Abstract:
The method for thermal management of a battery can include vehicle systems to control the thermal input to the battery and a dedicated battery thermal management system. The battery thermal management system includes transferring battery heat to coolant flowing in a circuit, if ambient air temperature is greater than the battery temperature, using an evaporator/chiller to transfer heat from the coolant to a refrigerant, using a condenser to transfer heat from the refrigerant to the coolant, and using a radiator to transfer heat from the coolant to ambient air; and if coolant can be maintained in the reference temperature range without using a heat source or refrigerant, using a radiator to transfer heat from the coolant to the ambient air.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to a dedicated temperature management system for an electric storage battery particularly one for of an electric vehicle. 
     A hybrid electric vehicle combines a conventional usually fossil fuel-powered engine with some form of electric propulsion. The battery electric vehicle (BEV) is a type of electric vehicle that uses chemical energy stored in rechargeable battery packs. As with other electric vehicles, BEVs use electric motors and motor controllers, instead of internal combustions engines, for propulsion. 
     Battery electric cars are becoming more attractive due to higher oil prices and the advancement of new battery technologies that provide higher power, energy density, improved acceleration and greater range with fewer cells. 
     Batteries are among the most expensive component of BEVs. Rechargeable batteries used in electric vehicles include lead-acid, NiCd, nickel metal hydride, lithium ion, and Li-ion polymer. Optimum performance of advanced high energy density batteries requires that the battery temperature be maintained in an optimal range, whether the vehicle is operating, charging or standing idle, and regardless of the thermal loads caused by ambient conditions such as air temperature. 
     An analysis of vehicle battery thermal loads indicates that the battery thermal management system capacity requirements is strongly influenced by the ambient soak conditions the vehicle must accommodate rather than the actual battery charge and discharge operational losses. 
     Battery insulation for cold and hot conditions, cabin solar shading and cabin solar powered ventilation reduce substantially the active heating load and cooling load. A dedicated battery active/passive thermal system can be used to control the ambient thermal loads of the battery. I Isolation of the battery pack by thermal insulation, and reduce the in-cabin soak temperatures during high solar, high temperature conditions can reduce the thermal loads on the battery thermal system and significantly reduce the system size, cost and reduce the energy require to thermally mange the battery. 
     A system that controls temperature of advanced high energy batteries would use the cabin air conditioning system for active cooling, a separate coolant circuit for passive cooling, and an electric heater for battery heating. 
     SUMMARY OF INVENTION 
     A method for controlling the temperature of a vehicle battery includes transferring battery heat to coolant flowing in a circuit, if ambient air temperature is greater than the battery temperature, using an evaporator/chiller to transfer heat from the coolant to a refrigerant, using a condenser to transfer heat from the refrigerant to the coolant, and using a radiator to transfer heat from the coolant to ambient air; and if coolant can be maintained in the reference temperature range without using a heat source or refrigerant, using a radiator to transfer heat from the coolant to the ambient air. 
     The invention contemplates a system that includes a circuit in which battery heat is transferred to coolant in the circuit, a pump for circulating coolant in the circuit, an evaporator/chiller for transferring coolant heat to a refrigerant, a condenser for transferring heat from the refrigerant to the coolant, and a radiator for transferring heat from the coolant to ambient air. 
     The thermal system, dedicated to controlling temperature of an electric storage battery, accommodates specific battery chemistry and its duty cycle, and is adaptable to liquid, air and refrigerant heat transfer media. 
     The system allows optimization of vehicle thermal and climate systems without having to compromise performance and efficiency due to the different and sometimes conflicting thermal demands of a battery. 
     The refrigeration portion is designed and fabricated in one-piece with no fittings or a minimum number of fittings, thereby eliminating most causes of system downtime, such as refrigerant leaks and providing the reliability and durability required for life-of-the vehicle battery life and full performance, with a minimum consumption of energy and little or no maintenance. 
     The system is intended to be located within a battery pack for simplification and efficiency but can be located elsewhere to accommodate other packaging requirements. Its location within the battery pack reduces plumbing and control interfaces. 
