Coolant system for a vehicle and a method of controlling a coolant system

1. A coolant system for a vehicle at least partly propelled by an electric traction motor, the coolant system being configured to supply coolant to a coolant circuit for an electric source arranged to supply electric power to the electric traction motor, wherein the coolant system comprises

a first coolant tank configured to contain a coolant fluid,

a coolant supply conduit connected to the first coolant tank, the coolant supply conduit being connectable to the coolant circuit for supply of coolant from the first coolant tank to the coolant circuit,

a second coolant tank comprising a filling portion for admitting coolant fluid into the second coolant tank,

a first coolant feeding conduit arranged in fluid communication between the first coolant tank and the second coolant tank,

a fluid pump arranged in the first coolant feeding conduit for controllable supply of coolant from the second coolant tank to the first coolant tank, and

a control unit connected to the fluid pump, the control unit comprising control circuitry configured to control operation of the fluid pump, wherein the control circuitry is configured to:

receive a signal indicative of a pressure level in the coolant circuit,

compare the pressure level with a predetermined pressure threshold level, and

control the fluid pump to supply a flow of coolant from the second coolant tank to the first coolant tank when the pressure level is below the predetermined pressure threshold level.

2. The coolant system according to claim 1 , further comprising a second coolant feeding conduit arranged in fluid communication between the first coolant tank and the second coolant tank.

3. The coolant system according to claim 2 , further comprising a valve arranged in the second coolant feeding conduit, wherein the valve is controllable between a first state in which coolant fluid is supplied from the first coolant tank to the second coolant tank, and a second state in which coolant fluid in the first coolant tank is prevented from reaching second coolant tank.

4. The coolant system according to claim 3 , wherein the control unit is connected to the valve, the control circuitry being configured to:

control the valve to assume the second state when the pressure level is below the predetermined pressure threshold level.

5. The coolant system according to claim 4 , wherein the control circuitry is further configured to:

control the valve to assume the first state when the pressure level is above the predetermined pressure threshold level.

6. The coolant system according to claim 1 , wherein the control unit is further connected to the first and second coolant tanks, wherein the control circuitry is configured to:

receive a signal indicative of a coolant level present in the first coolant tank,

receive a signal indicative of a coolant level present in the second coolant tank,

determine a difference between the coolant level in the first coolant tank and the coolant level in the second coolant tank;

compare the difference with a predetermined difference threshold limit; and

control the fluid pump to supply a flow of coolant from the second coolant tank to the first coolant tank when the difference exceeds the predetermined difference threshold limit.

7. The coolant system according to claim 3 , wherein the control unit is connected to the valve, the control circuitry being configured to:

control the valve to assume the second state when the difference exceeds the predetermined difference threshold limit.

8. The coolant system according to claim 1 , wherein the control circuitry is configured to:

receive a signal indicative of coolant filling of the second coolant tank at the filling portion, and

control the fluid pump to supply a flow of coolant from the second coolant tank to the first coolant tank.

9. The coolant system according to claim 1 , further comprising a pressure relief conduit arranged in fluid communication between the first coolant tank and the second coolant tank via a pressure relief device connected to the first coolant tank.

10. A vehicle comprising an electric traction motor and an electric source configured to supply electric power to the electric traction motor, the vehicle further comprises a coolant circuit connected to the electric source, and a coolant system according to claim 1 , wherein the coolant system is connected to the coolant circuit.

11. A method of controlling a coolant system of a vehicle, the coolant system being connected to a coolant circuit for an electric source arranged to supply electric power to an electric traction motor of the vehicle, wherein the coolant system comprises a first coolant tank configured to contain a coolant fluid, a second coolant tank comprising a filling portion for admitting coolant fluid into the second coolant tank, a first coolant feeding conduit arranged in fluid communication between the first coolant tank and the second coolant tank, and a fluid pump arranged in the first coolant feeding conduit for controllable supply of coolant from the second coolant tank to the first coolant tank, wherein the method comprises:

determining a pressure level in the coolant circuit,

comparing the pressure level with a predetermined pressure threshold level; and

controlling the fluid pump to supply a flow of coolant from the second coolant tank to the first coolant tank when the pressure level is below the predetermined pressure threshold level.

12. A computer readable medium carrying a computer program comprising program code means for performing the steps of claim 11 when the program means is run on a computer.

13. A computer program comprising program code means for performing the steps of claim 11 when the program is run on a computer.