Development of a non-destructive test (NDT) system for quality control of welds in ultracapacitor electrode structures allows the manufacturer to avoid placing defective electrodes into their cases and makes it possible for operators to detect defective electrode welds prior to sending ultracapacitors to the next assembly step.

This system can improve  product quality, reliability and product cost. Since the electrode jellyroll structures of ultracapacitors and conventional batteries are similar, this NDT system could also be used in the manufacture of batteries.

Welding quality is monitored without physical contact by use of new NDT devices. The air clearance between the electromagnetic sensor and the surface of the bottom collector slot is 0.25 mm. The non-contact mode of testing can also successfully be applied in quality evaluation of welding in automated ultracapacitor assembly line manufacturing.

The design of the new system allows determination of weld quality for each slot of the collector. For example, for a collector with four slots, the device uses eight transducers (four for cathode and four for anode collectors). Movable electronics modules are employed to control sensor parameters and for preliminary amplification and signal processing. The electromagnetic NDT system, designated as the EC-TLW, is fully integrated into a compact package.

Enerize has developed a non-destructive eddy current measurement system for Maxwell that can detect quality problems with our laser welds. This is a proof of concept system that will be used to optimize our laser welding process and ultimately improve our system equivalent series resistance (ESR) as we optimize weld quality. Eventually we would invest in an automated system that will test 100% of our welds.

—Robert Crawford, Maxwell’s director of operations

Enerize Corporation develops and markets proprietary technology and technical know-how in non-destructive testing equipment for real-time applications in the manufacture of the renewable energy devices. Enerize Corp. also develops advanced designs and high-performance, low-cost materials and technologies used in solar cells, lithium-ion batteries, fuel cells and supercapacitors.