Methods and systems for determining whether a voltage
Contents
1. INTERFACE wouer 1 GEO n Pu PACK 230 eu 1 232 CELL 1 PS 252 E 252 Patent Application Publication Jun 19 2014 Sheet 1 of 6 US 2014 0172332 A1 INTERFACE MEMORY 220 VEHICLE CONTROL MODULE 222 224 BATTERY CONTROL MODULE FIGI US 2014 0172332 A1 Jun 19 2014 Sheet 2 of 6 Patent Application Publication 001 08 e Od HEO 09 D 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 JOS SA ZL DA Or 0 GOE A 39V LION YO Vd Patent Application Publication Jun 19 2014 Sheet 3 of 6 US 2014 0172332 A1 SOC 4 FIG co N co c LO AP 90SP 34018 20 15 US 2014 0172332 A1 Jun 19 2014 Sheet 4 of 6 Patent Application Publication de 908 AP 90SP 34075 Patent Application Publication Jun 19 2014 Sheet 5 of 6 US 2014 0172332 A1 CREATE PRESENT SOC BASED ON TEMPERATURE AND VOLTAGE OFFSET IS MAXIMUM delta cal CALCULATE DIFFERENCE BETWEEN PREVIOUS SOC AND PRESENT SOC IS NEW DIFFERENCE LARGER THAN OLD STORE NEW DIFFERENCE AS MAXIMUM DELTA INCREMENT i CREATE NEW OFFSET Side Patent Application Publication Jun 19 2014 Sheet 6 of 6 US 2014 0172332 A1 US 2014 0172332 A1 METHODS AND2. text clearly indicates otherwise 0017 Unless otherwise indicated all numbers expressing quantities of ingredients properties such as molecular weight reaction conditions and so forth as used in the speci fication and claims are to be understood as being modified in all instances by the term about which is intended to mean up to 10 of an indicated value Additionally the disclosure of any ranges in the specification and claims are to be under stood as including the range itself and also anything sub sumed therein as well as endpoints Unless otherwise indi cated the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention Notwithstanding that numerical ranges and parameters setting forth the broad scope of the invention are approximations the numerical values set forth in the specific examples are reported as precisely as possible Any numerical values however inherently contain certain errors necessarily resulting from error found in their respec tive measurements 0018 As used herein the term pack is a combination of batteries battery cells in series and parallel 0019 As used herein OCV is an open circuit voltage estimation of a battery cell or pack OCV is equal to the measured voltage when the cell or pack is at equilibrium 0020 As used herein the term sig
3. SYSTEMS FOR DETERMINING WHETHER A VOLTAGE MEASUREMENT IS USABLE FOR A STATE OF CHARGE ESTIMATION FIELD 0001 The present invention relates generally to systems and methods for improvements in battery state of charge accuracy charge termination consistency capacity estima tion and energy delivery consistency More specifically embodiments herein detail an algorithm to calculate the change in state of charge for a given voltage change dSOC dV at a given temperature in a region around the present voltage measurement or estimation and to set a signal indi cating when the measurement should not be used due to potential error BACKGROUND 0002 Knowing the state of charge ofa battery is necessary for an indication of how much longer a battery will continue to perform prior to the need for either recharging or replace ment As technologies related to vehicles continue to advance the significance of understanding and monitoring battery life becomes increasingly significant 0003 Battery charge can be measured through several methods such as chemically through measurements and plottingofcurves related to discharge or even using electrical modeling 0004 One known method of providing direct measure ments is a method that converts a reading of the battery voltage to state of charge SOC using the known discharge curve voltage versus SOC of the battery Using such a method SOC is graphed in relation to an open circuit voltag
4. and can be any level automatically or manually determined and selected such as between 0 001 volts to about 0 5 volts Regarding the elements the number of iterations is the num ber of elements in the array minus 1 Several algorithm itera tions are conceived such as from about 1 to about 10 or about 10 to about 20 about 20 to about 50 or more Thresholds can be based on calculated or predetermined data or both and can be set automatically or via user manual input and can be set to account for errors of any level including such as error percentages of 1 5 percent or 5 20 percent or 20 30 percent or more The thresholds can also be based in part or in whole on comparison of line slopes such as those shown in FIG 3 and or FIG 4 US 2014 0172332 A1 0036 The specific steps of FIG 6 are start 41 create array 43 calculate SOC 45 calculate dSOC 47 determine maxi mum SOC 49 compare to threshold 51 output 53 and end 55 0037 The systems described herein such as controller 104 can be utilized in conjunction with computers and computer based systems As will be appreciated by those skilled in the art the embodiments can be utilized with a data processing or computer system in general and a digital computer in par ticular preferably include an input an output a processing unit often referred to as a central processing unit CPU and memory that can temporarily or permanently store such a code program or algorithm in the
