Charging method for secondary battery and vehicle

Abstract

The invention relates to a charging method for a secondary battery, in which a charging current (Ilade) for charging at least one galvanic cell (1) of the secondary battery with electrical energy is adjusted during the charging process by taking into account at least one of the following variables: a maximum cell voltage, a minimum anode voltage, a cell temperature (TZel) and / or a maximum charging current, and the heat thus dissipated is discharged through the cooling system which is at least temporarily activated during the charging process. The charging method according to the invention is characterized by the following charging phases: a) charging the battery (1) with a deactivated cooling system once the battery temperature (TZel) at the potential hottest point (HOTSPOT) of the battery (1) is below a set activation temperature (Tan, opt), the activation temperature (Tan, opt) depending on the battery type and the output temperature (Tstart) of the battery (1) at the beginning of the charging process; b) charging the battery (1) with a cooling system turned on at full load once the battery temperature (TZel) at the potential hottest point (HOTSPOT) of the battery (1) reaches a set activation temperature (Tan, opt); and c) once the temperature change of the battery temperature (TZel) at the potential hottest point (HOTSPOT) of the battery (1) reaches zero: reducing the cooling power (Pcool) of the cooling system and adjusting the cooling power (Pcool) such that the battery temperature (TZel) at the potential hottest point (HOTSPOT) of the battery (1) and / or at the potential coldest point (COLDSPOT) of the battery (1) remains substantially constant.

Description

[0001] The present invention relates to a charging method for a secondary battery of the type defined in more detail in the preamble of claim 1, and a vehicle for performing the method.

[0002] The proportion of vehicles with at least partially electrified drive systems (hereinafter referred to as electric vehicles) continues to increase. Traction batteries are typically installed in such electric vehicles to store electrical driving energy. While refueling internal combustion engine vehicles with liquid fuel at gas stations is relatively quick, charging the traction batteries at charging stations takes much longer. This is especially true for long-distance trips exceeding the vehicle's range, requiring one or more stops for charging. Such mandatory breaks can be disruptive to drivers. Furthermore, available charging stations, such as those at highway rest stops, may be occupied, particularly during holidays, necessitating extra waiting until an available charging station becomes available. Therefore, there is a need for methods and devices that can shorten the necessary charging time during the charging process.

[0003] In this context, the charging duration depends on the available charging power at the charging station. Higher charging voltage and current allow the vehicle's traction battery to charge more power for electric drive more quickly. However, the vehicle or its corresponding traction battery must be technically designed for the appropriate charging current and voltage. During charging, individual traction battery cells generate heat, requiring active cooling and, if necessary, reducing the charging current to prevent overheating. Furthermore, the maximum battery voltage must not be exceeded, and the minimum anode voltage must not fall below the electroplating limit.

[0004] Within the electroplating limit range, i.e., the anode potential limit region, the battery location that limits the battery current is the location with the lowest temperature, and therefore also the location with the highest overvoltage. Therefore, when performing the charging process, there is a conflict between the following objectives: the hottest point (also known as the hotspot) of a battery cell must not exceed the specified maximum value, but at the same time, the coldest point (also known as the coldspot) of a battery cell should be kept as warm as possible to minimize resistance and overvoltage. This leads to a conflict between cooling the individual cells of the traction battery as early as possible to prevent exceeding the allowable temperature of the active materials, but simultaneously cooling as little and as late as possible to ensure the coldest point is kept as warm as possible.

[0005] The inventors specifically solved this problem in the following paper:

[0006] Hendrik Pegel, Dominik Wycisk, Alexander Scheible, Luca Tendera, Arnulf Latz, Dirk Uwe Sauer; “Fast-charging performance and optimal thermal management of large-format full-tab cylindrical lithium-ion cells under varying environmental conditions”; Power Industry Journal, Vol. 556, 2023, 232408; ISSN 0378-7753. https: / / doi.org / 10.1016 / j.jpowsour.2022.232408

[0007] This paper investigates the thermal management of lithium-ion spherical batteries during charging. The aim is to determine, based on the battery's state of charge and the initial temperature of each cell, the temperature at which active cooling should be initiated to shorten the charging duration using the highest possible charging current. Therefore, it answers the question of how to cool the battery at the start of the charging process, ensuring that the hottest point temperature does not exceed its maximum value, while the coldest point temperature is warmed as much as possible. The results for the examined battery types are displayed in the form of a so-called cooling / heating card. This shows the battery temperature established by the charging process in each case, from which active cooling should be activated, based on the initial temperature. Furthermore, active heating of the cells may be advantageous at a cold initial temperature. Therefore, the cooling / heating card also indicates when to initiate active heating, at which battery temperature to deactivate active heating, and at which battery temperature active cooling is subsequently activated, based on the initial temperature.

