Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings; Jackets or wrappings
  • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
  • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/04—Construction or manufacture in general
  • H01M10/0413—Large-sized flat cells or batteries for motive or stationary systems with plate-like electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/04—Construction or manufacture in general
  • H01M10/0468—Compression means for stacks of electrodes and separators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/34—Gastight accumulators
  • H01M10/345—Gastight metal hydride accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/61—Types of temperature control
  • H01M10/613—Cooling or keeping cold
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/63—Control systems
  • H01M10/635—Control systems based on ambient temperature
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/64—Heating or cooling; Temperature control characterised by the shape of the cells
  • H01M10/647—Prismatic or flat cells, e.g. pouch cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/651—Means for temperature control structurally associated with the cells characterised by parameters specified by a numeric value or mathematical formula, e.g. ratios, sizes or concentrations
  • H01M10/652—Means for temperature control structurally associated with the cells characterised by parameters specified by a numeric value or mathematical formula, e.g. ratios, sizes or concentrations characterised by gradients
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/653—Means for temperature control structurally associated with the cells characterised by electrically insulating or thermally conductive materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/655—Solid structures for heat exchange or heat conduction
  • H01M10/6551—Surfaces specially adapted for heat dissipation or radiation, e.g. fins or coatings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/655—Solid structures for heat exchange or heat conduction
  • H01M10/6556—Solid parts with flow channel passages or pipes for heat exchange
  • H01M10/6557—Solid parts with flow channel passages or pipes for heat exchange arranged between the cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/656—Means for temperature control structurally associated with the cells characterised by the type of heat-exchange fluid
  • H01M10/6561—Gases
  • H01M10/6563—Gases with forced flow, e.g. by blowers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/60—Heating or cooling; Temperature control
  • H01M10/65—Means for temperature control structurally associated with the cells
  • H01M10/658—Means for temperature control structurally associated with the cells by thermal insulation or shielding
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/30—Arrangements for facilitating escape of gases
  • H01M50/317—Re-sealable arrangements
  • H01M50/325—Re-sealable arrangements comprising deformable valve members, e.g. elastic or flexible valve members
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/50—Current conducting connections for cells or batteries
  • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
  • H01M50/503—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the shape of the interconnectors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates generally to improvements for metal hydride batteries, battery modules made therefrom and battery packs made from the modules. More specifically, this invention relates to mechanical and thermal improvements in battery design, battery module design, and battery pack design.
• Rechargeable prismatic batteries are used in a variety of industrial and commercial applications such as fork lifts, golf carts, uninterruptable power supplies, and electric vehicles.
• Rechargeable lead-acid batteries are presently the most widely used type of battery.
• Lead-acid batteries are a useful power source for starter motors for internal combustion engines.
• their low energy density about 30 Wh/kg, and their inability to reject heat adequately, makes them an impractical power source for an electric vehicle.
• An electric vehicle using lead acid batteries has a short range before requiring recharge, require about 6 to 12 hours to recharge and contain toxic materials.
• electric vehicles using lead-acid batteries have sluggish acceleration, poor tolerance to deep discharge, and a battery lifetime of only about 20,000 miles.
• Ni-MH batteries Nickel metal hydride batteries
• lead acid batteries nickel metal hydride batteries
• Ni-MH batteries are the most promising type of battery available for electric vehicles.
• Ni-MH batteries such as those described in copending U.S. Patent Application No. 07/934,976 to Ovshinsky and Fetcenko, the disclosure of which is incorporated herein by reference, have a much better energy density than lead-acid batteries, can power an electric vehicle over 250 miles before requiring recharge, can be recharged in 15 minutes, and contain no toxic materials. Electric vehicles using Ni-MH batteries will have exceptional acceleration, and a battery lifetime of more than about 100,000 miles.
• Some extremely efficient electrochemical hydrogen storage materials were formulated, based on the disordered materials described above. These are the Ti-V-Zr-Ni type active materials such as disclosed in U.S. Patent No. 4,551 ,400 ("the '400 Patent") to Sapru, Hong, Fetcenko, and Venkatesan, the disclosure of which is incorporated by reference. These materials reversibly form hydrides in order to store hydrogen. All the materials used in the '400 Patent utilize a generic Ti-V-Ni composition, where at least Ti, V, and Ni are present and may be modified with Cr, Zr, and Al. The materials of the '400 Patent are multiphase materials, which may contain, but are not limited to, one or more phases with C 14 and C 15 type crystal structures.
• Ti-V-Zr-Ni alloys are also used for rechargeable hydrogen storage negative electrodes.
• One such family of materials are those described in U.S. Patent No. 4,728,586 ("the '586 Patent") to Venkatesan, Reichman, and Fetcenko, the disclosure of which is incorporated by reference.
• the '586 Patent describes a specific sub-class of these Ti-V-Ni-Zr alloys comprising Ti, V, Zr, Ni, and a fifth component, Cr.
• the '586 Patent mentions the possibility of additives and modifiers beyond the Ti, V, Zr, Ni, and Cr components of the alloys, and generally discusses specific additives and modifiers, the amounts and interactions of these modifiers, and the particular benefits that could be expected from them.
• the weight of the batteries is a significant factor because battery weight is the largest component of the weight of the vehicle. For this reason, reducing the weight of individual batteries is a significant consideration in designing batteries for electric powered vehicles.
• the weight of battery modules must be reduced, while still affording the necessary mechanical requirements of a module (i.e. ease of transport, ruggedness, etc.).
• the battery pack components must be as light weight as possible.
• Sources of heat are primarily threefold. First, ambient heat due to the operation of the vehicle in hot climates. Second, resistive or l 2 R heating on charge and discharge, where I represents the current flowing into or out of the battery and R is the resistance of the battery. Third, a tremendous amount of heat is generated during overcharge due to gas recombination.
• Ni-MH has such a high specific energy and the charge and discharge currents are also high. For example, to charge a lead- acid battery in one hour, a current of 35 Amps may be used while recharge of a Ni-MH battery may utilize 100 Amps for the same one-hour recharge.
• Ni-MH has an exceptional energy density (i.e. the energy is stored very compactly) heat dissipation is more difficult than lead-acid batteries. This is because the surface-area to volume ratio is much smaller than lead-acid, which means that while the heat being generated is 2.5- times greater for NiMH batteries than for lead acid, the heat dissipation surface is reduced.
• Ni-MH batteries While the heat generated during charging and discharging Ni-MH batteries is normally not a problem in small consumer batteries or even in larger batteries when they are used singly for a limited period of time, large batteries that serve as a continual power source, particularly when more than one is used in series or in parallel, such as in a satellite or an electric vehicle, do generate sufficient heat on charging and discharging to affect the ultimate performance of the battery modules or battery pack systems.
• large batteries that serve as a continual power source, particularly when more than one is used in series or in parallel, such as in a satellite or an electric vehicle, do generate sufficient heat on charging and discharging to affect the ultimate performance of the battery modules or battery pack systems.
• battery, battery module, and battery pack system designs which reduces the overall weight thereof and incorporates the necessary thermal management needed for successful operation in electric vehicles, without reducing its energy storage capacity or power output, increases the batteries' reliability, and decreases the cost.
