Method and apparatus for charging or discharging a battery system

Abstract

The invention relates to a method for charging or discharging a battery system (20), wherein the battery system (20) comprises at least two battery cells (21-x) connected in parallel and / or in series, which can only be charged or discharged together, wherein a voltage (U) is controlled as a control variable by means of a current (I) or a power (P) as a manipulated variable, wherein the current (I) or the power (P) is specified taking into account a first state-of-charge-dependent characteristic curve (3-1) and a second state-of-charge-dependent characteristic curve (3-2), and wherein the first state-of-charge-dependent characteristic curve (3-1) and the second state-of-charge-dependent characteristic curve (3-2) have at least sectionally opposite slopes. The invention further relates to a device (1) for charging or discharging a battery system (20).

Description

[0001] The invention relates to a method and a device for charging or discharging a battery system.

[0002] Depending on temperature, current application duration, and state of charge, lithium-ion cells can only absorb a limited charging current without sustaining damage. This maximum current also changes with the state of health (SOH) of the lithium-ion cells. Another challenge is that multiple cells can be connected in series or parallel within a battery system, and the cells can have different temperatures and / or states of health and / or charge. Consequently, it is currently necessary to know the state of health and age of all cells in the system, as well as the coldest and warmest points, at all times. This also means that temperature gradients within a cell must be known in order to actually know the coldest and warmest points in the entire battery system. These two points, together with the state of health and age of each cell, determine the maximum possible charging current at any given time.Since a relaxed cell can briefly absorb a higher current than the maximum possible continuous current, the temporal response of the cell to the charging current must also be known. In addition, the maximum permissible charging currents also depend on mechanical pressure or a force acting on the battery cells. Furthermore, a state of charge distribution, i.e. different states of charge, can occur between the individual battery cells within the battery system. In addition, a state of charge distribution can also occur within a battery cell. This state of charge distribution must be taken into account when selecting (regulating) the charging current, since the charging current generally depends on the state of charge. However, determining the state of charge of each individual cell in parallel-connected battery cells as well as the state of charge distribution within a battery cell cannot be technically implemented in practical operation.

[0003] DE 10 2021 108 085 A1 discloses a method for determining at least one control parameter for a charging device for supplying electrical charge to a lithium-based electrical energy storage device. For this purpose, the electrical energy storage device is subjected to an electrical charging current depending on at least one state parameter of the electrical energy storage device. To determine the at least one control parameter, a limit function is determined, by which an electrical limit voltage is assigned to a supplied electrical charge quantity, such that an anode potential is greater than a predetermined anode potential value if a terminal voltage is less than the limit voltage, wherein the predetermined anode potential value is greater than zero volts relative to a Li / Li+ reference electrode.

[0004] The invention is based on the object of improving a method and a device for charging or discharging a battery system.

[0005] The object is achieved according to the invention by a method having the features of patent claim 1 and a device having the features of patent claim 10. Furthermore, the object is achieved by a method having the features of patent claim 11 and a device having the features of patent claim 12. Advantageous embodiments of the invention emerge from the subclaims.

[0006] In particular, a method for charging or discharging a battery system is provided, wherein the battery system has at least two battery cells connected in parallel and / or in series, which can only be charged or discharged together, wherein a voltage is controlled as a controlled variable by means of a current or a power as a manipulated variable, wherein the current or the power is predetermined taking into account a first state-of-charge-dependent characteristic curve and a second state-of-charge-dependent characteristic curve, and wherein the first state-of-charge-dependent characteristic curve and the second state-of-charge-dependent characteristic curve have opposite gradients at least in sections.

[0007] Furthermore, in particular, a device for charging or discharging a battery system is created, wherein the battery system has at least two battery cells connected in parallel and / or in series, which can only be charged or discharged together, comprising a controller, wherein the controller is designed to regulate a voltage as a controlled variable by means of a current or a power as a manipulated variable, wherein the current or the power is predetermined taking into account a first characteristic curve dependent on the state of charge and a second characteristic curve dependent on the state of charge, and wherein the first characteristic curve dependent on the state of charge and the second characteristic curve dependent on the state of charge have opposite gradients at least in sections.