[0008] Furthermore, CN 1 15 709 670A discloses a thermal management method for the charging process of a storage battery, as well as hardware that can be used for this purpose. The thermal management method envisions that the battery is not cooled in a first stage of the charging process, and that a cooling system for the battery is activated in a second stage, which is achieved when a set temperature difference exists between the hottest point of the battery and the maximum temperature depending on the state of charge. In this case, the temperature of the cooling medium is regulated to maintain the battery temperature level within a set interval.

[0009] Furthermore, US2016 / 0 082 860A1 discloses a method for managing the temperature of a battery in an electric vehicle. In this method, battery heating or cooling is enabled or disabled based on a comparison of the temperature gradient on the battery with a reference curve. The cooling power can be adjusted based on the heat power released by the battery.

[0010] Furthermore, DE 10 2018 221 088 A1 discloses a battery system for electric vehicles and a method of operating the same. The battery system includes at least one battery module whose temperature can be regulated to a set temperature by means of heating and cooling devices. The flow rate of the cooling medium can be varied to adjust the cooling power.

[0011] Furthermore, DE 44 43 015 A1 discloses a method for operating a high-temperature battery. In this case, a regulating device is provided that determines a temperature setpoint based on the battery's state of charge and the power of a cooling device; if this temperature setpoint is exceeded, battery cooling is activated. The temperature setpoint corresponds to the temperature generated while fully utilizing the battery's thermal capacity and the maximum continuous current supplied to the battery, taking into account the maximum permissible battery temperature. In this case, the cooling power is determined by taking into account the inlet and outlet temperatures of the cooling medium.

[0012] The purpose of this invention is to provide a charging method for a primary battery in a secondary battery, which is an improvement over the prior art.

[0013] According to the invention, this objective is achieved by a charging method for a secondary battery having the features of claim 1. Advantageous designs and improvements, as well as vehicles for performing the method, arise from the relevant claims.

[0014] A general charging method for secondary batteries, wherein the charging current for charging at least one primary cell of the secondary battery with electrical energy is adjusted during charging by considering at least one of the following variables: maximum battery voltage, minimum anode voltage, battery temperature, and / or maximum charging current, and the heat dissipated thereby is discharged by a cooling system that is at least temporarily activated during charging, improved according to the invention by the following charging stages:

[0015] a) Once the battery temperature at the potential hottest point of the battery is below the set activation temperature, the deactivated cooling system is used to charge the battery, where the activation temperature depends on the battery type and the battery's output temperature at the start of the charging process;

[0016] b) Once the battery temperature at its potential hottest point reaches the set activation temperature, the battery is charged using the fully loaded cooling system; and

[0017] c) Once the temperature change at the battery's potential hottest point reaches zero: reduce and adjust the cooling power of the cooling system to maintain a substantially constant battery temperature at the battery's potential hottest point and / or potential coldest point; whereby...

[0018] The battery temperature decreases within a set charging state range before the battery reaches a full charge.

[0019] By means of the method according to the invention, the charging duration of the primary cell in a secondary battery can be further reduced. As previously mentioned, the local temperature of the battery active material determines the local resistance, and thus the local overvoltage. Therefore, the potential coldest point of the battery (hereinafter referred to as the Coldspot) limits the maximum available charging current, as the highest battery voltage must be expected here. The hotter the Coldspot, the higher the battery current available for charging the battery. With the increase of the charging current, the charging duration can be shortened. The applicant has recognized that this leads to the following problem regarding the execution of the charging process: how should cooling be regulated at higher charging states within the electroplating limits to avoid an unnecessary drop in the temperature of the Coldspot during charging? As a further boundary condition, it must be ensured that the maximum permissible temperature of the battery active material is not exceeded.

[0020] By means of the method according to the invention, the coldest point temperature of the battery can be increased more quickly compared to known charging methods, and the battery temperature at the potential hotspot (hereinafter also referred to as the hotspot) can be maintained at the highest possible level during charging, while preventing the battery temperature from exceeding the maximum effective temperature for the active materials of the battery used. This makes it possible to use the highest possible charging current throughout the charging process, thereby correspondingly shortening the charging time.

[0021] The primary battery is preferably a lithium-ion battery. This battery can correspond to any type of structure, such as a pouch cell, but preferably, it is designed as a spherical battery.

[0022] During charging, the charging current is adjusted according to a proven method. The method steps according to the invention involve battery cooling, thus the charging method according to the invention can also be referred to as a thermal management method.

