Battery assembly with cooling

1. A battery assembly comprising:

a housing having a top, sides, and a bottom;

a first battery pack in the housing; and

a second battery pack in the housing, the second battery pack being spaced from the first battery pack with a first flow path therebetween,

wherein a second flow path is between the battery packs and an inner surface of the housing,

wherein either the first flow path gradually narrows, or the second flow path gradually widens, in a flow direction of coolant to enable natural convection,

wherein the housing and the battery packs are adapted for the coolant to circulate between the first and second flow paths, and

wherein a distance between an upper surface of the first or second battery pack and the inner surface of the top of the housing is smaller near a center of the housing than near an edge of the housing.

2. The battery assembly of claim 1 , wherein, when the second flow path gradually widens, the first flow path remains the same in size in the flow direction of coolant in the first flow path.

3. The battery assembly of claim 1 , wherein, when the first flow path gradually narrows, the second flow path remains the same in size in the flow direction of coolant in the second flow path.

4. The battery assembly of claim 1 , wherein the housing comprises a heat conductive material along the second flow path.

5. The battery assembly of claim 4 , wherein the heat conductive material is selected from the group consisting of steel, stainless steel, aluminum, zinc-coated steel, and combinations thereof.

6. The battery assembly of claim 4 , wherein the housing comprises a heat insulating material at an interface between the first and second flow paths.

7. The battery assembly of claim 6 , wherein the heat insulating material comprises resin.

8. The battery assembly of claim 6 , wherein the heat insulating material is at a location substantially aligned with the first flow path, and a width of the heat insulating material is greater than a distance between the battery packs.

9. The battery assembly of claim 1 , wherein each of the battery packs comprises a battery module comprising a plurality of batteries and a support supporting the battery module, the support comprising a heat insulating material between the battery module and the second flow path.

10. The battery assembly of claim 9 , wherein the heat insulating material comprises resin.

11. The battery assembly of claim 9 , further comprising one or more protrusions located in the second flow path between the inner surface of the housing and the support.

12. The battery assembly of claim 11 , wherein the one or more protrusions protrude from at least one of the support or the inner surface of the housing at an oblique angle.

13. The battery assembly of claim 12 , wherein the one or more protrusions are integrally formed with at least one of the support or the housing.

14. The battery assembly of claim 9 , wherein the battery module further comprises at least one connection member for fixing the batteries to the support.

15. The battery assembly of claim 1 , wherein the housing comprises a cooling device along the second flow path.

16. The battery assembly of claim 1 , wherein a cross-section of the flow paths is nozzle-shaped or diffuser-shaped.

17. An electric vehicle comprising:

a frame;

a motor fixed to the frame for propelling the vehicle; and

the battery assembly according to claim 1 , wherein the battery assembly is fixed to the frame and configured to power the motor.