System And Method For Monitoring The State Of Charge Of A Battery

Transcript

US008154252B2 (12) Umted States Patent (10) Patent N0.: Lu et al. (54) (45) Date of Patent: Apr. 10, 2012 SYSTEM AND METHOD FOR MONITORING 6,341,974 B2 1/2005 Dykeman THE STATE OF CHARGE OF A BATTERY 7,528,579 B2 * 5/2009 Pacholok et al. ........... .. 320/145 2005/0151513 A1 _ (75) US 8,154,252 B2 . _ . 7/2005 Cook et al. 2006/0049797 A1 Inventors. Wenzhe Lu, Dublln, OH (US), S1m0n Cleggs Stroud (GB); Ian Leonard, Oxford (GB) 3/2006 100006 Salasoo et a1‘ 10/2007 Dougherty et al. 2007/0252600 A1 11/2007 Chou et al. 2009/0015202 A1* (73) Ass1gnee: Vanner, Inc., H1ll1ard, OH (US) (*) NOIiCeZ (21) A 1 N pp . 1/2009 Miura ......................... .. 320/132 OTHER PUBLICATIONS subject 10 any disclaimer, the term Ofthis Pawnt is extended or adjusted under 35 U~S~C- 15403) by 263 days~ 12/414 658 0.: Hope et al. 2006/0232240 A1 2007/0239374 A1 Solidstate Controls, Inc., “Battery Management System,” Product speci?cation note, p. 1-4, Dec. 2002 (abstract) [online]. Retrieved from the Internet on [Nov. 1, 2009]. http://WWW. solidstatecontrolsinc.com/products/pdf/bms2000v.pdf. , * cited by examiner (22) Filed: (65) Mar. 30, 2009 Primary Examiner * Huy Q Phan Assistant Examiner * Alesa Allgood (74) Attorney, Agent, or Firm * James R. Eley; Michael A. P1101‘ Pubhcatlon Data Us 2009/0243556 A1 Oct 1’ 2009 Forhan; Eley LaW Firm Co. LPA Related US. Application Data 57 (60) ABSTRACT Provisional application No. 61/040,885, ?led on Mar. ( 31’ 2008 A process for momtonng the status of a battery. Steps of the process include measuring a battery current and comparing the battery current to a predetermined threshold. A battery status is determined as one of charging, discharging and qui ) _ _ (51) Int C]_ H02J 7/00 (52) us. Cl. ...................................... .. 320/132- 320/162 escem- For a battery Charging Status determination’ the Charg (58) Field of Classi?cation Search ................ .. 320/132 320/149_ 324/427 429*434 132 149 160’ ’ ’ ’ ’ 3 2;‘ /1 62’ See application ?le for Complete Search history mg State of Charge of the battery is Compute/‘1' For battery discharge status determination, the discharge current is com pared to apredeterrnined threshold. Based upon the discharge current comparison, a basis for the discharge current is (200601) ' (56) References Cited US. PATENT DOCUMENTS 6,424,157 B1 * 7/2002 Gollomp et al. ............ .. 324/430 6,456,043 B1 9/2002 Finger 6,549,014 B1 * 4/2003 6,646,419 B1* selected from one of a plurality of predetermined discharge conditions and the discharging state of charge of the battery is computed for the select discharge condition. For a quiescent status, the quiescent state of charge of the battery is com puted. The computed state of charge of the battery is provided in a quantitative form. Kutkut et al. ............... .. 324/426 11/2003 Ying ........................... .. 320/132 14 Claims, 9 Drawing Sheets 10 c1‘ 24x PRIME MUVER I [IHAREER f 20 '5\_ CONTROLLER BATTERY f ‘2 22 '\- INDICATOR LOAD US. Patent Apr. 10, 2012 Sheet 1 M9 US 8,154,252 B2 10 \ 24 -\_ PRIME MOVER 18 7 > CHARGER / 20 l6\_ CONTROLLER (— 17 § BATTERY fl? 22 \- INDICATOR LOAD -/ Fig.1 14 US. Patent Apr. 10, 2012 Sheet 2 M9 BC=Batter Current Vca=Ce l l zol tage US 8,154,252 B2 Once per Second Serv ice Rout i ne Va=Bat tery Voltage Nj=Number of‘ Cells thC=Charge Threshold (3A) thD=Dischar e Threshold (-SA] osgiggégtgt First_time= irst Time Running Flog ‘ dVca=Change of Cell Voltage Since Last Second I I dischargemode and Calculate Vcu:Vu/Nj Yes —_ \ BC '5 negnt've '" pos't've '" Ch?rge mode +‘irst_time:: ? First_t ime=0 No ‘ Calculate voltage change since last Calculate dVca batter _state: STATUSJIUIESCENT second to Filter out voltage spikes I02 — \ No f discharge_count ++ Yes f 104 charge_count ++ BC Charge_count : 0 quiescent_count : 0 quiescent_count : O ‘ {out > 200 Yes charge_count = 0 U date Iin charge_count —— \ batter _state : STATU _EHARGE J Charge (3 US. Patent Apr. 10, 2012 US 8,154,252 B2 Sheet 3 0f 9 ; 200 I in=Current In Iout=Current Out CU=Initial Charge Tin=Time Charge Tout=Time Discharge Te=Elapsed Time