[0023] The locations of the hottest and coldest points vary depending on the geometry and technical configuration of the corresponding galvanic cell and cooling system. Depending on the battery structure and casing material, in the case of a circular battery mounted on a cooling plate for cooling, the hottest point is, for example, located on the inner upper ring of the active material, and the coldest point is located on the outer lower ring of the active material, in the area in contact with the cooling plate. The battery temperature at any desired point, particularly the temperatures of the hottest and coldest points, can be measured using temperature sensors, or estimated by calculation, supplemented or alternatively, using a simulation model of the galvanic cell. Similarly, other physical parameters, such as battery voltage and charging current, can be determined experimentally using measuring equipment and / or estimated using computational models.

[0024] Through charging phase a), the coldest point temperature is heated as quickly as possible, thus delaying and reducing the anode potential limit for as long as possible. In many cases, a higher charging current can also be used as quickly as possible. The execution of charging phase b) prevents the battery from heating to or exceeding its maximum permissible temperature range. For this purpose, it is crucial to measure or determine the battery temperature at the point where it heats up the most during the charging process, i.e., the hottest point temperature.

[0025] As charging duration increases, cooling must be adjusted in such a way that, if possible, the coldest point temperature can be further increased, or at least kept constant, while the hottest point temperature does not exceed the maximum permissible temperature of the active materials. Therefore, during charging, the battery temperature will decrease even with maximum cooling power; however, this should be prevented. To this end, the cooling power is reduced accordingly during charging phase c). Thus, the fact that the battery temperature change at the hottest point reaches zero means that the battery no longer heats up further at that point, but rather maintains its temperature constant, at least at that moment. With cooling maintained at maximum power, the sign will reverse, and the hottest point will cool. To record this point in time, the measured or calculated estimated hottest point temperature is evaluated. Since the hottest point temperature is difficult to detect experimentally, it is typically used for cylindrical batteries used in the automotive field; therefore, a calculated estimated hottest point temperature is usually employed.

[0026] In practice, the point at which the temperature of the hottest spot reaches its maximum value and begins to decrease can also be determined using the time derivative of any temperature sensor.

[0027] The hottest and / or coldest temperatures can be directly used as reference variables for adjusting cooling power. However, this requires a relatively complex regulator because the adjustment path between the cooling system and the hottest temperature is very complex due to geometry, internal thermal paths, and established temperature gradients.

[0028] As previously mentioned, the battery temperature decreases within a set state of charge range before the battery reaches full charge. If power is to be supplied via a secondary battery after the charging process is complete, the secondary battery or one or more primary cells of the secondary battery can be further heated. This is especially true when particularly high power is requested for a short period of time. As will be further mentioned, the method according to the invention can be used to charge the traction battery of a vehicle. If the vehicle user applies a heavy load to the traction battery after the charging process is complete, for example by sporty driving, there is a risk that the traction battery will be heated above its maximum permissible temperature. However, by lowering the battery temperature shortly before the end of the charging process, for example by further increasing the cooling power, a certain thermal buffer is provided, allowing increased drive power to be obtained without the risk of the traction battery overheating. Depending on the technical design of the traction battery and the charging station used, particularly the charging voltage and charging current used, the set state of charge range for lowering the battery temperature before reaching full charge can be variably selected. For example, an engineer can determine that the traction battery should be cooled to such an extent that, after the charging process is complete, it should provide maximum callable drive power for at least 10 minutes or at least the next 3 kilometers without the risk of overheating. Then, the appropriate state-of-charge range can also be determined through testing and / or simulation for different vehicle configurations and traction battery variants. Reducing battery temperature before the end of the charging process has the further positive effect of slowing down or halting temperature-related aging processes. Although the charging duration increases imperceptibly, this becomes less significant towards the end of the charging process.

[0029] Therefore, an advantageous improvement to the method according to the invention is provided for adjusting cooling power:

[0030] - Measure and / or calculate the estimated thermal power released by the battery;

[0031] - Measure and / or calculate estimates of the heat power that can be discharged or removed from the cooling system; and

[0032] - By adjusting the cooling power in this way, the heat power that is discharged or discharged essentially corresponds to the heat power released by the battery.

[0033] In addition to the thermal power of the battery (i.e., the primary heat source), the heat generated by the battery connectors and other secondary heat sources can be advantageously determined or estimated, and this heat can be taken into account when adjusting the cooling power. Therefore, the battery's cooling power can be better matched to the battery's total heat generation and adjusted accordingly.

[0034] This makes simple and robust regulation possible. The heat power released by the battery is the heat dissipated during charging. To keep the battery at a constant temperature, according to thermodynamic principles, the dissipated waste heat must be dissipated. Therefore, if the cooling power is matched with the heat power released by the battery and additional heat sources (e.g., in wiring and contact elements), it is equally possible to ensure that the hottest or coldest point temperature remains substantially constant without actually measuring the corresponding battery temperature. As a result, the method according to the invention can also be implemented simply and economically for the charging process of cylindrical batteries frequently installed in the automotive field.