     The system has outstanding efficiency since all of the active components can be designed and operated within their optimum design points. 
     The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is schematic diagram of a battery temperature control system, for which the coolant is a liquid; 
         FIG. 2  is illustrates the battery packs of a battery temperature control system, for which the coolant is chilled air; and 
         FIG. 3  is a schematic diagram showing details of the battery temperature control system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, the battery temperature system  8 , illustrated in Figure,  1  includes multiple battery packs  10 , each containing battery cells, temperature sensors  12  connected to a battery controller  14 , coolant reservoirs  16 , a battery thermal system  18 , a 12 volt supply bus  20 , and a 10 to 20 mm thickness of insulation  22 , preferably Cryogel insulation, enclosing the battery packs  10 . The battery thermal system  18  communicates through line  23  with a microprocessor-based controller  24 , which controls activation and deactivation of various components. Controller  24  produces control signals as determined by repetitive execution of a control algorithm stored in electronic memory accessible to the controller. 
     A battery thermal radiator  26  is supplied with hot coolant exiting the packs  10  through hydraulic passage  28  and returns low temperature coolant through hydraulic passage  30  to the battery packs  10  after transferring heat from the coolant to ambient air. Electric current supplied to motors  32 ,  33  is controlled by controller  24  and carried through electric lines  36 ,  37 , respectively, to drive fans  34 ,  35 . Fans  34 ,  35  facilitate heat transfer to the air by forcing ambient air at high speed through the battery radiator  26 , air conditioning system condenser  38 , TPIM radiator and transmission oil cooler  40 , and engine coolant radiator  42 , which are preferably arranged in series. 
     A sensor  44 , connected by line  46  to controller  24 , produces an electronic signal representing temperature of the ambient air upstream from the fans  34 ,  35 . 
     A sensor  48 , connected by line  50  to controller  24 , produces a signal representing temperature of the ambient in the vehicle&#39;s cabin, i.e., passenger compartment. 
     A solar sensor  52 , connected by line  54  to controller  24 , produces an electronic signal representing solar energy  56 , and line  54  supplies electric power to an actuator  58 , which opens and closes a windshield shade  60  under control of controller  24 . 
     Similarly, line  62  supplies electric power to an actuator  64 , which opens and closes a shade  66  that covers the backlight  68  at the rear of the cabin under control of controller  24 . 
     A solar panel  70 , comprising an array of photovoltaic cells, produces electric current, which is carried on line  72  to controller  24 . Line  74  carries electric current from battery packs  10  through controller  24  to a cabin blower air exhauster  76 , such as a fan, which forces air through a duct  78  from the vehicle cabin to the ambient atmosphere. 
     Controller  24  receives information regarding the vehicle&#39;s location and the season of the year on a line  80 , which carries an appropriate signal through a receiver  81  or similar device from a wireless communication system, such On Star, through which the vehicle occupants communicate external to the vehicle. 
     In operation, coolant, in the form of a 50/50 mixture of deionized water and ethylene glycol, flows from passage  30  through reservoirs  16  and through passages  82 ,  83  along the battery packs  10 . Heat from the battery packs  10  is transferred to coolant in passages  82 ,  83 . Return passages  84 ,  85  carry hot coolant from the battery packs  10  to radiator  26  through passage  28 . 
       FIG. 2  illustrates the battery packs  10  of the battery temperature control system  8 , for which the coolant is chilled air, which flows from the heat exchanger  140  through ducts  86 ,  87 ,  88  and along the battery packs  10 . Heat from the battery packs  10  is transferred to the coolant in ducts. Heated air is carried through line  28  to radiator  26 , where a heat exchange occurs with ambient air. The battery packs  10  of  FIG. 2  are connected to controller  24  as illustrated in  FIG. 1 . The sensors  44 ,  48 ,  52 , actuator  58 ,  64 , solar panel  70  and other equipment system  8  are interconnected as described with reference to  FIG. 1 . 