[0008] Furthermore, in particular, a method for charging or discharging a battery system is provided, wherein the battery system has a battery cell, wherein a voltage is controlled as a controlled variable by means of a current or a power as a manipulated variable, wherein the current or the power is predetermined taking into account a first state-of-charge-dependent characteristic curve and a second state-of-charge-dependent characteristic curve, and wherein the first state-of-charge-dependent characteristic curve and the second state-of-charge-dependent characteristic curve have opposite gradients at least in sections.

[0009] A device for charging or discharging a battery system is also provided, wherein the battery system has a battery cell, comprising a controller, wherein the controller is designed to regulate a voltage as a controlled variable by means of a current or a power as a manipulated variable, wherein the current or the power is predetermined taking into account a first characteristic curve dependent on the state of charge and a second characteristic curve dependent on the state of charge, and wherein the first characteristic curve dependent on the state of charge and the second characteristic curve dependent on the state of charge have opposite gradients at least in sections.

[0010] The method and device make it possible to control charging or discharging based on the state of charge of the battery system as a whole, in particular without requiring knowledge of the states of the individual battery cells. One of the basic ideas here is to use two state-of-charge-dependent characteristic curves for control, with these two characteristic curves having opposite gradients at least in some sections. This makes it possible to adhere to limit values ​​for electrical quantities during charging and discharging, especially when an estimate of the state of charge is subject to error.

[0011] A voltage, a current, an internal resistance, and a power during charging and discharging are, in particular, a total voltage, a total current, a total internal resistance, and a total power of the battery system. The values ​​for the individual battery cells are not recorded and / or used.

[0012] In particular, it is provided that a voltage is detected on the battery system, whereby this voltage is used as a control variable during regulation.

[0013] In particular, it is intended that the characteristic curves specify maximum values ​​(limit values) for suitable electrical quantities that must not be exceeded. By using two characteristic curves, two such quantities can be taken into account and / or used for control purposes according to this method. It can be provided that during control, compliance with the first characteristic curve is checked first and then compliance with the second characteristic curve. Alternatively, however, it can also be provided that during control, compliance with the second characteristic curve is checked first and then compliance with the first characteristic curve. Furthermore, compliance with both characteristic curves can also be checked simultaneously.

[0014] The first state-of-charge-dependent characteristic curve and the second state-of-charge-dependent characteristic curve are determined, in particular, under laboratory conditions, particularly in empirical tests, and / or with the help of simulations. This can be used, for example, to determine a characteristic curve for a state-of-charge-dependent maximum voltage. For example, measurements can be performed on 3-electrode laboratory cells. Furthermore, compressive force, thickness, or high-precision coulombmetry measurements can also be performed. Furthermore, a predefined current characteristic map can be applied to the cell, particularly taking a safety margin into account, and in this way, a state-of-charge-dependent characteristic curve for the maximum voltage can be determined. A simulation can be performed, for example, based on half-cell models.

[0015] Parts of the device, in particular the controller, can be implemented individually or collectively as a combination of hardware and software, for example, as program code executed on a microcontroller or microprocessor. However, it can also be provided that parts are implemented individually or collectively as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA).

[0016] In one embodiment, the characteristic curves have opposite gradients across all charge states. This allows for a particularly simple implementation of the method and device and ensures compliance with limit values ​​at all times.

[0017] In one embodiment, the first state-of-charge-dependent characteristic curve specifies a maximum voltage during charging or discharging that increases with the state of charge. This allows a voltage during charging and discharging to be limited. The underlying idea is that if the maximum charging or discharging current is determined for each state of charge and the anode potential is assumed to be the limiting factor, a temperature-independent state-of-charge-dependent full-cell voltage trajectory results. This full-cell voltage trajectory, in particular, then forms the state-of-charge-dependent first characteristic curve. This full-cell voltage trajectory increases with increasing state of charge.

[0018] In one embodiment, the first state-of-charge-dependent characteristic curve specifies a maximum internal resistance during charging or discharging that increases with the state of charge. The internal resistance can be calculated based on a current and an overvoltage (= external voltage, i.e., a voltage under load, minus the open-circuit voltage). The overvoltage can be estimated from a model in a conventional manner.

[0019] In one embodiment, the second state-of-charge-dependent characteristic curve specifies a maximum current during charging or discharging that decreases with the state of charge. This allows the current during charging and discharging to be limited.

