Measurement system and measurement method for measuring energy cells

Abstract

The invention relates to a measurement system (10) for measuring energy cells (20), for example battery cells, in particular of dry monocells, wherein the measurement system (10) has an alternating voltage measuring bridge or a self-balancing measuring bridge (auto-balancing bridge) (11) and is designed to measure the electrical capacitance (C) and / or the ohmic resistance (R) of an energy cell (20) by means of a high-frequency measurement. The invention also relates to a corresponding method.

Description

[0001] Measurement system and method for measuring energy cells

[0002] The present invention relates to a measuring system for measuring energy cells according to the preamble of claim 1 and a measuring method according to the preamble of claim 5.

[0003] During the manufacturing of energy cells or energy storage cells, especially battery cells, foreign matter can become deposited between the individual layers (anode, separator, and cathode) that make up the energy cell. This can, for example, destroy the separator layer during compression, which can lead to a short circuit in the individual cell and thus render it unusable.

[0004] Energy cells, especially battery cells, are usually made up of a stack of mono-cells. Detecting such a short circuit before stacking the mono-cells is therefore crucial, as a single defective mono-cell can render the entire stack or battery cell unusable. A short circuit can occur, for example, if the resistance deviates significantly from the typical insulation resistance of the mono-cell, for example, if the resistance is less than a specified limit resistance.

[0005] To further reduce the production costs of battery manufacturing, production speed must be further increased. The invention is based on the object of providing a measurement system and a measurement method that enables the production of energy cells with greater process reliability and process speed.

[0006] The invention solves this problem with the features of the independent claims. Further preferred embodiments of the invention can be found in the subclaims and the associated descriptions and drawings.

[0007] To solve this problem, a measuring system for measuring energy cells, preferably battery cells, in particular dry monocells, is proposed. The measuring system comprises an AC voltage measuring bridge or auto-balancing bridge and is configured to measure the electrical capacitance C and / or the ohmic resistance R of an energy cell using a high-frequency measurement.

[0008] The term "high frequency" generally refers, as distinct from the microwave range, to fields with a frequency below 100 MHz. Typically, the frequency is 0.5 kHz, for example, or even 1 kHz, or even 100 kHz, for example. Furthermore, a high-frequency measurement differs from a direct current measurement of an energy cell, especially a battery cell, where a direct current measurement determines the resistance via the charging and / or discharging of the cell.

[0009] An AC voltage measuring bridge, or self-balancing bridge, enables rapid measurement of the energy cell, especially a dry monocell of a battery cell. Measurement can be performed at low currents and voltages, which, among other things, enables simple EMC-compliant implementation. This also results in low power consumption and significantly reduces the risk of contact for the operator. Furthermore, a compact design is achieved, which further simplifies integration into a production process.

[0010] The proposed measuring system enables, in addition to measuring the ohmic resistance, a measurement of the capacity of a monocell, so that in addition to checking for a short circuit, further information about the quality of the respective energy cell, in particular the respective monocell, is available.

[0011] An AC measuring bridge or self-balancing measuring bridge is a measuring circuit in which the current through a reference impedance is varied in comparison to the current through an element or energy cell to be measured until the sum of the two currents is 0. The balancing is usually carried out by a targeted amplitude and phase change of the current flowing through the reference impedance. The complex impedance of the element or energy cell to be measured can then be calculated from the set amplitude and phase of the current through the reference impedance. If, for example, there is a parasitic short circuit (a low resistance in parallel), the angle to be set or the phase position and the amplitude of the control current change significantly. The detection of a short circuit, i.e. a low ohmic resistance, can therefore be achieved by comparing the angle of the control current to be set with a limit value.The energy cell to be measured can, in particular, be a monocell of a lithium battery. The measuring system is particularly suitable for measuring dry monocells of a battery, i.e., a monocell not yet filled with electrolyte. The monocell is primarily capacitive, which is why the reference impedance should also be capacitive. The measuring electronics, in particular the AC voltage measuring bridge or self-balancing measuring bridge, are preferably adapted to the capacitance of the energy cell, especially the monocell, which can be comparatively large.

