DE102022122230A1 - Diagnostic device for high-voltage storage in electrified motor vehicles - Google Patents

Abstract

The invention provides a diagnostic device for high-voltage storage in electrified motor vehicles, wherein the high-voltage storage comprises at least one battery cell module with a plurality of battery cells, with an electronic control unit which is designed such that a module swelling measure in the form of one of the overall Size proportional to the swelling force (hereinafter also referred to as “swelling force” for short) is estimated. According to the invention, the (total) swelling force is determined by adding a first manufacturing parameter-based static swelling force portion, which is determined at the beginning of the service life of the high-voltage battery, and a second operating parameter-based dynamic swelling force portion, which is continuously is determined over the service life of the high-voltage storage device. Preferably, the currently determined total swelling force is continuously compared with a first still permissible threshold value and, when it is exceeded, with a second no longer permissible threshold value Threshold value at least one first defined measure and when the second threshold value is exceeded at least one second defined measure can be activated, the second defined measure preferably differing from the first defined measure by an increasing operating restriction.

Description

The present invention relates to a diagnostic device for high-voltage storage in electrified motor vehicles, wherein the high-voltage storage comprises at least one battery cell module. A battery cell module is in particular a battery cell pack that is usually clamped in a frame device and has a large number of battery cells arranged next to one another. The structure holding the battery cells, such as in particular the module frame elements, is also referred to below as the module periphery.

At least partially electrically driven or movable motor vehicles, for example hybrid motor vehicles or electric motor vehicles, have a battery, often referred to as a high-voltage battery, in particular in the form of a rechargeable battery, for storing and providing electrical energy for driving the corresponding motor vehicle by means of an electromechanical energy converter . The battery or the high-voltage storage device is usually formed from a large number of battery cells, which are designed, for example, as respective pouch cells or prismatic cells, and is also referred to as a battery cell module. The respective battery cell is repeatedly charged (state of charge SoC becomes higher) and discharged (state of charge SoC becomes smaller) during operation of the motor vehicle, with the respective battery cell in the discharged state (SoC equal to or close to 0) and in the charged state (SoC greater than 0). has different external dimensions, that is, different dimensional dimensions. In other words, the battery cell swells due to electrical charging from a basic dimension at SoC ≈ 0 to a swelling dimension (SoC > 0). In addition, the battery cell expands irreversibly as it ages, which means that the basic dimension increases as the battery cell ages. Furthermore, a defective battery cell can swell or become swollen to the extent of swelling.

To hold the battery cells, a module periphery is provided, for example frame elements, whereby in particular joints of the frame can be heavily loaded if the battery cells and thus the entire battery cell module expand to the (module) swelling level. Furthermore, when manufacturing the conventional battery, it can happen that the battery cells are undesirably clamped too tightly if at least one or more of the battery cells have a greater thickness compared to a target thickness due to manufacturing tolerances. Excessive tension may result in damage to the electrodes and/or a separator and, as a result, a premature end to the service life. Furthermore, it is currently only possible with considerable effort to visually identify whether the conventional battery or a conventional battery module, i.e. one or more of the conventional battery cells, is damaged or worn. For a service technician, for example as part of vehicle maintenance and/or repair, the rigid frame appears unchanged, at least on the outside, regardless of whether battery cells have the basic size or the swelling size. In addition, the conventional, high-strength, rigid frame is to be viewed as an undeformable element in the event of an accident involving the motor vehicle equipped with the battery. This limits the amount of space that can be used for installing battery cells, since, for accident safety, spaces and/or elements (“deformation zones”) must be provided in the motor vehicle, which deform in the event of an impact - if possible in a controlled manner - in order to avoid the kinetic forces present in the crash Dissipate energies efficiently. The deformation zones must be kept free of undeformable elements (so-called block formers). Furthermore, deformation of the battery or battery module must be avoided, otherwise thermal runaway could occur due to mechanical overload in the event of a crash.

Due to the change in expansion that occurs during operation of the respective battery cell, constructive measures must be taken to absorb or compensate for the change in spatial expansion in the installed position of the battery cells. The change in spatial expansion is expressed in a volume difference of up to 10% per battery cell between the charged and discharged state.

