifth parameter SOC0 representing an initial state of charge of the battery, with SOC' = F(SOC, SOC0), where F(SOC, SOC0) is a continuous function with respect to the fifth parameter SOC0, and F(SOC, SOC0) belongs to the interval of definition, and
[0039] - calculation, by the battery management system, of the first parameter representing the current or power using at least the second parameter representing the internal temperature of the battery, and the third parameter SOC'. Brief description of the drawings
[0040] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings, in which:
[0041] [Fig.1] [Fig.1] is a graph showing two "maps" used in the prior art, and also illustrates calculations performed by a battery management system of an assembly according to the invention, the calculations using one of the two "maps",
[0042] [Fig.2] [Fig.2] is a schematic view of a vehicle comprising an assembly according to the invention,
[0043] [Fig.3] [Fig.3] is a schematic view of a detail of the battery shown in [Fig.2], and
[0044] [Fig.4] [Fig.4] is a block diagram illustrating calculations performed by the battery management system shown in [Fig.2]. DETAILED DESCRIPTION Vehicle
[0045] With reference to [Fig.2], a vehicle 10 according to the invention is described.
[0046] Vehicle 10 is, for example, an electric or hybrid car or truck.
[0047] The vehicle 10 includes a motor 12 and an assembly 14 adapted to supply an electric current 16 to the motor.
[0048] The assembly 14 includes a lithium-ion battery 18, and a battery management system 20 (in English “battery management system” or BMS).
[0049] The assembly 14 is advantageously suited for performing a rapid charge of the battery 18.
[0050] By “fast charging” is meant, for example, a charge from 10% to 80% of the maximum charge of the battery 18 in a period of 25 minutes or less. Battery
[0051] The battery 18 is intended to supply the current 16 in use, to be at rest, or to be charged by receiving a charging current 22 or power from the charging system 24 for a charging time.
[0052] The battery 18 includes, for example, a positive terminal 26 and a negative terminal 28 adapted to be selectively connected to the charging system 24 and the motor 12.
[0053] The battery 18 advantageously comprises a plurality of positive electrodes 30 electrically connected to the positive terminal 26, and a plurality of negative electrodes 32 electrically connected to the negative terminal 28 and intertwined with the positive electrodes. The battery 18 advantageously comprises layers of electrolyte 34 extending between the positive electrodes 30 and the negative electrodes 32.
[0054] As shown in [Fig.3], the positive electrodes 30, the negative electrodes 32 and the electrolyte layers 34 form, for example, at least one stack 36 extending along a stacking direction S.
[0055] The negative electrodes 32 advantageously have a larger size than the positive electrodes 30 perpendicular to the stacking direction S. Advantageously, the negative electrodes 32 overlap the positive electrodes 30 by a distance D, for example between 0.1 and 3 mm.
[0056] In practice, the battery 18 can comprise several electrochemical cells (not shown) containing several stacks. Battery management system
[0057] The battery management system 20 includes, for example, a memory 38 and a processor 40. The memory 38 contains instructions which, when read by the processor 40, cause the battery management system 20 to perform the following operations.
[0058] The battery management system 20 is adapted to control the current 22 or the power during the charging time.
[0059] The battery management system 20 is configured to calculate a first parameter I representing the current 22 or the power using at least a second parameter T representing an internal temperature of the battery 18, and a third parameter SOC' belonging to a predefined definition range.
[0060] By "representative parameter of X", we mean a parameter which is advantageously X itself, or from which X can be obtained.
[0061] The calculation uses, for example, a "map" such as that shown by curve Cl in [Fig. 1]. Such a curve Cl is an example, known to those skilled in the art, allowing, from a state of charge SOC', here expressed as a percentage of the maximum state of charge of the battery 18, the parameter I, here expressed in amperes. For example, if SOC' is approximately 50%, I is approximately 150 amperes.
[0062] In the example, to simplify the discussion, the "map" has been represented for an internal temperature T of 25°C, which leads to the curve CL. In practice, we place ourselves for example on a curve taking into account the internal temperature T of the battery 18, which may be different from 25 °C.
[0063] The curve Cl is for example decreasing and continuous with respect to the variable SOC'.
[0064] The definition range advantageously goes from a value LIM1, for example 20% on [Fig.1], to a value LIM2, for example 100%.