[0012] According to a further development, it is proposed that the measurement system be configured to measure energy cells in a continuous product stream of energy cells. This allows for online quality control without reducing production speed.

[0013] It is further proposed that the measuring system comprise a drum, wherein the measuring system is configured to measure energy cells conveyed on the drum. This allows the energy cell, in particular the monocell, to be measured during conveyance on the drum, so that online process control can be performed for each energy cell, in particular each monocell, in a manufacturing process without negatively impacting the process speed.

[0014] Alternatively, it is proposed that the measuring system comprise a conveyor belt, with the measuring system being configured to measure energy cells conveyed on the conveyor belt. This results in comparable advantages in terms of ensuring process quality while simultaneously maintaining high process speed.

[0015] Furthermore, to solve the problem, a measuring method for measuring energy cells, preferably battery cells, in particular monocells, is proposed, wherein the energy cell is measured by means of a self-balancing bridge measuring method (auto-balancing bridge method) with respect to electrical capacitance C and / or ohmic resistance R.

[0016] The energy cell can be measured very quickly using this measurement method, allowing every energy cell, especially every single cell, to be measured in a manufacturing process without negatively impacting the process speed. Determining the capacity provides information about the quality of the single cell and the production process. Energy cell measurements are preferably performed during continuous transport of the energy cells.

[0017] A further development proposes that the energy cell be measured on a moving conveyor belt or rotating drum. This allows for a continuous product flow, which has a positive impact on the process speed and energy efficiency of the manufacturing process.

[0018] The energy cell to be measured, especially a monocell, is preferably a so-called dry energy cell, meaning that no liquid electrolyte has been added to the energy cell prior to the time of measurement. It is further proposed that after measuring the ohmic resistance of an energy cell, the ohmic resistance R is compared with a threshold value, and the energy cell is ejected from a product stream if the resistance falls below this threshold value.

[0019] This allows for high-quality energy cell manufacturing, particularly when measuring the mono cells in the product stream, and avoids the use of mono cells in a stack to form a stacked energy cell. This avoids further waste that would arise from using a defective mono cell in a stacked arrangement.

[0020] According to a further development, it is proposed that after measuring the electrical capacitance C and / or the ohmic resistance R of an energy cell, in particular a monocell, the respective electrical capacitance C and / or the ohmic resistance R is stored in a data processing device.

[0021] This enables continuous quality monitoring of energy cell production.

[0022] According to a further development, it is proposed that after measuring the electrical capacity C of an energy cell, the electrical capacity C is compared with an upper and / or lower limit, and the energy cell is ejected from a product stream if the respective limit values ​​are exceeded or undershot. Such deviations outside of definable limit values ​​can indicate inferior quality, for example, due to lamination defects, which can be caused, among other things, by temperature variations.

[0023] According to a further development, it is proposed that after measuring the electrical capacity C of a plurality of energy cells, in particular monocells, which may each have different electrical capacities C, are combined to form a stack with a total capacity C_total above a lower limit value and below an upper limit value.

[0024] This allows energy cells formed from a stacked arrangement of monocells to be produced with a constant property profile.

[0025] The invention will be explained below using preferred embodiments with reference to the attached figures.

[0026] Fig. 1 shows a measuring system for measuring monocells on a drum; and

[0027] Fig. 2 a measuring system for measuring monocells on a conveyor belt.

[0028] Figure 1 schematically illustrates an embodiment of a measuring system 10 for measuring energy cells 20. The measuring system 10 comprises a self-balancing bridge 11, which is used to contact an energy cell 20, in this embodiment a dry monocell for a lithium battery. The self-balancing bridge 11 measures the electrical capacitance C and the ohmic resistance of the energy cell 20 using a high-frequency measurement. The self-balancing bridge 11 enables the simple measurement of both values ​​in a single, short measurement.

[0029] In the embodiment shown in Figure 1, the energy cell 20 is conveyed on a drum 12 in a continuous product flow. As illustrated by the arrows in Figure 1, the measurement of the energy cell 20 is performed by the measuring system 10 during continuous conveying. This, together with the short measurement duration using the auto-balancing bridge 11, enables online measurement of the energy cell 20 without interrupting or slowing the product flow.