BC=Battery Current 8 204 thBC=B0ast char e Threshold(§OA) Ahr=Ampere-haur Ratin Status Minor I Boast EF=Charge EFFiciencyl 30%) n=Peukert Number g 208 Status Minor No I F laat 210 Status M i nor I Bulk 7 Iin and Iaut are measured in As 1m IIin + (BC*EF/l00)"n T i n I T i n +1 (Ampere Seconds) l Te I T i n +Tout (secs ) When i n Charge we calculate SOC 2 C0 +I i n — No I Not us i ng In i t i al Ahr Ful ly + Ahr in —Ahr out Charged Iout 308 i Duiescent Quiescent t imeout I t i meout I 60 mi ns 3 mi ns \ J i END Fig. 2C END US. Patent Apr. 10, 2012 Sheet 5 of9 I in=Current In I0ut=Current Out US 8,154,252 B2 j 400 Quiescent C0=Initial Charge Tin=Time Charge T0ut=Time Discharge Te=Elapsed Time 402 Vca<2.2V 0R First_time ? Vca=Actual Cel I Vol tage Ahr=Ampere-hour Rating EF=Charge EFF i c i ency( 0%) n=Peukert Number 40B Status M i nor I ‘2 newSOC=New SOC Calculated From Vol tage \ Trickle Charge * newSOC I (445 Vca)—84l newSOC < O newSOC I O ? 412 Status M i nor I Open / Circuit POOR " I in I I in + (C/IOOO) Status Minor 410 f I open C ' rcu' t IBecause charge I vol tage is > 2-2/ cell SOME current MUST newSOC > [00% be going into ? the battery Yes ITEWSOCIIOOZ r ' F i rst_t ime I O Status Minor >404 so we Fake it Tin:‘|'in+1 ‘_ + I Ful ly Charged Te : T i n _|_ Tour (secs) v newSOC: 100% T newSOC I ( ( C0 + I 'l n — Iout )/(C 9* 60 * 60) T * 100 Let SOC approach newSOC at quiescent | timeout | qu i escent_ t ime > O Yes t ‘? 406< qu i escent_t ime I qu i escent_t ime -] SUC I SOC + quiescent (newSOC- SOC )/ < (qu i escent_t ime/60) t i me Z760 I: \ Reset Tin. Tout and Te it: SOCIImOZ Is qu iescent_t ime mul t iple 60 (a new minute)? US. Patent Apr. 10, 2012 Sheet 6 of9 US 8,154,252 B2 j 500 T=Battery Temperature Tr=Rated Temperature Tc=Temperature Constant SOC=State 0F Char e SoCc=Correction a? SOC Produce SOC adjusted For temperature SOCach=Achievable SOC SOH=State at‘ Health 3502 SoCc = 100 — SOH N0 Produce SOC adjusted For perFormance Yes SoCc I 90 Never let it go 4 50 < above a cei l i ng to , avo id 5 i l ly Figures SOCach : (SOC —SoCc )/ Calculate acheivable SOC v ( END of‘ Once perSecond Rout i ne ) Fig. 2E US. Patent Apr. 10, 2012 Sheet 7 of9 US 8,154,252 B2 Te =0. Te=Elapsed Time (Time Can ' t i nta Disharge: Te= ( T i n Continue +Tout l/BO) Tt=Peukert Time to Run(m i ns ) U=T ime to Run (mi ns ) Up=Adjusted T ime to Run (mi ns) Vc=Calculated Cel I Vol tage Ve=Endpvint Vol Inge u = (to +1 in —Iout)/( (—B[I)"n)/60 u=Constant in Minutes For a given Ve k=Constant For calculat i ng Vc y=Start i ng Val tage = u at Tc=Temperature Constant eie (C 60 5O) ) at TV 100 SOC=State of‘ Charge \ 5°H=Sme "F Hem“ Baund soc in [0.100] I ITable lookup u for given Vel 600 Tt 2 540 y : 2.073628 ? No , .) SUE S 90% ? Calculate SOH Yes only when depth at‘ v d ischarge is > 107° ( 608 SOH I 100 —(Vc— Vca)/(Vc— Ve ) * lOO +(Tr-T)*Tc*l00. bound in [50.150] Temperature and ‘ ‘ Yes T> Tr ? adjusted t ime ' T 610 perFormance to No up: u*s0H/100 ( END OF VCI I > run TY US. Patent Apr. 10, 2012 US 8,154,252 B2 Sheet 8 0f 9 EEPROM-Two Pages Page O-Primary Page l-Secondary Page 1 is used when nPageToWr i te I —l i Page 0 Failed $700 Read EEPROM Page 0 702 Erase Page l ‘I! f 706 nPageToWr i te = 1 704 < Wr i te Data to Page 1 Load Default Values nPageToWr i teI —l i i Erase Page 0 l Fig. 2G nPageToWrite = 0 End EEPROM 710 US. Patent Wr i te [late Apr. 10, 2012 Sheet 9 of9 US 8,154,252 B2 i800 to Page 0 V Wr i te Data to Page 1 l US 8,154,252 B2 1 2 SYSTEM AND METHOD FOR MONITORING THE STATE OF CHARGE OF A BATTERY it needs recharging. The SOC is also utiliZed to determine e?icient charging characteristics for charging the battery. One embodiment of the invention may be a process for This application claims priority to US. provisional patent application No. 61/040,885, ?led Mar. 31, 2008, the contents of Which are hereby incorporated by reference. monitoring the status of a battery. Steps of the process include measuring a battery current and comparing the battery current to a predetermined threshold. A battery status is determined as one of charging, discharging and quiescent. For a battery FIELD charging status determination, the