Thermal management system for rechargeable batteries
A thermal management system ( 270 ) for rechargeable secondary batteries having an electrically insulating material ( 262 ) lining the interior of a metal case ( 260 ). One or more cell packs ( 24 ) made of individual cells ( 12 ) arranged within end frames ( 220 ) is disposed in the metal case ( 260 ). A thermally conductive granular filler ( 264 ) occupies the interstices ( 264 A) between the individual cells ( 12 ) and the space between the cell pack and the electrically insulating material liner ( 262 ). The thermally conductive filler ( 264 ) decreases the thermal impedance from the cell pack ( 24 ) to the exterior surface of the metal case ( 260 ) to reduce cell pack temperature and increase battery life
1 . A thermal management system for a rechargeable battery comprising:
a metal case having an exterior surface and an interior surface lined with an electrically insulating material;
a cell pack made from individual battery cells arranged within end frames and disposed in said metal case on isolation mounts which support and space the cell packs from the interior surface; and
a thermally conductive granular filler in the form of free-flowing granules introduced into the free spaces within the battery to occupy the interstices between said individual cells and occupy the space between the cell pack and the electrically insulating material lining, wherein said thermally conductive filler decreases the thermal impedance from the cell pack to the exterior surface of the metal case to reduce cell pack temperature and increase battery life.
2 . The thermal management system according to claim 1 , wherein said metal case includes a five-sided box and a cover made from one of iron/carbon steel and high temperature steel, wherein all surfaces of the case are galvanized for rust prevention.
3 . The thermal management system according to claim 1 , wherein said metal case includes a five-sided box and a cover made from one of iron/carbon steel and high temperature steel, wherein all surfaces of the case are provided with a highly-crosslinked non-porous coating that protects the metal from biological, radioactive and chemical contamination and withstands chemical cleaning and decontamination without corroding.
4 . The thermal management system according to claim 3 , wherein said highly-crosslinked non-porous coating is selected from the group consisting of urethane, polyurethane, aliphatic polyurethane, epoxy, epoxy polyamide, epoxy polyamide enamel and combinations thereof.
5 . The thermal management system according to claim 3 , wherein said cover is sealed to said five-sided box to provide a waterproof metal case that protects the cell pack from moisture intrusion, wherein the metal case includes a pressure relief vent.
6 . The thermal management system according to claim 5 , wherein said pressure relief vent comprises an aperture through the metal case and a film adhered over the aperture.
7 . The thermal management system according to claim 1 , wherein said electrically insulating material lining said interior surface of said metal case comprises a thermoplastic film adhered to said interior surface.
8 . The thermal management system according to claim 7 , wherein said thermoplastic film is selected from the group consisting of polyester, nylon and polycarbonate.
9 . The thermal management system according to claim 8 , wherein said thermoplastic film is between 0.2 mm and 2.0 mm thick.
10 . The thermal management system according to claim 1 , wherein said metal case includes metal panels lined with the electrically insulating material that divide an internal space of the metal case into compartments, wherein said system includes multiple cell packs, each including dozens of cells, wherein each compartment contains one cell pack.
11 . The thermal management system according to claim 1 , wherein two cell packs are arranged adjacent to each other within the case with one lower end frame of the first cell pack facing one upper end frame of the second cell pack, wherein the thermally conductive granular filler is disposed between the facing end frames.
12 . The thermal management system according to a claim 6 , wherein said thermally conductive granular filler comprises alumina trihydrate having a particle size between 2-200 microns which decomposes when a battery cell malfunction heats the alumina trihydrate above around 220 degrees C. to release up to 35% of its weight as water vapor, wherein excessive water vapor pressure will breach the film adhered over the aperture to open the pressure relief vent.
13 . The thermal management system according to claim 1 , wherein said system includes electrically insulated sleeves which contain the cell packs.
14 . The thermal management system according to claim 1 , wherein said end frames are bonded to the battery cells with epoxy and wherein a silicone-based filler is disposed between the end frames and the metal case to stabilize the cell packs.
15 . The thermal management system according to claim 1 , wherein the thermal management system allows the battery to be cycled in excess of +70 amps charge and −70 amps discharge whereby the thermally conductive granular filler decreases thermal impedance from the cell pack to the outside surface of the metal case so that an over-temperature protection circuit is not tripped.
16 . The thermal management system according to claim 1 , wherein the thermally conductive granular filler has a particle size between 2-200 microns which decomposes when a battery cell malfunction heats the thermally conductive granular filler above around 220 degrees C. to release up to 35% of its weight as water vapor.
17 . The thermal management system according to claim 16 , wherein the electrically insulating material comprises a thermoplastic film.
18 . The thermal management system according to claim 17 , wherein the metal case comprises a waterproof sealed steel case provided with a non-porous coating that protects the metal from biological, radioactive and chemical contamination and withstands chemical cleaning and decontamination without corroding.
19 . The thermal management system according to claim 18 , wherein the steel case is galvanized and the non-porous coating comprises a highly-crosslinked resin coating.
20 . The thermal management system according to claim 19 , wherein the thermally conductive granular filler comprises alumina trihydrate.