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1. memory devices input output I O devices and other known components and may perform various con trol and or communication related functions For example control unit 64 could receive sensor signals from the various battery sensors 62 package the sensor signals into an appro priate sensor message and send the sensor message to battery charging control module 18 over a connection 54 such as a CAN bus a system management bus SMBus a proprietary communication link or any other communication means known to those skilled in the art It is possible for control unit 64 to gather battery sensor readings and store them in local memory so that a comprehensive sensor message can be US 8 054 039 B2 5 provided to battery charger control module 18 at a later time or the sensor readings can be forwarded to module 18 or some other destination as soon as they arrive at control unit 64 to cite a few possibilities In another capacity control unit 64 can store pertinent battery characteristics and background information pertaining to the battery s cell chemistry cell capacity upper and lower battery voltage limits battery cur rent limits battery temperature limits temperature profiles battery impedance number or history of charge discharge events etc Battery charging control module 18 monitors one or more conditions pertaining to external power supply 12 battery charger 14 and or battery unit 16 and uses the sensed con ditions2. Temperature Constraint and Generate Seventh Charging Control Signal 56 References Cited U S PATENT DOCUMENTS 6 424 122 B2 7 2002 Yagietal oo 320 132 7 560 902 B2 7 2009 Unger 320 141 2009 0103341 Al 4 2009 Leeetal ww 363 124 OTHER PUBLICATIONS Xantrex PROsine 2 0 Inverter Charger User s Manual 146 pages www xantrex com cited by examiner Primary Examiner Kenneth J Whittington 74 Attorney Agent or Firm Lionel D Anderson Reising Ethington P C 57 ABSTRACT A battery charging system and method for charging a plug in electric vehicle with power from an external power source such as a standard 110 volt or 220 volt AC wall outlet The method senses various internal and external conditions and uses this information to charge the plug in electric vehicle in an optimum fashion that reduces charging time yet avoids damage to components of the charging system In one embodiment the battery charging system includes an exter nal power source a battery charger with sensors for monitor ing the external power source and the charger a battery unit with sensors for monitoring the battery a battery charging control module for processing the information and a user interface that allows user specified custom charging con straints All of these components with the exception of exter nal power source may be located on the vehicle 18 Claims 2 Drawing Sheets Evaluate Minimum Volt
3. charging e g 14 16 hours quick charg ing 3 6 hours fast charging 1 hour or less timer controlled charging intelligent charging switcher charger types eng switch mode regulator linear charger types e g series regu lator shunt buck and inductive charger types etc In addi tion battery charger 14 may be designed for specific cell chemistries or for universal cell applicability and it may be self programmable or user programmable to name a few possibilities Itis to be understood that the foregoing description is not a definition of the invention but is a description of one or more preferred exemplary embodiments of the invention The invention is not limited to the particular embodiment s dis closed herein but rather is defined solely by the claims below Furthermore the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims except where a term or phrase is expressly defined above Various other embodi ments and various changes and modifications to the disclosed embodiment s will become apparent to those skilled in the art All such other embodiments changes and modifications are intended to come within the scope of the appended claims As used in this specification and claims the terms for example for instance such as and like and the
4. charging control signal It is possible for step 160 or any of the other steps for that matter to use a calibration or gain function as opposed to a single gain value that relates battery charger efficiency to battery charger temperature Step 170 evaluates a battery temperature constraint and generates a corresponding seventh charging control signal The temperature of battery unit 16 whether it be the tempera ture of the overall battery pack 60 a region or portion of the battery pack the temperature of an individual cell etc can affect the ability or efficiency of the battery unit to accept a charge In one embodiment step 170 compares a sensed battery temperature with one or more predetermined battery temperature limits or setpoints there could be lower and or upper temperature limits An error value is obtained and multiplied by a compensation or gain value as explained above The product of this calculation can be used to generate the seventh charging control signal In the event that both lower and upper temperature constraints are considered step 170 may generate two separate charging control signals one for the upper limit and one for the lower limit Depending on the particular application each of these charging control sig nals may request a reduction in battery charger output power as the battery temperature approaches either the upper or the lower limit Step 180 evaluates battery charge constraints and generates a c
5. sequentially or according to any other suitable monitoring arrangement as the present method is not limited to the exemplary sequence described here Step 110 evaluates a droop voltage constraint and gener ates a corresponding first charging control signal The droop voltage in battery charging system 10 generally represents the voltage difference of external power source 12 between an unloaded state i e when little or no current is being drawn by system 10 and a loaded state According to an exemplary embodiment step 110 measures the charger input voltage when no current is flowing through power coupling 30 the unloaded voltage and measures the charger input voltage when some current is flowing therethrough the loaded volt age at which time both the charger input voltage and the charger input current are measured Skilled artisans will appreciate that the unloaded charger input voltage and the 20 25 30 35 40 45 50 55 60 65 8 external power source voltage are generally the same because there are no power losses in power coupling 30 The droop voltage may then be calculated as the difference between the unloaded and loaded voltage readings Once the droop volt age is determined step 110 may use this constraint with proportional integral derivative PID or other closed loop techniques to determine a first charging control signal Such a process is illustrated in the following example however other n
