Isidor Buchmann, CEO & Founder, Cadex Electronics, Inc.
Battery users imagine a battery pack being an energy storage device that resembles a fuel tank dispensing liquid fuel. For simplicity reasons, a battery can indeed be perceived as a vessel storing electrical energy; however, measuring energy flowing into an electrochemical device and then drawing it out again is far more complex than handling liquid fuel. While a hydraulic fuel gauge measures liquids moving in and out of a tank of known size, a battery fuel gauge reads units of current. Battery size is specified in ampere hours (Ah), and what makes estimating battery state-of-charge (SoC) and state-of-health (SoH) so challenging is an unsteady state; a battery loses capacity with each charge and leaks energy in the form of self-discharge. MORE
James Niemann, Analog Design Engineer, Tektronix
One of the demonstrations we often set up at battery conferences is to use a source measure unit (SMU) to measure the internal resistance of an energy storage device such as a battery or a fuel cell. In such demonstrations, the SMU changes the load current from the battery operating current or the polarizing current to the open circuit potential and simultaneously measures the change in cell voltage. In this “current interrupt method,” the battery’s internal resistance is equal to the change in voltage divided by the change in current. MORE