• Thermal management of an electric vehicle battery system using a high energy battery technology has never before been demonstrated.
• Some technologies, such as Na-S, which operate at elevated temperatures are heavily insulated to maintain a specific operating temperature. This arrangement is undesirable due to a heavy penalty in overall energy density due to the excessive weight of the thermal management, high complexity and excessive cost.
• attempts at thermal management have utilized a water cooling system. Again this type of thermal management system adds weight, complexity and cost to the battery pack.
• the prior art does not teach an integrated battery configuration/internal design, battery module, and thermally managed battery pack system which is light weight, simple, inexpensive, and combines the structural support of the batteries, modules and packs with an air-cooled thermal management system.
• the battery includes: 1 ) a battery case which includes a positive battery electrode terminal and a negative battery electrode terminal; 2) at least one positive battery electrode disposed within the battery case and electrically connected to the positive battery electrode terminal; 3) at least one negative battery electrode disposed within the battery case and electrically connected to the negative battery electrode terminal; 4) at least one battery electrode separator disposed between the positive and negative electrodes within the battery case to electrically insulate the positive electrode from the negative electrode, but still allow for chemical interaction thereof; and 5) battery electrolyte surrounding and wetting the positive electrode, the negative electrode, and the separator.
• the battery case is prismatic in shape and has an optimized thickness to width to height aspect ratio.
• the battery module of the instant invention includes: 1 ) a plurality of individual batteries; 2) a plurality of electrical interconnects connecting the individual batteries of the module to one another and providing means for electrically interconnecting separate battery modules to one another; and 3) a battery module bundling/compression means.
• the batteries are bound within the module bundling/compression means under external mechanical compression which is optimized to balance outward pressure due to expansion of the battery components and provide additional inward compression on the battery electrodes within each cell to reduce the distance between the positive and negative electrodes, thereby increasing overall cell power.
• the module bundling/compression means is designed to: 1 ) allow for application of the required battery compression; 2) perform the requirec mechanical function of vibration resistant module bundler; and 3) be as light weight as possible.
• Yet another aspect of the present invention is the mechanical design of light-weight, fluid-cooled, battery pack systems.
• the instant fluid-cooled battery pack system includes: 1 ) a battery-pack case having at least one coolant inlet and at least one coolant outlet; 2) at least one battery module disposed and positioned within the case such that the battery module is spaced from the case walls and from any other battery modules within the case to form coolant flow channels along at least one surface of the bundled batteries, the width of the coolant flow channels is optimally sized to allow for maximum heat transfer, through convective, conductive and radiative heat transfer mechanisms, from the batteries to the coolant; and 3) at least one coolant transport means which causes the coolant to enter the coolant inlet means of the case, to flow through the coolant flow channels and to exit through the coolant outlet means of the case.
• the battery pack system is air-cooled.
• the above described mechanical design of the battery, module, and battery pack system is integrated electronically through a charger algorithm designed to charge the battery pack system quickly while extending the battery life through minimized overcharge and heat generation management.
• batteries, modules and packs can also include means for providing variable thermal insulation to at least that portion of the rechargeable battery system which is most directly exposed to said ambient thermal condition, so as to maintain the temperature of the rechargeable battery system within the desired operating range thereof under variable ambient conditions.
• Figure 1 is a highly stylized depiction of a cross-sectional view of the mechanically improved rechargeable battery of the invention, specifically illustrating the battery electrodes, separator, battery case, and the battery electrical terminals;
• Figure 2 is a stylized depiction of an exploded, cross-sectional view of the mechanically improved rechargeable battery, specifically illustrating how many of the battery components interact when assembled;
• Figure 3 is a blow-up of the terminal, can top, terminal seal and electrode comb depicted in Figure 2;
• Figure 4 is a stylized depiction of a cross-sectional view of the crimp seal formed to seal the battery terminal to the battery can top;
• Figure 5 is a stylized depiction of a cross-sectional view of one embodiment of the battery terminal, specifically illustrating how a pressure vent can be incorporated into the terminal;
• Figure 6 is a stylized depiction of a cross-sectional view of another embodiment of the battery terminal, specifically illustrating how a socket type electrical lead connector can be incorporated into the terminal;
• Figure 7 is a stylized depiction of an electrode comb;
• Figure 8 is a stylized depiction of a top view of a battery module of the instant invention, specifically illustrated is the manner in which the batteries are bundled, including their orientation, the bars and end-plates which hold the batteries under external mechanical compression, and the axis of compression;
• Figure 9 is a stylized depiction of a side view of the battery module of Figure 8, specifically illustrated is the manner in which the metal bars are set into slots in the ribs of the end-plates;
• Figure 10 is a stylized depiction of an end view of the battery module of Figures 8 and 9, specifically shown is the manner in which the end plates and the compression bars interact;
• Figure 11 is a stylized depiction of a top view of a battery module of the instant invention, specifically illustrating the module spacers of the instant invention and the spacer tabs attached thereto;
• Figure 12 is a stylized depiction of a side view of the battery module of Figure 11 , specifically illustrating the manner in which the module spacers are placed on the top and bottom of the battery module;
• Figure 13a is a stylized depiction of one embodiment of the end plates of the instant battery modules, specifically illustrated is a ribbed end plate;
• Figure 13b is a stylized depiction of a cross-sectional view of the ribbed end plate of Figure 13a;
• Figure 14 is a stylized depiction of one embodiment of the braided cable interconnect useful in the modules and battery packs of the instant invention; specifically shown is a flat braided cable electrical interconnect;
• Figure 15 is a stylized depiction of a top view of one embodiment of the fluid-cooled battery pack of the present invention, specifically illustrated is the matrix placement of the battery modules into the pack case, the manner in which the module spacers form coolant flow channels, the fluid inlet and outlet ports, and the fluid transport means;
• Figure 16 is plot of battery temperature versus stand time indicating the manner in which temperature controlled fan algorithms affect the battery temperature during pack self discharge;
• Figure 17 is a plot of battery resistance and battery thickness versus external compression pressure, optimal and functional ranges are clearly present;
• Figure 18 illustrates the effect of temperature upon the battery's specific energy, plotting battery temperature versus specific energy in Wh/Kg;
• Figure 19 illustrates the effect of temperature upon the battery's specific power, plotting battery temperature versus specific power in W/Kg;
• Figure 20 is a plot of coolant volumetric flow rate and the percentage of maximum heat transfer and coolant velocity versus centeriine spacing (related to average coolant channel width) for vertical coolant flow through the coolant flow channels;
• Figure 21 is a plot of coolant volumetric flow rate and the percentage of maximum heat transfer and coolant velocity versus centeriine spacing (related to average coolant channel width) for horizontal coolant flow through the coolant flow channels;
• Figure 22 is a plot of temperature rise from ambient and pack voltage versus time during charge and discharge cycles using a "temperature compensated voltage lid” charging method
• Figure 23 is a plot of temperature rise from ambient and pack voltage versus time during charge and discharge cycles using a "fixed voltage lid” charging method;
• Figure 24 is a plot of battery capacity measured in Ah verses battery type for the M series batteries;
• Figure 25 is a plot of battery power measured in W verses battery type for the M series batteries;
• Figure 26 is a plot of normalized battery capacity measured in mAh/cm 2 verses battery type for the M series batteries
• Figure 27 is a plot of normalized battery power measured in mW/cm 2 verses battery type for the M series batteries
• Figure 28 is a plot of specific battery power measured in W/Kg verses battery type for the M series batteries.