6. the sensor signals into an appropriate sensor message and send the sensor message to battery charging control module 18 over a connection 52 such as a CAN bus a system management bus SMBus a proprietary communication link or any other communication means known to those skilled in the art In another capacity control unit 44 may receive charging control signals or other instructions from battery charging control module 18 or some other device interpret the instructions and execute the instructions by correspondingly controlling devices within battery charger 14 For instance if battery charging control module 18 sends a charging control signal to battery charger 14 then control unit 44 can use the charging control signal to manipulate the pulse width modulated PWM duty cycle of switching power supply 36 This in turn causes switching power supply 36 to alter the amount of current and ultimately the amount of power that is provided by battery charger 14 to battery unit 16 These are of course only some of the possible arrangements and functions of control unit 44 as others are certainly possible 0 20 25 40 45 50 65 4 Battery unit 16 provides the plug in electric vehicle with electrical power and depending on the particular embodi ment may be the primary vehicle power source or may be used in conjunction with another power source for power supplementation purposes to cite two examples Many dif f
7. there is shown an exemplary method 100 for charging a plug in electric vehicle such as a PHEV where the method may use various readings conditions informa tion comparisons calculations etc to charge the vehicle in an optimum fashion An optimum charging process which may involve charging battery unit 16 in the shortest time possible can be affected by external conditions e g the power available from external power source 12 or internal conditions e g the power generation capabilities of battery charger 14 the power acceptance capabilities of battery unit 16 etc Thus exemplary method 100 can monitor these and other factors in a closed loop fashion in order to quickly charge battery unit 16 avoid damaging parts of battery charg ing system 10 and avoid overloading the circuit to which external power source 12 is connected As conditions pertain ing to the external power source the battery charger and or the battery unit change so too can the charging control signal which is periodically adjusted according to one or more closed loop techniques to optimally charge the plug in elec tric vehicle Periodically does not necessarily require that the charging control signal be modified according to a specific time interval but rather includes the broad concept of con US 8 054 039 B2 7 tinuously monitoring and making changes to the charging control signal in response to sensed conditions Beginning with step 102 t
8. to control the charging process in an optimum manner Depending on the particular embodiment battery charging control module 18 may be a stand alone vehicle electronic module it may incorporated or included within another vehicle electronic module such as a power train control mod ule or it may be part of a larger network or system such as a battery management system BMS a vehicle energy man agement system etc to name a few possibilities Battery charging control module 18 may also be or part of or interact with a system that determines a desired operating mode e g accelerating braking idling stopping etc and may imple ment electrical power management actions accordingly Bat tery charging control module 18 may perform a number of functions pertaining to the battery charging system 10 these could include for example cell protection charge control demand management SOC and SOH determination cell bal ancing history logging communications etc Battery charging control module 18 may include any vari ety of electronic processing devices memory devices input output I O devices and other known components and may perform various control and or communication related func tions The battery charging control module can be electroni cally connected to other vehicle devices and modules via a suitable vehicle communications network and can interact with them when required In an exemplary embodiment bat tery charg
9. vehicle battery as quickly as possible yet do so in a manner that avoids damage to the components of the charging system such components can include for example the power cou pling that a user selects to connect the vehicle to an external power source Although the following description is provided in the context of a particular battery charging system it should be appreciated that this system is merely exemplary and that other systems could also be used For example the battery charging system and method described below can be used with any type of electric vehicle including a plug in hybrid electric vehicle PHEV or a battery electrical vehicle BEV or any other vehicle where a vehicle battery is charged with an external power source According to this particular embodiment battery charging system 10 includes an external power source 12 a battery charger 14 a battery unit 16 a battery charging control module 18 and a user interface 20 All ofthese components with the exception of external power source 12 may be fixedly mounted and located on the vehicle External power source 12 provides battery charging system 10 with electrical power over a power coupling 30 and may be one of a number of different power supply types known in the art For example external power source 12 can be a standard AC power outlet that provides 110 v or 220 v of electricity at 60 Hz or it can be a portable generator such as the type that runs on natural
10. verbs comprising having including and their other verb forms when used in conjunction with a listing of one or more components or other items are each to be construed as open ended meaning that that the listing is not to be considered as US 8 054 039 B2 13 excluding other additional components or items Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation The invention claimed is 1 A method for charging a plug in electric vehicle com prising the steps of a sensing at least one condition pertaining to an external power source a battery charger located on the plug in electric vehicle or a battery unit located on the plug in electric vehicle wherein the sensed condition is at least partially based on an unloaded voltage of the external power source which is measured when the external power source is in an unloaded state and there is little or no current being drawn from the external power source by the battery charger located on the plug in electric vehicle b determining a charging control signal based on the sensed condition that is at least partially based on an unloaded voltage of the external power source and c charging the battery unit with the battery charger wherein the battery charger is operated according to the charging control signal and the charging control signal is periodically adjust
