Development of an Electronic Load Applied to the Characterization of Electric Batterie

Abstract

People use batteries as sources of power for electrical and electronic devices in their daily life. Nevertheless, these possess temporary supply limitations due to their state of charge (SOC). A technique used to determine the state of charge is counting amperes, identifying the amount of consumed and of missing amperes according to the initial capacity of the battery. An electronic load consisting of an operational amplifier and an IGBT were used in order to maintain a constant current in the battery discharge process, as well as a data acquisition system that specifies the time needed to obtain the variables of current defined by the electronic load, as well as the battery voltage. Without a heatsink, the Ice current of the IGBT does not remain constant, due to temperature increases exceeding 100°C in less than a minute. A dissipation system with and without ventilation was needed, and the one that kept the current constant was a heatsink for AMD processor with a thermal solution greater than 90W with active ventilation. The discharge curve was managed with it while maintaining the temperature of the IGBT at a maximum value of 46°C during the 4.5 hours, with a current of 4.19A. The initial capacity of the lead acid battery used was close to 19Ah, a little less than that defined by the manufacturer for the new battery (20Ah). One of the biggest problems in determining the state of charge by means of ampere counting is the accuracy of the sensor. To the current sensor used, you can implement filtering stages that improve the SOC value as future work. It should be used that the Vce is below the battery to be discharged. Therefore, this system could not be implemented in 2V batteries, because the Vce voltage in the IGBT exceeds 2V and cannot deliver a potential difference in the resistive load.