charging state of charge of the battery is computed. For battery discharge status determi The present invention relates generally to battery charging systems and methods, in particular to systems and methods for monitoring the state of charge of a battery and adjusting nation, the discharge current is compared to a predetermined threshold. Based upon the discharge current comparison, a basis for the discharge current is selected from one of a the charging characteristics to match to the state of charge. plurality of predetermined discharge conditions and the dis charging state of charge of the battery is computed for the select discharge condition. For a quiescent status, the quies cent state of charge of the battery is computed. The computed state of charge of the battery is provided in a quantitative BACKGROUND A typical vehicle poWer system consists of a battery, an alternator to charge the battery and to augment poWer sup plied by the battery, and one or more distribution buses. The poWer system is primarily utiliZed to start a prime mover, such 20 as an internal combustion engine, and to poWer a variety of loads connected to the distribution bus. There is a desire on the part of many vehicle manufacturers to increase the “elec tri?cation” of vehicles, i.e., reducing the number of accesso ries that depend directly on the internal combustion engine as comprises a battery, a charger con?gured to charge the bat tery, a controller to control the charging operation of the charger, signal inputs from the battery to the monitoring 25 a mechanical prime mover. Example accessories include poWer steering pumps, hydraulic drives, engine cooling fans, air conditioning compressors, oil and coolant pumps, and air compressors. Advantages of accessory electri?cation include performance, increased ?exibility in locating and mounting For example, a vehicle may have a ?rst battery system for operating a starter to start the internal combustion engine and a second battery system for poWering accessories. The dis charge and load characteristics can vary considerably betWeen the cranking and accessory batteries. For example, the cranking batteries are intended to provide high current for a relatively short period of time to start the engine, While the 35 40 upon the discharge current comparison, a basis for the dis charge current from one of a plurality of predetermined dis vided in a quantitative form. BRIEF DESCRIPTION OF THE DRAWINGS 45 Further features of the inventive embodiments Will become apparent to those skilled in the art to Which the embodiments relate from reading the speci?cation and claims With refer ence to the accompanying draWings, in Which: FIG. 1 is a block diagram shoWing the general arrangement of a system for monitoring the state of charge of a battery; current to the vehicle’s accessories for a relatively longer battery be charged in a manner conducive to satisfactory battery life. It is also important to charge the battery in an discharging and quiescent; for a battery charging status deter mination, compute the charging state of charge of the battery; for battery discharge status determination, compare the dis charge current to a predetermined threshold, selecting, based charge conditions, and compute the discharging state of charge of the battery for the select discharge condition; for quiescent status, compute the quiescent state of charge of the battery. The computed state of charge of the battery is pro accessory batteries are used to provide a smaller amount of period of time. The types of batteries used for cranking and for poWering accessories may also differ. For example, a cranking battery may use ?ooded lead-acid batteries While the accessory battery may use deep-cycle absorbed glass mat (“AGM”) batteries. Each type of battery can have differing charge requirements, as Well. As a consequence of the foregoing it is important that the portion of the controller, and a load coupled to the battery. A monitoring portion monitors the state of the battery. The monitoring portion is con?gured to compare the battery cur rent to a predetermined threshold; determine, from the battery current