[0020] In one embodiment, the second state-of-charge-dependent characteristic curve specifies a maximum power during charging or discharging that decreases with the state of charge. This makes it possible to limit the power during charging or discharging. The power can be a power calculated from the current and the voltage (ie, P = U*I; where P is the power, U is the voltage, and I is the current). In principle, however, the power can also be a power loss, which is calculated, for example, from the internal resistance and the current (ie, P = R*I 2 ) or calculated from the overvoltage and current (ie P = Uü*I).

[0021] It can also be provided that the first state-of-charge-dependent characteristic curve and / or the second state-of-charge-dependent characteristic curve depicts a combination of electrical variables and / or specifies limit values ​​for such a combination of electrical variables.

[0022] In one embodiment, a temperature of the battery system is detected and / or estimated, wherein the first state-of-charge-dependent characteristic curve and / or the second state-of-charge-dependent characteristic curve are temperature-dependent, taking the detected and / or estimated temperature into account. This allows temperature effects to be taken into account, allowing control during charging or discharging to be further improved.

[0023] In one embodiment, the state of charge of the battery system is estimated based on a temporal integration of the current during charging or discharging. For this purpose, a state of charge estimator integrates the current flowing during charging or discharging. This provides a balanced amount of charge that has flowed into and / or out of the battery system. Based on a starting value and a total amount of charge that the battery system can store, the current state of charge can be determined in this way. The state of charge (SOC) can be specified, for example, with reference to a maximum storable charge quantity as a percentage or absolutely in the unit ampere-hours (Ah).

[0024] In one embodiment, it is provided that a state of charge of the battery system is estimated based on an open-circuit voltage / state of charge (OCV / SOC) characteristic curve and / or using an electrical battery model. The open-circuit voltage / state of charge (OCV / SOC) characteristic curve makes it possible to estimate the state of charge based on a measurement of the open-circuit voltage in the unloaded state of the battery system. The electrical battery model makes it possible to estimate a state of charge in a conventional manner based on measurable electrical quantities (open-circuit voltage, voltage, current, internal resistance, etc.). The open-circuit voltage / state of charge (OCV / SOC) characteristic curve and / or the electrical battery model are determined, for example, using measurements under laboratory conditions, i.e., by means of empirical tests, and / or using simulations.

[0025] Further features for the design of the devices will become apparent from the description of embodiments of the method. The advantages of the devices are the same as those of the embodiments of the method. The embodiments of the method and the device for charging and discharging a battery system with only one battery cell are, in particular, the same as for a battery system with multiple battery cells.

[0026] The invention will be explained in more detail below using preferred embodiments with reference to the figures. Fig. 1 is a schematic representation of an embodiment of the device for charging or discharging a battery system; Fig. 2a, Fig. 2b, Fig. 2c schematic representations to illustrate the functioning of an embodiment of the method and the device; Fig. 3 Results of a simulated charging process on a battery system with two battery cells connected in parallel and a process-based control.

[0027] The Fig. Figure 1 shows a schematic representation of an embodiment of the device 1 for charging or discharging a battery system 20. The battery system 20 comprises two battery cells 21-x connected in parallel (alternatively also in a different configuration), which, however, can only be charged and discharged together. The battery cells 21-x are, in particular, Li-ion cells. A device for charging and discharging a battery system with only one battery cell is fundamentally designed in the same way as the device shown in Fig. 1, so that it will not be discussed separately.

[0028] The device 1 comprises a controller 2. The controller 2 is configured to regulate a (total) voltage U, composed of the voltages U1, U2 at the battery cells 3-x, as a controlled variable using a current I or a power P as a manipulated variable. The current I or the power P is divided between the currents I1, I2 or the powers P1, P2 at the individual battery cells 21-x. The voltage U and the current I or the power P refer to the battery system 20 as a whole, i.e., the corresponding values ​​for the individual battery cells 21-x are not known and are not recorded. The voltage U is recorded at the battery system 20 by means of a sensor system (not shown) set up for this purpose.

[0029] It is intended that the current I or the power P is specified during regulation taking into account a first state-of-charge-dependent characteristic curve 3-1 and a second state-of-charge-dependent characteristic curve 3-2. The first state-of-charge-dependent characteristic curve 3-1 and the second state-of-charge-dependent characteristic curve 3-2 have, at least in sections, opposite gradients. In particular, regulation is carried out in such a way that the maximum values ​​(limit values) specified by the characteristic curves 3-x are not exceeded.