[0035] By calculating a battery model, the thermal power released or energy loss by the battery can be determined simply and relatively accurately. This energy loss can also be estimated particularly easily using the measured clamping voltage, the known open-circuit voltage, and the measured operating current; however, this is slightly less accurate than the estimate using a battery model.

[0036] The thermal power of the cooling system can then be approximated by a computational model. However, it is particularly advantageous that the actual discharged thermal power can also be determined experimentally.

[0037] In this way, the cooling power set by the regulator can be quickly and easily corrected. This is a cascaded regulation that is easy to implement, very robust, and has provided excellent results in testing.

[0038] In this case, it must be considered that the battery system can have hundreds of cells, and the cooling power must be regulated in such a way that the cells are also sufficiently cooled, which will first reach the maximum temperature limit, i.e., the cells near the coolant outlet, because the coolant has already been preheated there. Therefore, the required cooling power is designed for that specific battery.

[0039] According to another advantageous design of the method based on the invention, the heat transfer coefficient between the interacting surfaces of the battery and the cooling system is adjusted to regulate the heat power to be discharged from the cooling system. For cooling the battery, proven methods and processes can be used. Heat can typically be dissipated through thermal conduction, thermal radiation, and convection. Preferably, a convection-based cooling system is used, particularly forced convection. By adjusting the heat transfer coefficient, the heat flow or heat power to be discharged can be adjusted particularly conveniently and precisely. For example, the surface wetted by the cooling medium, the mass flow rate of the cooling medium, and / or the temperature of the cooling medium can be changed.

[0040] Preferably, a fluid-based cooling system is used, wherein the cooling medium flows indirectly or directly to or around at least a portion of the battery, and the volumetric flow rate of the cooling medium is adjusted to suit the heat transfer coefficient. This makes it possible to adjust the cooling power in a particularly simple manner.

[0041] Circular batteries, fixed to a cooling plate, are typically installed in vehicles. A liquid coolant flows sequentially over the cooling plate. Therefore, heat is dissipated through the bottom of the circular battery. Thus, to allow indirect access to the battery, a cooling body is connected to the battery, and the cooling body is in turn indirectly connected to the battery, for example, through a thermal pad or thermal paste.

[0042] The cooling area of ​​the battery is known, and as previously mentioned, in the case of a circular battery connected to a cooling plate, it corresponds to the cross-sectional area of ​​the battery bottom. As a standard practice, the fluid temperature is measured at both the coolant flow direction and the coolant return direction. Alternatively, the average of the flow direction temperature and the return temperature can be used for the fluid temperature. The bottom temperature of the battery can also be measured or estimated using a computational model.

[0043] According to another advantageous design of this method, the rotational speed of the cooling medium supply pump is adjusted to regulate the volumetric flow rate of the cooling medium. This makes simpler and more robust regulation of the volumetric flow rate possible. Instead of influencing the volumetric flow rate, for example, by opening and closing orifices or valves located in the flow path, this reduces flow losses and correspondingly saves the drive energy required to operate the cooling medium supply pump. The response behavior, i.e., the effect of adjusting the rotational speed on the volumetric flow rate, is also particularly direct.

[0044] Another advantageous design of the method according to the invention provides that, if the battery's output temperature is lower than a set heating temperature, the battery is actively heated at least temporarily during charging phase a), wherein heating for this purpose is turned off when a heating deactivation temperature lower than the activation temperature is reached, and wherein the heating deactivation temperature depends on the battery type and the battery's output temperature at the start of the charging process. As previously mentioned, the maximum available charging current depends on the battery temperature and is limited by low temperatures. Therefore, at low temperatures, particularly near or below freezing, the charging process can only be carried out with a reduced charging current. However, if the battery is actively heated, the battery temperature at the coldest point increases accordingly, thus allowing charging with a higher charging current, which further shortens the charging duration. Here, different temperature limits are defined according to the battery's geometry and technical design, i.e., when active heating should be turned on and when active heating should be turned off again to avoid overheating.

[0045] According to another advantageous design of the method according to the invention, the computing unit for adjusting the cooling system reads the activation temperature from the cooling / heating card, wherein the cooling / heating card is initially created by performing measurements and / or simulations for the type of battery used, wherein, in order to determine the relationship between the activation temperature and the output temperature for different output temperatures, the cooling system is activated to a different battery temperature in each case, and the battery temperature is set as the activation temperature, under which the charging time of the battery relative to the corresponding output temperature is minimized.

[0046] According to charging stage b), the appropriate timing of activating the cooling system is particularly important for reducing charging duration. If the cooling system is activated too early, valuable residual potential used to increase the charging current and thus shorten the charging duration will be lost. Therefore, the coldest point can be further heated, allowing for the use of a higher charging current. On the other hand, if the cooling system is activated too late, the current charging current must suddenly and drastically decrease to avoid overheating when the hottest point reaches the permissible active material temperature. Therefore, residual potential for reducing charging duration is also lost.

