Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device

Abstract

Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device.

Description

[0001] The invention is based on a method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device, a device for operating an electrochemical energy storage unit and a use according to the preamble of the independent claims. State of the art

[0002] The process of adjusting the voltage of the battery cells of an electric vehicle (EV), the so-called balancing, can be carried out as active balancing (adjustment by discharging energy to the level of the worst cell - when the vehicle is stationary) or as passive balancing (adjustment by shifting energy from the better cells to the worse cells - while driving).

[0003] In the automotive sector, active balancing is used primarily for cost reasons. Balancing brings all cells to the same voltage level, allowing them to reach their final charge and discharge voltages together. This means they can use their maximum possible energy for propulsion, thus maximizing the range of the electric vehicle.

[0004] Whether balancing is necessary depends on the voltage difference between the cell with the highest and lowest voltage. This check takes place at regular intervals, depending on the settings of the corresponding application parameter. This value can shift to shorter intervals as the battery ages. For new batteries (SOH = 100%), a balancing check is performed every four weeks, for example, and weekly for aged cells. This balancing check is performed after the EV has been parked and not moved for approximately 30 minutes. The reason for this is that voltage measurements are more accurate when the battery is at rest, and the relaxed cells then display their actual voltage values.

[0005] Depending on the measured voltage values ​​and the resulting voltage difference, the balancing process then begins. This process can take one to two hours. During this time, the electric vehicle is not blocked, and the balancing process can be interrupted at any time by starting the vehicle, for example, when a driver begins a journey.

[0006] In this case, the balancing process is therefore not completely terminated. Depending on how long the balancing process was active, the voltages of the battery pack's cells will be closer or closer together, but not all at the same voltage level. Balancing will then be continued or discontinued at the next opportunity (depending on whether the voltage difference is below or above the applied threshold). It may also be that a balancing check is not triggered again for another four weeks or as soon as two weeks, depending on the balancing strategy implemented.

[0007] Depending on the balancing strategy regarding such an interruption, different effects arise for the battery and for the range behavior of the electrically powered vehicle.

[0008] So: A. Balancing should be continued as soon as the vehicle is in the next longer standstill phase; B. A check to see whether balancing is necessary should be carried out earlier than usual, e.g. after half the time; C. A check to see whether balancing is required is always carried out after the same time, regardless of whether the process has been aborted or not.

[0009] The interruption of the balancing process leads to a delay in the balancing process, which is reflected in a premature termination of the charging and discharging process and thus in a reduced range, as well as in the difficulty of compensating for the voltage differences when they become too large, since the active balancing can only be operated with small currents (up to 100 mA).

[0010] Regardless of the strategy, the penalty remains that an interruption results in another voltage difference check approximately 30 minutes after the electrically powered vehicle has been parked, with possible subsequent balancing, and if the driver has plugged in his charging cable, he can only charge after balancing.

[0011] If the balancing process takes place before a charging process, the interruption will delay the start of charging. Even though the electric vehicle is connected to the charging station, the battery will not be charged until the balancing process is complete. Since the balancing process runs in the background, the driver is unaware of it and mistakenly assumes their vehicle battery is being charged.

[0012] Each subsequent interruption leads to a delayed start of charging. Even if the voltages are closer together after a balancing interruption, and the next balancing check is scheduled for two or four weeks, for example, a much larger voltage difference can be expected, which makes the balancing process take longer and thus increases the likelihood of an interruption. Thus, the described problem leads to a cumulative accumulation of the residual energy that was not dissipated during previous balancing processes, or in the case described above, to constant voltage difference checks and balancing processes, which are repeated until the balancing process is completely completed.It is important not to lose sight of the ever-decreasing charge level of the battery, as charging is not possible during the standstill phase, the voltage difference check and the balancing process, even if the charging cable is connected.

[0013] Document EP 3 706 051 A1 discloses a battery balancing method comprising the following steps: Obtaining historical energy replenishment information, wherein the historical energy replenishment information comprises a fast charging utilization rate and / or a slow charging utilization rate; Assess whether the fast charging utilization rate and / or the slow charging utilization rate is higher than a corresponding set value; and Determining an energy replenishment strategy of a battery according to the assessment result, wherein determining an energy replenishment strategy comprises at least: determining an energy replenishment mode to be assumed to be one of fast charging, slow charging, and battery replacement; and Performing energy replenishment planning according to the energy replenishment strategy, wherein the energy replenishment planning includes planning of the battery and / or guidance for a user using the battery.