[0065] Alternatively, also known in itself to the person skilled in the art, the battery management system 20 implements an algorithm or a data block enabling the first parameter I to be obtained, directly or by interpolation, from the second parameter T and the third parameter SOC'.
[0066] The battery management system 20 is configured to calculate the third parameter SOC' from a fourth parameter SOC representing a (real) state of charge of the battery 18 and a fifth parameter SOC0 representing an initial state of charge of the battery 18 (at the beginning of charging), with SOC' = F(SOC, SOC0), where F is a continuous function with respect to the fifth parameter SOC0 and F(SOC, SOCo) belongs to the interval of definition.
[0067] The function F is advantageously suited to provide a "corrected" parameter SOC' that is within the definition interval. The battery management system 20 can calculate the first parameter I from SOC' and T advantageously without discontinuity related to SOC0, for example without a conditional test on SOC0. This avoids having to resort, for SOC0 values located outside the definition interval, to another "map", such as that represented by curve C2.
[0068] In other words, thanks to the function F, only one "map" is advantageously used. The calculation of the first parameter I from the second parameter T and the third parameter SOC' is advantageously not conditioned by the value of SOC0, since, even if SOC0 is outside the definition interval, SOC' is within the definition interval.
[0069] Advantageously, the battery management system 20 is configured so that, regardless of the values of the fourth parameter SOC and the fifth parameter SOC0j, the difference SOC' - SOC has a constant sign (positive or zero, or negative or zero), preferably positive or zero. In other words, the function F ensures a shift from SOC to SOC' that is always in the same direction, preferably to the right in [Fig. 1] (SOC'>SOC), or zero (SOC'=SOC).
[0070] According to variants not shown, and a priori less interesting, it would be possible to conceive of a shift which is not always in the same direction, that is to say where we sometimes have SOC' > SOC, sometimes SOC' < SOC, or a negative or zero shift.
[0071] According to a preferred embodiment, the battery management system 20 is configured so that, if SOC0 belongs to the definition interval, then SOC' = SOC. In other words, if SOC0 belongs to the definition interval, the function F does not perform any shifting.
[0072] Alternatively, it would be possible that, even if SOC0 belongs to the interval of definition, SOC' is different from SOC, but this would probably not be of great interest, as it amounts to "distorting" the "map".
[0073] The battery management system 20 is advantageously configured so that, if SOCo belongs to the other interval, then:
[0074] . SOC' = SOC + D(SOCo), if SOC + D(SOC0) is within the interval of definition,
[0075] . SOC' = LIM1 if SOC + D(SOC0) < LIM1,
[0076] . SOC' = LIM2 if SOC + D(SOC0) > LIM2,
[0077] D being a shift function dependent on the fifth parameter SOC0, and preferably being independent of the fourth parameter SOC.
[0078] In other words, the offset D is constant and depends only on the initial charge state SOC0. If this offset causes SOC' to fall outside the definition interval, we limit ourselves to the limits of the definition interval (in the example, its upper limit, which is, for example, 100%). This has the advantage of simplifying the calculations.
[0079] Alternatively, it would be possible to implement a shift D which also takes into account the value of SOC, i.e. which is not independent of the value of SOC.
[0080] Advantageously, the other interval has an upper bound equal to LIM1, and for example a lower bound equal to 0%. The battery management system 20 is for example configured so that, if SOC0 belongs to the other interval, i.e. if SOC0< LIM1, then SOC' = Min(SOC + LIM1 - SOC0 ; LIM2), "Min" being the "minimum" function.
[0081] In other words, the offset has the value LIM1 - SOC0 as long as SOC + LIM1 - SOC0 < LIM2, that is, as long as SOC < LIM2 - (LIM1 - SOC0). Otherwise, SOC' is limited to the value LIM2, in order to remain within the interval of definition.
[0082] Alternatively, it would be possible to choose a shift with a value greater than LIM1 -SOCq, but this would probably be less interesting.
[0083] Alternatively, LIM1 is for example between 10% and 30%, preferably between 15% and 25%, of the nominal or maximum state of charge SOCmax of the battery 18. This allows for different thresholds for SOC0 below which a shift is made. Functioning
[0084] The operation of the assembly 14 is derived from its structure and will now be briefly described, which illustrates a method according to the invention.
