Battery measurement
100% quality control In fractions of a second
BATTERY TEST AND MEASUREMENT MODULES FOR AUTOMATION, TESTING AND LABORATORIES
Whether telecommunications, tools, leisure or electromobility - many modern devices and vehicles today operate independently of the mains using rechargeable batteries. For these to function reliably, the individual battery cells must have the most homogeneous electrical properties possible and their mechanical connections must also be tested 100 %. As hundreds of individual cells are sometimes required for larger batteries, the measurements for cell evaluation must be carried out quickly, reliably and safely during the production process. Modern Industry 4.0-capable measuring devices for all relevant parameters relating to single-cell assessment create the prerequisites for this.
A battery is a combination of identical units, in the case of electric batteries of individual battery cells, in order to achieve a higher voltage or capacity when combined. However, this means that a battery is only as good as the weakest battery cell installed. Battery manufacturers must therefore test all individual cells and all pre-configured individual modules for ongoing production for their exact properties and classify them into quality groups. The battery in an electric car, for example, usually has several hundred cells installed in several modules. Testing this large number in the shortest possible time places special demands on the measurement technology. Many years of experience in the use of electrical and mechanical measuring methods is a prerequisite for summarising the essential properties for battery production in a family of measuring devices. The modern devices can then be used individually or in combination. They are suitable for Industry 4.0 and can be easily connected to standard fieldbuses, integrated into production systems or used for research and development.
The individual electrical properties of the individual cells are the most important factor in cell testing. If a cell with a lower capacity is installed in a series connection, the entire cell system can only deliver the lower amount of current. It can also lead to total failure, as the cell with the lower capacity is full first, but the others continue to be charged, causing the cell with the lowest capacity to overheat. The different cell can also overheat when discharging. Another problem is differing internal resistances, which lead to uneven charging and heating of the cells. As battery packs are made up of individual cells in different formats (round, pouch, prismatic), the measurement technology must be able to test all variants.
With often thousands of individual cells, a high inspection throughput is essential. The use of measuring devices in automated production testing of battery cells for seamless 100% quality assurance in fractions of a second therefore requires extensive expertise. The 2511 all-in-one module is a measuring device specially developed for such tasks.
In addition to an AC/DC internal resistance measurement with values from 0.1 µΩ ... 300 mΩ in 4 measuring ranges from 10 ... 300 mΩ, it offers a four-wire measuring method for maximum precision and allows measurement and evaluation results to be generated in the shortest possible time. The measurements can be carried out in the frequency range of 1 kHz, 100 Hz, 10 Hz, 1 Hz and at voltages of 0 ... ±5 VDC. The cascadable battery measurement module allows statements on electrolyte and electrode quality compared to the manufacturer's target specifications to be made in just a few milliseconds via single to multi-channel applications and temperature measurement.
The compact design and the PROFINET and EtherCAT fieldbus interfaces enable easy integration into production. Matching PC software for intuitive parameterisation/configuration facilitates the creation of individual measurement programs.
In battery packs, the individual cells must be connected. To do this, rigid busbar connectors, cables or spring contacts are pressed, screwed, welded or pressed onto the cells. The specified contact resistances must be adhered to very precisely in order to minimise power loss and self-heating of the battery. Given the high production volumes, measuring devices with very fast evaluation logic are also required here. With up to 100 measurements per second, the RESISTOMAT® model 2311 from burster is tailored to the requirements of high-speed applications in automation.
Lead and contact resistances at the test contacts are eliminated by the four-wire measurement method. Integrated cable break detection monitors the test leads. Despite a measuring range of 20 mΩ ... 200 kΩ with a resolution of up to 1 μΩ and a measuring accuracy of ≤ 0.03 % f.s., the test device achieves high-speed measurements from 10 ms per measurement including evaluation. Classifications and selections are performed by a 2- and 4-fold comparator with switching outputs. All device settings can be parameterised individually in up to 32 different measurement programs, optionally also via the Ethernet, USB (standard) or fieldbus interfaces (optional). The integrated data logger can store up to 900 measured values per measuring programme.
Mechanical parameters are also important in battery production. For example, measuring tightening torques and tightening forces on the production line ensures that contact surfaces are securely mounted and contact resistances are minimised. It is also important to measure the forces that occur when pressing high-current contacts onto PCBs or inserting individual cells into holding tubes or boxes. Recording and validating the joining forces immediately reveals any joining errors. Force/displacement press-fit monitoring with window and envelope curve technology allows, for example, the recording of min/max peak values and mean force values within a parameterised tolerance range.
With the DIGIFORCE® 9307 X/Y process controller, such test methods are easy to implement. With a connection via PROFINET, EtherCAT, EtherNet/IP and Ethernet UDP, the module supports flexible sequence control and measurement data acquisition. Up to 128 measurement programmes enable a high degree of product variance. If, for example, the force path is monitored for the insertion of individual cell plates/cell blocks into a cell housing, several units can always be joined simultaneously to optimise the cycle time and each individual plate can be recorded and evaluated with the help of cascaded DIGIFORCE controllers.
But not only time-critical measurements in the production line are important, measuring devices are also needed for laboratory measurements on the battery behaviour of individual cells and battery packs, for example in development or for spot checks. This also makes it easy to determine mechanical measurement values for long-term monitoring, e.g. of expansion during charging and discharging cycles or determination of the forces occurring with monitoring of the temperatures or for optimising the pressure distribution and service life.
The burster 8526 compression force sensor is suitable for such tasks in various applications thanks to its small design and three mounting holes. Even angular errors in the force application of up to 3° deviation from the measuring axis only have a very small effect on the measurement result. Its wide measuring range from 0 ... 100 N to 0 ... 1 MN allows the exact recording of forces and expansion with temperature during charging and discharging of the cells, not only for battery cells, for example. This in turn allows an exact evaluation of the long-term behaviour and the ageing process.
burster - precision measurement technology from a single source
From highly sensitive sensors and high-performance sensor electronics to comprehensive calibration solutions - burster offers a complete portfolio for precise and reliable measurement technology in medical technology. With many years of experience and technological expertise, burster ensures that medical applications benefit from the best possible measurement technology - for maximum safety and efficiency.