• Figure 29 is a plot of specific battery energy measured in Wh/Kg verses battery type for the M series batteries.
• One aspect of the instant invention provides for a mechanically improved rechargeable battery, shown generically in Figure 1.
• a mechanically improved rechargeable battery shown generically in Figure 1.
• rechargeable batteries such as the nickel-metal hydride battery system
• much emphasis is placed upon the electrochemical aspects of the batteries, while much less time and energy are spent in improving the mechanical aspects of battery, module and pack design.
• the instant inventors have investigated improvements in the mechanical design of rechargeable battery systems, looking at aspects such as energy density (both volumetric and gravimetric), strength, durability, mechanical aspects of battery performance, and thermal management.
• a mechanically improved rechargeable battery 1 which includes: 1) a battery case 2 which includes a positive battery electrode terminal 7 and a negative battery electrode terminal 8; 2) at least one positive battery electrode 5 disposed within the battery case 2 and electrically connected to the positive battery electrode terminal 7; 3) at least one negative battery electrode 4 disposed within the battery case 2 and electrically connected to the negative battery electrode terminal 8; 4) at least one battery electrode separator 6 disposed between the positive and negative electrodes within the battery case 2 to electrically insulate the positive electrode from the negative electrode, but still allow for chemical interaction thereof; and 5) battery electrolyte (not shown) surrounding and wetting the positive electrode 5, the negative electrode 4, and the separator 6.
• the battery case 2 is prismatic in shape and has an optimized thickness to width to height aspect ratio.
• battery specifically refers to electrochemical cells which include a plurality of positive and negative electrodes separated by separators, sealed in a case having positive and negative terminal on its exterior, where the appropriate electrodes are all connected to their respective terminals.
• This optimized aspect ratio allows the battery to have balanced optimal properties when compared with prismatic batteries which do not have this optimized aspect ratio.
• the thickness, width and height are all optimized to allow for maximum capacity and power output, while eliminating deleterious side effects. Additionally, this particular case design allows for unidirectional expansion which can readily be compensated for by applying external mechanical compression in that one direction.
• the instant inventors have found that the optimal electrode thickness to width ratio to be between about 0.1 to 0.75 and the optimal height to width ratio to be between 0.75 and 2.1. Specific examples of batteries and their electrode height to width ratio is given in Table 1.
• Figures 24-29 show how the different height to width aspect ratios of the M series of batteries (shown in Table 1) give different optimums depending upon the specific properties desired.
• Figures 24 and 25 which are plots of capacity in Ah and power in W verses battery type, respectively, indicate that for maximum capacity and power, the M cell is best.
• Figures 26 and 27 which are plots of normalized capacity in mAh/cm 2 and power in mW/cm 2 verses battery type, respectively, if the capacity and power are normalized to the area of the electrodes, the M-40 cell is the best.
• the M-40 cell is also the best, as shown by Figure 28 which plots the specific power of the batteries in W/Kg verses battery type.
• the M-20 cell is the best, as shown by Figure 29 which plots the specific energy of the batteries in Wh/Kg verses battery type.
• the instant inventors have noted that if the batteries are too high (tall) there is an increased tendency for the electrodes to crack upon expansion and contraction. There is also problems with increased internal electrical resistance of the electrodes, and gravimetric segregation of the electrolyte to the bottom of the battery leaving the upper portions of the electrodes dry. Both of these later problems reduce the capacity and power output of the batteries. If, on the other hand, the electrodes are too short, the capacity and power of the battery are reduced due to lowered inclusions of the electrochemically active materials and the specific energy density of the battery is reduced due to the change in the ratios of dead weight battery components to electrochemically active components.
• expansion includes both thermal and electrochemical expansion.
• the thermal expansion is due to heating of the battery components by the mechanisms described above and the electrochemical expansion is due to a changing between different lattice structures in the charged and discharged states of the electrochemically active materials of the battery.
• the battery case 2 is preferably formed from any material which is thermally conductive, mechanically strong and rigid, and is chemically inert to the battery chemistry, such as a metal.
• a polymer or composite material may be used as the material for the battery case.
• thermal heat transfer As detailed in U.S. Patent Application Serial No. 08/238,570, filed May 5, 1995, the contents of which are incorporated by reference, experiments with plastic cases show that the internal temperature of a plastic cased metal-hydride battery rises to about 80°C from ambient after cycling at C/10 to 120% of capacity, while a stainless steel case rises to only 32°C.
• thermally conductive polymer or composite material cases are preferred.
• the case is formed from stainless steel. It is advantageous to electrically insulate the exterior of the metal case from the environment by coating it with a non-conductive polymer coating (not shown).
• a non-conductive polymer coating (not shown).
• An example of one such layer is insulating polymer tape layer made from a polymer such as polyester. The mechanical strength and ruggedness of the polymer tape is important as well as its insulating properties. Additionally, it is preferably inexpensive, uniform, and thin.
• the interior of the battery case 2 must also be electrically insulated from the battery electrodes. This can be accomplished by coating an electrically insulating polymer (not shown) onto the interior of the battery case, or alternatively, enclosing the battery electrodes and electrolyte in an electrically insulating polymer bag (not shown), which is inert to the battery chemistry. This bag is then sealed and inserted into the battery case 2.
• the battery case includes a case top 3 onto which the positive battery electrode terminal 7 and the negative battery electrode terminal 8 are affixed, and a battery case can 9 into which the electrodes 4, 5 are disposed.
• Figure 3 shows that the case top 3 includes openings 13, through which the positive and negative battery terminals 7, 8 are in electrical communication with the battery electrodes 4, 5.
• the diameter of the openings 13 is slightly larger than the outer diameter of the terminal 7, 8, but smaller than the outer diameter of a seal 10 used to seal the terminal 7,8 to the case top 3.
• the terminals 7, 8 include a sealing lip 1 1 which assists in sealing the terminal 7, 8 to the case top 3, using the seal 10.
• the seal 10 is typically a sealing ring.
• the seal 10 includes a sealing lip slot 12 into which the sealing lip 11 of the terminal 7, 8 is fit. This slot 12 helps to form a good pressure seal between the terminal 7, 8 and the case top 3 and to keep the seal 10 in place when the terminal 7, 8 is crimped into the case top 3.
• the seal 10 is preferably formed of an elastomeric, dielectric, hydrogen impermeable material, such as, for example, polysulfone.
• the case top 3 also includes a shroud 14 surrounding the each of the openings 13 and extending outward from the case top 3. The shroud 14 has an inner diameter slightly larger than the outer diameter of the seal 10.
• the shroud 14 is crimped around the seal 10 and the sealing lip 11 of the battery terminal 7, 8, to form an electrically non- conductive pressure seal between the terminal 7, 8 and the case top 3.