comparison, the battery status as one of charging, 30 a reduction in engine loading, Which facilitates greater engine the accessories in the vehicle, reduced fuel consumption, more ef?cient accessory operation made possible by optimiZ ing the location and Wiring of the accessories, and reduced vehicle emissions corresponding to reduced engine loading and fuel consumption. Some vehicles may have several battery poWer supplies. form. Another embodiment of the present invention may be a system for monitoring the status of a battery. The system 50 FIG. 2A is a How diagram describing a system and method for monitoring the state of charge of a battery according to an embodiment of the present invention; FIG. 2B is a continuation of the How diagram of FIG. 2A; FIG. 2C is another continuation of the How diagram of FIG. 55 2A; FIG. 2D is still another continuation of the How diagram of FIG. 2A; e?icient manner, so as to maintain a high overall vehicle operating ef?ciency. FIG. 2E is a continuation of the How diagrams of FIGS. 2A, 2B, 2C and 2D; SUMMARY A system and method for monitoring the state of charge (“SOC”) of a battery is disclosed according to an embodiment to the present invention. The state of charge of a given battery, Which is its available capacity expressed as a percentage of its rated capacity, is monitored. The SOC is used to calculate hoW much longer the battery Will continue to perform before 60 FIG. 2F is a How diagram describing a virtual cell model algorithm of a system and method for monitoring the state of charge of a battery according to an embodiment of the present invention; 65 FIG. 2G is a How diagram describing a system and method for a poWer-up mode of a system and method for monitoring the state of charge of a battery according to an embodiment of the present invention; and US 8,154,252 B2 4 3 With reference to FIG. 2A, the appropriate operating mode FIG. 2H is a How diagram describing a system and method for a poWer-doWn mode of a system and method for monitor ing the state of charge of a battery according to an embodi ment of the present invention of the system is determined. At 102 a battery current “BC” is compared to a predetermined threshold charge value “thC.” If the battery current exceeds the threshold value a charge mode 200 is entered. Conversely, at 104 the battery current is com pared to a predetermined discharge threshold value “thD.” If the battery current is beloW the threshold value a discharge mode 300 is entered. If the battery current is betWeen thresh DETAILED DESCRIPTION The general arrangement of a system 10 for monitoring the olds thC and thD a quiescent mode 400 is entered. Details of charge mode 200 are shoWn in FIG. 2B, With additional reference to FIG. 1. At 202 the battery 12 current BC is compared to a predetermined battery current boost state of charge of a battery is shoWn in FIG. 1. In system 10 a battery 12 (Which may be a single battery or a plurality of batteries Wired in series and/or parallel) provides electrical poWer to one or more loads 14, such as engine controls and accessories connected to a vehicle electrical system. The state charge threshold value “thBC.” If the battery 12 current exceeds the threshold value thBC the system 10 indicates a of charge of battery 14 is monitored by a controller 16 via boo st mode charge cycle 204. In boost charging mode charger 20 increases the voltage it applies to battery 12 to a predeter signal inputs 17. Signal inputs 17 may include voltage and/or current measurements for battery 12 and/or individual cells mined level in order to achieve a desired, predetermined making up the battery. Controller 16 may provide predeter charging current. mined control signals 18 to a charger 20 corresponding to the state of charge of battery 14, thereby causing the charger to provide a determinable charging signal to the battery in order to restore the battery to a predetermined state of charge. Controller 16 may be realiZed using any combination of analog and/or digital electronic control architecture noW knoWn or later developed. For example, controller 16 may be At 206 the battery current BC is compared to a predeter 20 