Rechargeable battery pack with pouch cells and method

Abstract

The present invention relates to a rechargeable battery pack having at least two pouch cells stacked on top of each other, wherein each pouch cell is encapsulated in a metal foil, wherein the metal foils are electrically insulated from each other, and wherein each metal foil is electrically contacted in order to measure the capacitance of a capacitor formed by the metal foils.

Description

Technical Field

[0001] This invention relates to a rechargeable battery pack having at least two pouch cells stacked on top of each other. Rechargeable battery packs and pouch cells are known in principle from the prior art. The phenomenon of so-called swelling (also known as expansion) is also known from the prior art. This is problematic because it can cause the pouch cell casing to burst. Therefore, the rechargeable battery pack itself or its electronics may be damaged, potentially posing a risk to the user. Background Technology

[0002] European patent application EP 3 591 739 A1 describes a rechargeable battery pack with pouch cells, wherein the rechargeable battery pack has at least one current interruptor designed to at least temporarily interrupt the drawing of current from the pouch cells, wherein the current interruptor is triggered by the expansion of the pouch cells.

[0003] European patent application EP 3 588 607 A1 discloses a rechargeable battery pack having at least one pouch cell, wherein the rechargeable battery pack has at least one conductive filament that at least partially surrounds or defines the pouch cell in such a way that expansion of the pouch cell causes the filament to break. Summary of the Invention

[0004] The object of this invention is to provide an alternative configuration of rechargeable battery pack that provides a basis for improving operational safety.

[0005] This objective is achieved by making the metal foils electrically insulated from each other, and by making each metal foil electrically in contact with the others in order to measure the capacitance of the capacitor formed by the metal foils.

[0006] This invention includes the knowledge that metal foil encapsulating pouch cells, or foil having at least a metallic component, can be used as electrodes of a capacitor. Therefore, a capacitor, a parallel circuit, or a series circuit capacitor can be constructed from two or more pouch cells stacked on top of each other. The capacitance of a capacitor formed by one or more capacitors can advantageously be measured using a suitable capacitance measuring circuit. Deformation of the cell changes the distance between the electrodes, thereby changing the capacitor capacitance. The change in capacitance can be used to assess the swelling degree of one or more pouch cells in a rechargeable battery pack. The swelling of the pouch cells can have different characteristics. It is conceivable that the average distance between the electrodes increases during swelling. Alternatively, it is conceivable that the average distance between the electrodes decreases during swelling. However, in both cases, the capacitor capacitance changes, which can be used as a basis for capacitance detection.

[0007] In a particularly preferred configuration, the metal foils are spaced apart from each other by air gaps in the stacking direction. It has been found advantageous to introduce a dielectric into the air gaps. The dielectric can be, for example, a ceramic dielectric. It has been found advantageous that the dielectric is a plastic, especially a heat-resistant plastic. In a particularly preferred configuration, the plastic is selected from the group consisting of: polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polypropylene (PP), polytetrafluoroethylene (PTFE), polystyrene (PS), and polycarbonate (PC). It has been found advantageous to sandwich and / or flatly lie between at least two pouch cells stacked on top of each other. In this way, in addition to the desired dielectric properties, the pouch cells can also remain stable, or for example, be protected from influence during use of rechargeable battery packs. The dielectric can be part of a metal-plastic composite foil.

[0008] In a further preferred configuration, the metal foils are each provided as metal composite foils, particularly as aluminum composite foils. It has been found advantageous that the mutually facing sides of the metal foils each define an electrode. In a further preferred configuration, the electrodes are spaced apart from each other and electrically insulated from each other.

