An approach to improve battery run-time in mobile applications with supercapacitors

In this paper an approach to improve battery run-time in mobile applications with supercapacitors is explored. The performance of a battery-supercapacitor combination is analytically described using simplified equivalent circuit models. It is shown that there is an overall reduction in the internal losses and this translates into increased run-time. Three possible approaches are explored: (a) supercapacitors connected directly across the battery; (b) battery-inductor-supercapacitor connection; and (c) supercapacitor, and battery connected via a DC-DC converter. Analytical models, simulation and experimental results on a typical laptop computer are presented. These results show an increase in runtime of 4-12% is achievable. Also from these results it is shown that the use of a DC-DC converter appears to be a cost effective option, since it allows the use of reduced number of capacitors while maintaining a comparable performance.