For example, from the unpublished DE 10 2021 124 467 Internally, a special protective pressure clamping device is provided for a frame device which is designed to clamp a battery cell pack. However, the protective effect of constructive measures is limited.

The object of the present invention is to create a diagnostic option for battery cells or battery cell modules or high-voltage storage devices that change in terms of their spatial extent during operation.

This task is solved by the subject matter of the independent patent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description and the figure.

The invention generally relates to a diagnostic device for estimating swelling Measurement of a battery cell module for high-voltage storage in electrified motor vehicles, for monitoring a swelling force exerted on the module periphery due to the swelling level and for controlling a defined safety measure depending on the swelling force.

In addition, it should be noted that “swelling force” in the broadest sense also means a quantity proportional to the swelling force, e.g. amount of swelling, increase in volume, increase in thickness, etc.

The invention provides a diagnostic device for high-voltage storage in electrified motor vehicles, wherein the high-voltage storage comprises at least one battery cell module with a plurality of battery cells, with an electronic control unit which is designed such that a module swelling measure in the form of one of the overall Size proportional to the swelling force (hereinafter also referred to as “swelling force” for short) is estimated. According to the invention, the (total) swelling force is determined by adding a first manufacturing parameter-based static swelling force portion, which is determined at the beginning of the service life of the high-voltage battery, and a second operating parameter-based dynamic swelling force portion, which is continuously determined over the service life of the high-voltage storage device.

Preferably, the currently determined total swelling force is continuously compared with a first still permissible threshold value and, when this is exceeded, with a second no longer permissible threshold value.

The electronic control unit can activate at least a first defined measure when the first threshold value is exceeded and at least a second defined measure when the second threshold value is exceeded, the second defined measure preferably differing from the first defined measure by an increasing operating restriction.

The invention is based on the following considerations:

State of the art

• - Lithium-ion cells are often surrounded by metallic frames (e.g. consisting of a tie rod and pressure plate) with a physically given, limiting and statistically/process-dependently fluctuating load capacity.
• - The essential (thickness) dimensions of the cells are specified by industry standards and are subject to geometric tolerances (e.g. PHEV2: 26.5mm +/- 0.5).
• - Design and dimensioning are carried out generically, taking into account a customer distribution in the company or "the 99% customer" (ie 1% loads a component higher than the estimated value) and at the same time under process-reliable specification of the load capacities (cf. 3 , industry standard).
• - So far no software solution for this problem in the context of mechanical state estimation for swelling force (also called “swelling force”).
• - No reliable way to detect damage to the module periphery, especially the battery cell module frame.

Technical problem

Despite the design for “99% customers” and process-reliable specifications, a residual risk remains. There are socially accepted limits or failure rates for this, see the dashed line in 3 . In the present context, components with low load-bearing capacity (statistical fluctuations in the process) that affect customers with the highest load (“100% customer”) are therefore critical. It is uneconomical to respond to this residual risk with hardware measures.

According to the invention, in order to solve this residual risk problem, a diagnostic device with an electronic control unit for carrying out a software-based product- and customer-specific protection function is proposed.

Basic principle of the invention

Basically, according to the invention, a prediction of the mechanical swelling state (“swelling force development”) initially takes place based on the estimation of a swelling measure or a swelling force, taking into account the relevant manufacturing and operating parameters and preferably other boundary conditions. This enables product- and customer-specific monitoring of the safety-relevant status instead of additional generic design designs.

• (1) Zell(dicken)toleranz bzw. Konkavität/Konvexität der Zelle und/oder
• (2) Verpresskraft zur geometrisch definierten Erzeugung des Zellstapels und/oder
• (3) Verpressgeschwindigkeit zur Berücksichtigung der Deformationsratenabhängigkeit und/oder
• (4) Dickentoleranz des Zellzwischenmaterial (bspw. „Heatshield“)

The following essential manufacturing parameters can preferably be taken into account alone or in any combination:

• (1) Cell (thickness) tolerance or concavity/convexity of the cell and/or
• (2) Pressing force for geometrically defined creation of the cell stack and/or
• (3) Pressing speed to take into account the deformation rate dependency and/or
• (4) Thickness tolerance of the cell intermediate material (e.g. “Heatshield”)

Taking the manufacturing parameters into account leads to a production-related static initial swelling force proportion at the beginning of the service life of a high-voltage storage device (“begin-of-life state”).