• the crimp terminal seal provides vibration resistance when compared to the threaded seal of the prior art.
• the case top 3, case can 9, and annular shroud 14 may be formed from 304L stainless steel.
• Figure 4 shows a portion of the battery of the present invention specifically depicting the fashion in which the battery terminal 7, 8 is crimp sealed into the case top 3. From this figure, it can be clearly determined how the shroud 14 of the case top 3 is crimp sealed around the seal 10 which is, in turn, sealed around the sealing lip 11 of the battery terminal 7, 8. In this manner the vibration resistant pressure seal is formed.
• the method of attaching the terminal 7, 8 to the case top 3 involves crimp sealing the terminal 7, 8 to the case top 3.
• This crimp sealing method has a number of advantages over the prior art. Crimp sealing can be done rapidly on high speed equipment leading to a direct cost reduction. In addition, this method uses less material than the prior art which reduces the weight of the terminals resulting in an indirect cost reduction. The higher surface area of this design coupled with the decreased weight of the materials also results in increased heat dissipation from the terminals. Yet another advantage of the present invention is that it permits forming the battery case and other parts from any malleable material and specifically does not require laser sealing, special ceramic to metal seals, or special (and thereby expensive) methods of any kind.
• the battery terminals 7, 8 are typically formed from a copper or copper alloy material, preferably nickel plated for corrosion resistance. However, any electrically conductive material which is compatible with the battery chemistry may be used. It should be noted that the battery terminals 7, 8 described in context with the present invention are smaller in annular thickness and of a greater diameter than those of the prior art. As a result, the terminals of the present invention are very efficient dissipaters of heat, and thus contribute significantly to the thermal management of the battery.
• the terminals 7, 8 may also include an axially aligned central opening 15.
• the central opening 15 serves many purposes. One important consideration is that it serves to reduce the weight of the battery. It can also serve as an opening into which an external electrical connector may be friction fit. That is a cylindrical or annular battery lead connector may be friction fitted into the central opening 15 to provide an external electrical connection to the battery. Finally, it can serve as the location for a pressure release vent for venting excessive pressure from the interior of the battery.
• the opening 15 can extend partially through the terminal (if it is intended to serve only as a connector socket) or all the way through (if it is intended to contain a pressure vent and serve as a connector socket).
• the vent 16 includes: 1) a vent housing 17 having a hollow interior area 21 in gaseous communication with the surrounding atmosphere and the interior of the battery case via the openings 15, 18 and 23; 2) a pressure release piston 19 is positioned within the hollow interior area 21 , the pressure release piston 19 is sized to seal the axial opening 16 and has a seal groove 20 on its surface opposite the axial opening 16; 3) an elastomeric, dielectric seal (not shown) is mounted within the seal groove, the seal groove 20 is configured to encapsulate all but one surface of the seal, thereby leaving the non-encapsulated surface of the seal exposed; and 4) a compression spring 22 is positioned to urge the pressure release piston 19 to compress the seal in the seal groove 20 and block the axial opening 18 in the terminal 7, 8.
• the elastomeric, dielectric seal is formed of a hydrogen impermeable polysulfone material. Additionally it is preferable that the vent be designed to release internal pressure in excess of about 120 pounds per square inch to insure battery integrity, since the battery cans are generally rated for at most about 150 pounds per square inch.
• vents may be used in the batteries of the instant invention.
• rupture disks, pressure plugs and septum vents may be used.
• One such septum vent is described in U.S. Patent No. 5,171 ,647, the contents of which are hereby incorporated by reference.
• the pressure vent be located within a hollow battery terminal, the vent can just as effectively be located elsewhere on the battery top in its own protective housing or merely attached to an opening in the top of the battery case.
• Another alternative embodiment of the battery terminal is presented in
• FIG 6 which shows a terminal 7, 8 into which an external battery lead connector 24 can be friction fit.
• the connector 24 is attached to an external battery lead 25.
• Lead 25 may be any of the type typically known in the art such as a solid bar; a metal ribbon; a single or multi strand wire; or a braided, high current, battery cable (as is described hereinbelow).
• the lead connector 24 is a hollow annular barrel connector which is friction fit into the axially aligned central opening 15 of the battery terminal 7, 8.
• the lead connector 24 is held in the battery terminal 7, 8 via a barrel connector web 26.
• a solid barrel connector is described in U.S. Patent No. 4,657,335, dated April 14, 1987 and 4,734,063, dated March 29, 1988, each to Koch et al. and entitled
• FIG. 5 and 6 may be combined into a single embodiment which incorporates both the pressure vent 16 and the external battery lead connector 24.
• a rupture disk i.e. a non-resealable means of releasing excess pressure
• the pressure vent 16 can be included instead of or in addition to the pressure vent.
• the crimp seal terminals and case top are the preferred embodiment of the instant invention, other types of terminals and, therefore, other types of case tops may be used. Specifically, a screw on terminal incorporating an o-ring type of seal may be employed. Generally, any type of known sealed terminal may be used as long as it can contain the operating pressures of the battery and is resistant to the electrochemical environment of the battery. While any battery system may benefit from the present improvements in battery, module, and pack configuration, it is preferred that the positive electrodes are formed from a nickel hydroxide material and the negative electrodes are formed from a hydrogen absorbing alloy. Preferably, the negative electrode material is an Ovonic metal-hydride alloy.
• the electrodes are separated by non-woven, felted, nylon or polypropylene separators and the electrolyte is an alkaline electrolyte, for example, containing 20 to 45 weight percent potassium hydroxide.
• Such separators are described in U.S. Patent No. 5,330,861 , the contents of which are incorporated by reference.
• Ni-MH batteries for consumer applications on the market used pasted metal hydride electrodes in order to achieve sufficient gas recombination rates and to protect the base alloy from oxidation and corrosion.
• Such pasted electrodes typically involved mixing the active material powder with plastic binders and other nonconductive hydrophobic materials.
• An unintended consequence of this process is a significant reduction in the thermal conductivity of the electrode structure as compared to a structure of the present invention which consists essentially of a 100% conductive active material pressed onto a conductive substrate.
• a sealed prismatic Ni-MH battery according to the present invention the buildup of heat generated during overcharge is avoided by using a cell bundle of thermally conductive metal hydride electrode material.
• This thermally conductive metal hydride electrode material contains metal hydride particles in intimate contact with each other. Oxygen gas generated during overcharge recombines to form water and heat at the surface of these particles. In the present invention, this heat follows the thermally conductive negative electrode material to the current collector and then to the surface of the case. The thermal efficiency of the bundle of thermally conductive metal hydride electrode material is further improved if this electrode bundle is in thermal contact with a battery case that is also thermally conductive.
• the metal hydride negative electrode material is preferably a sintered electrode such as described in U.S. Patent Nos. 4,765,598; 4,820,481 ; 4,915,898, 5,507,761 ; and U.S. Patent Application Serial No. 08/259,793 (the contents of which are incorporated by reference) fabricated using sintering so that the Ni-MH particles are in intimate thermal contact with each other.
• the positive electrode used in the present invention are formed from nickel hydroxide materials.