5. computer s memory such that the instructions contained in the code are operated upon by the processing unit based on input data such that output data generated by the code and the processing unit can be conveyed to another program or a user via output In one form a data containing portion of the memory also called working memory is referred to as random access memory RAM while an instruction containing portion of the memory also called permanent memory is referred to as read only memory ROM A data bus or related set of wires and associated circuitry forms a suitable data communication path that can interconnect the input output CPU and memory as well as any peripheral equipment in such a way as to permit the system to operate as an integrated whole Such a computer system is referred to as having a von Neumann architecture also referred to as a general purpose or stored program computer 0038 In specific embodiments herein described when a threshold is exceeded the controller 104 or a computer or computer part can communicate the signal not use the data to auser viaa signal light such as a signal light associated with a vehicle a signal can also be communicated to a device to display the output 0039 In specific embodiments described herein the algo rithm uses an SOC OCV look up table that varies with tem perature 0040 In specific embodiments described herein the algo rithm takes into account rounding errors
6. if the answer to 9 is Yes 39 After 21 repeat step 3 Is i less than NumStep The other side of the flowchart answers No 25 to the question of Is i less than Numstep 3 If No 25 then ask Is the maximum delta greater than cal 27 If No 29 then set use flag 31 output of use the data If Yes 33 then set the do not use flag 35 output of not use the data Then the end of steps 37 is reached 0035 FIG 6 is a schematic illustration of an embodiment showing a flowchart for use with methods and systems described herein The chart shows that embodiments of meth ods and systems described herein can include the aforemen tioned controller 104 and an algorithm where the controller 104 can start the algorithm so as to create an array of voltages from the provided voltage measurement or the open circuit voltage estimation a step size and a total number of ele ments calculate the SOC for each voltage in the array given the sensed temperature calculate the difference between each dSOC in the array determine the maximum dSOC from the array determine if the maximum dSOC is above a threshold for usable data and to set an output to not use the data when the maximum dSOC is above a threshold for usable data or setting the output to use the data when the maximum dSOC is not above a threshold for usable data The step size refers to the difference between array points for SOC determinations
7. vehicle 100 via interface 218 In some embodiments vehicle control module 222 may also communicate with other processing circuits e g an engine control unit an on board diagnostics system or the like or other sensors e g a mass airflow sensor a crankshaft position sensor or the like via interface 218 0028 In specific embodiments the controller 104 is located in different places in different applications including in a car such as in the passenger cabin and or under seats and or in a trunk The controller 104 also can be located in a laboratory used herein to refer to a building or location uti lized for testing equipment or performing other research or where manufacturing is performed A signal of use the data US 2014 0172332 A1 or not use the data of a voltage measurement for SOC estimation as described herein can be automatically displayed on a car dash or other display for a user 0029 FIG 2 shows a schematic illustration of Pack Volt age versus SOC percentage for a lithium iron phosphate bat tery As can clearly be seen FIG 2 shows very large regions of SOC percentage changes with little change in voltage SOC percentage of 40 60 70 95 This graph shows that a change in voltage correlates very well for a change in SOC percentage when the line slope is steep and very poorly when the line is flat slope of nearly zero For example when the voltage changes from about 377 volts to about 375 volts SOC pe
8. when determining error levels and threshold levels where the rounding errors relate to A D and or CAN BUS 0041 In specific embodiments herein described methods and systems can include one or more of at least one battery that is a lithium iron phosphate battery or a battery pack from about 1 to about 10 batteries or from about 10 to about 20 batteries a controller that can be located within a vehicle such as in a trunk or in a passenger cabin or under a car seat a controller that is located in a laboratory and coupled to a calculation device for running the algorithm a step size from about 0 5 volts to about 0 1 volts or from about 0 1 volts to 0 01 about volts or from about 0 01 volts to 0 001 about volts at least one sensor that can be one two or three sensors or more sensors configured to measure temperature differences between about 1 and about 0 1 degree Celsius or between about 0 1 and about 0 01 degree Celsius or between about 0 01 and about 0 001 degree Celsius EXAMPLES 0042 The present invention will be better understood by reference to the following example which is offered by way of illustration not limitation Jun 19 2014 Example 1 0043 An algorithm as shown in FIG 5 outlines specific embodiments of the current invention Steps of the embodi ments are shown below 1 Algorithm start This is a call of the function The call occurs when a voltage needs to be evaluated This voltage can be measured or