11. 36 a filter network 38 cooling unit 40 one or more sensors 42 a control unit 44 and any other suitable components known in the art US 8 054 039 B2 3 Depending on the particular arrangement transformer 32 steps up and or steps down the input voltage from external power source 12 to a different and in some cases program mable output voltage Rectifier 34 rectifies the AC signal into a DC signal and includes a half wave full wave or other type ofknown rectifying arrangement Switching power supply 36 takes the rectified signal and according to one embodiment rapidly switches a power transistor or other switch between saturation on and cutoff off according to a variable duty cycle whose average corresponds to the desired output voltage In this way switching power supply 36 is able to control the amount of current and hence power that is pro vided by battery charger 14 to battery unit 16 Filter network 38 which is optional may include any combination of elec trical components that can be used to filter process or con dition the output signal before providing it to battery unit 16 Cooling unit 40 also an optional component may use any combination of fans water jackets heat sinks or any other suitable cooling means to reduce the temperature of battery charger 14 during charging Although not shown here battery charger 14 could have multiple power outputs including a high voltage output connected to batt
12. Bulbseyo DILL agoe pue WUIEISUO sso JAMO ayenjeag jeuBbls josjuoD Bulbseyg puoses ouo uey SI p u 9 pue zujesuop Lemgieuee pue pujesuog mesq auno ajenjeng efeuon dooig ayenjeag jeubis yun Aieyeg au Jo pue JaBiey Aiayeg ay eounog Jamog jewayxg zol au 9 Bululeu d sJuoipuon asues US 8 054 039 B2 1 SYSTEM AND METHOD FOR CHARGING A PLUG IN ELECTRIC VEHICLE TECHNICAL FIELD The present invention generally relates to charging batter ies and more particularly to a system and method that moni tors and or controls charging conditions so that a vehicle battery is charged in an optimum fashion BACKGROUND A plug in electrical vehicle may require electricity in between vehicle operation in order to charge a rechargeable battery pack In most applications a battery charger receives power from a power source such as a 110 v AC outlet and then rectifies and or transforms the power to a form and level that is suitable for charging the battery pack that resides on the vehicle The charging conditions within the system such as the temperature of the battery charger the amount of charge on the battery etc can affect the charging process SUMMARY OF THE INVENTION According to one embodiment there is provided a method for charging a plug in electric vehicle The method generally comprises the steps of a sensing at least one condition pertaining to an external power source a bat
13. a2 United States Patent Bauerle et al US008054039B2 US 8 054 039 B2 Nov 8 2011 a0 Patent No 45 Date of Patent 54 15 73 21 22 65 51 52 58 SYSTEM AND METHOD FOR CHARGING A PLUG IN ELECTRIC VEHICLE Inventors Paul A Bauerle Fenton MI US Vernon L Newhouse Farmington MI US Jeffrey T Wolak Brighton MI US Assignee GM Global Technology Operations LLC Detroit MI US Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 445 days Appl No 12 340 079 Filed Dec 19 2008 Prior Publication Data US 2010 0156355 A1 Jun 24 2010 Int CI HO02J 7 14 2006 01 HO02J 7 04 2006 01 HSC ease ENER 320 109 320 162 Field of Classification Search 320 109 320 145 132 152 157 158 159 162 163 320 164 903 903 907 180 65 1 65 21 180 65 29 See application file for complete search history 102 Evaluate Droop Voltage Evaluate Current Draw Constraint and Generate Constraint and Generate First Charging Control Second Charging Signal Control Signal 110 Evaluate Charger Temperature Consiraint and Generate Sixth Charging Control Signal Sense Condition s Pertaining to the External Power Source the Battery Charger and or the Battery Unit Evaluate Power Loss Constraint and Generate Third Charging Control Signal Evaluate Battery
14. age Constraint and Generate Fifth Charging Contral Signal Evaluate Power Draw Constraint and Generate Fourth Charging Control Signal Evaluate Battery Charge Constraint s and Generate Eighth Charging Control Signal Consider the Charging Control Signals Sent by Steps Control Signal 110 180 and Select the Most Restrictive One 200 Operate the Battery Charger with an Overall Charging 202 US 8 054 039 B2 Sheet 1 of 2 Nov 8 2011 U S Patent aansig tL s A ddns samog BulyoHMS JeBieyo Aiayeg 8E MIOMJON Jet eippDoul 07u09 Buibieyy Aueyeg SOU Jas mun ouod Lpg siosuas Aleyeg zg o yoed Arsyeg 09 94 yun Ausyeg US 8 054 039 B2 Sheet 2 of 2 Nov 8 2011 U S Patent Jeubis joijuog jeubis josyjuoD Buibieyo Burbieug UL eyesauagy yno ayeJauas pue juledjsuod abeo pue julejysuod wnwuy ayenjeag meig Jamod ayenjeag Z aANS1 zoz leuis jouog Buibreyo Ilea Ue YIM JeBieyD Aieyeg ey aesodo BUC SAIOUISEY JSOW 24 929S PUL 08L 0LL ooz sdas Aq juss sjeuBbis jouop Dubiguc au Japisuay 084 jeubls josju0y Buibreyo u46 a esaued pue s jureujsuoy eyg A yeg genjen JeuBbls joujuoy Buey o yjUeAes ayelauesy pue juleyjsuoD aunyesaduud Aiayeg ayenjeag jeuBls josu0D Busey yxs aiglauar pue uiensuop amyesadwaL JaBiey anpe EI 4 Ott OLL IEUDIG joujuoy
15. aving an input coupled to the battery charger and one or sensor s for monitoring battery conditions and US 8 054 039 B2 15 a battery charging control module being located on the plug in electric vehicle and being coupled to both the battery charger and the battery unit wherein the battery charging control module receives readings from the bat tery charger sensor s and the battery sensor s and uses those readings to control the output power that the bat tery charger provides the battery unit and one of the readings that is used in the control of the output power is 16 an unloaded voltage reading for the external power source which is representative of the external power source when it is in an unloaded state and there is little or no current being drawn from the external power source by the battery charger
16. charging process 7 The method of claim 6 wherein the user specified set point pertains to the maximum amount of current that can be drawn from the external power source 8 The method of claim 6 wherein the user specified set point pertains to the maximum amount of power that can be drawn from the external power source 9 The method of claim 5 wherein step b i allows a negative error value in order to address overshoot by the method 10 The method of claim 5 wherein step b uses propor tional integral derivative PID control to obtain the charging control signal 11 The method of claim 1 wherein step c further com prises operating the battery charger according to the charging control signal and the charging control signal uses pulse width modulation PWM to vary the amount of current that is provided by the battery charger to the battery unit 20 25 30 35 40 45 55 60 65 14 12 The method of claim 1 further comprising the step of evaluating one or more fault conditions and if a fault con dition is detected then stopping the charging process 13 The method of claim 1 further comprising the step of generating a diagnostic trouble code DTC that provides information regarding the sensed condition 14 The method of claim 1 further comprising the steps of putting the external power source in an unloaded state where there is little or no current being drawn from the external power