• the positive electrodes may be sintered such as described in U.S. Patent No. 5,344,728 (incorporated by reference), as well as pasted into nickel foam or nickel fiber matte as described in U.S. Patent No. 5,348,822 and continuations thereof (incorporated by reference).
• One aspect of the present invention recognizes that in sealed Ni-MH batteries, heat generation is particularly high during overcharge, especially under commercially desirable fast charge applications. It is noteworthy that the heat generated during overcharge is due to oxygen recombination on the surface of the metal hydride electrode. Consequently, it is possible to utilize a thermally conductive metal hydride electrode in conjunction with a pasted positive electrode. This preferred embodiment is especially useful for optimizing specific energy, overall performance, and cost of the battery. For a more detailed description of the use of sintered electrodes see U.S. Patent
• each of the electrodes 4, 5 which form an electrode stack have electrical connector tabs 27 attached to them. These tabs 27 are used to transport the current created in the battery to the battery terminals 7, 8.
• the tabs 27 are electrically connected to the terminals 7, 8 which may include a protrusion 28 for just such an attachment. Alternatively this protrusion 28 can be used to electrically and physically connect the terminal 7, 8 to the an electrode tab collector comb 29.
• the comb 29 is typically an electrically conductive bar which includes a plurality of parallel electrode tab collecting slots 30 which hold the electrode tabs 27 by friction, welding, or brazing.
• Figure 7 also shows the battery terminal connector opening 31 in the tab collecting comb 29.
• the battery terminal welding/brazing lip 28 is press fit into the opening 31 , and may thereafter be brazed or welded into place if needed or desired.
• the comb 29 provides a vibration resistant connector for transferring electrical energy from the electrodes 4, 5 to the terminals 7, 8.
• the comb 29 provides greater vibration resistance compared to the prior art method of bolting the collected tabs 27 to the bottom protrusion 28 of the terminal 7, 8.
• the prior art method of connecting the tabs 27 to the terminal 7, 8 also requires longer tabs and a longer case (a case having a greater head space). This adds to the total weight and volume of the batteries.
• the absence of bolts significantly reduces the head space of the battery resulting in an increase in the volumetric energy density.
• the comb 29 and battery terminals 7, 8 are preferably formed from copper or a copper alloy, which is more preferably nickel coated for corrosion resistance. However, they may be formed from any electrically conductive material which is compatible with the chemistry of the battery. While the electrode tab collector comb is the preferred means of attaching the electrode tabs to the battery terminals, other prior art means such as bolts, screws, welding or brazing may be used as well, and therefore the instant inventions is not seen to be limited to the preferred embodiment.
• the positive and negative battery electrodes 4, 5 can be disposed in the battery case 2, such that their respective electrical collection tabs 27 are disposed opposite one another at the top of the case. That is, all of the negative electrode electrical collection tabs are positioned on one side of the battery and all of the positive electrode electrical collection tabs are positioned on the opposite side of the battery.
• the positive and negative battery electrodes have notched corners (not shown) where the opposite polarity electrode electrical collection tabs are located, thereby avoiding shorts between the electrodes and eliminating unused, dead-weight electrode material. Shorts can occur when the electrical collection tabs of one electrode become twisted or have sharp protrusions which then can pierce the electrode separator and short to the adjacent, opposite polarity electrode.
• the dead weight electrode material is caused by incorporation of active material into electrodes which are inactive because they are not adjacent to their counter electrode materials.
• the batteries can have any number of electrodes, depending upon their thickness, preferably the battery includes 19 positive electrodes and 20 negative electrodes altematingly disposed within said case. That is, the electrodes are alternated with negatives on the outside with alternating positive and negatives throughout the electrode stack. This configuration avoids possible shorts when the batteries are under external mechanical compression. That is, if there were a positive and a negative electrode at the outside of the electrode stack, there would be a possibility that the electrodes would form an electrical short path through the metal battery case when the battery is exposed to external mechanical compression.
• separators 6 While it is only necessary to have electrode separators 6 surrounding one set of the battery electrodes (i.e. separators around only the negative or only the positive electrodes) it may be advantageous to include separators 6 surrounding each set of electrodes. Data indicates that the use of double separators can reduce the self discharge level of the batteries. Specifically, charge retention increased from about 80% after two days for batteries with a single separator to about 93% after two days for batteries having double separators.
• the separators 6 are typical polypropylene separator materials well known in the prior art. They have an oriented grain or groove structure thought to be caused by the machine formation thereof and it is preferred that the grains or grooves of the polypropylene separator material are aligned lengthwise along the electrodes. This orientation lowers friction and prevents catching and sticking of the grains or grooves of one separator with those of an adjacent separator during mechanical compression and/or expansion of the electrodes because the sticking and catching can cause cracking of the electrodes.
• FIG. 8- 12 Another aspect of the present invention includes an improved, high- power battery module (a "battery module” or “module” as used herein is defined as two or more electrically interconnected cells), specifically shown in Figures 8- 12.
• a battery module or “module” as used herein is defined as two or more electrically interconnected cells
• the batteries in a module must be densely packed, portable, and mechanically stable in use. Additionally, the materials used in construction of the battery modules (aside from the batteries themselves) must not add excessive dead weight to the module or the energy densities of the modules will suffer. Also, since the batteries generate large amounts of heat during cycling, the materials of construction should be thermally conductive and small enough not to interfere with heat transfer away from the batteries or to act as a heat sink, trapping heat within the batteries and modules. In order to meet these and other requirements the instant inventors have designed the improved, high- power battery module of the instant invention.
• the battery module 32 of the instant invention includes: 1 ) a plurality of individual batteries 1 ; 2) a plurality of electrical interconnects 25 connecting the individual batteries 1 of the module 32 to one another and providing means for electrically interconnecting separate battery modules 32 to one another; and 3) a battery module bundling/compression means (described below).
• the batteries are bound together under external mechanical compression (the benefits of which are described below) within the module bundling/compression means such that they are secure and do not move around or dislodge when subjected to the mechanical vibrations of transport or use.
• the battery modules 32 are typically bundles of prismatic batteries of the instant invention. Preferably they are bundled such that they are all oriented in the same fashion with each battery having its electrical terminals located on top (see Figures 9 and 12).
• the batteries are oriented within the module such that their narrowest sides face the sides of the module and their wider sides (those which, on expansion of the batteries, will warp) are placed adjacent to other batteries in the module. This arrangement permits expansion in only one direction within the module, which is desirable.
• the batteries 1 are bound within the module bundling/compression means under external mechanical compression which is optimized to balance outward pressure due to expansion of the battery components and provide additional inward compression on the battery electrodes within each battery to reduce the distance between the positive and negative electrodes, thereby increasing overall battery power.
• the expansion of prismatic batteries preferably used in the instant modules has been tailored to be unidirectional, therefore, compression to offset the expansion is only required in this one direction (see arrow 33 for compression direction). If not offset, this expansion will cause bowing and warpage of the battery's external case and larger separation gaps between the electrodes than optimal, thereby reducing the power of the batteries. Also, it has been found that overcompensation for the expansion is useful to a point.
• Figure 17 shows the correlation of module compression to battery resistance.
• Modules having end plates (described below) were compressed using differing amounts of force and the internal battery resistance (related to total power output and charging efficiency) and battery thickness were measured.
