DE102017207001A1 - Method for carrying out a charging process in a battery system - Google Patents

Abstract

The invention relates to a method (100) for carrying out a charging process (L) in a battery system (1). The following steps are provided: a) initiation of the charging process (L) in the battery system (1), b) detection of at least one state of charge information (110) which is specific for a state of charge in the battery system (1), c) initiating an interruption phase (U) in dependence on the detected state of charge information (110), so that the charging process (L) is interrupted during the interruption phase (U), d) detecting at least one compensation current information (120) which is specific for at least one compensation current in the battery system (1) in the interruption phase (U), e) determining a matched end of charge (E) in dependence on the compensation current information (120), f) Continuing the charging process (L) taking into account the adapted charging end (E).

Description

The present invention relates to a method for carrying out a charging process in a battery system according to the independent method claim. Furthermore, the invention relates to a system and a charging device according to the independent device claims.

State of the art

It is known from the prior art that battery cells (for example lithium-ion battery cells) can be interconnected in series and / or in parallel. This serves, in particular, to be able to provide the required power and the required energy content, for example for electric traction batteries. Such an interconnection can, for example, take place in that cells or modules or strands are connected in parallel to form a battery pack.

For charging such battery packs different charging strategies can be used, such. As a CC-CV (Constant Current Constant Voltage) or pulse charge.

Disclosure of the invention

The invention relates to a method with all features of the independent method claim, a system having the features of claim 11 and a loading device with all features of claim 12. Further features and details of the invention will become apparent from the respective dependent claims, the description and the drawings. In this case, features and details that are described in connection with the method according to the invention apply, of course, also in connection with the system according to the invention and the charging device according to the invention, and in each case vice versa, so that with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or may be ,

In particular, the invention provides a method for carrying out a charging process in a (rechargeable) battery system, preferably a lithium-ion battery system.

Preferably, the battery system is designed as a battery pack and / or comprises at least one battery pack, preferably a rechargeable battery, preferably as a parallel connection of battery units, in particular battery cells (short: cells) or battery modules (short: modules) or battery strings (short: strands) ,

• - eine inhomogene Temperaturverteilung,
• - ein inhomogener Alterungszustand,
• - eine inhomogene Kapazitäts- und/oder Innenwiderstandsverteilung aufgrund von Fertigungstoleranzen,
• - eine inhomogene Anbindung der parallelen Batterieeinheiten.

For example. It may be possible in such a parallel connection of battery units that it comes due to inhomogeneities during operation to different states of charge. For example. At least one of the following inhomogeneities can occur in the battery system:

• an inhomogeneous temperature distribution,
• an inhomogeneous state of aging,
• an inhomogeneous capacitance and / or internal resistance distribution due to manufacturing tolerances,
• - an inhomogeneous connection of the parallel battery units.

In particular, such inhomogeneities can lead to an inhomogeneous capacitance and internal resistance distribution of the individual cells, which can lead to an inhomogeneous loading of the parallel battery units during charging or discharging. In particular, due to the different charge states caused thereby at the end of a load phase (i.e., eg, charging and / or discharging and / or breaking the charge) during non-load phases (eg, in a balance phase), this leads to equalizing currents between the parallel connected battery units.

For example. the equalizing currents can lead to an overload. If z. For example, if one of the cells of the battery system (eg, in a parallel string) is already charged to 100% SOC (state of charge) after the end of the charging phase, then an equalizing current may possibly flow into this cell (from another parallel strand). and the cell will be overcharged by this equalizing current (ie, SOC> 100%). Possibly. then the cell voltage can exceed a maximum allowable cell voltage. The maximum permissible cell voltage is, for example, 4.2 V.

The method according to the invention therefore preferably serves to prevent and / or reduce overcharging in the battery system, in particular in the cells, preferably without actively interrupting the equalizing currents, particularly preferably without the use of additional switching elements for interrupting (ie also reducing) the equalizing currents. In particular, according to the method according to the invention, an adaptation of the charging process takes place so that the end of charging (for example the maximum SOC) is adapted flexibly, and thus preferably prevents at least one of the cells of the battery system from being overloaded by equalizing currents. This has the particular advantage that no overcharging takes place by equalizing currents and / or the usable capacity can be increased by a flexible adjustment of the end of loading.

