An automotive electric vehicle system, the system comprising: a high voltage battery system including an enclosure; an electric powertrain system; a radiator ; coolant lines that permit flow of coolant between the high voltage battery system , the powertrain system and the radiator ; one or more valves for routing coolant along the coolant lines; and a controller configured to control the valves to facilitate the flow of coolant among a plurality of different, selectable coolant flow states involving the high voltage battery system , the powertrain system, and the radiator ; and a heating, ventilation and air conditioning (HVAC) system, the HVAC system comprising a compressor , a condenser , an expansion valve , a cabin heat exchanger arranged in a heat pump configuration to provide cabin heating using a refrigerant, refrigerant lines connecting the compressor , the condenser , the heat exchanger and the expansion valve , and a further heat exchanger configured to exchange heat between a refrigerant and the coolant to extract heat from the battery system; wherein the high voltage battery system is configured to serve as a thermal heat store and as a source of heat for another vehicle system, and characterized in that : the controller controls the control valves based on control factors including: external control inputs comprising at least one of historical information, trending information and predictive information; and a prioritisation of desired performance factors including at least one of satisfying a battery system requirement, satisfying a powertrain system requirement, and satisfying a desired cabin environment requirement. a high voltage battery system including an enclosure; an electric powertrain system; a radiator ; coolant lines that permit flow of coolant between the high voltage battery system , the powertrain system and the radiator ; one or more valves for routing coolant along the coolant lines; and a controller configured to control the valves to facilitate the flow of coolant among a plurality of different, selectable coolant flow states involving the high voltage battery system , the powertrain system, and the radiator ; and a heating, ventilation and air conditioning (HVAC) system, the HVAC system comprising a compressor , a condenser , an expansion valve , a cabin heat exchanger arranged in a heat pump configuration to provide cabin heating using a refrigerant, refrigerant lines connecting the compressor , the condenser , the heat exchanger and the expansion valve , and a further heat exchanger configured to exchange heat between a refrigerant and the coolant to extract heat from the battery system; wherein the high voltage battery system is configured to serve as a thermal heat store and as a source of heat for another vehicle system, and characterized in that : the controller controls the control valves based on control factors including: external control inputs comprising at least one of historical information, trending information and predictive information; and a prioritisation of desired performance factors including at least one of satisfying a battery system requirement, satisfying a powertrain system requirement, and satisfying a desired cabin environment requirement. external control inputs comprising at least one of historical information, trending information and predictive information; and a prioritisation of desired performance factors including at least one of satisfying a battery system requirement, satisfying a powertrain system requirement, and satisfying a desired cabin environment requirement. <EOS>