• an optimal compression range for these modules between of between about 70 and 170 psi (about 1100-2600 pounds force over an area of about 100 cm 2 ) and a functional range of between about 50 to about 180 psi (about 800 to about 2800 over an area of about 100 cm 2 ).
• compression above than the upper limit and compression below the lower limit of the functional range causes an increase in internal resistance of the batteries and therefore reduced power.
• the optimal and functional compression ranges are different for different size batteries, the resistance versus compression plots for these different size batteries are all similar in that there are functional and optimal ranges of compression for proper cell performance.
• the battery modules can be bound together under high mechanical compression using metal bars 34 (preferably stainless steel) which are positioned along all four sides of the battery module 32 and are welded at the four corners of the module where the bars meet, thereby forming a band around the periphery of the battery module.
• metal bars 34 preferably stainless steel
• the welded metal bars 34 are centrally positioned between the top and bottom of the battery module, which is where the expansion is most severe. Compression of the batteries in areas not containing the electrode stack is not useful since it does not compress the electrodes. In fact, it can be detrimental, since it results in shorting of the electrodes to the metal can, through the interior insulator.
• the thickness and width dimensions at the top and bottom perimeter of the battery cases are between 0.5 and 1.0 mm smaller than the overall thickness and width dimensions. These reduced dimensions insure that all of the compressive force is translated to the electrode plate stack and separators only.
• the welded metal bars 34 include two or three sets of bars centrally positioned between the top and bottom of the battery module. If three sets of bars are used, a first set of bars should be disposed half way between the top and bottom of the battery module, a second set of bars is then positioned between the first set of bars and the top of the battery module, and the third set of bars is positioned between the first set of bars and the bottom of the battery module. This allows for uniform compression distribution and eases the stress on any one set of bars. This compression distribution also permits use of the smallest, lightest metal bars, thereby reducing module dead weight. Another preferred design uses metal end plates 35 at the ends of the module.
• the stainless steel bars are positioned along the sides of the battery module and are welded at the corners of the module to rectangular metal tubing (45 in Figure 9) which replaces the end bars and holds the end plates 35 in position.
• the end plates 35 are preferably formed from aluminum and may include ribs 36 protruding perpendicular to the plane of the end plates 35, thereby providing added strength to the plates 35 and allowing for lighter materials to be used. (One embodiment of the end plates is shown in Figures 13a and 13b. Other embodiments are described in U.S. Patent Application
• the end plates 35 may preferably be thermally isolated or insulated from the batteries bundled within the module 32 by a thermally insulating material such as a thermally insulating layer of polymer or polymer foam. This insulation prevents uneven battery temperature distribution within the module which may be caused by the cooling fin action of the ribs 36 of the end plates 35.
• the ribs 36 can provide added thermal dissipation for the batteries 1 within the module 32, if needed, by thermally sinking the end plates 35 to the adjacent batteries 1.
• Each of the modules 32 may additionally include module spacers 37 (see Figures 11 and 12) which hold the modules 32 at a distance from any other modules 32 and from a battery pack case. These module spacers 37 are placed on the top and bottom of the module 32 to provide protection to the corners of the batteries 1 within the module 32 and the electrical interconnects 25 and terminals 7, 8 of the batteries 1. More importantly, tabs 38 on the sides of the spacers 37 hold the modules 32 at the optimal distance apart.
• the spacers 37 are preferably formed from a light weight, electrically non-conductive material, such as a durable polymer. Also, it is important to the overall pack energy density that the spacers include as little total material as possible to perform their required function and still be as light as possible.
• the batteries and modules of the present invention are preferably electrically interconnected by conductive leads 25 (see Figures 8 and 9) which provide a low resistance pathway therebetween.
• the total resistance, including the lead resistance and the contact resistance should preferably not exceed 0.1 mohm.
• the leads are fastened to the terminals by a screw or bolt or preferably the socket barrel connector 24 discussed hereinabove.
• the electrical interconnects 25 of the battery module 32 of the instant invention are preferably braided cable interconnects (see Figure 14), which provide for high thermal dissipation and flexibility of module design/configuration. That is, the braided cable interconnects 25 serve two important functions within the battery modules of the present invention (besides their normal function of transporting the electrical energy out of the batteries).
• the braided cable 25 is flexible which accommodates expansion and contraction of the individual batteries 1 that results in a change of distance between the terminals 7, 8 of the individual batteries within the module 32.
• the braided cable interconnect 25 has a significantly higher surface area than a solid cable or bar. This is important to the thermal management of the batteries, modules and packs of the instant invention because the electrical interconnect is part of a thermal pathway which begins within the interior of the battery, passes up through the electrodes 4, 5, through the electrode tab 27, through the battery terminal 7, 8 and out to the electrical interconnect 25. Therefore, the higher the surface area of the electrical interconnect 25, the greater the thermal dissipation and the better the thermal management of the batteries 1.
• the braided cable electrical interconnects 25 are preferably formed from copper or a copper alloy which is preferably coated with nickel for corrosion resistance.
• FIG. 15 Yet another aspect of the present invention (shown in Figure 15) is the mechanical design of fluid-cooled battery pack systems (as used herein the terms “battery pack” or “pack” refer to two or more electrically interconnected battery modules).
• battery pack or "pack” refer to two or more electrically interconnected battery modules.
• Some of the negative characteristics which are encountered when the battery pack systems have no or improper thermal management include: 1) substantially lower capacity and power; 2) substantially increased self discharge; 3) imbalanced temperatures between batteries and modules leading to battery abuse; and 4) lowered cycle life of the batteries. Therefore, it is clear that to be optimally useful the battery pack systems need proper thermal management.
• Nickel-metal hydride batteries show charge efficiency performance degradation at extreme high temperatures over 43°C due to problems resulting from oxygen evolution at the nickel positive electrode. To avoid these inefficiencies the battery temperature during charge should ideally be held below 43°C. Nickel-metal hydride batteries also show power performance degradation at temperatures below about -1°C due to degraded performance in the negative electrode. To avoid low power, the battery temperature should be held above about -1°C during discharge.
• Figure 18 shows the relationship between battery specific energy measured in Wh/Kg and the battery temperature for nickel-metal hydride batteries of the instant invention. As can be seen, the specific energy of the battery starts to fall off beyond about 20°C or so and drops drastically beyond about 40°C.
• Figure 19 shows the relationship between battery specific power measured in W/Kg and the battery temperature for nickel-metal hydride batteries of the instant invention. As can be seen, the specific power of the battery risis with temperature but levels off above about 40°C.
• the instant fluid-cooled battery pack system 39 includes: 1 ) a battery-pack case 40 having at least one coolant inlet 41 and at least one coolant outlet 42; 2) at least one battery module 32 disposed and positioned within the case 40 such that the battery module 32 is spaced from the case walls and from any other battery modules 32 within the case 40 to form coolant flow channels 43 along at least one surface of the bundled batteries, the width of the coolant flow channels 43 is optimally sized to allow for maximum heat transfer, through convective, conductive and radiative heat transfer mechanisms, from the batteries to the coolant; and 3) at least one coolant transport means 44 which causes the coolant to enter the coolant inlet means 41 of the case 40, to flow through the coolant flow channels 43 and to exit through the coolant outlet means 42 of the case 40.