17. ed in response to changes in the sensed condition 2 The method of claim 1 wherein step a further com prises sensing at least one condition that pertains to the exter nal power source and is selected from the group consisting of droop voltage in the external power source current draw from the external power source power loss in a power coupling power draw from the external power source or minimum voltage of the external power source 3 The method of claim 1 wherein step a further com prises sensing at least one condition that pertains to the bat tery charger and is selected from the group consisting of charger temperature charger voltage or charger current 4 The method of claim 1 wherein step a further com prises sensing at least one condition that pertains to the bat tery unit and is selected from the group consisting of battery temperature battery voltage battery current battery state of charge SOC or battery state of health SOH 5 The method of claim 1 wherein step b further com prises determining the charging control signal by using closed loop control to 1 compare the sensed condition to a setpoint to obtain an error value ii multiply the error value by a gain value to obtain a product and iii use the product to obtain the charging control signal 6 The method of claim 5 wherein step b i allows a user specified setpoint in order to enable the user to control one or more constraints on the
18. erent battery types and arrangements may be used including the exemplary one schematically shown here which includes a battery pack 60 one or more battery sensors 62 and a control unit 64 Battery pack 60 may include a collection of identical or individual battery cells connected in series par allel or a combination of both in order to deliver a desired voltage amperage capacity power density and or other per formance characteristics Generally it is desirable to provide high power and energy densities which has led to the devel opment and use of many types of batteries including chemi cal non chemical and others Some examples of chemical batteries that could be used include lead acid advanced lead acid nickel metal hydride NiMH nickel cadmium NiCd lithium ion zinc bromide lithium polymer sodium nickel chloride NaNiCl zinc air vanadium redox and others Other chemical battery types include aluminum air iron air lithium iron sulfide nickel iron nickel zinc silver zinc sodium sulfur zinc chlorine zinc manganese and more According to one embodiment battery unit 16 includes a large number of lithium ion cells each of which exhibits between 2 v 4 v when charged and is connected in a series and or parallel configuration with its adjacent cells Skilled artisans will appreciate that the system and method described herein are not limited to any one particular type of battery or battery arrangement as a number of d
19. ery unit 16 connection 50 and a lower voltage output not shown connected to a 12 v battery for example Battery charger sensors 42 may include any combination of hardware and or software components capable of monitoring battery charger conditions such as charger temperature charger input voltage typically an AC signal charger output voltage typically a DC signal charger current etc Depend ing on the particular embodiment these sensors may be inte grated within battery charger 14 they may be external sensors located outside of the battery charger or they may be pro vided according to some other known arrangement The charger temperature sensor may sense the temperature of one or more components within battery charger 14 including the temperature of the least efficient component that is the com ponent of the battery charger that exhibits the most heat Battery charger sensors 42 may be coupled directly to control unit 44 or they could be coupled to an any number of other devices components modules etc including some located outside of battery charger 14 like battery charging control module 18 Control unit 44 may include any variety of electronic pro cessing devices memory devices input output I O devices and other known components and may perform various con trol and or communication related functions For example control unit 44 could receive sensor signals from the various battery charger sensors 42 package
20. esses for each of these constraints have been omitted It should be appreciated that the preceding closed loop control discussion may pertain to one or more of the following steps as well Step 120 evaluates a current draw constraint and generates a corresponding second charging control signal The current draw constraint relates to the maximum amount of current that battery charging system 10 is allowed to draw from external power source 12 and it can be a predetermined limit or it can be user specified There are a number of reasons why US 8 054 039 B2 9 method 100 may want to monitor and limit the current draw by battery charging system 10 one of which is to avoid tripping a circuit breaker of external power source 12 Con sider the example where a maximum current draw limit of 15 amps setpoint is allowed and the battery charger input current is measured at 10 amps According to one embodi ment step 120 calculates an error of 5 amps multiplies the 5 amp error by a calibration or gain value and uses the product to derive a second charging control signal The larger the error in current draw i e the further away the actual current draw is from its upper limit the more aggressively the second charging control signal may attempt to increase the output power of battery charger 14 Step 130 evaluates a power loss constraint and generates a corresponding third charging control signal The power loss constraint relates to the maxi
21. exter nal power source a battery charger and or a battery unit wherein at least one of the plurality of conditions is a droop voltage that generally represents the difference between an unloaded voltage of the external power source and a loaded voltage of the external power source wherein the unloaded voltage is measured when the external power source is in an unloaded state and there is little or no current being drawn from the external power source by the battery charger and the loaded voltage is measured when the external power source is in a loaded state and there is some current being drawn from the external power source by the battery charger b evaluating each of the sensed conditions with a particu lar battery charging constraint c reviewing each of the evaluations and identifying the most restrictive constraint wherein the most restrictive constraint is the one that requests the least amount of current from the battery charger and d operating the battery charger so that it does not violate the most restrictive constraint 18 A system for charging a plug in electric vehicle com prising a battery charger being located on the plug in electric vehicle and having an input coupled to an external power source an output coupled to a battery unit and one or more sensor s for monitoring external power source conditions and or battery charger conditions a battery unit being located on the plug in electric vehicle and h