[0085] When the battery 18 is in use, the battery supplies the current 16, for example to the motor 12.
[0086] Next, battery 18 can be inactive for a rest period.
[0087] After that, a user (not shown) of the vehicle 10 wishes to perform a fast charge of the battery 18.
[0088] The battery management system 20 controls the current 22 or the charging power during the charging time.
[0089] To determine the first parameter I representative of the current 22 or the power, the battery management system 20 acquires the second parameter T, the fourth parameter SOC, and the fifth parameter SOC0.
[0090] As shown in [Fig.4], the determination includes a step 44 of calculation, by the battery management system 20, of the third parameter SOC' from the fourth parameter SOC and the fifth parameter SOC0, with SOC' = F(SOC, SOCq), then a step 46 of calculation, by the battery management system 20, of the first parameter I using at least the second parameter T and the third parameter SOC'.
[0091] In the example, at step 46, if SOC0 belongs to the interval of definition [LIM1;LIM2], extending, for example, from 20% to 100%, then SOC' = F(SOC, SOC0). Advantageously, F(SOC, SOC0) = SOC, which is indeed within the interval of definition. For example, SOC0 = SOC(0) = 40%. Initially, SOC = SOC0 = 40%, and SOC' = SOC = 40%.
[0092] In step 48, the parameter I is calculated from SOC' and T, for example, using a "map" (or any other means known to those skilled in the art, such as an algorithm or a function). In the example, T = 25°C and curve Cl is used. On curve Cl (point Al), SOC' = 40% gives I = 225 A.
[0093] Then, since I is positive, SOC increases with time, up to the value LIM2 for a full charge. We trace the curve Cl from point Al to the right. When SOC' reaches LIM2, SOC' is limited to the value LIM2.
[0094] If SOCq does not belong to the interval of definition [LIM1;LIM2], then F(SOC, SOCo) provides an initial value of SOC' which is in the interval of definition. SOC0 is for example in the adjacent interval [0;LIM1[, which here is [0%;20%[.
[0095] For example, SOC0 = SOC(0) = 10%. Initially, SOC = SOC0 = 10%. In this case, advantageously, F(SOC, SOC0) = SOC + LIM1 - SOC0 = SOC + 20% - 10% = SOC + 10%. In other words, SOC' is initially 20%, which is indeed within the interval of definition.
[0096] On the curve Cl, point A allows us to obtain I = 300 A from SOC' and T. Then, SOC increases over time from its initial value of 10% in the example. Advantageously, the function F provides SOC' = SOC + 10%, by a shift, for example, constant, and SOC' is indeed within the interval of definition, as long as SOC is less than LIM2 - 10%. We traverse the curve Cl from point A to the right. When SOC reaches the value LIM2 - 10%, that is, 90% in the example, we have F(SOC, SOC0) = LIM2. In other words, the value of SOC' is then limited so as not to exceed LIM, that is, 100% in the example.
[0097] In the example, the shift between SOC and SOC' achieved by the function F is Max (LIM1 - SOCo ;0), which is a function evolving continuously with the value of SOC0. "Max" here is the "maximum" function. Benefits
[0098] Thanks to the characteristics described above, the ease of use of the battery 18 is maintained. Indeed, since the function F is continuous with respect to SOC0, the values of I calculated by the battery management system 20 do not experience discontinuities depending on whether SOC0 is slightly lower or slightly higher than LIM1, contrary to the prior art. In particular, the user therefore does not perceive any significant difference depending on whether the initial state of charge is above or below LIM1. The battery management system 20 nevertheless takes into account the initial state of charge of the battery 18.
[0099] For example, the charging time from 19% to 80% is 34 minutes, and the charging time from 20% to 80% is 33 minutes. The 30-minute difference mentioned above is no longer present.