1. a) Initiieren des Ladevorgangs bei dem Batteriesystem,
2. b) Erfassen wenigstens einer Ladezustandsinformation, welche für einen Ladezustand bei dem Batteriesystem spezifisch ist (bspw. proportional dazu ist), insbesondere während des Ladevorgangs und/oder außerhalb einer Unterbrechungsphase, vorzugsweise wiederholt und/oder zyklisch während des Ladevorgangs,
3. c) Initiieren einer Unterbrechungsphase in Abhängigkeit von der erfassten Ladezustandsinformation, sodass der Ladevorgang während der Unterbrechungsphase unterbrochen (pausiert) wird,
4. d) Erfassen wenigstens einer Ausgleichsstrominformation, welche für wenigstens einen Ausgleichsstrom bei dem Batteriesystem in der Unterbrechungsphase spezifisch ist, bspw. proportional dazu ist, insbesondere zyklisch und/oder wiederholt,
5. e) Bestimmen eines angepassten Ladeendes in Abhängigkeit von der Ausgleichsstrominformation,
6. f) Fortsetzen des Ladevorgangs unter Berücksichtigung des angepassten Ladeendes.

Advantageously, in the method according to the invention, at least the subsequent steps can be carried out, in particular successively or in any desired order, wherein individual steps may possibly also be carried out repeatedly:

1. a) initiate the charging process in the battery system,
2. b) detecting at least one state of charge information that is specific (eg proportional) for a state of charge in the battery system, in particular during the charging process and / or outside an interruption phase, preferably repeatedly and / or cyclically during the charging process,
3. c) initiating an interruption phase in response to the detected state of charge information such that the charging process is interrupted (paused) during the interruption phase,
4. d) detecting at least one compensating current information which is specific for at least one compensating current in the battery system in the interruption phase, for example being proportional thereto, in particular cyclically and / or repeatedly,
5. e) determining an adapted end of charge as a function of the compensation current information,
6. f) Resuming the charging process, taking into account the adjusted end of charging.

Preferably, according to step f), the charging process continues to a maximum until the adapted end of charge (and then possibly completely stopped), so that after the adjusted end of charge overcharging eg in cells of the battery system is avoided by the equalizing current. This has the advantage that a reliable end of charge can be determined reliably and quickly, which makes it possible to avoid overcharging. In particular, the adapted charging end can still provide (at least approximately) a maximum possible and / or meaningful charge.

For example. In step b) and / or c) a state of charge (SOC) is determined on the basis of the state of charge information, the initiation of the interruption phase preferably taking place when the state of charge exceeds a predetermined minimum value. The minimum value is, for example, in a range of 60% to 90%, preferably 80% to 85%. For example. the interruption phase is initiated only when the state of charge is less than 90%. The equalizing currents flowing in this interruption phase (i.e., a charging interruption) can then be detected or measured, for example, according to step d) and / or determined on the basis of the compensation current information. Preferably, a charge quantity and / or a calculated charge quantity transmitted by the compensation currents can be determined on the basis of the compensation current information. The calculated charge amount is, for example, a charge amount which approximately corresponds to a charge amount transferred during a compensation phase.

Preferably, a time duration of the interruption phase is a maximum of 0.5 min or a maximum of 1 min or a maximum of 2 min, so that after exceeding this period of time the charging process is continued again (according to step f). In particular, this does not make it possible to determine the amount of charge transferred completely by the equalizing currents during a typical equalizing phase, since the equalizing current may still continue to flow after that period of continuous interruption (eg over 10 minutes). Therefore, an evaluation, in particular an extrapolation and / or on the basis of stored characteristic diagrams, preferably takes place for the purpose of determining the charge quantity calculated for the adapted end of charge on the basis of the compensation current information. The advantage here is that the actual charging process is not significantly extended by the short interruption in the interruption phase, which is shorter than a theoretical full compensation phase.

Hierbei ist:

SOC_In:

das neue angepasste Ladeende (mit Berücksichtigung der Ausgleichsströme) in %,

SOC_Ia:

das alte Ladeende (ohne Berücksichtigung der Ausgleichsströme) in %,

ΔQ_a :

eine berechnete Ladungsmenge durch den Ausgleichsstrom in Ah (Amperestunden),

C_n:

eine Nennkapazität der Batteriezelle in Ah,

SOH_c:

ein Alterungszustand (Kapazität) der Zelle in %.