mined fraction of the amp-hour rating “Ahr” for the battery. If 25 mode charge cycle 208 is indicated. In ?oat charging mode only a small amount of charging current is applied to battery 12 by charger 20, the charging current being suf?cient to overcome internal discharge losses of the battery. the battery 12 current is beloW this threshold value a ?oat any conventional microprocessor, microcomputer, computer, If the battery current is betWeen thresholds thBC andAhr a or programmable logic device and may include a predeter bulk charge mode 210 is indicated. In bulk charging mode charger 20 supplies the maximum available charging current or maximum voltage that the charger is capable of delivering to the battery 12. With continued reference to FIG. 2B, step 212 determines Whether or not battery 12 is fully charged. If so, steps 214 mined set of instructions, such as a computer program, in a memory portion. The instructions alloW system 10 to function in accordance With a predetermined set of criteria, rules and 30 algorithms. A control signal 18 may be provided to charger 20 by controller 16. The control signal may take any conven tional form, such as analog or digital signals, including pro prietary and standardized serial and parallel data buses. Controller 16 may include a monitoring portion directed to 35 monitoring the state of the battery 12 and providing status indications used by the instructions to generate the aforemen tioned control signal. In some embodiments of the present invention the monitoring portion may be separate from con troller 16. In addition, some embodiments may or may not collectively control the operation of charger 20 in quiescent mode, detailed further beloW, for a predetermined period of time. If not, steps 216 collectively control charging of battery 12 and monitor the SOC of the battery, sWitching to quiescent mode for a predetermined period of time When a predeter mined maximum SOC is reached. In charging mode, Peukert’s equation is used to calculate 40 SOC, using Equations 1, 2 and 3 beloW: provide status indications to the controller. Charger 20 may be any conventional type of battery charger using any combination of analog and/or digital elec tronic control architecture, noW knoWn or later developed, to provide a predetermined charging signal to battery 12 to Cout:((—Iout)"n)* Tout Equation 2 SOC:(C0+Cin—Cout)/Cbatt Equation 3 Where “in” is de?ned as charge, and “out” is de?ned as dis charge. I is charging/ discharging current in Amps, T is charg ing/discharging time in hours, C is the Peukert capacity of digital form. the operating mode of the battery. When battery current is greater than charging threshold (thC), it is in charging mode. When battery current is smaller than discharging threshold (thD), it is in discharge mode. Otherwise it is considered to be in quiescent mode. Equation 1 45 restore the state of charge of the battery to a predetermined level. The charging signal may comprise a determinable volt age and/or current provided to battery 12 in analog and/or FIGS. 2A through 2G describe an example method for monitoring the state of charge of a battery according to an embodiment of the present invention. In FIGS. 2A through 2G positive values are used to represent charging current and negative values are used to represent discharging current. Charging and discharging thresholds are used to determine Cin:((Iin*Ef/100)"n)*T1n 50 battery (With C0 as initial capacity and Cbatt as rated battery capacity) in Amp -hours, and n is Peukert’ s exponent for that particular battery type. C0 is calculated from the SOC of the previous mode from Which it is transited. 