[0100] Furthermore, a single "card" is advantageously used to obtain the charging current or power. Advantageously, no conditional testing on the fifth parameter SOC0, representative of an initial state of charge of the battery 18, for example on the state of charge or the open-circuit voltage, is necessary. List of digital references
[0101] 10 vehicle
[0102] 12 motor
[0103] 14 assembly
[0104] 16 current
[0105] 18 battery
[0106] 20 battery management system
[0107] 22 charging current or power
[0108] 24 charging system
[0109] 26 positive terminal
[0110] 28 negative terminal [YES] 30 positive electrodes
[0112] 32 negative electrodes
[0113] 34 electrolyte layers
[0114] 36 stack
[0115] 38 memory
[0116] 40 processor
[0117] 42 sensor
[0118] 44 third parameter calculation step SOC'
[0119] 46 first parameter calculation step I
Claims
Demands
1. Assembly (14), in particular for a vehicle (10), comprising: - a lithium-ion battery (18) intended to supply a current (16) in use, to be at rest, or to be charged by receiving a current (22) or power from a charging system (24) during a charging time, and - a battery management system (20) adapted to control the current (22) or power during the charging time, the battery management system (20) being configured to calculate a first parameter (I) representative of the current (22) or power using at least a second parameter (T) representative of an internal temperature of the battery (18), and a third parameter SOC' belonging to a predefined definition range,characterized in that the battery management system (20) is configured to calculate the third parameter SOC' from a fourth parameter SOC representing a state of charge of the battery (18) and a fifth parameter SOC0 representing an initial state of charge of the battery (18), with SOC' = F(SOC, SOC0), where F is a continuous function with respect to the fifth parameter SOCo and F(SOC, SOCo) belongs to the interval of definition.
2. Assembly (14) according to claim 1 or 2, wherein the battery management system (20) is configured so that, regardless of the values of the fourth parameter SOC and the fifth parameter SOC0j, the difference SOC' - SOC has a constant sign, and is preferably positive or zero.
3. Assembly (14) according to claim 1 or 2, wherein the battery management system (20) is configured so that, if SOC0 belongs to the range of definition, then SOC' = SOC.
4. Assembly (14) according to claim 3, wherein the definition interval is [LIM1;LIM2], LIM1 and LIM2 being two predefined values, the battery management system (20) being configured such that, if SOC0 belongs to another predefined interval adjacent to the definition interval, then: . SOC' = SOC + D(SOCo), if SOC + D(SOC0) is within the definition interval, . SOC' = LIM1 if SOC + D(SOCo) < LIM1, . SOC' = LIM2 if SOC + D(SOC0) > LIM2, D being a shift function dependent on the fifth parameter SOCq, and independent of the fourth parameter SOC.
5. Assembly (14) according to claim 4, wherein the other interval has an upper bound equal to LIM1, the battery management system (20) being configured so that, if SOC0 belongs to the other interval, then SOC' = Min(SOC + LIM1 - SOC0 ; LIM2), "Min" being the "minimum" function.
6. Assembly (14) according to claim 4 or 5, wherein LIM1 is between 10% and 30%, preferably between 15% and 25%, of a nominal or maximum state of charge (SOCmax) of the battery (18).
7. Assembly (14) according to any one of claims 4 to 6, wherein LIM2 is 100% of a nominal or maximum state of charge (SOCmax) of the battery (18).
8. Assembly (14) according to any one of claims 1 to 7, wherein the battery (18) comprises a plurality of positive electrodes (30) electrically connected to a positive terminal (26) of the battery (18), a plurality of negative electrodes (32) electrically connected to a negative terminal (28) of the battery (18) and intertwined with the positive electrodes, and layers of electrolyte (34) to form at least one stack (36) extending along a stacking direction (S), the negative electrodes (32) having a larger dimension than the positive electrodes (30) perpendicular to the stacking direction (S).
9. Vehicle comprising an assembly (14) according to any one of claims 1 to 8.
10. A charging method comprising the following steps: - obtaining an assembly (14) according to any one of claims 1 to 8, or a vehicle according to claim 8, - monitoring, by the battery management system (20), the current (22) or the power during the charging time, - calculating, by the battery management system (20), the third parameter SOC' from the fourth parameter SOC representing a state of charge of the battery (18) and the fifth parameter SOCq representing an initial state of charge of the battery (18), with SOC' = F(SOC, SOCq), where F is a continuous function with respect to the fifth parameter SOC0, and F(SOC, SOC0) belongs to the interval of definition, and - calculation, by the battery management system (20), of the first parameter (I) representing the current (22) or the power using at least the second parameter (T) representing the internal temperature of the battery (18), and the third parameter SOC'.