News and New Products

Float like a battery, sting like a capacitor

By Bill Schweber -- EDN, 4/15/2004

A new button-cell hybrid from Evans Capacitor looks like a standard button-cell battery, and it uses the same 2325 holder as a battery, but it’s not a battery (Picture). It’s a 1800-μF, 50V supercapacitor that targets use in aerospace, medical, and other applications requiring a one-time or refillable jolt of energy. It offers high energy density despite weighing only 8g and measuring only 23 mm in diameter and 2.5 mm thick.

The exterior of the unit is nickel-plated for low contact resistance and houses a sintered tantalum pellet as the positive electrode with a TaO₅ (tantalum-pentoxide) dielectric film, combined with a negative-electrode, conductive-metal oxide based on a RuO₂ (ruthenium-dioxide) film. The vendor says that internal resistance is one-thousandth that of electrochemical capacitors. This technology is internally complex and costs more than a standard battery, but if you need the performance and inherent ruggedness, the $150 (one piece) is likely worth it.

Evans Capacitor Co, 1-401-435-3555, www.evanscap.com.