• the battery pack system 39 includes a plurality of battery modules 32, typically from 2 to 100 modules, arranged in a 2 or 3 dimensional matrix configuration within the case.
• the matrix configuration allows for high packing density while still allowing coolant to flow across at least one surface of each of the battery modules 32.
• the battery-pack case 40 is preferably formed from an electrically insulating material. More preferably the case 40 is formed from a light weight, durable, electrically insulating polymer material. The material should be electrically insulating so that the batteries and modules do not short if the case touches them. Also, the material should be light weight to increase overall pack energy density. Finally, the material should be durable and capable of withstanding the rigors of the battery pack's ultimate use.
• the battery pack case 40 includes one or more coolant inlets 41 and outlets 42, which may be specialized fluid ports, where required, but are preferably merely holes in the battery pack case 40 through which cooling-air enters and exits the battery pack.
• the fluid cooled battery-pack system 39 is designed to use electrically- insulating coolant, which may be either gaseous or liquid.
• the coolant is gaseous and more preferably the coolant is air.
• the coolant transport means 44 is preferably a forced-air blower, and more preferably a blower which provides an air flow rate of between 1-3 SCFM of air per cell in the pack.
• the blowers do not need to continuously force cooling air into the battery pack, but may be controlled so as to maintain the battery pack temperatures within the optimal levels.
• Fan control to turn the fan on and off and preferably to control the speed of the fan is needed to provide for efficient cooling during charging, driving, and idle stands.
• cooling is most critical during charge, but is also needed during aggressive driving.
• Fan speed is controlled on the basis of the temperature differential between the battery pack and ambient, as well as on the basis of absolute temperature, the latter so as not to cool the battery when already it is already cold or so as to provide extra cooling when the battery nears the top of its ideal temperature range.
• fans are also needed in idle periods after charge.
• FIG. 16 shows a fan on time of 2.4 hours after the initial post charge cooldown.
• Fan control allows for the use of powerful fans for efficient cooling when needed without the consumption of full fan power at all times, thus keeping energy efficiency high.
• the use of more powerful fans is beneficial in terms of maintaining optimal pack temperature which aids in optimization of pack performance and life.
• One example of a fan control procedure provides that, if the maximum battery temperature is over 30°C and the ambient temperature is lower (preferably 5°C or more lower) than the maximum battery temperature then the fans will turn on and circulate cooler air into the coolant channels.
• Another useful fan control algorithm operates the fans at variable rates depending upon certain criterion. These criterion include 1 ) maximum battery temperature; 2) ambient temperature; 3) present battery usage (i.e. charging, charge waiting, high temperature, high depth-of-discharge (dod) while driving, standing, etc.); 4) voltage of any auxiliary battery which powers the coolant fans. This algorithm is shown in Table 2.
• Tbatmax is the maximum module temperature
• Tamb is the ambient air temperature
• PWM is the fan percentage pulse width modulation (PWM) control signal
• Vauxbat is the Auxiliary fan battery voltage
• Minspeed is the minimum fan speed
• the flow rate and pressure of the cooling fluid needs to be sufficient to provide sufficient heat capacity and heat transfer to cool the pack.
• the flow rate of the fluid needs to be sufficient to provide for steady state removal of heat at the maximum anticipated sustained heat generation rate to result in an acceptable temperature rise.
• a flow rate of 1-3 CFM of air per cell is needed to provide adequate cooling simply on the basis of the heat capacity of air and achieving an acceptable temperature rise.
• Radial blower type fans may be used to provide the most effective airflow for thermal management. This is due to the higher air pressure generated by these fan types as contrasted with that generated by axial fans.
• a pressure drop of at least 0.5" of water is required at the operating point of the fan as installed in the pack. To produce this pressure drop at high flow rates generally requires a fan static pressure capability of 1.5" to 3" of water.
• the fans can heat the battery pack when it is too cold. That is, if the battery pack is below its minimum optimal temperature, and the ambient air is warmer than the battery pack, the fans may be turned on to draw warmer ambient air into the battery pack. The warmer air then transfers its thermal energy to the battery pack and warms it to at least the low end of the optimal range of temperature.
• One or more coolant transport means 44 can be positioned at the coolant inlet 41 to force fresh coolant into the battery pack case 40, through coolant flow channels 43, and out of the coolant outlet 42.
• one or more coolant transport means 44 can be positioned at the coolant outlet 42 to draw heated coolant out of the battery pack case 40, causing fresh coolant to be drawn into the battery pack case 40 via the coolant inlet 41 , and to flow through the coolant flow channels 43.
• the coolant may flow parallel to the longest dimension of the coolant flow channels 43 (i.e. in the direction of the length of the battery modules) or, alternatively, it may flow perpendicular to the longest dimension of said coolant flow channels 43, (i.e. in the direction of the height of the battery module). It should be noted that since the coolant withdraws the waste heat from the batteries as it flows through the cooling channels 43, the coolant heats up. Therefore, it is preferable that the fluid flow perpendicular to the longest dimension of the cooling channels 43. This is because as the coolant heats up, the temperature difference between the batteries and the coolant decreases and therefore, the cooling rate also decreases. Thus the total heat dissipation is lowered. To minimize this effect, the coolant flow path should be the shorter of the two, i.e. along the height of the batteries.
• coolant transport means 44 may preferably be a pump.
• the coolant transport means may preferably include a coolant return line attached to the coolant outlet 42 which recycles heated coolant to a coolant reservoir (not shown) from which it is transferred to a coolant heat exchanger (not shown) to extract heat therefrom and finally redelivered to the coolant pump 44 for reuse in the cooling of the battery pack 39.
• the optimized coolant flow channel width incorporates many different factors. Some of these factors include the number of batteries, their energy density and capacity, their charge and discharge rates, the direction, velocity and volumetric flow rate of the coolant, the heat capacity of the coolant and others. It has been found that independent of most of these factors, it is important to design the cooling channels 43 to impede or retard the cooling fluid flow volume as it passes between the modules.
• the retardation in flow is predominantly due to friction with the cell cooling surfaces, which results in a flow reduction of 5 to 30% in flow volume.
• the gaps between modules form the major flow restriction in the cooling fluid handling system, this produces a uniform and roughly equal cooling fluid flow volume in the gaps between all modules, resulting in even cooling, and reducing the influence of other flow restrictions (such as inlets or exits) which could otherwise produce nonuniform flow between the modules.
• the same area of each cell is exposed to cooling fluid with similar velocity and temperature.
• Battery modules are arranged for efficient cooling of battery cells by maximizing the cooling fluid velocity in order to achieve a high heat transfer coefficient between the cell surface and the cooling fluid.
• the optimal coolant flow channel width depends on the length of the flow path in the direction of flow as well as on the area of the coolant flow channel in the plane perpendicular to the flow of the coolant. There is a weaker dependence of optimal gap on the fan characteristics.
• the width of the coolant flow channels 43 is between about 0.3-12 mm, preferably between 1-9 mm, and most preferably between 3-8 mm.