9. 208 which performs cell balancing on bat tery pack 102 in response to receiving a control command from controller 104 via bus line 213 In other embodiments cell balancing controller 208 is omitted and controller 104 may provide control commands directly to battery pack 102 via bus line 213 to perform cell balancing 0027 Still referring to controller 104 the controller 104 is shown to include processor 219 which may be one or more processors e g a microprocessor an application specific integrated circuit ASIC field programmable gate array or the like communicatively coupled to memory 220 and inter faces 216 and 218 Memory 220 may be any form of memory capable of storing machine executable instructions that implement one or more of the functions disclosed herein when executed by processor 519 For example memory 520 may be a RAM ROM flash memory hard drive EEPROM CD ROM DVD other forms of non transitory memory devices or any combination of different memory devices In some embodiments memory 220 includes vehicle control module 222 which provides control over one or more com ponents of vehicle 100 For example vehicle control module 222 may provide control over the engine of vehicle 100 or provide status condition information e g vehicle 100 is low on fuel vehicle 100 has an estimated number of miles left to travel based on the present SOC of battery pack 102 etc to one or more display devices in the interior of
10. US 20140172332A1 as United States a2 Patent Application Publication 0 Pub No US 2014 0172332 Al Johnson et al 43 Pub Date Jun 19 2014 54 71 72 73 21 22 METHODS AND SYSTEMS FOR DETERMINING WHETHER A VOLTAGE MEASUREMENT IS USABLE FOR A STATE OF CHARGE ESTIMATION Applicant GM Global Technology Operations LLC Detroit MI US Inventors Kurt M Johnson Brighton MI US Brett B Stawinski Royal Oak MI US Brian J Koch Berkley MI US Damon R Frisch Troy MI US Patrick Frost Novi MI US Assignee GM Global Technology Operations LLC Detroit MI US Appl No 13 717 958 Filed Dec 18 2012 Publication Classification 51 Int Cl GOIR 31 36 2006 01 52 U S CI GOIR 31 362 2013 01 Mibi uo eri MI ARAM Gag 702 63 57 ABSTRACT Systems and methods for improvements in battery state of charge accuracy charge termination consistency capacity estimation and energy delivery consistency More specifi cally embodiments herein detail systems and methods using an algorithm to calculate the change in state of charge for a given voltage change dSOC dV at a given temperature in a region around the present voltage measurement or estimation and to set a signal indicating when the measurement should not be used due to potential error INTERFACE 218 PROCESSOR 219 MEMORY 220 VERICLE CONTROL MODULE 22 224 BATTERY CONTROL MODULE c 216
11. calculating the state of charge SOC for each voltage in the array given the sensed temperature calculating the difference between each subsequent state of charge dSOC in the array US 2014 0172332 A1 determining the maximum dSOC from the array determining if the maximum dSOC is above a threshold for usable data and setting an output to not use the data when the maxi mum dSOC is above the threshold for usable data or setting the output to use the data when the maxi mum dSOC is not above the threshold for usable data 2 The method of claim 1 wherein the at least one battery is a lithium iron phosphate battery 3 The method of claim 1 wherein the at least one battery is a battery pack 4 The method of claim 1 wherein the at least one battery is a battery pack comprising about 1 to about 10 batteries 5 The method of claim 1 wherein the at least one battery is a battery pack comprising about 10 to about 20 batteries 6 The method ofclaim 1 wherein the at least one controller is a located within a vehicle 7 The method of claim 1 wherein the at least one controller is located at least one of in a trunk of a car in a passenger cabin of the car or under a seat of the car 8 The method of claim 1 wherein the at least one controller is located in a laboratory and coupled to a calculation device for running the algorithm 9 The method of claim 1 wherein the step size is from about 0 5 volts to about 0 1 volts 10 T
12. diments are shown as follows Iteration 1 V 3 68 V SOC 50 Iteration 2 V 3 69 V SOC 50 8 dSOC 0 8 maximum dSOC 0 8 Itera tion 3 V 3 7 V SOC 51 5 dSOC 0 7 maximum dSOC 0 8 Iteration 4 V 3 71 V SOC 52 6 dSOC 1 1 maximum dSOC 1 1 Iteration 5 V 3 72V SOC 52 9 dSOC 0 3 maximum dSOC 1 1 Regarding algo rithm output DataQuality this can be set to Do Not Use because 1 1 gt 1 0045 While certain representative embodiments and details have been shown for purposes of illustrating the inven tion it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention which is defined in the appended claims 1 A method for determining whether a voltage measure ment or an open circuit voltage estimation is usable for a state of charge estimation the method comprising providing at least one battery at least one sensor coupled to said battery and at least one controller coupled to the at least one battery sensing a temperature of the at least one battery with the at least one sensor providing at least one of the voltage measurement or the open circuit voltage estimation for the at least one bat tery starting an algorithm with the at least one controller wherein the algorithm comprises creating an array of voltages from the provided voltage measurement or the open circuit voltage estimation a step size and a total number of elements
