A battery electric device includes a battery cell, e.g., a pouch, prismatic, or cylindrical cell, connectable to an electric load, and a direct-to-air thermoelectric assembly (TEA) or another heat pump connected to a surface of the cell. A pressure control device maintains constant pressure on the cell surface when the cell is connected to the load. Connection to the load causes the TEA/heat pump to pump heat from the cell. A sensor, e.g., thermocouple(s) and/or heat flux sensor(s), generate an output voltage signal indicative of the quantity of heat. A battery system includes the device and a processor in communication with the cell, the load, and the power supply. The processor generates an electronic control signal in response to the quantity of heat.