[0047] Therefore, for different states of charge (SOC) and at different output temperatures, there exists a separate optimal value for each condition, at which the cooling system should be activated due to the battery temperature generated during charging. These optimal temperatures are determined in the form of activation temperatures through a series of tests to be performed in advance. This method is similar to the method disclosed in the inventors' paper for determining the cooling / heating card. See also: Hendrik Pegel, Dominik Wycisk, Alexander Scheible, Luca Tendera, Arnulf Latz, Dirk Uwe Sauer; "Fast-charging performance and optimal thermal management of large-format full-tab cylindrical lithium-ion cells under varying environmental conditions"; Power Supply Journal, Vol. 556, 2023, 232408; ISSN 0378-7753. https: / / doi.org / 10.1016 / j.jpowsour.2022.232408 .

[0048] Another advantageous design of the method according to the invention provides that a calculation unit for regulating heating reads the heating temperature and heating deactivation temperature from a cooling / heating card, wherein, in order to determine the relationship between the heating temperature, heating deactivation temperature, and output temperature at different output temperatures, heating is enabled and deactivated at different battery temperatures, and the battery temperature is set to the heating temperature and heating deactivation temperature at which the charging time of the battery relative to the corresponding output temperature is minimized. The way the battery is heated also affects the charging duration. Therefore, the battery should be heated as quickly as possible so that a relatively high charging current can be used as early as possible, thereby reducing the charging duration. Therefore, the size of the heater should be large enough. Determining the starting temperature that has a positive impact on the charging duration by activating the heater is similar to determining it by a series of tests initially performed. Herein lies the question of at what battery temperature heating should be deactivated again so that, on the one hand, the battery temperature at the coldest point is brought to the highest possible temperature, while avoiding overheating of the hottest point. By subsequently activating the cooling system, the battery can be further heated even at a relatively cold starting temperature or ambient temperature than if no subsequent cooling were performed, resulting in a higher charging current being used more quickly. The question of when to activate or deactivate the heater will also be answered in conjunction with the initial series of tests to be performed. In this regard, we will again refer to the papers of the inventors that have already been cited.

[0049] According to the present invention, in a vehicle comprising a traction battery, a cooling system, and at least one control device, the traction battery, cooling system, and at least one control device are configured to perform the described method. The vehicle can be any road vehicle, such as a car, truck, van, bus, etc. It can also be a railway vehicle, ship, or aircraft. The same or different control devices can be used to monitor the traction battery and regulate the cooling system. In this case, at least one control device can also be formed by the battery management system of the traction battery. By applying the method according to the present invention, the vehicle according to the present invention can shorten the charging time of the charging process for charging the traction battery, which improves the comfort of the vehicle user. Therefore, according to the present invention, the disclosed charging method is used for charging the traction battery of a vehicle.

[0050] Other advantageous designs of the charging method for secondary batteries according to the present invention also arise from embodiments, which will be described in more detail below with reference to the accompanying drawings.

[0051] in:

[0052] Figure 1 A schematic cross-sectional view of the primary cell of a secondary battery is shown;

[0053] Figure 2 The first graph shows the changes in battery voltage and anode voltage over time during the charging process of the primary battery;

[0054] A second graph shows the battery temperature and the battery's C-rated value at different locations on the battery during the charging process of the primary battery, as well as...

[0055] A third figure shows the heat power released by the battery during the charging process and the corresponding cooling power of the cooling system used to cool the battery; and

[0056] Figure 3 Two graphs are shown illustrating the duration of the charging process and the cooling / heating card, which activates the cooling system based on the start-up conditions selected by the cooling / heating card.

[0057] Figure 1 A primary cell 1 for forming a secondary battery is shown. For example, this is a lithium-ion battery designed as a spherical cell. For example, the spherical cell type is 18650, 21700, or 46800. However, it can also be a pouch cell, etc. Several such cells 1 can also be connected together to form a battery module. One or more primary cells 1 form a secondary battery.

[0058] Figure 1 The primary battery 1 shown is charged using the charging method according to the present invention. During the charging process, the primary battery 1 becomes hot. The resulting heat dissipation is discharged through a cooling system. Figure 1 Therefore, the primary cell 1 is mounted on the cooling plate 3, which has at least one channel 4 for volumetric flow rate. Guide the cooling medium. Figure 1 In the middle, the potential coldest point, COLDSPOT, is located in the lower region of the galvanic cell 1 facing the cooling plate 3 on the outer circumference. The potential hottest point, HOTSPOT, is located at the relatively free end of the inner galvanic cell 1. Figure 1 The coldest and hottest areas shown are typically very small, especially along the longitudinal direction of the battery, with the hottest area located only at the very upper inner edge of the battery and the coldest area located at the outer lower edge of the battery.