13. dule level of battery pack 102 0025 Vehicle 100 is also shown to include a number of sensors connected to battery pack 102 Voltage sensors 202 measure the voltage of battery pack 102 modules 230 and or cells 232 and provides voltage values to interface 216 of controller 104 via bus line 210 Current sensors 204 measure the current of battery pack 102 modules 230 and or cells 232 and provides current values to interface 216 of controller 104 via bus line 212 Temperature sensors 206 measures the tem perature of battery pack 102 modules 230 and or cells 232 and provides temperature values to interface 216 of controller 104 via bus line 214 Sensors 202 204 and 206 may be any number of sensors or configurations to measure the voltages currents and temperatures associated with battery pack 102 For example temperature sensor 206 may be a single tem perature sensor while voltage sensors 202 and current sen sors 204 may be a combined integrated circuit that measures both voltages and currents It should be appreciated that any number of different combinations of sensors and sensor con figurations may be used without deviating from the prin ciples or teachings of the present disclosure 0026 The controller 104 can include an interface 218 memory 220 processor 219 vehicle control module battery control module 224 and one or more interfaces 216 218 In some embodiments vehicle 100 may also include cell bal ancing controller
14. e OCV estimation which is the voltage at equilibrium and therefore current equals zero With this method however the voltage reading is significantly affected by the battery current due to the battery s electrochemical kinetics as well as tem perature especially if the battery is not truly at rest when readings are made Therefore such methods are often made more accurate by compensating the voltage reading with a correction term proportional to the battery current and by using a look up reference table of the battery s open circuit voltage estimation versus temperature 0005 In lithium iron phosphate batteries LiFeP regions of the SOC OCV curve have large changes in SOC for small changes of OCV estimations In these regions voltage sens ing inaccuracies analog to digital A D resolution and con troller area network CAN database resolution are some potential causes of SOC inaccuracy There is a need in the art for systems and methods providing users with knowledge that an estimated SOC based on voltage in these regions may contain large errors and should not be used 0006 Current systems are exceedingly complex and there is a need in the art for increased simplicity efficiency and decreased errors Specific embodiments described herein lead to improvements in SOC accuracy charge termination consistency capacity estimation and energy delivery consis tency SUMMARY 0007 Embodiments of the present invention provide f
15. estimated 2 If the number of steps is less than a calibration proceed other wise skip to step 7 Step 3 Use the voltage and measured temperature to estimate a state of charge SOC Step 4 If this is the first time through the loop proceed to step 6 else proceed to step 5 Step 5 Calculate the change between the previously calculated SOC and the presently calculated SOC If this change is the largest change since the algorithm started in step 1 store this change as the maximum change Step 6 Increment the number of steps and return to step 2 Step 7 Once all of the steps have been calculated and the maximum change in SOC has been determined compare the maximum change in SOC to a calibration 8 If this calibra tion is less than the maximum change in SOC the algorithm output that is used to signal the quality of the voltage mea surement or estimation is set to not use the data otherwise the output is set to use the data Step 9 Algorithm end The number of iterations is recommended to be odd with the center value of voltage in the array equal to the voltage from step 1 0044 An example of iterations is described as follows a temperature of 25 degrees Celsius is sensed with the voltage to be analyzed being 3 7 V the number of steps 5 and the voltage step size dV being 0 01 volts this value is in specific embodiments set based on Max change in SOC 1 Mul tiple iterations of specific embo
16. he method of claim 1 wherein the step size is from about 0 1 volts to about 0 01 volts 11 The method of claim 1 wherein the step size is from about 0 01 volts to about 0 001 volts 12 The method of claim 1 wherein the at least one sensor is at least two sensors 13 The method of claim 1 wherein the at least one sensor is at least three sensors 14 The method of claim 1 wherein the at least one sensor is configured to measure temperature differences between about 1 and about 0 1 degree Celsius Jun 19 2014 15 The method of claim 1 wherein the at least one sensor is configured to measure temperature differences between about 0 1 and about 0 01 degree Celsius 16 The method of claim 1 wherein the at least one sensor is configured to measure temperature differences between about 0 01 and about 0 001 degree Celsius 17 A system for determining whether a voltage measure ment or an open circuit voltage estimation is usable for a state of charge estimation comprising at least one battery at least one sensor coupled to said battery and at least one controller coupled to the at least one battery wherein the at least one sensor is configured to sense a temperature and provide the voltage measurement or the open circuit voltage estimation of the at least one bat tery and the at least one controller is configured to start an algorithm so as to create an array of voltages from the provided voltage measurement or the open ci
