Calendar ageing and health diagnosis of supercapacitor

► Supercapacitor calendar ageing protocol – description of the test bench that we have conducted. ► Ageing and health diagnosis of supercapacitors are described. ► The first approach diagnosis method based on the slope comparison of charge and discharge voltage curves. ► The second approach diagnosis method evaluates the stored energy in the supercapacitors before and after ageing. A new method of supercapacitor online health diagnosis based on an electric model and on experimental results obtained by calendar ageing tests is proposed. The calendar ageing of supercapacitor is mainly related to thermal and voltage constraints from the application. This ageing causes the degradation of supercapacitor performances which can finally lead to failures. In vehicle applications, the goal is to avoid these failures which may have serious consequences and high non-quality costs. The device survey and ageing state detection are a priority for anticipating the problems. This paper presents the case of calendar ageing tests on supercapacitors made of activated carbon and organic electrolyte. The ageing is performed at constant temperature (65°C) under a 2.9Vdc bias voltage. These tests permit to highlight online and in real-time the measurable external indicators of ageing.