Preferably, the adjusted end of charge is determined on the basis of the following calculation, for example by calculating a processing device: $$\text{SOC\_In = SOC\_Ia-}\Delta \text{q\_a /}\left(\text{C\_n * SOH\_c}\right)$$

Here is:

SOC_In:

the new adjusted end of charge (taking into account the equalizing currents) in%,

SOC_Ia:

the old end of charge (without taking into account the equalizing currents) in%,

ΔQ_a:

a calculated amount of charge through the equalizing current in Ah (ampere hours),

c_n:

a nominal capacity of the battery cell in Ah,

SOH_c:

an aging state (capacity) of the cell in%.

The adaptation of the charging end can, for example, from an old end of loading with a state of charge from 100% to a customized end of charge with a state of charge of less than 100% (for example 99.4%). In other words, then, according to step f), the charging process is continued up to a charge state of less than 100%, which corresponds to the adjusted charge end (for example 99.4%).

In particular, the time of initiation of the interruption phase according to step c) is dependent on an evaluation of the detected state of charge information. The evaluation can be carried out, for example, electronically, for example by a processing device such as a microprocessor or the like.

For example. the state of charge information is a battery voltage or other parameter which is particularly proportional to and / or correlated with the state of charge of the battery. Preferably, the compensation current information is an amount of charge or the like which is correlated with a compensating current and / or a charge quantity which is transmitted in particular during the interruption phase between battery units of the battery system (for example battery cells, battery modules or battery strings).

According to an advantageous embodiment of the invention can be provided that according to step e) the adjusted end of charge as a reduction of a predetermined end of charging (old end of charge) is determined so that an overcharge in the battery system is avoided by a further equalizing current after completion of charging, preferably the adapted end of charge is calculated on the basis of the predetermined end of charge and / or the compensation current information and / or at least one rated capacity in the battery system and / or at least one aging state in the battery system.

It may also be possible that, based on the compensation current information, a (possibly also calculated) charge quantity is determined which is specific for a charge quantity transferred by the equalization current in the interruption phase or compensation phase. In particular, the (calculated) charge amount is specific for a charge amount in the compensation phase, which preferably lasts longer than the interruption phase. In the compensation phase, for example, the entire possible compensation current would flow, which may not be the case in the interruption phase due to a predetermined maximum duration of the interruption phase. The limitation of the interruption phase to a maximum duration has the advantage that the charging process need not be interrupted unnecessarily long.

Advantageously, it may be provided in the invention that (in particular in accordance with step e) for determining the adjusted end of charge) a ratio of a charge quantity specific to the compensation current, in particular a charge quantity transferred and / or calculated in the interruption phase, and a further parameter to one another is determined , wherein the further parameter preferably comprises at least one capacity-dependent and / or aging-dependent parameter of the battery system. The capacity-dependent parameter is, for example, a nominal capacity of the battery cell and / or the aging-dependent parameter is, for example, an aging state of the cell. For example. In this case, the ratio is determined by a calculation of a processing device, so that a reliable and rapid determination of the adapted end of loading is possible.

It may be advantageous if, within the scope of the invention, the compensating current is determined, in particular measured, as the compensating current between parallel-connected cells and / or modules and / or strings of the battery system. In particular, a module in this case comprises a plurality of cells and / or a strand comprises a plurality of modules in series, where appropriate, the strands are connected in parallel. This has the advantage that an increased energy content can be provided.

A further advantage within the scope of the invention can be achieved if a (calculated) charge quantity is determined by an estimation method, in particular by an extrapolation, on the basis of the compensation current information. This has the advantage that the interruption phase can have a short time duration, so that the charging process does not have to be interrupted for a significantly long time. The extrapolation, which is carried out, for example, by a processing device, can furthermore make a particularly reliable estimation of the charge quantity.

In addition, it is advantageous if a (calculated) charge quantity is determined by a comparison of the compensation current information with a specification, in particular with predefined characteristic maps. This has the advantage that the interruption phase can have a short time duration, so that the charging process does not have to be significantly interrupted. Nevertheless, a (calculated) amount of charge can be determined, which corresponds approximately to an amount of charge in an uninterrupted compensation phase.

In a further possibility, it may be provided that the charging process is carried out with a, in particular constant, charging current, wherein preferably the charging current in the interruption phase predominantly or substantially 0 A (ampere) is reduced, so that in particular a compensation current can flow. Favor is the equalizing current less than the charging current and / or operating current of the battery system. Thus, the equalizing current can be reliably determined.

