Abstract
The growing electrification of vehicles and tools increases the demand for low resistance contacts. Today’s batteries for electric vehicles consist of large quantities of single battery cells to reach the desired nominal voltage and energy. Each single cell needs a contacting of its cell terminals, which raises the necessity of an automated contacting process with low joint resistances to reduce the energy loss in the cell transitions. A capable joining process suitable for highly electrically conductive materials like copper or aluminium is the laser beam welding. This study contains the theoretical examination of the joint resistance and a simulation of the current flow dependent on the contacting welds’ position in an overlap configuration. The results are verified by examinations of laser-welded joints in a test bench environment. The investigations are analysing the influence of the shape and position of the weld seams as well as the influence of the laser welding parameters. The investigation identifies a tendency for current to flow predominantly through a contact’s edges. The use of a double weld seam with the largest possible distance greatly increases the joint’s conductivity, by leveraging this tendency and implementing a parallel connection. A simplistic increase of welded contact area does not only have a significantly smaller effect on the overall conductivity, but can eventually also reduce it.
Highlights
Over the past years, the demand for large battery packs for electric vehicles (EV) has steadily increased with the ongoing electrification of the transportation sector and a growing demand for greater ranges
State of the art EV battery packs consist of a large quantity of cells connected in series to achieve the desired voltage level and in parallel in order to enable higher charge- and discharge-currents
The resulting transition resistances are in the range of the basic material does not induce a mechanical force [4]
Summary
The demand for large battery packs for electric vehicles (EV) has steadily increased with the ongoing electrification of the transportation sector and a growing demand for greater ranges. Laser beam welding is a promising technology to contact battery cells enabling lead to failure or accelerated aging. Laser beam welding is a promising technology to contact battery automated, fast and precise production of conductive joints. The overall performance of the battery pack is improved by the ohmic resistance of the joints and heat loss inside the battery cell. For the investigation, which can yield lower weld qualities [5,6,7] These phases can be identified in cross sections, see Figure the different colours in the mixing zone (dark grey and yellow areas) give a first indication on the. This paper papershowcases showcasesan anevaluation evaluationofofvarious various laser welded joints connection of pouch terminals to the battery pack in an overlap configuration.
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