22. f power that is allowed to be drawn from external power source 12 and may be calculated as the unloaded charger input voltage mul tiplied by the charger input current As with the current draw limit the power draw limit or setpoint may be specified and changed by a user via user interface 20 Consider the example where a power draw of 1 100 watts is measured 110 volts 10 amps a default maximum power draw of 1 650 watts is allowed and the user provides a user specified maximum power draw limit of 1 500 watts According to one embodi ment step 140 first selects the more restrictive of the two maximum power draw limits in this case the user specified 1 500 watts compares the measured amount of 1 100 watts to the 1 500 watt limit to obtain an error of 400 watts and multiplies the error by a calibration or gain value in order to derive or otherwise determine the fourth charging control signal Step 150 evaluates a minimum voltage constraint and gen erates a corresponding fifth charging control signal It is pos sible for external power source 12 to experience voltage fluc tuations including so called brownout situations where the supply voltage drops below an ordinary and normal level Consider the example where an unloaded voltage level of 110 volts is sensed and a minimum voltage level of 106 v is stored as a default setpoint The calculated error is 4 volts and can be multiplied by a calibration or gain value to determine the fifth c
23. f the charger but also the unloaded voltage at external power source 12 and the charger input current is representative of both the current entering battery charger 14 and the line current provided by the external power source Next the method compares or evaluates each of the sensed conditions with a specific predetermined limit and uses the output of this comparison to generate a corresponding charg ing control signal that is representative of that particular con straint The various charging control signals are evaluated together and the most restrictive constraint is used to gener ate the actual charging control signal that is sent from charg ing control module 18 to battery charger 14 and controls the charging process This way battery charger 14 can be pushed to charge battery unit 16 as quickly or aggressively as pos sible but is still limited by the most restrictive of the various charging conditions According to an exemplary embodi ment each of the charging control signals generated in steps 110 180 controls the amount of current provided by battery charger 14 to battery unit 16 so that step 200 can make an apples to apples comparison and select the most restrictive one e g the one with the lowest duty cycle Thus the charg ing control signal selected in step 200 is generally represen tative of the most restrictive of the various conditions and constraints that were evaluated Steps 110 180 may be per formed concurrently
24. gas propane gasoline diesel or the like In one embodiment external power source 12 is a renewable power source such as a remote charging station powered by energy from solar panels wind turbines hydro electric means biomass etc External power source 12 may be connected to battery charger 14 in one of a variety of different ways including via conductive connections induc tive connections as well as other connections known in the art In an exemplary embodiment power coupling 30 is a specialized vehicle power coupling such as those described in specifications SAE J 1772 and J 1773 and includes a first end for plugging into a standard AC wall outlet and a second end for plugging into the vehicle This enables a user to easily plug and unplug the vehicle from a common AC wall outlet such as those found in most garages Skilled artisans will appreciate that the system and method described herein are not limited to any particular external power source as a number of different power source types could be used Battery charger 14 is connected to both external power source 12 and battery unit 16 and uses the power from the external power source to charge the battery unit according to charging control signals from battery charging control mod ule 18 According to an exemplary embodiment battery charger 14 is a programmable charger that is mounted in the vehicle and includes a transformer 32 a rectifier 34 a switch ing power supply
25. harging control signal If the unloaded voltage approaches 20 25 30 35 40 45 50 55 60 65 10 the minimum voltage level of 106 volts then the fifth charg ing control signal can be modified to request less output power from battery charger 14 If the unloaded voltage actu ally falls beneath the minimum voltage level of 106 volts then the fifth charging control signal may request that battery charger 14 supply no power to battery unit 16 until this low voltage or brownout condition abates Step 160 evaluates a battery charger temperature constraint and generates a corresponding sixth charging control signal The amount of power that can be delivered by battery charger 14 to battery unit 16 may be affected or limited by the tem perature of the charger For example if the internal tempera ture of battery charger 14 exceeds an upper threshold various components of the battery charger can be damaged or destroyed hence the use of cooling unit 40 Moreover the actual charging efficiency or the ability of the battery charger to generate a constant high voltage signal and control the amount of output power sent to the battery unit may be some what temperature dependent In an exemplary embodiment step 160 compares the charger temperature readings from sensors 42 to a predetermined limit or setpoint to obtain an error value and multiplies the error value by a calibration or gain value in order to determine the sixth
26. he method senses one or more conditions pertaining to external power source 12 battery charger 14 battery unit 16 and or any other external or inter nal conditions pertaining to the charging process In an exem plary embodiment battery charger sensors 42 sense charger temperature charger input voltage charger output voltage and or charger current and battery unit sensors 62 sense battery temperature battery voltage battery current battery SOC and or battery SOH Of course other combinations of sensor readings and conditions could also be gathered Each sensor reading could be representative of a single sampled reading of a number of readings averaged or filtered over time or of readings processed according to some other signal processing or filtering technique known in the art Once the sensor readings are obtained they can be provided to battery charging control module 18 for further processing It is pos sible for these sensor readings to be provided to battery charg ing control module 18 in response to a query or request from the module or they can be provided on a periodic basis without being requested for example It should be appreci ated that some of the battery charger conditions may actually pertain to certain aspects of external power source 12 even though they are sensed and provided by battery charger sen sors 42 For instance the charger input voltage is representa tive of not only the voltage seen at the input o
