Pressure management device for battery pack

1. A battery pack comprising:

a battery pack housing having a lid joined to an open end via a fluid-impermeable seal;

a battery module disposed within the battery housing and comprising a plurality of electrochemical cells; and

a pressure compensation device positioned within the battery pack housing, the pressure compensation device comprising a first bladder fluidly coupled to a second bladder by a primary fitting,

wherein the battery pack housing is filled with a dielectric fluid, and

wherein the pressure compensation device comprises a second fluid.

2. The battery pack of claim 1 , further comprising a third bladder fluidly coupled to the second bladder by a secondary fitting.

3. The battery pack of claim 1 , wherein the first bladder is at least partially positioned between the lid and the battery module.

4. The battery pack of claim 1 , wherein the primary fitting protrudes through the lid of the battery housing and is coupled to a vent block having a bore positioned outside of the battery pack housing, wherein the bore opens at a predetermined fluid pressure.

5. The battery pack of claim 1 , wherein the second bladder is disposed around the battery module.

6. The battery pack of claim 2 , wherein at least two battery modules are grouped together as a cassette, and the second bladder is disposed around the cassette.

7. The battery pack of claim 6 , wherein the battery pack comprises a first pair of cassettes, and the second bladder is disposed between the cassettes of the first pair of cassettes.

8. The battery pack of claim 7 , further comprising a second pair of cassettes, and the third bladder is disposed between the cassettes of the second pair of cassettes.

9. The battery pack of claim 2 , wherein at least one of the first bladder, the second bladder, and the third bladder comprises a pair of metal-and-polymer laminated sheets coupled together along a seal line.

10. The battery pack of claim 9 , wherein the pair of metal-and-polymer laminated sheets are coupled together along the seal line via heating.

11. The battery pack of claim 2 , wherein the secondary fitting comprises a flexible tube.

12. The battery pack of claim 1 , further comprising a protective sheet positioned between the first bladder and the battery module.

13. The battery pack of claim 1 , wherein at least one of the first bladder and the second bladder comprises a fluid permeable support shell.

14. The battery pack of claim 13 , wherein the support shell comprises a first half-shell and a second-half shell positioned around a corresponding bladder.

15. A battery pack comprising:

a battery pack housing having a lid joined to an open end via a fluid-impermeable seal;

a cassette disposed within the battery housing comprising at least a pair of battery modules, wherein each of the battery modules comprise a plurality of electrochemical cells; and

a pressure compensation device positioned within the battery pack housing, the pressure compensation device comprising:

a first bladder at least partially positioned between the lid and the cassette,

a second bladder fluidly coupled to the first bladder by a primary fitting and disposed at least partially around the cassette, and

a third bladder fluidly coupled to the second bladder by a secondary fitting,

wherein the battery pack housing is filled with a dielectric fluid,

wherein the pressure compensation device comprises a second fluid,

wherein the primary fitting protrudes through the lid of the battery housing and is coupled to a vent block having a bore positioned outside of the battery pack housing, and

wherein the bore opens at a predetermined fluid pressure.

16. The battery pack of claim 15 , wherein the battery pack comprises a first pair of cassettes, and the second bladder is disposed between the cassettes of the first pair of cassettes.