55 of battery 12 discharge monitoring 300 With system 10. At With continued reference to FIG. 1, FIG. 2C shoWs details 302 the battery discharge current “—BC” is compared to a cold start threshold “thCS” to establish a basis for the discharge, such as an example embodiment Wherein load 14 is a starter motor for a prime mover for a vehicle. If the discharge current 60 exceeds the threshold “cold start,” steps collectively labeled the system and method for monitoring the state of charge of a 304 are executed to monitor charging of battery 12 and moni tor the SOC of the battery, sWitching to quiescent mode for a battery includes three modes of battery operation: charging mode (FIG. 2B), discharging mode (FIG. 2C) and quiescent mum SOC is reached. With general reference to FIGS. 2A-2G it can be seen that mode (FIG. 2D). As Will be detailed further beloW, in the various modes different algorithms are used to estimate the state of charge (SOC) of a battery. predetermined period of time When a predetermined maxi 65 At 306 battery discharge current is compared to a start threshold “thS.” If the discharge current exceeds this thresh old the steps collectively labeled 308 are executed to monitor US 8,154,252 B2 5 6 charging of battery 12 and monitor the SOC of the battery, switching to quiescent mode for a predetermined period of for the voltage to stabiliZe. It is dependent on the previous mode and the time elapsed from mode transition. The SOC Will approach neWSOC smoothly and reach the accurate value. A set of temperature compensation steps are shoWn in FIG. 2E. If the battery 12 temperature “T” is less than a predeter mined rated temperature “Tr” normal charging of the battery time When a predetermined maximum SOC is reached. If the battery discharge current is betWeen thresholds thCS and thS, a battery monitoring process “VCII,” detailed below, is indicated. In discharging mode (FIG. 2C), a combination of Peukert’ s occurs in the manner previously described, as indicated by equation and a virtual cell model algorithm (FIG. 2F) is used to calculate SOC, SOH (state of health), and Up (predicted 502. HoWever, if the battery temperature exceeds the rated temperature an achievable state of charge under such condi time to run) of a battery. Details of virtual cell mathematical tions is computed in steps collectively labeled 504. A control algorithm 600 for calculating the state of charge/ modeling techniques are described in US. patent application Ser. No. 11/035,609, commonly assigned With the instant state of health by means of a virtual cell computation is shoWn in FIG. 2F. A state of charge value is computed at 602. A application, the entire contents of Which are incorporated herein by reference thereto. In any mode, the calculated SOC, SOH and Up are compensated using ambient temperature as starting voltage for battery 12 and charging time is then computed at collective steps 604. Battery 12 cell voltage is a variable, as shoWn in FIG. 2E. then calculated at 606. A state of health value “SOH” is then Quiescent mode 400 is shoWn in FIG. 2D according to an embodiment of the present invention. At step 402 battery 12 cell voltage “Vca” is compared to a predetermined value. If the cell voltage is greater than the predetermined value a trickle charge mode is entered, shoWn collectively as 404. Once battery 12 is fully charged, as at 406, a quiescent mode 20 FIG. 2G. Data is Written to tWo “pages,” page 0 and page 1. Page 0 data is tested at 702 and, if not corrupted, page 1 data is stored at collective steps 704. If not, page 1 data is read at 706 and, if not found to be corrupted at 708, Written to page 0 is entered. If Vca is less than the predetermined value a state of charge value is computed at 408. If the computed state of charge value is less than Zero an “open circuit” fault is 25 at 710. 30 A system 10 poWer-doWn process 800 is shoWn in FIG. 2H. During poWer-doWn system 10 status data is Written to page 0 and page 1 (see FIG. 2G). With general reference to FIG. 2G, one advantage of the disclosed invention is the saving of battery data at poWer doWn. The saved data Will be read and checked at poWer up. Thus, every time the battery-monitoring device is turned on, it can start from the previous state of battery instead of resetting everything to a default condition. This alloWs the system and method to more accurately track 35 battery SOC. detected at 410. Conversely, if SOC equals Zero a poor con nection is detected at 412. In quiescent mode 400 the battery 12 current is very small. Consequently, battery voltage is used to calculate the SOC as a percentage, using Equation 4beloW: SOCI(a*Vca)-b, Equation 4 Where