27. ifferent battery types could be employed Battery sensors 62 may include any combination of hard ware and or software components capable of monitoring bat tery conditions such as battery temperature battery voltage battery current battery state of charge SOC battery state of health SOH etc These sensors may be integrated within battery unit 16 e g an intelligent or smart battery they may be external sensors located outside of the battery unit or they may be provided according to some other known arrange ment The battery temperature sensors may monitor and determine the battery temperature on a cell by cell basis as the average or collective temperature of a block of cells or region of the battery unit as the average or collective tem perature of the entire battery unit or according to some other temperature determining method known in the art Measuring battery temperature on an individual cell basis may be ben eficial if for example the middle cells exhibit different tem peratures than the edge or boundary cells of battery pack 60 The same principal of determining battery temperature on a cell by cell collective or other basis also applies to battery voltage battery current battery SOC battery SOH etc Out put from battery sensors 62 may be provided to control unit 64 battery charging control module 18 or some other appro priate device Control unit 64 may include any variety of electronic pro cessing devices
28. ing control module 18 includes an electronic pro cessing device that executes instructions for software firm ware programs algorithms scripts etc that are stored in memory devices of module 18 and govern the battery charg ing processes and methods described herein Battery charging control module 18 could also store or maintain look up tables e g performance response curves representing cell dis charge charge performance as a function of temperature etc various sensor readings e g sensor readings pertaining to battery charger conditions battery conditions etc and predetermined values used by one or more algorithms e g predetermined condition values condition calibration values etc for example These are of course only some of the possible functions and capabilities of battery charging control module 18 as other embodiments could also be used User interface 20 is an optional component that according to the embodiment shown here conveys battery charging information to a user receives charging limitations and user specified conditions from a user and facilitates any other communication between battery charging system 10 and a user For example user interface 20 may display the current charge status of battery unit 16 to the driver in a numerical graphical or other type of electronic presentation In another example user interface 20 also permits a user to enter user specified condition calibration values or
29. mum amount of power loss that is allowed in power coupling 30 This evaluation may be helpful in cases where a power outlet is corroded a power coupling is deteriorated or in cases where a user selects an inappropriate electrical connection such as a thin wire exten sion cord for example Generally speaking the power loss in power coupling 30 can be estimated by multiplying the droop voltage by the battery charger input current Consider the example above where the droop voltage is 2 5 volts the battery charger input current or line current is 10 amps and the maximum amount of allowed power loss or setpoint is 40 watts The calculated power loss is 25 watts however not all of the droop voltage and hence power loss may be attributable to losses in power coupling 30 as explained above For pur poses of conservatively estimating the power loss in power coupling 30 step 130 may assume that all of the calculated power loss is due to losses in the power coupling The calcu lated power loss of 25 watts can be subtracted from the setpoint of 40 watts to obtain an error value of 15 watts which in turn can be multiplied by a gain factor to produce the third charging control signal Once the third charging control sig nal is determined it can be provided to step 200 as mentioned above Step 140 evaluates a power draw constraint and generates a corresponding fourth charging control signal The power draw constraint relates to the maximum amount o
30. mum charging curves or other functions as opposed to being a single gain value e g a gain that is determined according to a complex relationship that relates droop voltage to battery charger output current using gains that are selected from a finite number of states e g if the droop voltage is less than a certain amount then the charging control signal requests a first amount of battery charger cur rent and if the droop voltage is greater than a certain amount then the charging control signal requests a second amount of battery charger current and allowing for negative error val ues to address instances of over shoot e g if the sensed droop voltage is 4 5 volts this produces an error value of 4 0 v 4 5 v 0 5 v to cite a few examples Once the first charg ing control signal is determined in step 110 it is provided to a state machine neural network or any other logical process ing device for subsequent processing in step 200 as will be explained It should be appreciated that the closed loop system described above is only one possible technique and method that could be used to evaluate a droop voltage constraint and to generate a corresponding first charging control signal as other embodiments including both closed loop and non closed loop could also be used Because similar processes and techniques can also be used to evaluate the various con straints in steps 120 180 duplicate discussions of closed loop control proc
31. of the constraints and charging control signals discussed above could utilize user specified limitations or setpoints For example a user may establish or adjust the maximum current draw allowed in step 120 or the maximum power draw allowed in step 140 Ifa user knows that a particular AC outlet in the garage is part of a widely used circuit then they may want to lower the current draw limit from 15 amps to 10 amps to avoid tripping the corresponding circuit breaker The user could provide this information via user interface 20 Con versely if an AC outlet in the garage has been specifically wired on its own dedicated 20 amp circuit then the user could increase the maximum allowed power draw to 2 200 watts for example Such an increase could result in a quicker charge assuming that it does not run afoul of any of the other constraints discussed herein Once the various constraints have been evaluated and cor responding charging control signals have been generated step 200 considers the signals and produces an overall charg ing control signal to send to battery charger 14 for controlling the charging process According to an exemplary embodi ment step 200 examines the various signals sent in steps 110 180 selects the charging control signal that represents the most restrictive constraint e g the signal with the small est duty cycle or the signal that otherwise requests the least amount of output power by the battery charger and send