It is also conceivable that, according to step f), the charging process is continued up to a predefined end of charging (for example up to an SOC of 100%) if the equalizing current information substantially does not indicate any compensating current (ie a charge amount substantially equal to 0 Ah) and otherwise the charging is continued until the matched end of charge, preferably wherein the adjusted end of charge is less than the predetermined end of charge. This has the advantage that after the adjusted end of charge overcharging can be avoided because the state of charge of the cells then possibly has a certain "reserve".

It is also conceivable within the scope of the invention that (according to step e)) the adapted end of charge is determined as a function of a predetermined end of charge, wherein in particular the predetermined end of charge is specified without taking into account the equalizing currents. In particular, the predetermined end of charge is 100% SOC (of the battery system or the battery) to ensure a complete charge.

• - wenigstens eine Steuerungseinheit, welche vorzugsweise dazu ausgeführt ist, ein erfindungsgemäßes Verfahren durchzuführen,
• - wenigstens ein Sensorelement zur Erfassung wenigstens einer Ausgleichsstrominformation bei einem Batteriesystem.

Likewise provided by the invention is a system comprising:

• at least one control unit, which is preferably designed to carry out a method according to the invention,
• - At least one sensor element for detecting at least one compensation current information in a battery system.

In this case, provision is made in particular for the sensor element to be connected to the control unit electrically or via radio.

Thus, the system according to the invention brings about the same advantages as have been described in detail with reference to a method according to the invention.

Likewise provided by the invention is a charging device for a battery system. In this case, provision is made in particular for the loading device to comprise a control unit which is designed to carry out a method according to the invention. Thus, the loading device according to the invention brings about the same advantages as have been described in detail with reference to a method and / or a system according to the invention.

• 1 eine schematische Darstellung eines Batteriesystems,
• 2 eine weitere schematische Darstellung eines Batteriesystems,
• 3 ein beispielhaftes Diagramm mit einer gemessenen Ausgleichsstrominformation,
• 4 eine schematische Darstellung zur Visualisierung eines erfindungsgemäßen Verfahrens,
• 5 eine weitere schematische Darstellung zur Visualisierung eines erfindungsgemäßen Verfahrens und eines erfindungsgemäßen Systems sowie einer erfindungsgemäßen Ladevorrichtung.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, embodiments of the invention are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination. Show it:

• 1 a schematic representation of a battery system,
• 2 a further schematic representation of a battery system,
• 3 an exemplary diagram with a measured compensation current information,
• 4 a schematic representation of the visualization of a method according to the invention,
• 5 a further schematic representation of the visualization of a method according to the invention and a system according to the invention and a loading device according to the invention.

In the following figures, the identical reference numerals are used for the same technical features of different embodiments.

In 1 schematically is a battery system according to the invention 1 shown. It is shown that the battery system 1 may be embodied as a battery pack and / or this may have, wherein the battery pack may be formed as a parallel connection of battery units. In particular, while the battery units z. B. cells 2 , Modules 3 and / or strands 4 include.

Exemplary are in 1 a first strand 4.1 and a second strand 4.2 connected in parallel, which each modules 3 include, namely a first module 3.1 , a second module 3.2 , a third module 3.3 and a fourth module 3.4 , It can be provided with each strand and 1 to n modules, where n can be any number and here is 2. In another example, in 2 a first module 3.1 and a second module 3.2 connected in parallel, each cell 2 include, a first cell 2.1 , a second cell 2.2 , a third cell 2.3 , as well as a fourth cell 2.4 , It can be provided for each module and 1 to m cells, where m can be any number and here is 2.

In 3 is an illustration of compensation current information 120 exemplified a measurement result. A measured compensation current information 130, which was detected, for example, by a current measurement, is shown with a current value I over the time t with a continuous line. Based on this measured information, it is possible to calculate a calculated compensation current information 140 to determine (shown as a dashed line). For this purpose, for example, an extrapolation of the measured values can be carried out. This also makes it possible to determine a calculated amount of charge.

In 4 schematically is a method according to the invention 100 visualized. It is shown that first a charging process L is performed, which is then interrupted in an interruption phase U. After a measurement of compensation current information 120 the charging process L is continued again until a (matched) end of charge E. The end of charge E indicates, for example, a state of charge, to which the charging process L is to be ended. The indicated state of charge of the adapted charging end E is less than the state of charge of the predefined charging end VE, the latter being, for example, 100% SOC.