[0030] A state of charge (SOC) is estimated using a state of charge estimator 4 of the device 1. It can be provided that the state of charge (SOC) of the battery system 20 is estimated based on a temporal integration of the current I during charging or discharging. Alternatively or additionally, it can be provided that the state of charge (SOC) of the battery system 20 is estimated based on an open-circuit voltage-state of charge (OCV / SOC) characteristic curve and / or using an electrical battery model.

[0031] In the example shown, it is particularly provided that the first state-of-charge-dependent characteristic curve 3-1 specifies a maximum voltage Ulim that increases with the state of charge SOC during charging or discharging.

[0032] Furthermore, in the example shown, it is further provided in particular that the second state-of-charge-dependent characteristic curve 3-2 specifies a maximum current Ilim during charging or discharging that decreases with the state of charge SOC.

[0033] In the example shown, it is particularly intended that the characteristic curves 3-1, 3-2 have opposite gradients across all states of charge SOC.

[0034] Alternatively, it can be provided that the first state-of-charge-dependent characteristic curve 3-1 specifies a maximum internal resistance during charging or discharging that increases with the state of charge SOC.

[0035] Alternatively, it can be provided that the second state-of-charge-dependent characteristic curve 3-2 specifies a maximum power during charging or discharging that decreases with the state of charge SOC.

[0036] It can be provided that a temperature T of the battery system 20 is detected and / or estimated, wherein the first state-of-charge-dependent characteristic curve 3-1 and / or the second state-of-charge-dependent characteristic curve 3-2 are temperature-dependent, and wherein the detected and / or estimated temperature T is taken into account. For example, it can be provided that the characteristic curves 3-x are selected or parameterized based on the detected and / or estimated temperature T.

[0037] The Fig. 2a, Fig. 2b and Fig. 2c show schematic representations to illustrate the operation of an embodiment of the method and device. Each of the three figures shows a specific case of charge states at a single point in time.

[0038] In the Fig. 2a, the state of charge estimator 4 estimates a state of charge SOC which corresponds to an average of the states of charge SOC1, SOC2 of the two battery cells 21-x ( Fig. 1). For example, due to a higher temperature in the battery cell 21-2 compared to the battery cell 21-1, the battery cell 21-2 has a lower internal resistance. As a result, the (total) charging current I is divided into two unequal partial currents I1 and I2. The charging current I2 is greater than the charging current I2. As a result, the state of charge SOC2 of the battery cell 21-2 increases faster than the state of charge SOC1 of the battery cell 21-1. Since the state of charge estimator 4 ( Fig. 1) can only detect the (total) current I or the (total) voltage U of the parallel-connected battery cells 21-x, only a resulting average value of the state of charge SOC from the states of charge SOC1, SOC2 of the battery cells 21-x is detected. The charge control by the charge controller 2, which releases a maximum permissible voltage Ulim based on the state of charge SOC and the first state-of-charge-dependent characteristic curve 3-1, would release an excessively high voltage (here Ulim) in the case of battery cell 21-1. However, according to the method described in this disclosure, the current I would be limited to the current Ilim, which is smaller than Ilim1, based on the second state-of-charge-dependent characteristic curve 3-2. Since both limitations are taken into account during control, the result would be neither a current limit violation nor a voltage limit violation.A control system with a single characteristic curve, for example only the first state-of-charge-dependent characteristic curve 3-1, would have resulted in the maximum voltage for battery cell 21-1 being exceeded. In the case of battery cell 21-2, a value for the current limit that is too high would initially be assumed (Ilim instead of Ilim2), but the value for the voltage limit Ulim is smaller than Ulim2, which also limits the resulting current I. Since both limits are taken into account in the control system, the result would therefore be neither a current limit violation nor a voltage limit violation. A control system with a single characteristic curve, for example only the second state-of-charge-dependent characteristic curve 3-2, would have resulted in the maximum current for battery cell 21-2 being exceeded.