The additional consideration of the following operating parameters leads to an aging-related dynamic second swelling force component over the service life, which is added to the first swelling force component at the beginning of the service life. This results in a total swelling force that acts on the high-voltage storage device over time and is estimated by recording and taking into account the parameters mentioned.

• (1) Ladungsdurchsatz (Laden und Entladen, ggf. nach Leistung klassifiziert) und/oder
• (2) Schnelllade-Anteil und/oder
• (3) Temperatur aus Betrieb und Standzeiten und/oder
• (4) Entladungsausmaß („Degree of Discharge“ (=DoD))

Essential operating parameters for estimating the aging-related dynamic second swelling-force component are, for example, the following alone or in any combination with one another:

• (1) Charge throughput (charging and discharging, if necessary classified by power) and/or
• (2) Fast charging portion and/or
• (3) Temperature from operation and downtime and/or
• (4) Degree of Discharge (=DoD)

The currently determined (total) swelling force (“swelling state”) is then continuously compared with a first still permissible threshold value (e.g. 80% to less than 99% of a component load capacity, in the sense of the degree of utilization or damage) and at this Exceeding is compared with a second threshold value that is no longer permissible (e.g. greater than or equal to 99% of a component load capacity).

The electronic control unit activates first defined measures when the first threshold value is exceeded and second defined measures when the second threshold value is exceeded.

The second defined measures differ from the first defined measures in that there is an increasing operational restriction.

• - die Ausgabe einer Aufforderung an den Fahrer zum Aufsuchen einer Werkstatt und/oder
• - das Angebot zur Auswahl einer Reichweiten-, Antriebsleistungs- und/oder Ladeleistungsreduzierung zugunsten der Lebensdauer des Hochvoltspeichers an den Fahrer und/oder
• - eine frühere Kühlungsaktivierung und/oder
• - die Beschränkung des Ladungszustands auf einen alterungsmindernden Wert bei längerer Abstellzeit des Fahrzeugs und/oder
• - die Aktivierung eines definierten Batterie-Erholungsprogramms zur zumindest teilweisen Reversion des Alterungszustandes.

A first measure could be, for example:

• - issuing a request to the driver to go to a workshop and/or
• - the offer to the driver and/or to choose a range, drive power and/or charging power reduction in favor of the service life of the high-voltage battery
• - earlier cooling activation and/or
• - limiting the state of charge to an age-reducing value when the vehicle is parked for a longer period of time and/or
• - the activation of a defined battery recovery program for at least partial reversal of the aging state.

• - eine automatische Leistungsreduktion des Antriebsstrangs und/oder
• - die Einschränkung von vergleichsweise sportlichen oder anderweitig belastenden Fahrmodi zur Minderung der extern wirkenden mechanischen Lasten (z.B. weiche Fahrwerkseinstellungen) und/oder
• - eine automatische Stilllegung des Fahrzeugs.

A second measure can, for example, be one or more of the following operating restrictions, which can be associated with information output to the driver:

• - an automatic power reduction of the drive train and/or
• - the restriction of comparatively sporty or otherwise stressful driving modes to reduce external mechanical loads (e.g. soft chassis settings) and/or
• - an automatic shutdown of the vehicle.

The respective battery cell is designed, for example, as a solid-state battery cell.

Further features of the invention can emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description as well as the features and combinations of features shown below in the description of the figures and/or in the figures alone can be used not only in the combination specified in each case, but also in other combinations or on their own, without the scope of the invention to leave.

• 1 eine schematische Ansicht einer erfindungsgemäßen Diagnose-Vorrichtung für eine Hochvoltbatterie mit einem Schätzmodul zur Ermittlung des Batteriemodul-Schwellungsmaßes,
• 2 mögliche Details eines Schätzmoduls zur Ermittlung des Batteriemodul-Schwellungsmaßes und
• 3 der Erfindung zugrundeliegende Erkenntnisse zum möglichen schematischen Verlauf eines Batteriemodul-Schwellungsmaßes.