[0059] By performing the charging method according to the invention, the primary battery 1 is now being charged. In this case, the heat power to be discharged by the cooling system is specifically adjusted according to the charging stage.

[0060] Figure 2 The charging method according to the present invention is illustrated in three figures, which are divided into three charging stages a), b), and c). The horizontal axis of the three figures represents time t. In the figures, some variables are qualitative, and some variables are quantitative.

[0061] exist Figure 2 The above figure shows the battery voltage U. Zelle and anode voltage U AnodeIn addition, the full-cell voltage limit U grenz The electroplating limit 5 is plotted as a horizontal line. The middle plot shows the battery temperature T at different locations. Zelle And the C rating of battery 1. In addition, the overheat limit T... max and current limit I max The figures are represented by horizontal lines. The bottom figure shows the heat power P dissipated by battery 1. verlust Cooling power P of the cooling system cool And the heat transfer coefficient h at the heat exchange surface between battery 1 and the cooling system.

[0062] During charging phase a), battery 1 is charged with the cooling system disabled. During charging phase b), the cooling system operates at its maximum cooling power P. cool Connect and operate at full load. During the charging phase c), reduce cooling power P. cool Adjusting cooling power P cool This causes the battery temperature T of the potential hottest point (HOTSPOT) and potential coldest point (COLDSPOT) of the primary cell 1 to be... Zelle It remains essentially constant. In the illustrated embodiment, the hottest temperature T... hot It remains basically constant, while the coldest point temperature T cold The charging current I increases continuously. lade The adjustment is based on previously known conventional charging methods, and is first performed at the current limit I. max The maximum value is reached, and then decreases as the charging duration increases. This is to adjust the cooling power P. cool It can perform operations based on the measured hottest temperature T. hot The adjustment, or the execution of power-based adjustment, wherein the cooling power P cool The heat dissipation power P corresponding to the primary battery 1 verlust Therefore, the heat dissipation and discharge remain in balance, keeping the temperature state of the galvanic cell 1 basically constant.

[0063] The top graph shows that as the charging duration increases, the battery voltage U... Zelle The voltage is continuously increasing. Battery 1 is charging. In this case, the anode voltage U... Anode The voltage continues to decrease until it reaches the plating limit of 5 shortly before reaching it. The anode voltage U from different simulations is plotted here. Anode Several curves. To ensure the shortest charging duration, the anode voltage U... Anode Conduction should occur along the plating limit 5, which is the case here. Theoretically, the plating limit 5 is 0mV, but for safety reasons, it is adjusted to be slightly above 0mV. Therefore, battery 1 can operate continuously at the anode potential limit, i.e., the plating limit 5, with the highest possible coldest point temperature T.cold and minimum overvoltage.

[0064] As can be seen from the middle graph, the temperature of the hottest spot, T... hot Along the overheat limit T max The cooling power P in the charging phase (c) is adjusted as much as possible to reliably prevent overheating of the active materials in battery 1. cool This avoids cooling the potentially coldest point of the COLDSPOT during high-charge states. Instead, even the coldest point temperature T... cold This increases the local limiting resistance, thereby reducing the ability to use a higher charging current I. lade To perform the charging process. Furthermore, during charging phase c), the hottest temperature T... hot Slightly reduce, thus reaching the overheat limit T max The buffering mechanism is in place. Furthermore, a slight temperature gradient is maintained within battery 1, which is not completely reduced, allowing battery 1 to cool rapidly back to its normal operating temperature after the charging process.

[0065] The figure below shows the heat P dissipated from battery 1 during charging. verlust Or the process of heat power. When switching from charging phase a) to charging phase b), the cooling system is switched on to full load. The maximum possible heat transfer coefficient h is established accordingly and maintained during charging phase b). The heat discharged from the cooling system, i.e., the cooling power P. cool It initially rises very rapidly to its maximum value, then declines again, and then rises slowly until the end of charging phase b). During charging phase c), the cooling power P... cool Follow the heat dissipation power P verlust Therefore, the cooling system is adjusted to bring the temperature of the hottest spot T to a suitable level. hot To maintain a relatively constant level, the volumetric flow rate of the liquid cooling medium is reduced by decreasing the speed of the cooling medium supply pump, thereby reducing the heat transfer coefficient h. Therefore, the heat transfer coefficient h is adjusted in such a way that the heat flow discharged by the cooling medium at the system boundary is proportional to the cooling power P. cool This precisely corresponds to the heat generated by battery 1. In this case, potential heat sources in the battery casing and the battery connector (if needed) can also be considered.

