Enhanced performance of EV batteries is a major factor in the steady increase in electric vehicle sales. And better performance stems, in part, from recent developments in laser welding of dissimilar metals which increases efficiency by increasing energy storage, reducing size, and preserving reliability. It’s a fact that welding a less resistive metal to the standard stainless-steel terminal of a lithium ion battery can reduce resistance and improve battery efficiency. Traditional resistance spot welding, however, can’t effectively join highly-conductive dissimilar metals like copper and aluminum because the resultant intermetallic mix is brittle. But lasers CAN do the job with surprising results!
Successful manufacturers constantly look for ways to improve quality while reducing costs. That’s why many are looking beyond conventional spot welding technology for something to help them achieve their cost reduction goals. Resistance welding traditionally utilizes alternating current (AC); however, this technology has limitations in the control of the output energy. Resistance welding with direct current (DC) using inverter technology, however, dramatically improves weld process control through closed loop feedback. This provides a consistent output, in turn lowering scrap and increasing production yield.
"Ugh - my battery just died!" "Can I use your charger?" "Mind if I recharge my phone?" Batteries are everywhere, and we've become increasingly dependent on them in many aspects of our daily lives: portable electronic devices, cordless power tools, energy storage, and hybrid and EV cars. Thus, the demand to manufacture batteries that meet or exceed quality and production requirements for these products, is great.
Resistance spot welding, micro TIG welding, and laser welding processes all enable high quality volume production. The selection of one technology over another is usually made based on the application's specific requirements and the alignment of the technology to these needs.
Battery tabs seem to have been getting thicker and more conductive over the last several years, as customers seek better performance and higher currents from their battery packs. These thicker battery tabs are usually made of nickel, but nickel-plated copper tabs are gaining in popularity due to their higher conductivity. We’ve had success welding the thicker nickel tabs, but have found the nickel-plated copper to be very difficult to weld. How to overcome that? Add slots and projections to the tab design to focus the current and minimize current shunting. Welding success also depends, in part, on the battery itself; those with thick caps can easily handle the high force and current needed to weld the thicker tabs. If the battery caps are too thin, however, they may get deformed or blown through.