     The battery thermal system  18 , shown in greater detail in  FIG. 3 , includes an electronically actuated three-way control valve  90 , expansion bellows  92  for maintaining constant coolant pressure in lines  82 - 85 , heater  94 , coolant temperature sensor  96 , and coolant pump  98 . A coolant passage  100  connects an output of control valve  90  to coolant pump  98   
     A self-contained subassembly  102 , which can be installed at any appropriate location in the vehicle, includes two, three-way control valves  104 ,  106 , coolant pump  108 , air separator extractor  110 , refrigerant condenser  138 , refrigerant evaporator/chiller  114 , refrigerant compressor  116 , coolant passages connecting these components to battery thermal system  18  and battery radiator  26 , and refrigerant passages. 
     Each of the three-way controls valves  90 ,  104 ,  106  operates in exclusive-OR logic, i.e., its input is connected to one of its outputs but not to both outputs, in response to a control signal sent to the valve from controller  24 . 
     The battery temperature system  8  operates in a first mode when the temperature of ambient air is substantially less than the temperature of the battery packs  10 , such as when the ambient air is cold. During first mode operation, control valves  104 ,  106  are closed, and valve  90  has an open connection between passages  84 ,  85  and passage  100 . Coolant pump  98  pumps coolant through passages  82 - 85 . Valve  90  connects return passages  84 ,  85  to passage  100 . Heater  94  increases the temperature of the coolant circulating through the battery packs  10  to a reference temperature. The on and off states of heater  94  are changed by controller  24  in response to temperature of coolant circulating through the battery packs  10 , monitored by sensor  96  and reported to the controller. 
     The battery temperature system  8  operates in a second mode when the temperature of ambient air is less than the temperature of the battery packs  10 , such as when the ambient air has a moderate temperate. During second mode operation, control valve  90  has an open connection between coolant return passages  84 ,  85  and passage  120 , control valve  104  has an open connection between passage  120  and passage  122 , and control valve  106  has an open connection between passage  30  and passages  124 ,  139 . Coolant pump  98  pumps coolant through passages  82 - 85 . Valve  90  connects return passages  84 ,  85  to the air separator extractor  110  through passage  120 , control valve  104  and passage  122 . Coolant exits air extractor through passage  28 , flows through the battery radiator  26  wherein it transfers heat to the ambient air, and returns to passage  100  of battery temperature system  8  through control valve  106  and passage  124 . Heater  94  increases the temperature of the coolant circulating through the battery packs  10  to a reference temperature. The on and off states of heater  94  are changed by controller  24  in response to temperature of coolant circulating through the battery packs  10 , monitored by sensor  96  and reported to the controller. 
     The battery temperature system  8  operates in a third mode when the temperature of ambient air is substantially greater than the temperature of the battery packs  10 , such as when the ambient air is hot. During third mode operation, control valve  90  has an open connection between coolant return passages  84 ,  85  and passage  120 , control valve  104  has an open connection between passage  120  and passage  126 , and control valve  106  has an open connection between return passage  30  and coolant pump  108 . Coolant pump  98  pumps coolant through passages  82 - 85 . Valve  90  connects return passages  84 ,  85  to control valve  104 , which directs coolant to evaporator/chiller  114  through passage  126 . In evaporator/chiller  114 , heat is exchanged from the coolant to refrigerant circulating in a refrigerant system. Coolant exits evaporator/chiller  114  and returns to passage  100  of battery temperature system  8  through passages  128 ,  139 . 
     The refrigerant is preferably 134A or 1234YF, such as is used for vehicle cabin air conditioning. Refrigerant exiting evaporator/chiller  114  as a low temperature vapor is compressed to a high temperature and high pressure vapor in compressor  116 . Heat from the refrigerant is exchanged to air in the tubes of condenser  38  and exists as a low temperature, high pressure liquid. Refrigerant in that state expands through expansion valve  130  and returns through refrigerant line  132  to the plates of evaporator/chiller  114 . 
     The system  8  maintains battery pack temperatures within specified limits for specified periods of time for the life of the vehicle. The system is not dependent on vehicle climate and thermal systems that would be forced to operate below maximum efficiency. 
     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.