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Cell Welding
20 Ah Prismatic Cell Interconnects
Cell interconnects (tabs) should NOT be soldered to the battery terminals or attached
using extreme heat.
A123 recommends resistance or laser welding tabs to the terminals of the cell. Because it is impossible to cover
every possible weld schedule, A123 recommends meeting with welding consultants to discuss weld schedules
optimized to your specific application. Welding consultants that may be able to assist include:
•
http://www.welding-consultant.com
•
http://www.ccl.fraunhofer.org/
For reliable welded connections at the terminals, A123 recommends copper or copper alloy straps welded to the
copper tabs and aluminum straps welded to the aluminum tabs. Cell interconnects (straps) should be neither
soldered on the cells tabs nor attached using extreme heat. A123 recommends tabs be resistance or laser-welded
to the tabs of the cells.
Resistance welding provides a controlled constant current between electrodes for a consistent period of time
through the welded materials. These parameters can be specified and regulated for a high-quality weld every time.
Laser welding provides a consistent amount of heat to a controlled location, which contributes to a high quality
manufacturing process. The angle of incidence, power, dwell time, and materials are always the subject of a trial
and error process initially until the desired results are produced. A welding expert is a valuable resource to employ
during the set-up of this part of the assembly line.
A123 uses a laser process to weld extruded bus bars to the cell’s tabs. On the negative side, the 0.53 mm extruded
copper bus bars are shaped to slip over the negative copper tabs. On the positive side, the bus bars are 0.84 mm
thick extruded aluminum
Figure 27 – Bus bar concept diagram and resulting welded cross sections
The copper tab laser is set up with the following parameters: Using a 2.1 kW laser beam travelling at 3 m/min, 0
mm focus, 8 ° incident angle, and 70 °C temperature.
The aluminum tab laser is set up at 1.2 kW, 3 m/min, 0 mm focus, 8 °C and 50 °C temperature.
These parameters may or may not work for all applications, but are a good place to start experimentation.
