A new parameters identification procedure for simplified double layer capacitor two-branch model

Supercapacitors are electrical energy storage devices that offer high power density and a high number of charge and discharge cycles. Even though the amount of stored energy they maintain is not comparable that of classical batteries, supercapacitors can offer advantages in several industrial applications. This paper introduces a simplified model, named the "two-branch" model, to characterize the electrical behaviour of double layer capacitors (DLCs). This model is similar to some models in literature from a circuit point of view (e.g. three-branch model), but the parameters identification process is easier and faster. Experimental charge and charge-discharge tests have been executed on supercapacitors of two different makes (Epcos and Maxwell) and for several different sizes (between 110 F and 600 F). Moreover a new identification procedure, for describing short-term behaviour, is proposed for the new simplified two-branch model. This new procedure is simpler than for the other lumped models therefore it can be adopted fruitfully also from them. The experimental results and the performed simulations are reported in order to verify the validity of the new simplified proposed model and of the new parameter identification process. (C) 2009 Elsevier B.V. All rights reserved.