[0014] The document DE 10 2019 214 343 A1 discloses a method for balancing charge states of an electrical energy storage device with a plurality of battery cells, comprising the following steps: a) detecting a voltage value representing an electrical voltage of a battery cell; b) determining a positive maximum electrical charge of the battery cell with respect to an electrical reference voltage level of all battery cells of the electrical energy storage device with balanced charge states; c) determining a negative maximum electrical charge of the battery cell with respect to an electrical reference voltage level of all battery cells of the electrical energy storage device with balanced charge states; d) determining an electrical charge of the battery cell to be balanced; e) determining a charge error of the electrical charge to be balanced; f) determining an electrical charge of the battery cell to be balanced; (g) calculating a duration for equalising the state of charge of the battery cell based on the electrical charge to be equalised if the electrical charge to be equalised exceeds a predetermined threshold; h) Balancing the charge level of the battery cell for the duration.

[0015] The object of the present invention is to further improve the state of the art. This object is achieved by the features of the independent claims. Disclosure of the inventionAdvantages of the invention

[0016] The procedure according to the invention with the characterizing features of the independent claims has the advantage that the method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device comprises the following steps: a) Determining a duration value representing a predicted available duration; b) determining a first target time requirement value which represents a time requirement for balancing charges of the electrochemical energy storage cells of the electrochemical energy storage device; c) determining a second target time requirement value which represents a time requirement for charging the electrochemical energy storage cells of the electrochemical energy storage device; d) comparing a sum of the determined first target time requirement and the second target time requirement with the determined time duration; e) predictively balancing charges of the plurality of electrochemical energy storage cells of the electrochemical energy storage device when the time duration value is greater than or equal to the sum of the first target time requirement value and the second target time requirement value.

[0017] Advantageously, based on user behavior, for example daily trips to work, weekly trips to the shops, parking phases at work, overnight, weekend trips in the case of an electrically powered vehicle with the electrochemical energy storage device, and charging behavior, for example usually twice a week from a certain time overnight or below a certain state of charge, a state of charge compensation is only started predictively when it can be assumed that the electrochemical energy storage device is no longer being moved.

[0018] Further advantageous embodiments are the subject of the subclaims.

[0019] The duration value is determined depending on at least one driving behavior and / or a charging behavior of at least one user of the electrochemical energy storage device.

[0020] The actual demand is determined depending on voltage differences between electrochemical cells of the electrochemical energy storage device and / or a state of health (SOH) of the electrochemical energy storage device.

[0021] The first target time requirement is determined depending on voltage differences between electrochemical energy storage cells of the electrochemical energy storage and / or a state of health (SOH) of the electrochemical energy storage.

[0022] The second target time requirement is determined depending on the current state of charge (SOC) and / or state of health (SOH) of the electrochemical energy storage device.

[0023] A device according to the invention for operating an electrochemical energy storage unit comprises an electrochemical energy storage device with a plurality of electrochemical energy storage cells, a current sensor for detecting an electrical current of the electrochemical energy storage device, a voltage sensor for detecting an electrical voltage of the electrochemical energy storage device, and at least one means, in particular an electronic control unit, which are configured to carry out the steps of the method according to the invention.

[0024] According to an advantageous embodiment of the invention, a computer program is provided, comprising instructions which cause the device for operating a battery to carry out the method steps according to the invention.

[0025] Furthermore, a machine-readable storage medium is provided on which the computer program is stored.

[0026] Advantageously, a method according to the invention for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device is used in electrochemical energy storage devices for electric vehicles, fuel cell vehicles, hybrid vehicles, plug-in hybrid vehicles, aircraft, pedelecs or e-bikes, for portable devices for telecommunications or data processing or for electric hand tools. Short description of the characters

[0027] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description.

[0028] Further advantages and advantageous embodiments of the inventive objects are illustrated by the drawings and explained in the following description. It should be noted that the drawings are for descriptive purposes only and are not intended to limit the invention in any way. Furthermore, the features described below may constitute an object of the invention, individually or in any combination, unless the context explicitly indicates otherwise.

[0029] They show: Fig. 1 shows a flowchart of an embodiment of a method according to the invention for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device; Fig. 2 shows a schematic representation of an embodiment of a method according to the invention for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device; Fig. 3 a schematic representation of time sequences for the predictive balancing of charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device. Detailed description of the implementation examples

[0030] The same reference numerals denote the same device components in all figures.

[0031] Fig. 1 shows a flowchart of an embodiment of a method according to the invention for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device.

[0032] In step 100, a time variable is recorded which represents a duration of a rest state of the electrochemical energy storage device.