An exemplary embodiment of the invention is shown in the drawing. It shows

• 1 a schematic view of a diagnostic device according to the invention for a high-voltage battery with an estimation module for determining the battery module swelling measure,
• 2 possible details of an estimation module for determining the battery module swelling measure and
• 3 The findings underlying the invention regarding the possible schematic course of a battery module swelling measure.

In 1 the essential components of the diagnostic device according to the invention are shown in their mode of operation. The diagnostic device comprises an electronic control unit 1, which is designed in particular by appropriate programming (computer program product) in such a way that a total swelling force F is obtained by adding a first manufacturing parameter-based static swelling force component ΔF_P at the beginning of the service life of the high-voltage battery and a second operating parameter-based aging-related dynamic swelling force component ΔF_B is determined over the service life (t). For this purpose, the control unit 1 contains a memory area with manufacturing parameters P from production and receives operating parameters B of the motor vehicle that has been put into operation as input signals. The estimation of the total swelling force F takes place in an estimation module 3.

The output signal of the estimation module 3 in the form of the determined total swelling force F is continuously compared with a first still permissible threshold value S1 and, when it is exceeded (F>S1), with a second no longer permissible threshold value S2.

The electronic control unit 1 activates at least one first defined measure M1 when the first threshold value S1 is exceeded and at least one second defined measure M2 additionally or alternatively when the second threshold value S2 is exceeded. The second defined measure M2 differs from the first defined measure M1 in that it has an increasing operational restriction.

A first defined measure M1 here is, for example, at least the output A of a request to the driver to visit a workshop.

A second defined measure M2 here is, for example, at least an automatic power reduction R of the drive train together with an output A of a request to the driver to visit a workshop.

The selection of a first defined measure M1 and/or a second defined measure M2 can also be activated depending on whether a predetermined mileage KM has been exceeded, for example only after 300,000 km.

In a further development of the invention, further threshold values and corresponding measures could also be defined.

In 2 the estimation module 3 and the manufacturing, operating and possibly other marginal parameters that are preferably to be taken into account are presented in more detail.

• - Zelldicke und deren Toleranz
• - Form (Konkavität/Konvexität) der Zelle
• - Verpresskraft, maximale Verpresskraft
• - Verpressgeschwindigkeit, maximale Verpressgeschwindigkeit
• - Dickentoleranz des Zellzwischenmaterials
• - etc.

The following can preferably be taken into account alone or in any combination as essential manufacturing parameters P for determining the manufacturing parameter-based static swelling force component ΔF_P:

• - Cell thickness and its tolerance
• - Shape (concavity/convexity) of the cell
• - Pressing force, maximum pressing force
• - Pressing speed, maximum pressing speed
• - Thickness tolerance of the cell intermediate material
• - Etc.

• - Ladungsdurchsatz, Laufleistung (Laden und Entladen, ggf. nach Leistung klassifiziert), z.B. mittels Multiplikation des Strom I mit der Zeit t, in der der Hochvoltspeicher eingeschaltet ist => dies führt zur Schätzung eines Basis-Schwellungs-Kraft-Anteils ΔF0
• - Häufigkeit eines Schnellladebetriebs I>xx [A] => dies führt zur Schätzung eines Schnelllade-Schwellungs-Kraft-Anteils ΔF1
• - Mittlere Zelltemperatur T über der Lebenszeit => dies führt zur Schätzung eines Zelltemperatur-Schwellungs-Kraft-Anteils ΔF2
• - Mittleres Entladungsausmaß („Degree of Discharge“ (=DoD)), z.B. durch Auswertung von Zellspannung U und Zeit t bei eingeschaltetem Hochvoltspeicher => dies führt zur Schätzung eines Entladungs-Schwellungs-Kraft-Anteils ΔF3
• - Zusätzlich kann mindestens ein Teil-Kraftanteil ΔF (ΔF0 bis ΔF3) zur Schätzung des zweiten Schwellungs-Kraft-Anteils ΔF_B abhängig von der absoluten aktuellen Höhe der Teil-Kraftanteile ΔF, z.B. durch einen Faktor f_V, weniger stark oder gar nicht berücksichtigt werden.