[0030] Figure 2 schematically shows a further embodiment of a measuring system 10, wherein, in contrast to the embodiment of Figure 1, the energy cell 20 is continuously conveyed on a conveyor belt 13, while the energy cell 20 is measured by means of the self-balancing measuring bridge (auto-balancing bridge) 11.

[0031] In the embodiment of Figures 1 and 2, a data processing device 14 is provided which is designed to store the recorded measurement data, preferably ohmic resistance R and electrical capacitance C.

[0032] Both measurement data of the respective energy cell 20 can be used to evaluate quality. The stored measurement data of the respective energy cell 20 can then be compared with predetermined limit values ​​in the data processing device 14, whereby, in particular, energy cells 20 with an ohmic resistance below a certain limit value are generally unusable due to a detected short circuit in the energy cell 20. Unusable energy cells 20 can thus be detected in the running product stream and removed from the product stream by an ejection device 16 controlled by the data processing device. Any short circuits in a monocell can therefore be detected early, so that these unusable energy cells 20, in particular monocells, are not stacked into a stack 15, for example.Therefore, the measurement can prevent the production of unusable stacks 15 due to short circuits in individual monocells.

[0033] In an advantageous embodiment, the total capacity C_ges of a stack 15 with a fixed number of individual energy cells 20 or monocells can be optimized by means of the data processing device 14, so that measured energy cells 20 with their respective electrical capacities C can be sorted and combined into a plurality of stacks 15 which lie in a predetermined range of a total capacity C_ges or an average capacity of the individual energy cells 20 of the stack 15, whereby the same properties can be achieved across a plurality of stacks.

Claims

Claims:

1. Measuring system (10) for measuring energy cells (20), preferably battery cells, in particular dry mono cells, characterized in that the measuring system (10) has an AC voltage measuring bridge or self-balancing measuring bridge (Auto-Balancing Bridge) (11), and is configured to measure the electrical capacitance C and / or the ohmic resistance R of an energy cell (20) by means of a high-frequency measurement.

2. Measuring system (10) according to claim 1 , characterized in that the measuring system (10) is set up for measuring energy cells (20) of a continuous product stream of energy cells (20).

3. Measuring system (10) according to claim 1 or 2, characterized in that the measuring system (10) has a drum (12), wherein the measuring system (10) is configured for measuring energy cells conveyed on the drum.

4. Measuring system (10) according to claim 1 or 2, characterized in that the measuring system (10) has a conveyor belt (13), wherein the measuring system (10) is set up for measuring energy cells (20) conveyed on the conveyor belt (13).

5. Measuring method for measuring energy cells (20), preferably battery cells, in particular dry monocells, characterized in that the energy cell (20) is measured using a self-balancing bridge measurement method (auto- The measuring method according to claim 5 is characterized in that the measurement of the energy cell (20) is carried out on a moving conveyor belt (13) or a rotating drum (12). The measuring method according to claim 5 or 6 is characterized in that, after measuring the ohmic resistance of an energy cell (20), the ohmic resistance R is compared with a limit value, and the energy cell (20) is ejected from a product stream if this limit value is not exceeded. The measuring method according to any one of claims 5 to 7 is characterized in that, after measuring the ohmic resistance R of an energy cell (20), the ohmic resistance R is compared with a limit value, and the energy cell (20), in particular a single cell, is stacked with further energy cells (20), in particular single cells, if this limit value is exceeded.Measurement method according to one of claims 5 to 8, characterized in that after measuring the electrical capacitance C and / or the ohmic resistance R of an energy cell (20), in particular a mono cell, the respective electrical capacitance C and / or the ohmic resistance R is stored in a data processing device (14). A measuring method according to any one of claims 5 to 9, characterized in that, after measuring the electrical capacitance C of an energy cell (20), the electrical capacitance C is compared with an upper and / or lower limit value, and the energy cell (20) is ejected from a product stream if the respective limit values ​​are exceeded or not met. A measuring method according to any one of claims 5 to 10, characterized in that, after measuring the electrical Capacity C of a plurality of energy cells (20), in particular mono cells, which may each have different electrical capacities C, are combined to form a stack (15) with a total capacity C_total above a lower limit and below an upper limit.

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