17. nal refers to a Boolean value or other designation used in certain embodiments herein to designate whether an open circuit voltage estima tion should be used 0021 As used herein the term calculation device refers to a computer or other device that can perform algorithms 0022 In specific embodiments the new algorithm see FIG 5 and Example 1 tests the SOC OCV curve at voltages near the measurement and at the same temperature to deter mine the difference in SOC between these points A small difference in SOC indicates that the error introduced by the measurement is likely small and should be trusted 0023 In specific embodiments of the invention the present temperature of the battery is tested via one or more sensors also coupled to the controller so as to communicate information between parts of the system By testing at the present temperature of the battery the new algorithm can create the use do not use signal at a higher resolution than could be performed with current methods 0024 FIG 1 illustrates a system including a battery pack anda controller 104 located within a vehicle A vehicle 100 is shown according to an exemplary embodiment Battery pack 102 includes modules 230 which provide cumulative electri cal power to propel vehicle 100 Each of modules 230 con tains a plurality of battery cells 232 Similarly battery cells Jun 19 2014 232 are connected together to provide cumulative power at the mo
18. ning whether a voltage measurement or an open circuit voltage estimation is usable for a state of charge estimation comprising at least one battery at least one sensor coupled to said battery and at least one controller coupled to the at least one battery In specific embodiments the at least one sensor is configured to sense a temperature and provide the voltage measurement or the open circuit voltage estimation of the at least one battery and the at least one controller is configured to start an algorithm More specifi cally in various embodiments the controller is configured to start the algorithm so as to create an array of voltages from the provided voltage measurement or the open circuit voltage estimation a step size and a total number of elements The algorithm also can calculate the state of charge SOC for each voltage in the array given the sensed temperature cal culate the difference between each subsequent state of charge dSOC in the array and determine the maximum dSOC from the array This allows for the algorithm to determine if the maximum dSOC is above a threshold for usable data and set an output to not use the data when the maximum dSOC is above the threshold for usable data or setting the output to use the data when the maximum dSOC is not above the threshold for usable data BRIEF DESCRIPTION OF THE FIGURES 0009 FIG 1isa schematic illustration of a system includ ing a battery pack and a controlle
19. or determining whether a voltage measurement or an open cir cuit voltage estimation is usable for a state of charge estima Jun 19 2014 tion This method comprises providing at least one battery at least one sensor coupled to said battery and at least one controller coupled to the at least one battery The method additionally comprises sensing a temperature of the at least one battery with the at least one sensor providing at least one of the voltage measurement or the open circuit voltage esti mation for the at least one battery and starting an algorithm with the at least one controller Specific embodiments of the algorithm involve creating an array of voltages from the pro vided voltage measurement or the open circuit voltage esti mation a step size and a total number of elements as well as calculating the state of charge SOC for each voltage in the array given the sensed temperature and calculating the dif ference between each subsequent state of charge dSOC in the array Specific embodiments of the algorithm also com prise determining the maximum dSOC from the array deter mining if the maximum dSOC is above a threshold for usable data and setting an output to not use the data when the maximum dSOC is above the threshold for usable data or setting the output to use the data when the maximum dSOC is not above the threshold for usable data 0008 Also provided herein are embodiments for novel systems for determi
20. ovided 1 is Jun 19 2014 iteration number NumStep is a calibratable number of iterations to perform SOC is state of charge Offset is an addition or subtraction of a value a correction term and can be calculated or determined using one or more reference tables when a voltage measurement is performed when a battery is not in equilibrium then an offset value can be added or subtracted to correct the value thereby providing an esti mation The algorithm can utilize an offset to make correc tions to add or subtract values for more accurate determina tions such as creating SOC estimations the values can be obtained from reference charts accessible by one or more computers running the algorithm or in communication with the controller 104 that can run the algorithm or the values can be predetermined 0034 The FIG 5 flowchart steps include as follows Start 1 ask Is i less than NumStep 3 if Yes 5 create present SOC based on temperature and voltage plus offset if required 7 ask Does i equal zero 9 if No 11 calculate the difference between previous SOC and present SOC 13 ask Is the new difference larger than the old difference 15 and if Yes 17 then store the new difference as maximum delta 19 before the step of Increment I create new offset 21 If the new difference is not larger than the old difference No 23 then go directly to 21 also go directly to 21