[0066] By dividing the charging process into charging stages a), b), and c), the maximum charging current I can be provided in each case. lade This shortens the overall charging time.

[0067] While charging phase c) allows for a shorter charging duration near the end of the charging process, i.e., within the range of a higher state of charge, charging phases a) and b) allow for an accelerated charging duration at the beginning and middle of the charging process. Therefore, according to the invention, a shorter charging duration can be achieved solely through charging phase c). Phase c) is particularly useful at high temperatures to avoid unnecessary cooling. This primarily occurs in higher states of charge with corresponding heating; however, in some cases, it may occur in low states of charge even if the temperature limit is reached prematurely at a high initial temperature.

[0068] However, another problem arises: when, i.e., at the battery temperature T caused by charging... Zelle =T hot In this case, it is best to switch from charging phase a) to charging phase b). Typically, any desired activation temperature T... an,opt (see Figure 3 Both can be used for this purpose. Figure 3 For clarity, only a few points are provided with corresponding reference numerals in the accompanying diagram. However, the battery temperature T... Zelle There is an optimal temperature point from which the cooling system should be activated at full load. Therefore, if activated too early, the potentially coldest point, COLDSPOT, has not yet been sufficiently heated, resulting in higher resistance and thus requiring a lower charging current I. lade This is to prevent overvoltage. On the other hand, if the cooling system is activated too late, i.e., waits until the battery temperature T... Zelle If the current is higher, there is a risk of overheating at the hottest spot, so in order to adequately cool the charging current I... lade The charging time must be reduced suddenly and rapidly, which also leads to an increase in charging time again.

[0069] Optimal start-up temperature T an,opt and the corresponding initial temperature T start The relationship between them is Figure 3 Explanation. In this case, the initial temperature T start It is related to the ambient temperature. Therefore, we assume the battery temperature T Zelle Corresponding to ambient temperature. Then generated based on measurement series and / or simulation. Figure 3 The cooling / heating card 2 is shown. This displays the initial temperature T on the horizontal axis. start The vertical axis displays different temperatures T. In each case, for different output temperatures T... start Perform several charging processes, where, for the corresponding output temperature T start Charge until the battery reaches the set temperature T. ZelleThen the cooling system was activated. Curve 6 was plotted on cooling / heating card 2, marking the corresponding initial temperature T. start Optimal start-up temperature T an,opt .

[0070] The following points should be noted: Figure 3 The graph shown only relates to the output temperature T. start Optimal start-up temperature T an,opt The determination of . Therefore, in order to determine Figure 3 The information shown indicates that during charging phase c), no cooling power adjustment is performed; instead, the system continues to operate at its maximum value. Therefore, in Figure 3 The corresponding charging duration t appears in the following figure. lade Only affected by the activation temperature T an,opt The choice of power P allows for the exclusion of cooling power P during charging phase c). cool Adjustment to the optimal start-up temperature T an,opt The definite potential impact.

[0071] The cooling / heating card 2 is divided into three zones: 7.1, 7.2, and 7.3. In zone 7.1, the cooling system is operational. In zone 7.2, neither the cooling nor the heating system is operational. In zone 7.3, the heater is used to preheat battery 1, then from the heating shutdown temperature T. aus,heiz Start shutting down.

[0072] At an initial temperature of approximately 25°C, T start As described above, the cooling system is directly switched on to full load at the start of the charging process. Therefore, the duration of charging phase a) here is 0 seconds.

[0073] The diagram below shows the output temperature T of the primary cell 1. start As the charging process begins, the primary battery 1 is heated, causing it to move upwards to a warmer temperature within the cooling / heating card 2. This is due to the initial temperature T of 15°C. start Arrow 8 is used as an example.

[0074] However, for example, -10°C, this means additionally through region 7.3. This means that heating is also enabled when the charging process begins. It is charged and operates heating until the heating shutdown temperature T is reached. aus,heiz The boundary between regions 7.2 and 7.3 is determined by the heating temperature T. heiz This is used for characterization. When the heating shutdown temperature is reached, the heater stops and enters zone 7.2. Charging continues until the activation temperature T is reached. an,opt The overheat limit T is also shown. max Among these, cooling is used to prevent the battery temperature T from rising. Zelle Exceeding this limit.

[0075] From the following figure Figure 3 It can be seen that the charging time can be shortened, especially at the cold output temperature T. start In the case of standard adjustment of the cooling system, curve 9.1 shows the charging duration when cooling is not required. Curve 9.2 shows the charging duration when the cooling system is switched to the corresponding activation temperature T as described above. start,opt The charging duration occurs (without heating). Curve 9.3 shows the charging duration set with battery 1 preheated.