32. on PID techniques could be used as well Assume that step 110 calculates a droop voltage of 2 5 volts and a predetermined droop voltage or setpoint of up to 4 0 volts is allowed by the system this predetermined limit could be stored in the memory of battery charging control module 18 for example The 2 5 volts is a calculated estimate because some portion of the measured droop voltage could be caused by factors other than battery charging system 10 such as other devices drawing current from the circuit when the unloaded voltage is determined etc An error is determined by subtracting the calculated droop voltage from the setpoint in this case 4 0 v 2 5 v 1 5 v The 1 5 v error is then multi plied by a droop voltage calibration value or gain in order to obtain a product that can be used to generate the first charging control signal which is representative of the constraints on the droop voltage Persons skilled in the art will know of a number of different ways and techniques that could be used with the preceding steps including the following using abso lute setpoints e g 4 0 volts using percentage setpoints e g a voltage drop of 10 using user specified setpoints that can be modified using empirically tested gains that have predictable outcomes on the condition being evaluated e g for each amp of additional battery charger current the droop voltage is expected to increase by 0 5 volts using gains that are derived from opti
33. ondition or during the normal charging process For example if step 130 detects a high power loss that is likely attributable to a bad power coupling then a corresponding DTC could be generated that provides information on the problem It is also possible for method 100 to periodically sample the unloaded voltage of external power source 12 and to update any calculations such as droop volt age with the new readings For example method 100 could stop the charging process every so often say every 10 min utes and wait for 100 ms or so to take a new unloaded voltage reading It is also possible for one or more of the steps in method 100 to employ a hysteresis factor when determining their requested charging control signals If battery charger 14 is also used to supply other power sources such as low volt age batteries etc then method 100 could take that additional power draw into account when determining the optimum power output of battery charger 14 It should be appreciated that a variety of different battery charger types schemes and charging techniques could be used with method 100 and or system 10 including constant voltage charging semi constant voltage charging constant current charging semi constant current charging constant current constant voltage charging taper current charging pulsed charging burp charging i e reflex or negative pulse charging IUI charging trickle charging float charging ran dom charging slow
34. orresponding eighth charging control signal The battery charge constraints considered and evaluated in this step could include any conditions that pertain to the charge or charging status of the battery For example step 180 could compare a battery voltage reading a battery current reading a battery SOC reading a battery SOH reading or some other battery performance reading to a predetermined limit or setpoint in order to obtain an error value The error value could then multiplied by a compensation or gain value as explained above to derive the eighth charging control signal It should be appreciated that this step is not limited to producing a single charging control signal as separate signals could be generated for each of the constraints listed above For instance a charging control signal could be generated for a battery voltage constraint a separate charging control signal could be generated for a battery current constraint and another charging control signal could be generated for a SOC constraint One or more of these charging control signals US 8 054 039 B2 11 such as the ones relating to the SOC and the SOH constraints could include cutoffs ifthe SOC or other condition exceeds a certain amount It should be appreciated that any combination of con straints and charging control signals could be evaluated and generated and that the present method is not limited to the exemplary combination provided above Moreover any
35. other input into bat tery charging system 10 To illustrate if a user intends on supplying battery charging system 10 with electricity from a particular AC wall outlet but knows that a number of other loads already exist on the same circuit then the user could 20 25 30 35 40 45 50 55 60 65 6 enter a current limit for example 10 amps This user speci fied parameter could then limit the AC current draw from external power source 12 to no more than 10 amps even if optimum charging conditions permitted otherwise In another example where battery charging system 10 is to be powered by a remote charging station of limited power for example a solar powered remote charging station the user could enter a power limit of 400 watts for example User defined limits on current voltage power or any other charging parameter could be entered via user interface 20 User inter face 20 may be part of battery charging control module 18 or it can be an independent interface Depending on the particu lar embodiment user interface 20 may be mounted on the dashboard e g with a driver information center DIC or elsewhere or it simply may include an electronic connection or port for connecting with a laptop or other computing device This way a user can provide user specified param eters and charging commands to battery charging system 10 via a wired or wireless connection During an exemplary charging operation ex
36. s reached a charging or other limit The charging method described herein may be particularly useful in less than ideal charging conditions that is when the power provided by external power source 12 is unstable or inconsistent when power coupling 30 is experiencing some type of operational issues or when some other condition either internal or external to the system presents challenges to the charging process Moreover battery charging system 10 may be used with a variety of different vehicles and is not limited to any one vehicle make and model Such flexibility 20 25 30 35 40 45 50 55 60 65 12 could reduce the cost of the system as a new battery charger would not need to be individually developed for each vehicle rather engineers could simply alter the various setpoint val ues calibration or gain values other software settings etc In addition to the different steps and techniques described above one or more of the following optional features could also be employed by exemplary method 100 In addition to the constraints of steps 110 180 method 100 could watch for a variety of different fault conditions where if any one of these fault conditions or hard limits is detected the method stops the charging process and notifies the user vehicle etc of the situation One way to perform such notification is through the use of a diagnostic trouble code DTC which could be used with a fault c