Vca is the actual cell voltage of battery in Volts. The tWo constants a and b may differ for different types of batter 1es. Since different algorithms are used for different battery In some embodiments of the present invention an aural or visual indication 22 (FIG. 1) regarding the state of the battery being charged may be provided to an operator. modes, consideration is preferably made during mode transi tion to avoid discontinuity of calculated SOC. When transited from any other mode to charging/ discharging mode, the ini tial battery capacity C0 can be calculated from the SOC of the computed at 608. Finally, the discharging time for battery 12 is adjusted at 610, taking into account the battery’s state of health and temperature. A process 700 for storing system 10 status data is shoWn in 40 previous mode, using Equation 5 beloW: In still other embodiments a prime mover 24 (FIG. 1) such as a vehicle engine may be automatically started to provide energy for charging the battery When the need for such a charge is detected by the system. Similarly, the prime mover C0:Cbatt*SOC, Cin:0, Cout:0 Equation 5 may be turned off When it is determined from monitoring the state of the battery that charging is no longer needed. This assures the SOC for the neW mode Will start from the value at the end of the previous mode. Transition from any other mode to quiescent mode (FIG. 2D) is someWhat more complex. Due to the typically sloW 45 the battery. Load shedding may be accomplished in a prede termined manner, such as in order of a predetermined loWest chemical reaction inside a battery, it takes some time for the to highest priority, for example. battery voltage in quiescent mode to stabiliZe When transited from charging or discharging mode. The time needed is deter 50 While this invention has been shoWn and described With respect to a detailed embodiment thereof, it Will be under stood by those skilled in the art that changes in form and detail thereof may be made Without departing from the scope of the 55 described herein is directed to monitoring the state of a bat mined by the details of the previous mode (start, cold start, partially charged, fully charged, and so on). Before the volt age is ?nally stabiliZed, the SOC calculated from voltage is not accurate. A curve-?tting technique is used here to esti mate the SOC in quiescent mode. At the beginning of the transition (from other mode to quiescent mode), the SOC is equal to the value at the end of the previous mode. Once the voltage has stabiliZed, the SOC is equal to the value calcu lated from the voltage. BetWeen these tWo moments, the calculated SOC is preferably curve-?tted, using Equation 6 claims of the invention. For example, although the invention tery under charge, it is readily apparent that the invention may be implemented in the form of an apparatus to control the operation of charger 20 (FIG. 1) in a predetermined manner, 60 such as tailoring the bulk, boost and ?oat charging modes to the state of charge and/ or state of health of battery 12, as Well as the demands imposed upon battery 12 by load 14. What is claimed is: beloW: S OCIoldS OC+(neWSOC-oldSOC)/ (timei remaineditoistableivoltageiinirninute) Some embodiments may further include means for shed ding loads 14 connected to the battery based upon the state of 1. A process for monitoring the status of a battery, com Equation 6 Where oldSOC is the SOC from previous calculation, neW SOC is the SOC calculated from voltage, and time_ remained_to_stable_voltage_in_minute is the time remained 65 prising the steps of: measuring a battery current; comparing the battery current to a predetermined thresh old; US 8,154,252 B2 8 7 determining, from the battery current comparison, the bat battery in the ?rst location is invalid and, if valid, pro viding the computed charge of the battery stored in the second location; and tery status as one of charging, discharging and quies cent; for a battery charging status determination, computing the charging state of charge of the battery; 5 for battery discharge status determination, comparing the second locations are both invalid. discharge current to a plurality of