In 5 a further illustration for visualizing a method 100 according to the invention and a system according to the invention is shown. It can be seen that a loading device according to the invention 10 may be provided, which at least one control unit 11 includes. The control unit 11 uses, for example, at least one sensor element 20 for detecting at least one compensation current information 120 in a battery system 1 , The sensor element 20 can be part of the charging device 10 be or separately trained. This detection of the at least one compensation current information 120 takes place, for example, in an interruption phase U, which is initiated in particular as a function of a detected state of charge information 110, for example by the control unit 11 , Based on the compensation current information 120 a modified end of charge E can be determined. The adapted end of charge E is in particular earlier than a predetermined end of charge VE. The predefined end of charge VE is, for example, identical to the adapted end of charge if, on the basis of the compensation current information 120, it is determined that no equalizing current is flowing. Then the charging process can be resumed. For example. then interrupts the control unit 11 the charging process when the adapted charging end E. is reached

The above explanation of the embodiments describes the present invention solely by way of example.

Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

Claims (12)

Method (100) for carrying out a charging process (L) in a battery system (1), characterized by the following steps: a) initiating the charging process (L) in the battery system (1), b) detecting at least one state of charge information (110) which c) initiating an interruption phase (U) in response to the detected state of charge information (110) so that the charging process (L) is interrupted during the interruption phase (U), d) detecting at least one of them Equalizing current information (120) specific to at least one equalizing current in the battery system (1) in the interruption phase (U), e) determining a matched end of charge (E) in response to the equalizing current information (120), f) continuing the charging process (L ) taking into account the adjusted end of loading (E). Method (100) according to Claim 1 , characterized in that according to step e) the adapted end of charge (E) is determined as a reduction of a predetermined end of charge (VE), so that an overcharge in the battery system (1) is avoided by a further compensation current after completion of the charging process (L) Preferably, the adjusted end of charge (E) is calculated based on the predetermined end of charge (VE) and / or the compensation current information (120) and / or at least one rated capacity in the battery system (1) and / or at least one aging state in the battery system (1). Method (100) according to Claim 1 or 2 , characterized in that on the basis of the compensation current information (120), an amount of charge is determined which is specific for an amount of charge transferred by the equalizing current in the interruption phase (U). Method (100) according to one of the preceding claims, characterized in that, according to step e) for determining the adjusted end of charge (E), a ratio of a charge quantity specific to the equalization current and a further parameter to each other is determined, wherein preferably the further parameter is at least one Capacity-dependent and / or aging-dependent parameters of the battery system (1). Method (100) according to one of the preceding claims, characterized in that, on the basis of the compensating current information (120), the compensating current as a compensating current between parallel connected cells (2) and / or modules (3) and / or strands (4) of the battery system (1) determined, in particular measured, is. Method (100) according to one of the preceding claims, characterized in that a charge quantity is determined by an estimation method, in particular by an extrapolation, on the basis of the compensation current information (120). Method (100) according to one of the preceding claims, characterized in that a charge quantity is determined by a comparison of the compensation current information (120) with a specification, in particular with predefined characteristic fields. Method (100) according to any one of the preceding claims, characterized in that the charging process (L) is carried out with a, in particular constant, charging current, wherein the charging current in the interruption phase (U) is predominantly or substantially reduced to 0 A. Method (100) according to one of the preceding claims, characterized in that, according to step f), the charging process (L) is continued up to a predetermined end of charge (VE) when the equalizing current information (120) indicates substantially no equalizing current, and otherwise the charging process (L) is continued to the adjusted end of charge (E), the adjusted end of charge (E) being less than the predetermined end of charge (VE). Method (100) according to one of the preceding claims, characterized in that, in accordance with step e), the adapted end of charge (E) is determined as a function of a predetermined end of charge (VE), wherein the predetermined end of charge (VE) is specified without taking into account the equalizing current. System comprising: at least one control unit (11), which is designed to carry out a method (100) according to one of the preceding claims, - At least one sensor element (20) for detecting at least one compensation current information (120) in a battery system (1), wherein the sensor element (20) is electrically or via radio to the control unit (11). Charging device (10) for a battery system (1), characterized in that the charging device (10) comprises a control unit (11) which is designed to carry out a method (100) according to one of the preceding claims.

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