[0009] In a particularly preferred configuration, the rechargeable battery pack has a capacitance measurement circuit electrically connected to a metal foil. The capacitance measurement circuit may be provided in the form of an integrated circuit and / or may be part of the battery management system of the rechargeable battery pack or the electric handheld power tool. In the latter case, the capacitance measurement circuit may be wholly or partially integrated into the electric handheld power tool itself. The capacitance measurement circuit can advantageously be used to measure the capacitance between electrodes. It has been found that continuous monitoring of the capacitor capacitance is advantageous. Alternatively, the capacitor capacitance may be monitored discontinuously, for example, when the rechargeable battery is first used or periodically under certain load conditions. In a particularly preferred configuration, the rechargeable battery pack and / or the battery management system of the rechargeable battery pack is designed to interrupt or reduce the current drawn from the rechargeable battery pack when the value of the capacitor capacitance changes beyond a predetermined threshold.

[0010] In a further preferred configuration, the rechargeable battery pack includes a filter circuit configured to filter out changes in capacitor capacitance caused by impacts and / or vibrations. In other words, changes in capacitor capacitance (which are merely temporary and determined by capacitance measurement circuitry) can be provided to a battery management system that is not typically provided. It has been found advantageous that the filter is configured to filter out merely temporary changes in capacitor capacitance caused by thermal expansion.

[0011] In a further preferred configuration, the rechargeable battery pack has multiple pouch cells stacked on top of each other, wherein the metal foil of two adjacent pouch cells defines a corresponding capacitor capacitance. The capacitor capacitance formed in this way can be coupled in series or parallel and connected to a capacitance measurement circuit. Alternatively, a capacitance measurement circuit can be provided for each pair of corresponding adjacent pouch cells.

[0012] It has been found that rechargeable battery packs are advantageous when designed for connection to electric hand-held power tools. Rechargeable battery packs are advantageously an integral part of a system incorporating electric hand-held power tools.

[0013] The present invention also proposes a method for measuring the swelling of pouch cells in rechargeable battery packs of the aforementioned type, wherein the change in capacitance of the capacitor formed between the metal foils is assessed as a measure of the pouch cell swelling. It has been found that, as part of this method, it is advantageous to interrupt or reduce the current drawn from the rechargeable battery pack when the capacitor capacitance changes by a predetermined threshold.

[0014] Further advantages will become apparent from the following description of the accompanying drawings, which illustrate various exemplary embodiments of the invention. The drawings, description, and claims contain numerous combinations of features. Those skilled in the art will also readily consider these features individually and combine them to form further useful combinations. Attached Figure Description

[0015] In the accompanying drawings, identical and similar parts are indicated by the same reference numerals.

[0016] Figure 1A A first preferred exemplary embodiment of a rechargeable battery pack according to the present invention is shown in its normal state with pouch cells.

[0017] Figure 1B A first preferred exemplary embodiment of a rechargeable battery pack according to the present invention is shown in the expanded or swollen state of the pouch cells. Detailed Implementation

[0018] Figure 1 illustrates a preferred exemplary embodiment of the rechargeable battery pack 100 according to the present invention.

[0019] The rechargeable battery pack, for example, is equipped with two pouch cells 10, 10' stacked on top of each other in the stacking direction SR. Each pouch cell 10, 10' is encapsulated in metal foils 11, 11'. The metal foils 11, 11' are provided as aluminum composite foils and are electrically insulated from each other. The metal foils 11, 11' are spaced apart from each other in the stacking direction by an air gap 15.

[0020] The facing sides of the metal foils 11 and 11' each define electrodes 12 and 12', wherein there is a capacitor between the electrodes 12 and 12' that are spaced apart from each other and electrically insulated from each other.

[0021] The capacitance value depends on the distance between electrodes 12 and 12'. This will be explained in more detail with reference to the sub-diagram, where... Figure 1A The rechargeable battery pack 100 is shown in normal (desired) condition ZN, that is, the pouch cells 10, 10' are not swollen.