[0033] In step 101, the detected time value is compared with a predetermined target time value, which represents a minimum time period for the idle state of the electrochemical energy storage device.

[0034] In step 102, a time duration value is determined which represents a predicted available time duration.

[0035] In step 103, a first target time requirement is determined, which represents a time requirement for balancing charges of the electrochemical energy storage cells of the electrochemical energy storage device.

[0036] In step 104, a second target time requirement is determined, which represents a time requirement for charging the electrochemical energy storage device to a predetermined state of charge, for example a state of charge of 100%.

[0037] In step 105, a sum of the determined first target time requirement and second target time requirement is compared with the determined time duration.

[0038] In order to also ensure that the time required for a state of charge equalization and a charging process is sufficient until, for example, an electrically driven vehicle with the electrochemical energy storage device is used again on a regular basis, the first target time required for a state of charge equalization, in particular as a function of voltage differences between electrochemical energy storage cells of the electrochemical energy storage device, and the second target time required for charging times of the electrochemical energy storage device, in particular as a function of a current state of charge (SOC) of the electrochemical energy storage device, are precisely determined.

[0039] The state of health (SOH) of the electrochemical energy storage device is particularly important, as depending on the state of health, charge equalization times will increase if a state of charge check is not performed early. Charging processes will also be longer with an age-dependent charging strategy.

[0040] A predictive balancing of charges of the plurality of electrochemical energy storage cells of the electrochemical energy storage device takes place in step 107 if the time duration value is greater than or equal to the sum of the first target time requirement value and the second target time requirement value.

[0041] Otherwise, the method continues in step 106 and checks whether the balancing of charges can be performed or continued at a later time. If this is not the case, the method continues in step 107. Otherwise, the method continues in step 109.

[0042] If the time until the next use of the electrochemical energy storage device, for example, starting a vehicle, is insufficient, the state of charge equalization must be omitted and a charging process must be given priority. The actual state of charge equalization only takes place during the next regularly scheduled long shutdown phase, during which time a complete state of charge equalization is possible.

[0043] Depending on the state of charge of the electrochemical energy storage device or regular personal charging rhythms, if this is not too far in the future, for example 1 to 2 days, a charge level equalization can be delayed so long that it occurs immediately before a charging process.

[0044] In step 108, a check is made to determine whether charge balancing has essentially been completed or whether the charge balancing process was interrupted, for example, by a vehicle start. If the process was interrupted, the process continues in step 100.

[0045] In step 109, the method is terminated and a charging process of the electrochemical energy storage device is started.

[0046] Fig. 2 shows a schematic representation of an embodiment 200 of a method according to the invention for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device of an electrically driven vehicle 201.

[0047] In the illustrated embodiment 200, the method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device runs in an electronic control unit 202 (BMS) of the electrically driven vehicle 201 and at least partially in an electronic control unit (“cloud”) 203 spatially separated from the electronic control unit 202.

[0048] During operation of the vehicle 201, load profiles 204(1), 204(2), 204(3) of the electrochemical energy storage device are determined in the control unit 203 via a data connection 205, in particular a wireless data connection. If a trigger for state of charge compensation is then sent from the electronic control unit 202 to the control unit 203 via the data connection 205, a start time for state of charge compensation is determined in accordance with user behavior based on the load profiles, voltage differences between electrochemical energy storage cells of the electrochemical energy storage device, a state of health (SOH) of the electrochemical energy storage device, and / or a current state of charge (SOC), and is transmitted to the electronic control unit 202 via a data connection 207.

[0049] Compared to the standard procedure of only performing a state of charge balancing at night, the user-dependent, predictive procedure has the advantage that a state of charge balancing can be carried out at optimized times to suit usage and charging behavior.

[0050] Fig. 3 shows a schematic representation of time sequences for the predictive balancing of charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device.

[0051] The time sequence 301 (1) shows an essentially optimal time sequence of a driving cycle 302 (1), a charge state compensation 303 (1) and a charging process 304 (1).

[0052] During the driving cycle 302(1), a check 306(1) is performed to determine whether a state of charge equalization is required. After a rest phase 305(1) of the electrochemical energy storage device, the state of charge equalization 303(1) is started at a time 307(1). The duration of the rest phase 305(1) is a predetermined period of time, for example, 30 minutes after, for example, a vehicle shutdown phase. The state of charge equalization 303(1) is essentially completely completed after, for example, 1 to 2 hours.

[0053] After the state of charge equalization 303(1), the charging process 304(1) of the electrochemical energy storage device is started. The charging process 304(1) is essentially completely completed after 4 to 6 hours, for example.