[0039] In the Fig. 2b, the state of charge estimator 4 ( Fig. 1) due to an error, a state of charge SOC that is greater than the average SOC from the states of charge SOC1, SOC2 of the two battery cells 3-x. The charge control, which releases a maximum voltage U based on the state of charge SOC, would release an excessively high voltage Ulim in the case of battery cell 3-1 and battery cell 3-2. However, according to the process, the second state-of-charge-dependent characteristic curve 3-2 limits the current to Ilim, so that the value is smaller than Ilim1 and Ilim2. Since both limitations are taken into account in the control, the result would therefore be neither a current limit violation nor a voltage limit violation. Control with a single characteristic curve, for example only the first state-of-charge-dependent characteristic curve 3-1, would have led to the maximum voltage being exceeded for both battery cells 21-1, 21-2.

[0040] In the Fig. 2c, the state of charge estimator 4 ( Fig. 1) a state of charge SOC that is lower than the average of the states of charge SOC1, SOC2 of the two battery cells 3-x. The charging control would initially assume a value for the current limit that is too high (Ilim instead of Ilim1 and Ilim2). However, according to the method, the value of the voltage limit Ulim is lower than Ulim1 and Ulim2, which also limits the resulting current I during charging. Since both limits are taken into account in the control, the result would therefore be neither a current limit violation nor a voltage limit violation. Control with a single characteristic curve, for example only the second state of charge-dependent characteristic curve 3-2, would have led to the maximum current being exceeded for both battery cells 21-1, 21-2.

[0041] The scenarios shown are merely exemplary and serve to illustrate the method and device described in this disclosure. In principle, the characteristic curves 3-x can also depict other variables and / or have a different profile.

[0042] The Fig. Figure 3 shows the results of a simulated charging process on a battery system with two battery cells connected in parallel, as described in Fig. 1, and a process-based control system. One battery cell has a temperature of 10°C, the other a temperature of 50°C. The simulation parameters used are as follows: - Cell chemistry: NMC - Cell capacity: 100 Ah - Heat capacity of a cell: 2000 J / K - Isothermal boundary conditions - Heat exchange coefficient between parallel cells: 0 W / K - Initial charge level at the beginning of the simulation: 5% (of the maximum charge) - Resistance of the connecting elements of the parallel-connected cells: 0 Ohm - Contact resistance: 0 Ohm - Internal cell resistance at 10°C: 1 mOhm to 3 mOhm - Internal cell resistance at 50°C: 0.5 mOhm to 1.5 mOhm - first state-of-charge dependent characteristic curve specifies the maximum voltage Ulim (limit voltage) - second state-of-charge dependent characteristic curve specifies the maximum current Ilim (limit current)

[0043] In the Fig.3 Top left shows a (total) current I, the respective maximum currents Ilim1, Ilim2 and the currents I1, I2 of the battery cells, each in A; top right shows the (total) state of charge SOC and the states of charge SOC1 and SOC2 of the battery cells in %; bottom left shows a (total) voltage U, a respective voltage U1, U2 at the battery cells as well as a maximum voltage Ulim (limit voltage) and the maximum voltages Ulim1 and Ulim2, which result from SOC1 and SOC2 respectively, each in V, and bottom right shows a temperature T1, T2 of the two battery cells in °C. The quantities are each shown over the time axis with the unit seconds.

[0044] It is noted that, in particular, only Ulim, I, and SOC, as well as the temperatures, are used for the control. In particular, I1, I2, Ulim1, Ulim2, SOC1, and SOC2 are unknown in reality and, within the context of the simulation, serve only to illustrate the method described in this disclosure.

[0045] It is clearly visible that the currents I1 and I2 always remain below the relevant maximum currents Ilim1 and Ilim2 due to the control process. The voltages U1 and U2 also always remain below the maximum voltage Ulim. List of reference symbols 1 device 2 controllers 3-1 first state-of-charge dependent characteristic curve 3-2 second state-of-charge dependent characteristic curve 4 state of charge estimators 20 Battery system 21-x battery cell I Current I1 current (first battery cell) I2 current (second battery cell) Ilim maximum current Ilim1 maximum current (starting from SOC1) Ilim2 maximum current (starting from SOC2) P Performance P1 power (first battery cell) P2 power (second battery cell) SOC (total) state of charge SOC1 state of charge (first battery cell) SOC2 state of charge (second battery cell) T Temperature U (total) voltage U1 voltage (first battery cell) U2 voltage (second battery cell) Ulim maximum voltage Ulim1 maximum voltage (starting from SOC1) Ulim2 maximum voltage (starting from SOC2) 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] DE 10 2021 108 085 A1