21. r such as a controller located within a vehicle 0010 FIG 2 is a schematic illustration of Pack Voltage versus SOC percentage for a lithium iron phosphate battery 0011 FIG 3 is a schematic illustration of variance of the slope for one step size 0012 FIG 4 is a schematic illustration of variance of the slope for a given step size with temperature 0013 FIG 5 is a flow diagram showing an algorithm for use with methods and systems described herein 0014 FIG 6 is a flowchart for use with methods and systems described herein DETAILED DESCRIPTION 0015 Specific embodiments ofthe present disclosure will now be described The invention may however be embodied US 2014 0172332 A1 in different forms and should not be construed as limited to the embodiments set forth herein Rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art 0016 Unless otherwise defined all technical and scien tific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs The terminology used herein is for describing particular embodiments only and is not intended to be limiting of the invention As used in the specification and appended claims the singular forms a an and the are intended to include the plural forms as well unless the con
22. rcentage drops from only from about 100 to about 98 per cent SOC However as the voltage drops from about 375 volts to about 373 volts the SOC percentage drops from about 98 to about 71 Therefore a given voltage reading or even a measure of a voltage change in the flat regions of the graph would not be an accurate way to calculate the change in state of charge Embodiments herein described provide for a deter mination of when such data should be used and when it should not be used 0030 FIG 3 is a schematic illustration of variance of the slope for one step size This graph shows that as the SOC percentage falls from 100 to 0 the dSOC dV can either be approximately flat at near full charge or at very low charges or can be very steep at about 40 60 percent and at 70 95 percent When the slope of the line this graph is steep a given voltage measurement or measurement of voltage change would run the risk of being a poor estimate of a change in a SOC as the SOC is changing so rapidly around this voltage point Therefore embodiments herein described account for this variability by accounting for the slope changes and by estimating SOC using voltages higher and lower than the measurement using voltage steps 0031 FIG 4 is a schematic illustration of variance of the slope for a given step size with temperature In the same way that FIG 3 showed 1 step size this graph shows multiple step sizes from 90 to 100 percent unlike FIG 3 which
23. rcuit voltage estimation a step size and a total number of elements calculate the state of charge SOC for each voltage in the array given the sensed temperature calculate the difference between each subsequent state of charge dSOC in the array determine the maximum dSOC from the array determine if the maximum dSOC is above a threshold for usable data and set an output to not use the data when the maximum dSOC is above the threshold for usable data or setting the output to use the data when the maximum dSOC is not above the threshold for usable data 18 The system of claim 17 wherein the at least one battery is a lithium iron phosphate battery 19 The system of claim 17 wherein the at least one battery is a battery pack 20 The system of claim 17 wherein the at least one battery is a battery pack of from about 1 to about 10 batteries
24. showed form 0 to 100 percent FIG 4 shows more than one step size and indicates temperature significance with measurements FIG 4 shows that temperature must be closely accounted for to determine accurate measurements In the method being disclosed the slope ofthe 20 degree Celsius dSOC dV curve remains larger than the 30 degree Celsius dSOC dV curve at higher states of charge In prior art temperatures between 20 and 30 degrees Celsius could be evaluated as equivalent resulting in the rejection of state of charge estimates with low error at higher temperatures 0032 Still regarding FIG 4 FIG 4 illustrates that it would be appropriate to use the OCV at 94 SOC if the temperature was greater than 26 degrees Celsius but that a change in temperature could lead to significant error As shown as much as 15 SOC error could be introduced if the tempera ture was only 20 degrees Celsius Likewise given a tempera ture of 20 degrees Celsius the OCV would have to show about 97 percent before it would have less than 2 percent error based on the curve 0033 FIG 5 is a schematic illustration of an embodiment showing an algorithm for use with methods and systems described herein The algorithm runs when a determination of a battery charge is required which can be at times automati cally determined or pre programmed into the controller 104 or an associated computer or computer system or can be manually started In the chart of the algorithm pr
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