Heat battery

A heat battery located in a substantially vertical or substantially horizontal orientation comprising:

• a battery cell case;
• phase change material (PCM) located within the battery cell case;
• at least one or a plurality of heat exchangers located within the battery cell case and immersed in the PCM;
• an expandable device in the form of an inflatable gas balloon member which is capable of being inflated and/or deflated, the expandable device is located within the battery cell case and is capable of expanding and/or contracting to manage expansion and/or volumetric changes within the battery cell case;
• a gas filling valve which extends through the battery cell case and is connected to the expandable device, wherein the gas filling valve is used to increase and/or decrease the pressure and/or amount of gas held within the expandable device;
• control sensors which are used to monitor the expansion and/or contraction of the PCM by monitoring the level of the PCM;
• a controller configured to pressurize and/or depressurize the inflatable gas balloon member based on the control sensors monitoring the level of the PCM such that the cross-sectional diameter of the inflatable gas balloon member is expanded and/or contracted and such that the inflatable gas balloon member is inflated and/or deflated to adapt for the expansion and/or contraction of the PCM and/or any gas/air trapped within the battery cell case and to prevent over-pressurization within the battery cell case;
• and
• wherein the expandable device is located within and against an inner surface of the battery cell case and also extends across an upper surface of the PCM and along an upper surface of the at least one or the plurality of heat exchangers.