Abstract:
A system ( 40 ) for an automotive vehicle has a temperature sensor ( 90 ) generating a temperature signal indicative of the temperature outside the vehicle and a battery. A battery controller ( 54 ) is coupled to the temperature sensor ( 90 ) and the battery ( 64 ). The controller monitors a state of charge of the battery ( 64 ), monitors a temperature outside of the vehicle and compares the state of charge to a predetermined state of charge. The predetermined state of charge is a function of the temperature. The controller ( 54 ) generates an indicator when the state of charge reaches the predetermined state of charge.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to hybrid electric automotive vehicles, and more specifically, to monitoring the state of charge of the batteries of the hybrid electric vehicle. 
     Automotive vehicles with internal combustion engines are typically provided with both a starter motor and alternator. In recent years, a combined alternator and starter motor has been proposed. Such systems have a rotor mounted directly to the crankshaft of the engine and a stator sandwiched between the engine block and the bell housing of the transmission. During initial startup of the vehicle, the starter/generator functions as a starter. While functioning as a starter, the starter/generator rotates the crankshaft of the engine while the cylinders are fired. 
     After the engine is started, the starter/generator is used as a generator to charge the electrical system of the vehicle. 
     In foreseeable automotive applications, the engine may be shut down during stops (e.g., red lights). When the accelerator is depressed, the starter/generator starts the motor and the engine will resume firing. Thus, many startups may occur over the course of a trip. 
     Electrical energy from the 42 volt battery of the vehicle is used to turn the starter/generator which in turn is used to start the motor. Consequently, it is important to maintain the battery so that a certain state of charge is provided to allow the battery to provide enough power to the starter/generator to start the engine. Known systems include ammeters to show the charging of the battery but do not provide an indication as to the capacity of the battery to energize a starting component such as the starter/generator. Also, other factors such as the outside temperature of the vehicle are also not considered in such determinations. 
     It would therefore be desirable to provide a battery charge monitor to provide an indication to the vehicle operator that the battery may not have sufficient charge or capacity to power the starter/generator to start the engine. 
     SUMMARY OF INVENTION 
     The present invention provides a way in which to notify vehicle operators as to the state of the battery. The notification is preferably provided early enough to allow changes to be made so that the vehicle will have enough power to start. 
     In one aspect of the invention, a method of indicating for a battery of an automotive vehicle comprising monitoring a state of charge of the battery, monitoring a temperature outside of the vehicle, comparing the state of charge to a predetermined state of charge, the predetermined state of charge being a function of the temperature, and generating an indicator when the state of charge reached the predetermined state of charge. 
     In a further aspect of the invention, a system for an automotive vehicle has a temperature sensor generating a temperature signal indicative of the temperature outside the vehicle and a battery. A battery controller is coupled to the temperature sensor and the battery. The controller monitors a state of charge of the battery and compares the state of charge to a predetermined state of charge. The predetermined state of charge is a function of the temperature. The controller generates an indicator when the state of charge reaches the predetermined state of charge. 
     One advantage is that the indicator may be provided to the operator in time so that an evasive action may be performed to prevent the state of charge or the battery health to degrade to a point where the battery cannot provide enough power to start the vehicle. 
     Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic view of an automotive vehicle having a starter/generator system according to the present invention. 
     FIG. 2 is a more detailed schematic view of the engine accessory assembly of FIG.  1 . 
     FIG. 3 is a flowchart illustrating the operation of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention is described with respect to a particular configuration of a starter/generator relative to a hybrid electric vehicle. However, the teachings of the present invention may be applied to various type of vehicles have battery powered electrical systems. 
     Referring now to FIG. 1, an automotive vehicle  10  is illustrated having an internal combustion engine  12  having cylinders  14  with pistons  16  located therein. Each cylinder  14  is coupled to a fuel pump  18  through a fuel injector (not shown) or other fuel delivery system. Each cylinder  14  also has a spark plug  20  or other ignition source coupled to a powertrain control unit. A powertrain control unit  22  controls the ignition timing and fuel pump operation  18  in a conventional manner subject to the improvements of the present invention. 
     Engine  12  is coupled to a transmission  26 . Transmission  26  may be automatic, manual or continuously variable. Transmission  26  is coupled to a differential  28  to drive an axle  30  to provide power to wheels  32 . Of course, the present invention is also applicable to four wheel drive systems in which all of the wheels  32  are driven. A starter/generator system  40  that includes a starter/generator  42  and its associated control electronics is coupled to engine  12 . In the present invention, starter/generator  42  is positioned between a housing  44  of transmission  26  and the engine  12 . Of course, those skilled in the art will recognize other positions are available including but not limited to belt driven types. Starter/generator  42  has a stator fixedly attached to bell housing  44  and a rotor  48  coupled to a crankshaft  50  of engine  12 . A clutch  52  is used to engage and disengage engine  12  from transmission  26 . As will be further described below, starter/generator  42  is used as a starter during engine startup and as an alternator to supply power to recharge the batteries of the vehicle and to supply electrical loads. Clutch  52  allows starter/generator  42  to start the engine prior to engagement of the transmission. 
