Aircraft including mitigation system for rechargeable batteries
An aircraft comprises a rechargeable battery including an array of battery cells, and means for mitigating consequences of failure of the rechargeable battery due to aircraft operating cycles.
1. An aircraft comprising:
a fuselage defining an interior environment inside the fuselage and an exterior environment outside of the fuselage;
a rechargeable battery disposed in the fuselage and including an array of battery cells;
a metal enclosure surrounding the battery and defining a cavity sized to receive the battery, the metal enclosure including:
at least one containment wall formed of a ductile material; a wall opening formed in the at least one containment wall;
a ventilation conduit extending from the wall opening to an opening in composite skin of the fuselage, thereby to establish fluid communication between the cavity and the exterior environment, the ventilation conduit made of metal except for an end portion at the skin, the end portion functioning as an electrical insulator;
a normally closed vent valve disposed in the wall opening and configured to open when a pressure inside the enclosure corresponds to a battery failure event; and
at least one continuously open orifice formed in the at least one containment wall, fluidly communicating between the cavity and the interior environment of the fuselage.
2. The aircraft of claim 1 , in which the at least one continuously open orifice is configured to permit pressure equalization between the cavity and the interior environment of the fuselage over a pressure equalization duration that is greater than a predetermined activation time of the vent valve, and to restrict mass rate of air flow into the enclosure during a battery failure event.
3. The aircraft of claim 1 , in which the at least one continuously open orifice is configured to permit pressure equalization between the cavity and the interior environment of the fuselage over a pressure equalization duration that is greater than a predetermined activation time of the vent valve.
4. The aircraft of claim 3 , in which the at least one continuously open orifice is further configured to restrict mass rate of air flow into the enclosure during a battery failure event.
5. The aircraft of claim 1 , in which the end portion of the ventilation conduit includes a tube made of an electrically non-conductive material, the tube having a length of at least two inches.
6. The aircraft of claim 5 , in which the end portion of the ventilation conduit further includes a flange fitting at an end of the tube, the flange fitting having a portion that extends into the opening of the composite skin of the fuselage, the aircraft further comprising a thermal spacer located between the flange fitting and the composite skin.
7. The aircraft of claim 1 , further comprising a plurality of dielectric separators between the battery cells for creating thermal barriers between opposing surfaces of the battery cells, the dielectric separators made of a fiber composite.
8. The aircraft of claim 7 , wherein the fiber composite includes fibers in a phenolic resin matrix.
9. The aircraft of claim 7 , wherein the fiber composite includes a glass fiber phenolic.
10. The aircraft of claim 7 , wherein the battery cells are prismatic, wherein the dielectric separators form a lattice, and wherein the battery cells populate spaces formed by the lattice.
11. The aircraft of claim 1 , further comprising a chassis including a lower fixation plate, the battery cells on the lower fixation plate, the lower fixation plate including a plurality of flow channels positioned to collect condensate from the battery cells and direct the collected condensate away from the battery cells.
12. The aircraft of claim 11 , in which the lower fixation plate further includes a substrate; and wherein the flow channels include drainage holes in the substrate, each drainage hole located beneath portions of at least two battery cells.
13. The aircraft of claim 12 , wherein the flow channels further include grooves in the substrate, the grooves extending between the drainage holes.
14. The aircraft of claim 13 , wherein the lower fixation plate further includes a lattice of cell dividers on the substrate, the battery cells located between the cell dividers, the grooves extending between the drainage holes, along the cell dividers.
15. The aircraft of claim 1 , in which a side of each battery cell includes a rupture plate, the aircraft further including a chassis including a frame having vent cutouts, wherein the battery cells are oriented such that their rupture plates are coincident with the vent cutouts.
16. The aircraft of claim 1 , further including a battery monitoring unit (BMU) configured to receive signals from the battery cells, and process the signals to determine status of the battery cells; wherein the signals include at least one of a temperature signal, a voltage signal, or a current signal.
17. The aircraft of claim 16 , in which the BMU is configured to removably connect the battery to a master/module interface; and deliver power from the battery to the master/module interface.
18. The aircraft of claim 17 , in which the BMU is further configured to interrupt delivery of battery power to the master/module interface.
19. The aircraft of claim 18 , in which the BMU is configured to operate the battery in a voltage range that reduces heat and is further configured to prevent over-charging damage.
20. The aircraft of claim 1 , wherein the rechargeable battery is a lithium cobalt oxide battery.
21. The aircraft of claim 1 , wherein the battery is a main battery.
22. The aircraft of claim 1 , wherein the battery is an auxiliary power unit (APU) battery.
23. The aircraft of claim 1 , further comprising:
a plurality of dielectric separators between the battery cells for creating thermal barriers between opposing surfaces of the battery cells, the dielectric separators made of a fiber composite; and
a chassis including:
a lower fixation plate, the battery cells disposed on the lower fixation plate, the lower fixation plate including a plurality of flow channels positioned to collect condensate from the battery cells and direct the collected condensate away from the battery cells; and
vent holes coincident with rupture plates of the battery cells.
24. The aircraft of claim 23 , in which the chassis containing the battery cells is located within the enclosure.