predetermined thresh 10. A system for monitoring the status of a battery, com prising: olds, selecting, based upon the result of the discharge current comparison, a basis for the discharge current from one of a plurality of predetermined discharge con a battery; a charger con?gured to charge the battery; ditions, and computing the discharging state of charge of the battery for the select discharge condition; and for quiescent status, computing the quiescent state of charge of the battery; and providing the computed state of charge of the battery in a quantitative form. a controller to control the charging operation of the charger; a plurality of signal inputs from the battery to the monitor ing portion of the controller; a load coupled to the battery; and a monitoring portion to monitor the state of the battery, the monitoring portion being con?gured to compare the bat 2. The process of claim 1, further comprising the step of computing the discharging state of charge of the battery using a virtual cell model. 3. The process of claim 1, further comprising the step of computing the discharging state of health of the battery using 20 4. The process of claim 1, for a battery charging status determination, compare the discharge current to a plu rality of predetermined thresholds, selecting, based 25 status as one of boost charging, bulk charging and ?oat charg ing. 5. The process of claim 1, for a battery charging status determination, further including the step of transitioning 30 from charging status to quiescent status When the battery is 6. The process of claim 1, for a battery quiescent status an aural or visual indication regarding the state of the battery 35 charging connection. 12. The system of claim 10 Wherein the computed state of charge is coupled to the controller to control the operation of the charger in a predetermined manner. 40 second locations. 9. The process of claim 8, further comprising the steps of: checking the computed state of charge of the battery in the ?rst location and, if valid, providing the computed charge of the battery stored in the ?rst location; checking the computed state of charge of the battery in the second location if the computed state of charge of the mined discharge conditions, and compute the discharg ing state of charge of the battery for the select discharge condition; for quiescent status, compute the quiescent state of charge of the battery; and provide the computed being charged. determination, further including the steps of monitoring for 7. The process of claim 1, further including the step of adjusting the computed state of charge of the battery based upon the temperature of the battery. 8. The process of claim 1, further comprising the step of storing the computed state of charge of the battery in ?rst and upon the discharge current comparison, a basis for the discharge current from one of a plurality of predeter state of charge of the battery in a quantitative form. 11. The system of claim 10, further including at least one of fully charged. an open circuit connection and monitoring for a poor battery tery current to a predetermined threshold; determine, from the battery current comparison, the battery status as one of charging, discharging and quiescent; for a battery charging status determination, compute the charging state of charge of the battery; forbattery discharge status a virtual cell model. determination, further including the steps of comparing the battery current to a predetermined threshold, determining, from the battery current comparison, the battery charging providing a predetermined default state of charge if the computed state of charge of the battery in the ?rst and 45 13. The system of claim 12, further including a prime mover con?gured to be controlled by the controller, the prime mover being started and stopped by the controller to provide energy for charging the battery in a predetermined manner. 14. The system of claim 12, further including a plurality of loads con?gured to be controlled by the controller, the loads being connected and disconnected from the battery based upon the state of the battery and a predetermined priority.