     Starter/generator system  40  has a system controller  54  that is coupled to powertrain control unit  22  and to a power inverter  56 . In practice, the power inverter  56  and system controller  54  may be contained in a single package. The inverter  56  is used to convert DC power to AC power in the motoring mode and AC power to DC power in power generation mode as will be further described below. 
     Power inverter  56  is coupled to an energy storage device  58  such as an ultra capacitor, a first DC to DC converter  60 , and a second DC to DC converter  62 . DC to DC converter  60  is coupled to a 42 volt battery  64 . DC to DC converter  62  is coupled to a 12 volt battery  66 . Of course, the actual battery voltage is dependent on the particular system to which it is attached. 
     Referring now to FIG. 2, a more detailed block diagrammatic view of the system  40  is illustrated in further detail. Both a 42 volt battery  64  and a 12 volt battery  66  from FIG. 1 are included. Also, the DC power source may be the starter/alternator  42  illustrated in FIG.  1 . The starter/alternator  42  is coupled to the 42 volt bus  70  through a regulator  72 . Of course, other loads  74 A,  74 B, and  74 C are also coupled to bus  70 . 
     Battery controller  54  is coupled to 42 volt battery  64  through a voltage monitor  76  and a current monitor  78 . By monitoring the battery voltage and current through voltage monitor  76  and current monitor  78 , the state of charge of the 42 volt battery  64  may be determined. 
     Battery controller  54  is also coupled to an indicator  80 . Indicator  80  may comprise an audible indicator, a visual indicator, or a combination of the two. Indicator  80  may also be located remotely from the vehicle and may comprise a cell phone, page or e-mail device. For these devices a vehicle communications telematic system  82  is coupled to battery controller  54 . Vehicle communication telematic system  82  may couple information to a cell tower  84  or a satellite  86 . The telematic system  82  may also be coupled to the vehicle global positioning system  88 . 
     Battery controller  54  may also be coupled to a temperature sensor  90  for determining the outside temperature at the exterior of the vehicle. By knowing the exterior temperature the state of charge may be predicted to insure the starting capacity of the vehicle. Also, vehicle communication telematic system  82  may also be used to obtain a prediction of the weather through a satellite  86  from a forecasting service such as the National Weather Forecasting Service  92 . Such information may be automatically received based on the position indicated by global positioning system  88 . 
     Battery controller  54  may also be coupled to ignition system  94 , which counts the battery cycles of the system. 
     By monitoring the state of charge of battery  64  and state of health prediction, the battery controller  54  may indicate to the vehicle operator long before problems arise that the battery may in the near future not be capable of starting the vehicle. As will be further described below, evasive measures may be performed such as disabling one or all of the loads  74 A- 74 C from the bus  70 . 
     Referring now to FIG. 3, the state of charge is monitored in step  100 . The state of charge may be monitored by monitoring the current and voltage of battery  64  using voltage monitor  76  and current monitor  78 . Outside temperature is monitored by temperature sensor  90  in step  102 . In step  104 , the state of health of the battery is also monitored. The state of health of the battery may be provided by monitoring the number of cycles through ignition system  94 , the discharge of battery  64  during each of the cycles, and the state of charge voltage measured in step  100 . In step  106 , the weather forecast is monitored using vehicle telematic system  82 , satellite  86 , and the forecasting service  92 . In step  108 , the measured state of charge from step  100  is compared to a predetermined state of charge. If the measured state of charge is less than the predetermined state of charge, step  110  is executed in which loads may be disabled based upon a state of charge or the state of health. In step  108 , if the state of charge is not less than the predetermined state of charge, step  112  is executed. In step  112 , if the state of health is not less than the predetermined state of health, step  100  is again executed. In step  112 , if the state of health is less than a predetermined state of health, step  110  is executed. Based on the measured state of charge and the measured state of health, loads may be disabled accordingly to provide an evasive action to maintain the power in the battery at a predetermined level so that the battery may provide enough power to the starter/alternator so that the starter/alternator may start the engine. In step  114 , the operator of the vehicle is warned of the low state of health or the low state of charge or both. The vehicle operator may be warned visually or audibly through indicator  80  or if the vehicle is sifting in the vehicle operator&#39;s remote, a page through satellite  86  or through a cell tower  84  may be provided to operator device  96 . 
     The predetermined state of charge in step  108  and the predetermined state of health  112  may be adjusted based upon the outside temperature monitored and a forecasted temperature as determined in step  106 . By providing an indicator to the operator in step  114 , evasive measures such as replacement of the battery or battery components or proper servicing may be performed to allow the vehicle to start. 
     While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.