NOVELTY - Controlling the temperature of a traction battery in a hybrid vehicle comprises: (a) providing a first temperature regulating circuit for the internal combustion engine; (b) providing a second temperature regulating circuit for the traction battery; (c) heating the traction battery; and (d) transferring power to the heater via a direct current (DC)/DC converter in the second temperature regulating circuit from the electrical motor.    USE - The method is used for controlling the temperature of a traction battery in a hybrid vehicle (claimed).    ADVANTAGE - The power for heating the battery is provided from the internal combustion engine via a DC/DC converter and the electrical motor. The lifetime of the battery may also be extended. The time for reaching a working temperature of the battery may also be decreased. Electrical components lifetime may be increased and its performance may be secured. The first end second temperature regulating circuits can be controlled independently of each other.    DETAILED DESCRIPTION - Controlling the temperature of a traction battery in a hybrid vehicle, where the hybrid vehicle comprises an internal combustion engine and an electric motor for traction power, comprises: (a) providing a first temperature regulating circuit for the internal combustion engine; (b) providing a second temperature regulating circuit for the traction battery; (c) heating the traction battery by an electrical heater provided in the second temperature regulating circuit in series with a pump, a radiator, and the traction battery; and (d) transferring power to the heater via a direct current (DC)/DC converter in the second temperature regulating circuit from the electrical motor, where the electrical motor is driven by the internal combustion engine, while the battery is below a predetermined temperature interval. An INDEPENDENT CLAIM is included for a system for controlling the temperature of a traction battery in a hybrid vehicle, where the hybrid vehicle comprises an internal combustion engine and an electric motor for traction power, and the system comprises a first temperature regulating circuit for the internal combustion engine, a second temperature regulating circuit for the traction battery, a heater, a pump, and a radiator provided in the second temperature regulating circuit, where the heater is provided with power via a DC/DC converter from the electrical motor, where the electrical motor is driven by the internal combustion engine.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a temperature regulating circuit for regulating a temperature of a traction battery in a hybrid vehicle.    Heater (102)    Optional valve (104)    Pass liquid coolant circuit (106)    Radiator (108)    Traction battery (110)    Pump (112)    Main liquid coolant circuit (116)