• the optimal achievable mean module spacing is about 3-4 mm (105 mm centeriine spacing).
• the optimal achievable mean module spacing is about 7-8 mm (109 mm centeriine spacing). Slightly closer intermodule spacing at the far end of this row will result in a higher airflow rate and consequently a higher heat transfer coefficient, thus compensating for the higher air temperature downstream.
• a secondary inlet or series of inlets partway along the horizontal coolant flow path can also be used as a means of introducing additional coolant, thus making the heat transfer between the battery cells and the coolant more uniform along the entire flow path.
• centeriine spacing is sometimes used synonymously with coolant flow channel width.
• the reason for this is that the quoted coolant flow channel widths are average numbers.
• the reason for this averaging is that the sides of the battery modules which form the flow channels 43 are not uniformly flat and even, the banding which binds the modules together and the sides of the batteries themselves cause the actual channel width to vary along its length. Therefore, it is sometimes easier to describe the width in terms for the spacing between the centers of the individual modules, i.e. the centeriine width, which changes for batteries of different sizes. Therefore, it is generically more useful to discuss an average channel width, which applies to battery modules regardless of the actual battery size used therein.
• Figures 20 and 21 plots the relationship between the coolant flow channel width (i.e. centeriine spacing) verses the coolant volumetric flow rate, percentage of maximum coolant velocity and percentage of maximum heat transfer for vertical and horizontal coolant flow, respectively.
• the graphs are for air as the coolant and assumes turbulent flow and a 30% free air restriction.
• optimal spacings which differ dependant upon the direction of coolant flow. It is most efficient to operate within a range of ⁇ 10% of optimal heat transfer, however if needed, the system can be operated outside of this range by increasing the volumetric flow rate of the coolant.
• the curves denoted by the squares(") represent the volumetric flow rate of the coolant(air) and are read from the left hand ordinate
• the curves denoted by the triangles (*) and the diamonds ( ⁇ ) represent the percentage of maximum heat transfer and percentage of maximum coolant flow velocity, respectively, and are read from the right hand ordinate.
• each module includes coolant-flow-channel spacers 37 which hold the modules 32 at the optimal distance from any other modules 32 and from the battery pack case 40 to form the coolant flow channels 43.
• the coolant- flow-channel spacers 37 are preferably positioned at the top and bottom of the battery modules 32, providing protection to the corners of the modules 32, the battery terminals 7, 8 and the electrical interconnects 25. More importantly, tabs on the sides of the spacers 38 hold the modules at the optimal distance apart.
• the spacers 37 are preferably formed from a light weight, electrically non-conductive material, such as a durable polymer.
• Ni-MH batteries operate best in a specific temperature range. While the cooling system described above enables the battery pack systems of the instant invention to maintain operating temperatures lower than the high temperature limit of the optimal range (and sometimes to operate above the lower temperature limit of the optimal range, if the ambient air temperature is both warmer than the battery and warmer than the lower temperature limit of the optimal range), there are still times when the battery system will be colder than the lower limit of optimal temperature range. Therefore, there is a need to somehow provide variable thermal insulation to some or all or of the batteries and modules in the battery pack system.
• Temperature dependent charge regimens allow for efficient charging under a variety of ambient temperature conditions.
• One method involves charging the batteries to a continuously updated temperature dependent voltage lid which is held until the current drops to a specified value after which a specified charge input is applied at constant current.
• Another method involves a series of decreasing constant current or constant power steps to a temperature compensated voltage limit followed by a specified charge input applied at a constant current or power.
• Another method involves a series of decreasing constant current or constant power steps terminated by a maximum measured rate of temperature rise followed by a specified charge input applied at a constant current or power.
• temperature dependant voltage lids ensures even capacity over a wide range of temperatures and ensures that charge completion occurs with minimal temperature rise. For example, use of fixed voltage charge lids results in an 8°C temperature rise in one case where use of temperature compensated charging resulted in a 3°C temperature rise under similar conditions. Absolute charge temperature limits (60°C) are required for this battery to avoid severe overheating which can occur in the case of simultaneous failure of charger and cooling system. Detection of rate of change of voltage with respect to time (dV/dt) on a pack or module basis allows a negative value of dV/dt to serve as a charge terminator. This can prevent excessive overcharge and improves battery operating efficiency as well as serving as an additional safety limit.
• Figures 22 and 23 illustrate how "temperature compensated voltage lid” charging regimens can reduce temperature rise during charging of the battery pack systems These figures plot the temperature rise of a battery pack arid the pack voltage versus time during charge and discharge of the pack In
• Figure 22 (temperature compensated voltage lid), the upper curve represents pack voltage and the lower curve represents pack temperature above ambient
• Figure 22 indicates that at the end of the charge cycle, indicated by the peak of the voltage curve, the battery pack only experienced a 3°C temperature rise above ambient
• Figure 23 indicates an 8°C temperature rise from ambient when employing a "fixed voltage lid” charging method
• the dashed curve represents pack voltage and the solid curve represents pack temperature Therefore, it can be seen that much of the conventional charge generated heat has been eliminated by the use of a "temperature compensated voltage lid” charging regimen.
• the thermal insulation need will also be variable.
• variable thermal insulation means can be used on individual batteries, battery modules and battery pack systems alike.
• the means provides variable thermal insulation to at least that portion of the rechargeable battery system which is most directly exposed to said ambient thermal condition, so as to maintain the temperature of the rechargeable battery system within the desired operating range thereof under variable ambient conditions.
• the inventors have combined temperature sensor means, compressible thermal insulation means and a means to compress the compressible thermal insulation means in response to the temperature detected by the thermal sensor.
• the temperature sensor indicates that the ambient is cold, the thermal insulation is positioned in the needed areas to insulated the affected areas of the battery, module or battery pack system.
• the temperature sensor causes the thermal insulation to be partly or wholly compressed such that the insulation factor provided to the battery system by the compressible insulation is partially or totally eliminated.
• the thermal sensors may be electronic sensors which feed information to piston devices which variably increases or decreases the compression upon a compressible foam or fiber insulation.
• the sensor and compression devices may be combined in a single mechanical devices which causes variable compression upon the thermal insulation in direct reaction to the ambient thermal condition.
• a combined sensor/compression device and be formed from a bimetallic material such as the strips used in thermostats. Under low ambient temperatures, the bimetal device will allow the thermal insulation to expand into place to protect the battery system from the cold ambient conditions, but when the temperature of the battery or ambient rises, the bimetal device compresses the insulation to remove its insulating effect from the battery system.
• variable thermal insulation can be used to completely surround the entire battery, module or battery pack system, it is not always necessary to do so.
• the variable thermal insulation can be just as effective when it only insulates the problems spots of the system.
• the battery modules and pack systems of the instant invention which employ ribbed end plates, it may only be necessary to thermally insulate the ends of the modules which are most directly influenced by low temperature ambient conditions.

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• 1997
  • 1997-01-13 KR KR10-2004-7003613A patent/KR100449983B1/ko not_active IP Right Cessation
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  • 1997-01-13 WO PCT/US1997/000805 patent/WO1998031059A1/en active IP Right Grant
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