[0003]

Claims

[1] Method for charging or discharging a battery system (20), wherein the battery system (20) has at least two battery cells (21-x) connected in parallel and / or in series, which can only be charged or discharged together, wherein a voltage (U) is controlled as a controlled variable by means of a current (I) or a power (P) as a manipulated variable, wherein the current (I) or the power (P) is specified taking into account a first charge state-dependent characteristic curve (3-1) and a second charge state-dependent characteristic curve (3-2), and wherein the first charge state-dependent characteristic curve (3-1) and the second charge state-dependent characteristic curve (3-2) have opposite gradients at least in sections. [2] Method according to claim 1, characterized by that the characteristic curves (3-x) have opposite gradients across all states of charge (SOC). [3] Method according to claim 1 or 2, characterized bythat the first state-of-charge-dependent characteristic curve (3-1) specifies a maximum voltage (Ulim) that increases with the state of charge (SOC) during charging or discharging. [4] Method according to claim 1 or 2, characterized by that the first state-of-charge-dependent characteristic curve (3-1) specifies a maximum internal resistance during charging or discharging that increases with the state of charge (SOC). [5] Method according to one of the preceding claims, characterized by that the second state-of-charge-dependent characteristic curve (3-2) specifies a maximum current (Ilim) during charging or discharging that decreases with the state of charge (SOC). [6] Method according to one of claims 1 to 4, characterized by that the second state-of-charge-dependent characteristic curve (3-2) specifies a maximum power during charging or discharging that decreases with the state of charge (SOC). [7] Method according to one of the preceding claims, characterized bythat a temperature (T) of the battery system is detected and / or estimated, wherein the first state-of-charge-dependent characteristic curve (3-1) and / or the second state-of-charge-dependent characteristic curve (3-2) are temperature-dependent, and wherein the detected and / or estimated temperature (T) is taken into account. [8] Method according to one of the preceding claims, characterized by that a state of charge (SOC) of the battery system (20) is estimated based on a temporal integration of the current (I) during charging or discharging. [9] Method according to one of the preceding claims, characterized by that a state of charge (SOC) of the battery system (20) is estimated based on an open circuit voltage-state of charge (OCV / SOC) characteristic curve and / or by means of an electrical battery model. [10] Device (1) for charging or discharging a battery system (20), wherein the battery system (20) has at least two battery cells (21-x) connected in parallel and / or in series, which can only be charged or discharged together, comprising: a controller (2), wherein the controller (2) is designed to control a voltage (U) as a controlled variable by means of a current (I) or a power (P) as a manipulated variable, wherein the current (I) or the power (P) is specified taking into account a first charge state-dependent characteristic curve (3-1) and a second charge state-dependent characteristic curve (3-2), and wherein the first charge state-dependent characteristic curve (3-1) and the second charge state-dependent characteristic curve (3-2) have opposite gradients at least in sections. [11] Method for charging or discharging a battery system (20), wherein the battery system (20) comprises a battery cell (21-x), wherein a voltage (U) is controlled as a controlled variable by means of a current (I) or a power (P) as a manipulated variable, wherein the current (I) or the power (P) is specified taking into account a first charge state-dependent characteristic curve (3-1) and a second charge state-dependent characteristic curve (3-2), and wherein the first charge state-dependent characteristic curve (3-1) and the second charge state-dependent characteristic curve (3-2) have opposite gradients at least in sections. [12] Device (1) for charging or discharging a battery system (20), wherein the battery system (20) has a battery cell (21-x), comprising: a controller (2), wherein the controller (2) is designed to control a voltage (U) as a controlled variable by means of a current (I) or a power (P) as a manipulated variable, wherein the current (I) or the power (P) is specified taking into account a first charge state-dependent characteristic curve (3-1) and a second charge state-dependent characteristic curve (3-2), and wherein the first charge state-dependent characteristic curve (3-1) and the second charge state-dependent characteristic curve (3-2) have opposite gradients at least in sections.

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