[0054] The time sequence 301 (2) shows a time sequence with a plurality of driving cycles 302 (2a), 302 (2b) and a delay in the start of charging. During the first driving cycle 302 (2a), a check 306 (2) is performed to determine whether a state of charge adjustment is necessary. After a rest phase 305 (2a), for example, 30 minutes, a state of charge adjustment 303 (2a) is started at a time 307 (2a).

[0055] The state of charge equalization 303(2a) is interrupted, for example after 30 minutes, by the second driving cycle 302(2b) and is not fully completed.

[0056] After the second driving cycle 302(2b) and a rest phase 305(2b), for example, 30 minutes, a state of charge equalization 303(2b) is started at a time 307(2b), which continues the interrupted state of charge equalization 303(2a). The state of charge equalization 303(2b) is essentially completely completed after, for example, 40 minutes to 1.5 hours.

[0057] After the state of charge equalization 303(2b), a charging process 304(2) of the electrochemical energy storage device is started. The charging process 304(2) is essentially completed after 4 to 6 hours, for example.

[0058] The time sequence 301 (3) shows a time sequence with a plurality of driving cycles 302 (3a), 302 (3b) as well as a carryover of residual energy, which is reflected in different cell voltages and must be additionally converted into heat in a subsequent state of charge equalization at resistors. During the first driving cycle 302 (3a), a check 306 (3) is performed to determine whether state of charge equalization is necessary. After a rest phase 305 (3a), for example, 30 minutes, a state of charge equalization 303 (3) is started at a time 307 (3a).

[0059] The state of charge equalization 303(3) is interrupted, for example after 40 minutes, by the second driving cycle 302(3b) and is not fully completed.

[0060] After the second driving cycle 302(3b) and a rest phase 305(3b), for example, 30 minutes, no further state of charge equalization is initiated at a time 307(3b) because the predicted available time is insufficient. Therefore, a charging process 304(3) of the electrochemical energy storage device is initiated.

[0061] For example, the charging process 304(3) is essentially completed after 4 to 6 hours. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 706 051 A1

[0013] DE 10 2019 214 343 A1

[0014]

Claims

[1] Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device, comprising the following steps: a) (102) determining a duration value representing a predicted available duration; b) (103) determining a first target time requirement value which represents a time requirement for balancing charges of the electrochemical energy storage cells of the electrochemical energy storage device; c) (104) determining a second target time requirement value which represents a time requirement for charging the electrochemical energy storage device to a predetermined state of charge; d) (105) comparing a sum of the determined first target time requirement and the second target time requirement with the determined time duration; e) (107) Predictive balancing of charges of the plurality of electrochemical energy storage cells of the electrochemical energy storage device when the time duration variable is greater than or equal to the sum of the first target time requirement variable and the second target time requirement variable. [2] Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device according to claim 1, wherein the time duration variable is determined as a function of at least one driving behavior and / or a charging behavior of at least one user of the electrochemical energy storage device. [3] Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device according to one of the preceding claims, wherein the actual demand value is determined as a function of voltage differences between electrochemical cells of the electrochemical energy storage device and / or a state of health (SOH) of the electrochemical energy storage device. [4] Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device according to one of the preceding claims, wherein the first target time requirement is determined as a function of voltage differences between electrochemical energy storage cells of the electrochemical energy storage device and / or a state of health (SOH) of the electrochemical energy storage device. [5] Method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device according to one of the preceding claims, wherein the second target time requirement is determined as a function of a current state of charge (SOC) and / or a state of health (SOH) of the electrochemical energy storage device. [6] Device for operating an electrochemical energy storage unit, comprising an electrochemical energy storage device with a plurality of electrochemical energy storage cells, a current sensor for detecting an electrical current of the electrochemical energy storage device, a voltage sensor for detecting an electrical voltage of the electrochemical energy storage device, and at least one means, in particular an electronic control unit, which are configured to carry out the steps of the method according to one of claims 1 to 5. [7] A computer program comprising instructions causing the apparatus according to claim 6 to carry out the method steps according to any one of claims 1 to 5. [8] A machine-readable storage medium on which the computer program according to claim 7 is stored. [9] Use of a method for predictively balancing charges of a plurality of electrochemical energy storage cells of an electrochemical energy storage device according to one of claims 1 to 5 in electrochemical energy storage devices for electric vehicles, fuel cell vehicles, hybrid vehicles, plug-in hybrid vehicles, aircraft, pedelecs or e-bikes, for portable devices for telecommunications or data processing or for electric hand tools.

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