37. s the overall or selected charging control signal from battery charg ing control module 18 to battery charger 14 Skilled artisans will know of a variety of tools and techniques that could be used to perform step 200 including the use of a state ma chine neural network or any other logical processing device or network It is not necessary that all of the charging control signals from steps 110 180 which are actually charge request signals be sent in the form a PWM current controlling signal Rather they could be in various forms and could be translated or interpreted at step 200 they could be non PWM current controlling signals or they could control other aspects of the battery charger power output other than current to provide a few possibilities In step 202 battery charger 14 is operated according to the overall charging control signal that was previously sent As already mentioned the overall battery charging control signal could be used to manipulate the amount of current provided by battery charger 14 to battery unit 16 by means of PWM or some other control technique This way method 100 may charge the plug in vehicle in an aggressive manner that aims to reduce the charging time yet do so in a way that balances a number of parallel constraints driven by one or more inter nal and or external conditions Method 100 could then be repeated until step 180 sends a state of charge SOC control signal indicating that battery unit 16 ha
38. source by the battery charger and periodically sampling the unloaded voltage of the external power source and using the unloaded voltage of the external power source to make at least one calculation selected from the group consisting of droop voltage in the external power source power loss in a power cou pling power draw from the external power source or minimum voltage of the external power source 15 The method of claim 1 wherein step a further com prises sensing a plurality of conditions pertaining to the exter nal power source the battery charger or the battery unit step b further comprises evaluating the plurality of sensed con ditions determining corresponding constraints for each of the plurality of sensed conditions and determining the charging control signal based on the most restrictive of the plurality of constraints and step c further comprises operating the bat tery charger according to the charging control signal which is representative of the most restrictive constraint wherein at least one of the plurality of conditions is at least partially based on an unloaded battery charger input voltage 16 The method of claim 1 wherein the plug in electric vehicle is a plug in hybrid electric vehicle PHEV and the external power source is an alternating current AC wall outlet 17 A method for charging a plug in electric vehicle com prising the steps of a sensing a plurality of conditions pertaining to an
39. ternal power source 12 provides a high voltage AC signal e g 110 volts 220 volts etc to battery charger 14 Rectifier 34 which may include a full wave rectifier or bridge rectifies the high volt age AC signal into a high voltage rectified signal The high voltage rectified signal is then provided to transformer 32 which steps up the input voltage to provide a constant high voltage DC signal The high voltage DC signal is filtered and connected to battery unit 16 via switching power supply 36 which may use pulse width modulation PWM or some other technique to vary the power provided to the battery unit For example assume that a 110 volt AC input is rectified and stepped up to a relatively constant 500 volt DC output Bat tery charging control module 18 can control the output power supplied from battery charger 14 to battery unit 16 by pro viding a charging control signal to manipulate the amount of current provided at this elevated and constant voltage One way to manipulate or control the current is to adjust the duty cycle of a PWM signal sent to switching power supply 36 although other techniques could certainly be used It should be appreciated that battery charging system 10 is not limited to the foregoing example where the voltage is maintained relatively constant and the current is adjusted it is also pos sible to control the voltage or some other aspect of the output power provided by battery charger 14 Turning to FIG 2
40. tery charger located on the plug in electric vehicle or a battery unit located on the plug in electric vehicle b determining a charging control signal based on the sensed condition and c charging the battery unit with the battery charger wherein the battery charger is operated according to the charging control signal and the charging control signal is periodically adjusted in response to changes in the sensed condition According to another embodiment there is provided a method for charging a plug in electric vehicle The method generally comprises the steps of a sensing one or more condition s pertaining to an external power source a battery charger and a battery unit b evaluating each of the sensed conditions with a particular battery charging constraint c reviewing each of the evaluations and identifying the most restrictive constraint wherein the most restrictive constraint is the one that requests the least amount of current from the battery charger and d operating the battery charger so that it does not violate the most restrictive constraint According to another embodiment there is provided a system for charging a plug in electric vehicle The system generally comprises a battery charger that is located on the plug in electric vehicle and has an input coupled to an exter nal power source an output coupled to a battery unit and one or more sensor s for monitoring external power source con ditions and or batter
41. y charger conditions a battery unit that is located on the plug in electric vehicle and has an input coupled to the battery charger and one or sensor s for moni toring battery conditions and a battery charging control mod ule that is located on the plug in electric vehicle and is coupled to both the battery charger and the battery unit The battery charging control module receives readings from the battery charger sensor s and the battery sensor s and uses those readings to control the output power that the battery charger provides the battery unit BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments of the invention will hereinafter be described in conjunction with the appended drawings wherein like designations denote like elements and wherein 20 25 30 35 40 45 50 55 60 65 2 FIG 1 is a block diagram of an exemplary system for charging a vehicle battery such as those found on a plug in electric vehicle and FIG 2 is a flowchart illustrating an exemplary method for charging a vehicle battery and may be used with the system shown in FIG 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG 1 there is shown an exemplary battery charging system 10 for a plug in electric vehicle that senses various conditions within the system and uses the sensed conditions to charge the vehicle battery in an optimum fashion Battery charging system 10 attempts to charge the
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