[0022] Figure 1B A rechargeable battery pack 100 in a swollen (aged) state ZA is shown, wherein the pouch cells 10, 10' are significantly swollen in the stacking direction SR. Figure 1B Under the swollen (aged) state ZA, electrodes 12 and 12' are, for example, compared to Figure 1A The electrodes 12 and 12' are spaced further apart from each other (at least on average, they are further apart). This results in... Figure 1A The capacitance CN of the capacitor between electrodes 12 and 12' of the rechargeable battery pack 100 is greater than that existing in Figure 1B The capacitance CA of the capacitor between electrodes 12 and 12' of the rechargeable battery pack 100.

[0023] This change in capacitor capacitance can be used to detect the swelling of the pouch cells 10, 10'. For this purpose, each of the metal foils 11, 11' is electrically contacted via electrical contact points 13, 13', thereby also electrically contacting the electrodes 12, 12'. Electrical contact points 13, 13' are then electrically connected to a capacitance measurement circuit 20, which can be used to measure the change in capacitor capacitance as the cells age.

[0024] As from Figure 1A and Figure 1B As can be seen from this, the additional dielectric 17 is introduced into the air gap 15 between the pouch cells 10 and 10'.

[0025] It should be mentioned that, for the measurement principle presented herein, the air present between the pouch cells 10 and 10' is sufficient on its own to serve as a dielectric. Due to the introduction of the dielectric 17 (here, for example, in the form of a plastic strip), the capacitance of the capacitor is advantageously increased in principle, and the pouch cells 10 and 10' simultaneously support and abut against each other. List of reference numerals 10, 10' pouch cells 11, 11' Metal Foil 12, 12' electrodes 13, 13' electrical contact points 15 Air gap 17 Dielectric 20. Capacitance Measurement Circuit 100 rechargeable battery pack SR stacking direction CA expanded soft-pack battery cell capacitor capacitance The capacitor capacitance of a standard pouch cell in CN ZA swelling state ZN normal state

Claims

1. A rechargeable battery pack (100) having at least two pouch cells (10, 10') stacked on top of each other, wherein each of the pouch cells (10, 10') is encapsulated in a metal foil (11, 11'). Its features are, These metal foils (11, 11') are electrically insulated from each other, and the rechargeable battery pack (100) has a capacitance measurement circuit (20) which is electrically connected to the capacitance measurement circuit (20) in order to measure the capacitance of the capacitor formed by these metal foils (11, 11').

2. The rechargeable battery pack (100) as described in claim 1. Its features are, The rechargeable battery pack (100) has a battery management system designed to interrupt or reduce the current drawn from the rechargeable battery pack when the value of the capacitor changes by a predetermined threshold.

3. The rechargeable battery pack (100) as described in claim 1 or 2. Its features are, The rechargeable battery pack (100) has a filter circuit configured to filter out changes in the capacitance of the capacitor caused by impacts and / or vibrations.

4. The rechargeable battery pack (100) as described in claim 1 or 2. Its features are, These metal foils (11, 11') are spaced apart from each other by air gaps (15) in the stacking direction (SR).

5. The rechargeable battery pack (100) as described in claim 4. Its features are, The dielectric (17) is introduced into the air gap (15).

6. The rechargeable battery pack (100) as described in claim 5. Its features are, The dielectric (17) is plastic.

7. The rechargeable battery pack (100) as described in claim 5. Its features are, These metal foils (11, 11') are each provided as metal composite foils.

8. The rechargeable battery pack (100) as described in claim 7. Its features are, These metal foils (11, 11') are each provided as aluminum composite foils.

9. The rechargeable battery pack (100) as claimed in claim 7. Its features are, The dielectric (17) is part of the metal composite foil.

10. A method for measuring the swelling of a pouch cell in a rechargeable battery pack (100) as described in any one of claims 1 to 9, wherein, The change in capacitance of the capacitor formed between these metal foils (11, 11') was evaluated as a measure of the swelling of these pouch cells (10, 10').

11. The method as described in claim 10, Its features are, When the capacitance of the capacitor changes by a predetermined threshold, the current drawn from the rechargeable battery pack (100) is interrupted or reduced.

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