A thermal management system for an energy storage system for an aircraft includes a pump circulating a thermal management fluid through the thermal management system and an energy storage device of the aircraft. A controller circuitry may control a variable pumping capacity of the pump based on sensing pressure or temperature of the thermal management fluid at the energy storage device. The controller circuitry may default operation of the pump to a first pumping capacity in response to the pressure or temperature being within a predetermined operating range and a predetermined failure condition or a power demand of an aircraft engine supply bus exceeding a predetermined threshold. The controller controlling operation of the pump to a second pumping capacity in response to absence of the power demand signal of the aircraft engine supply bus and the pressure or temperature being within the predetermined operating range.