The following can preferably be taken into account alone or in any combination as essential operating parameters for determining the second operating parameter-based aging-related dynamic swelling force component ΔF_B:

• - Charge throughput, mileage (charging and discharging, if necessary classified according to power), e.g. by multiplying the current I by the time t in which the high-voltage storage is switched on => this leads to the estimation of a basic swelling force component ΔF0
• - Frequency of a fast charging operation I>xx [A] => this leads to the estimation of a fast charging swelling force component ΔF1
• - Average cell temperature T over the lifetime => this leads to the estimation of a cell temperature-swelling-force component ΔF2
• - Average extent of discharge (“Degree of Discharge” (=DoD)), e.g. by evaluating cell voltage U and time t with the high-voltage storage device switched on => this leads to the estimation of a discharge swelling force component ΔF3
• - In addition, at least one partial force component ΔF (ΔF0 to ΔF3) for estimating the second swelling force component ΔF_B can be taken into account to a lesser extent or not at all, depending on the absolute current level of the partial force components ΔF, for example by a factor f_V.

According to 3 The battery cells Z are arranged in a row along a longitudinal direction of the battery to form a battery cell module 2. A frame device, which is not described in more detail, has, for example, tie rods that absorb the (total) swelling force F (see force-effect arrows). The tension clamps are there elements spaced apart from one another along a transverse direction of the battery cell module 2.

The time-force diagram in 3 shows schematically target and possible actual curves of the swelling force F applied over the service life t, which acts on the module periphery. A crucial component during assembly is the first manufacturing parameter-based swelling force component ΔF_P. Another crucial component during operation is the second operating parameter-based aging-related swelling force component ΔF_B. The swelling force F can also depend on further boundary parameters, which can preferably also be taken into account in the swelling force estimate. A particularly influential operating parameter, for example, is the degree of discharge (DoD).

The time t0, which corresponds to the beginning of the service life of the high-voltage storage device, can, for example, be the beginning of the commissioning of the motor vehicle.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The 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

• DE 102021124467 [0005]

Claims (7)

Diagnostic device for high-voltage storage in electrified motor vehicles, the high-voltage storage comprising at least one battery cell module (2) with a plurality of battery cells (Z), with an electronic control unit (1) which is designed such that a total swelling force (F) by adding a first manufacturing parameter-based static swelling force component (ΔF_P), which is determined at the beginning of the service life (t0) of the high-voltage battery, and a second operating parameter-based dynamic swelling force component (ΔF_B), which can be determined continuously over the service life (t) of the high-voltage storage device. Diagnostic device according to Claim 1 , characterized in that the currently determined total swelling force (F) is continuously compared with a first still permissible threshold value (S1) and, when this is exceeded, with a second no longer permissible threshold value (S2). Diagnostic device according to one of the preceding claims, characterized in that the electronic control unit (1) takes at least one defined measure (M1) when the first threshold value (S1) is exceeded and at least one second defined measure when the second threshold value (S2) is exceeded (M2) can be activated. Diagnostic device according to one of the preceding claims, characterized in that the second defined measure (M2) differs from the first defined measure (M1) by an increasing operating restriction. Diagnostic device according to Claim 3 or 4 , characterized in that a first defined measure (M1) - the issuance (A) of a request to the driver to visit a workshop and / or - the offer to select a range, drive power and / or charging power reduction and / or - a earlier cooling activation and/or - limiting the state of charge when the vehicle is parked for a longer period of time and/or - activating a defined battery recovery program. Diagnostic device according to Claim 3 , 4 or 5 , characterized in that a second defined measure (M2) alternatively or in addition to an output (A) to the driver - an automatic power reduction (R) of the drive train and / or - the automatic restriction of mechanically stressful driving modes and / or - an automatic The vehicle is decommissioned. Diagnostic device according to one of the preceding claims, characterized in that the selection of a first defined measure (M1) and/or a second defined measure (M2) can be activated depending on whether a predetermined mileage (KM) is exceeded.

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