A charger for charging an energy storage device having a core with an electrolyte, the charger including: a controller comprising hardware, the controller being configured to: obtain a measurement and/or approximation of a temperature of the electrolyte; determine whether the obtained temperature is below a predetermined threshold considered to at least reduce the charging efficiency of the energy storage device; and input a predetermined voltage and/or current input to terminals of the energy storage device causing internal components of the energy storage device to generate heat if the temperature is determined to be less than the predetermined threshold, wherein the energy storage device includes an internal surface capacitance, which can store electric field energy between internal electrodes of the energy storage device, and the controller is configured to input an AC current to the terminals with a frequency high enough to effectively short the internal surface capacitance.