engleski

Impact of balance resistor uncertainty on voltages across supercapacitors

In some applications, due to a relative low operating voltage of a supercapacitor cell, it is necessary to connect it in series to achieve a required operating voltage. However, due to the variation of supercapacitor parameters, there is a voltage imbalance across the supercapacitors connected in series, hence they should be balanced (equalized) by means of an appropriate technique. For this purpose, several active and passive balancing techniques are used. In this paper, the technique of passive voltage balancing using resistors is described. The phenomenon and the physical cause of voltage imbalance on supercapacitor (SC) cells are explained in detail. The paper gives a mathematical model that accurately describes voltage balancing using resistors. An uncertainty analysis was introduced to describe the expected voltage variation of supercapacitors before and after passive voltage balancing using resistors. All relevant expressions which determine the expected voltage variation before and after implementation of voltage balancing are derived. The derived expressions allow determination of voltage variance and uncertainty on SCs in the most unfavorable case of voltage imbalance. Based on the presented theory and derived expressions, the guidelines in the implementation of passive techniques for voltage balancing using resistors are given.

Balancing ; Electric double layer capacitor ; Supercapacitor ; Ultracapacitor ; Uncertainty ; Voltage balancing ; Voltage distribution

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