[0076] To further improve charging duration, therefore based on Figure 3 The knowledge shown, during the charging phase c)( Figure 3 The cooling system is adjusted (not shown in the image).

Claims

1. A charging method for a secondary battery, wherein, The charging current (I) used to charge at least one primary cell (1) of the secondary battery with electrical energy lade During charging, the parameters are adjusted by considering at least one of the following variables: maximum battery voltage, minimum anode voltage, and battery temperature (T). Zelle (and / or the maximum charging current, and the heat dissipated therefrom is discharged through a cooling system that is at least temporarily activated during the charging process,) It is characterized by the following charging stages: a) Once the battery temperature (T) at the potential hottest point of the battery (1) is reached... Zelle ) lower than the set activation temperature (T) an,opt The battery (1) is charged using the deactivated cooling system, wherein the activation temperature (T) is... an,opt Depending on the battery type and the output temperature (T) of the battery (1) at the start of the charging process. start ); b) Once the battery temperature (T) at the potential hottest point of the battery (1) is reached... Zelle ) Reaching the set activation temperature (T) an,opt The battery (1) is charged using a fully loaded cooling system; and c) Once the battery temperature (T) at the potential hottest point of the battery (1) is reached... Zelle The temperature change reaches zero: reduce the cooling power (P) of the cooling system. cool And adjust the cooling power (P) cool ), such that the battery temperature (T) at the potential hottest point (HOTSPOT) and / or the potential coldest point (COLDSPOT) of the battery (1) Zelle ) remains essentially constant; and among them Before the battery (1) reaches full charge, the battery temperature (T) Zelle The charging rate decreases within the set charging state range.

2. The method according to claim 1, Its features are, In order to adjust the cooling power (P) cool ): -Measure and / or calculate the estimated thermal power (P) released by the battery (1). verlust ); - Measure and / or calculate the estimated heat power that can be discharged or removed from the cooling system; and - Adjust the cooling power (P) in this way cool The heat power that can be discharged or discharged is substantially equivalent to the heat power (P) released by the battery (1). verlust ).

3. The method according to claim 1 or 2, Its features are, Adjust the heat transfer coefficient between the interaction surfaces of the battery (1) and the cooling system to regulate the heat power to be discharged from the cooling system.

4. The method according to claim 3, Its features are, A fluid-based cooling system is used, wherein a cooling medium flows indirectly or directly to or around at least a portion of the battery (1), and the volumetric flow rate of the cooling medium is adjusted to suit the heat transfer coefficient.

5. The method according to claim 4, Its features are, Adjust the speed of the cooling medium supply pump to match the volumetric flow rate of the cooling medium.

6. The method according to any one of claims 1 to 5, Its features are, If the output temperature (T) of the battery (1) start The temperature is lower than the set heating temperature (T). heiz If the battery is actively heated at least temporarily during the charging phase a), then when the temperature is below the activation temperature (T), the battery is heated (1). an,opt Heating shutdown temperature (T) aus,heiz When the heating for this purpose is turned off, and wherein the heating shutdown temperature (T) is... aus,heiz The output temperature (T) of the battery (1) at the start of the charging process depends on the battery type and the battery's output temperature (T). start ).

7. The method according to any one of claims 1 to 6, Its features are, The calculation unit used to adjust the cooling system reads the activation temperature (T) from the cooling / heating card (2). an,opt ), wherein the cooling / heating card (2) is initially created by performing measurements and / or simulations for the type of battery used, wherein, in order to determine different output temperatures (T start ) start-up temperature (T) an,opt ) and output temperature (T start The relationship between the cooling system and the battery temperature (T) is such that the cooling system is activated in each case at different battery temperatures (T). Zelle ), and the battery temperature (T) Zelle ) is set to the activation temperature (T) an,opt ), wherein the battery (1) described below is relative to the corresponding output temperature (T start Charging time (t) lade (Minimum) 8. The method according to claims 6 and 7, Its features are, The calculation unit for adjusting heating reads the heating temperature (T) from the cooling / heating card (2). heiz ) and the heating shutdown temperature (T) aus,heiz ), where, in order to determine different output temperatures (T) start Heating temperature (T) heiz ), heating shutdown temperature (T) aus,heiz ) and output temperature (T start The relationship between ) at different battery temperatures (T) Zelle Heating is enabled and disabled at the specified temperature (T). Zelle The temperature is set to the heating temperature (T). heiz ) and heating shutdown temperature (T) aus,heiz ), wherein the battery (1) described below is relative to the corresponding output temperature (T start Charging time (t) lade (Minimum) 9. A vehicle comprising a traction battery, a cooling system, and at least one control device. Its features are, The traction battery, the cooling system, and the at least one control device are configured to perform the method according to any one of claims 1 to 8.

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