A SYSTEM AND METHOD FOR ESTIMATING SOC AND SOH OF A BATTERY

FIELD OF THE INVENTION

[001] The present invention generally relates to a system and method for estimating State-Of-Charge (SOC) and State-Of-Health (SOH) estimation of a battery, and more particularly, but not exclusively, to a simplified and more accurate estimation of SOC and SOH estimation for an automotive vehicle battery.

BACKGROUND OF THE INVENTION

[002] In modern automotive industry, the automotive vehicles are manufactured by incorporating a number of electrical and electronics components to increase safety and comfort for the driver as well as passengers. The automotive vehicles include an alternator and a battery for powering the electrical and electronics components. The alternator is used to power the electrical and/or electronics components when the engine is running and the battery is used to power the electrical and/or electronics component when the engine is OFF. Typically lead acid battery is used in the automotive industry. In recent development of automotive industry, vehicle manufacturer are desire to increase the electrification of vehicle component i.e. reducing the number of accessories that depend directly on the alternator for receiving the power. The electrification of accessories in the vehicle will improve the engine performance but it will increase the number of loads acting on the battery. Similarly, an electric vehicle is run by electric energy outputted from the battery. Hence, the battery is an important and necessary component in the modern automotive vehicles.

[003] During the lifetime of a battery, its performance or "health" tends to deteriorate gradually due to irreversible physical and chemical changes which take place with usage and with age until eventually the battery is no longer usable or dead. Hence the battery management is essential for the automotive vehicles and/or electric vehicles to improve the overall performance of the vehicle.

[004] State-Of -Charge (SOC) and State-Of-Health (SOH) of the battery is a reliable indicator for the battery management. The SOC provides a measure of how much energy remains stored in a battery. For example, in hybrid electrical vehicles and automotive vehicle, SOC can be used for driver notification about the battery status. There are several conventional methods and systems for estimating SOC are available. The conventional system and method are uses either current value or voltage value of the battery for estimating the SOC and the SOH of the battery. The conventional method which is uses voltage based SOC estimation does not provides an accurate estimation in real time. Hence, to get accurate measurements in the voltage based SOC estimation method, the battery needs to rest for at least an hour to attain equilibrium. The current integration or column counting based method for estimating the SOC also does not produce the accurate results for various reasons. Further, the current integration method uses more complex calculation such as integration, differentiation and transformation for estimation the SOC. Hence, the time for estimating the SOC is increases and also the system for estimating the SOC in the current integration method also complex in nature. In some of the conventional method, in addition to voltage or current, the temperature and hysteresis value of the battery is used for estimating the SOC. Thus increases the overall complexity of the system and method.

[005] In other side, if the calculation of the SOC i.e. remaining capacity of the battery is inaccurate, the operation efficiency of the vehicle is reduces, and a dangerous situation may be created. For example, the actual SOC in percentage is 90%, if a calculated SOC is 40%, the battery management system determines that the battery needs to be charged, and resulting in overcharging the battery or the battery management system instructs the driver/user to replace the new battery, resulting in expensive operating cost due to wastage of good battery. Similarly, an actual capacity is 30%, if a calculated capacity is 90%, the battery management system determines that the battery needs to be discharged, resulting in over-discharging the battery. Similarly, the overcharging and over-discharging of the battery can cause a dangerous situation such as firing or explosion of the battery.

[006] Accordingly there is a need in the art to provide a solution to one or more of above said problems. The present invention solves one or more of these problems in a unique and economical manner.

SUMMARY OF THE INVENTION

[007] It is a feature of the present invention to provide a system and a method which substantially overcomes the one or more of the above mentioned disadvantages.

[008] It is the principal object of the present embodiment is relates to a system and method for estimating State-Of-Charge and State-Of-Health of a battery.

[009] Another object of the present embodiment is relates to a reduced complexity method for estimating the SOC and SOH of the battery used in an automotive vehicle. The method uses both measured current value and the voltage value for estimating the SOC and SOH of the battery for improving the accuracy. The method does not consider the temperature and hysteresis value for estimating the SOC and SOH for reducing the complexity.

[0010] A method for estimating a State-Of-Charge and a State-Of-Health of a battery is provided. The method includes (i) receiving, at a calculation unit, a voltage value (V) and a current value (I) sensed in a sensor unit at a predefined intervals, (ii) estimating (a) a current discharge time (T;) for the current value and (b) a voltage discharge time (Tv) for the voltage value, (iii) estimating the SOC based on an maximum SOC, the current value (I), and the voltage discharge time and (iv) estimating the SOH based on the SOC. In another preferred embodiment, the method also includes (a) estimating an ideal SOC based on the maximum SOC, and the current value, (b) estimating the SOH based on the ideal SOC and the SOC, (c) initializing a value of the SOC to a value of the maximum SOC in each of the predefined interval. The voltage discharge time is computed based on a voltage fall rate, and the voltage fall rate is computed based on the current discharge time. The battery is a vehicle battery and the SOH and the SOC is estimated for the vehicle battery in real time.

[0011] In another aspect, a system for estimating a State-Of-Charge and a State-Of-Health of a battery is provided. The system includes (i) a sensor unit for sensing a voltage value and a current value of the battery in a predefined interval and (ii) a calculation unit that receives the voltage value and the current value sensed in the sensor unit in the predefined interval and estimates the SOC and the SOH.

BRIEF DISCRIPTION OF THE ACCOMPANYING DRAWINGS

[0012] The advantages and features of the invention will become more clearly apparent from the following description which refers to the accompanying drawings given as non-restrictive examples only and in which:

[0013] Figure 1 illustrates a system for estimating a SOC and SOH of a battery according to a preferred embodiment herein; and

[0014] Figure 2 is a flow diagram that illustrates a method for estimating a SOC and SOH of a battery according to a preferred embodiment herein.

DETAILED DISCRIPTION OF THE INVENTION

[0015] The present invention will be described herein below with reference to the accompanying drawings. A method for estimating the SOC and SOH of the battery is described.

[0016] The following description is of exemplary embodiment of the invention only, and is not limit the scope, applicability or configuration of the invention. Rather, the following description is intended to provide a convenient illustration for implementing various embodiments of the invention. As will become apparent, various changes may be made in the function and arrangement of the structural/operational features described in these embodiments without departing from the scope of the invention as set forth herein. It should be appreciated that the description herein may be adapted to be employed with alternatively configured devices having different shaped, components, and the like and still fall within the scope of the present invention. Thus the detailed description herein is presented for purposes of illustration only and not of limitation.

[0017] The present embodiment provides a method for estimating the SOC and SOH of the battery accurately with a reduced complexity. The battery is referred herein and exemplified as an automotive vehicle battery in the figures. However, the battery may comprise any device capable of operating similar to the automotive vehicle battery.

[0018] Figure 1 illustrates a system 100 for estimating the SOC and the SOH of the battery 102 according to a preferred embodiment herein. The system 100 includes a sensor unit 104 and a calculation unit 106. The sensor unit 104 includes a voltage sensor 104a for sensing the voltage value of the battery 102 and the current sensor 104b for sensing the current value of the battery 102. The calculation unit 106 is connected to the sensor unit 104 for estimating the SOC and the SOH of the battery 102. The sensor unit 104 is configured to sense the voltage value and the current value of the battery 102 in a predefined time interval. The calculation unit 106 receives the current value and the voltage value from the sensor unit 104 and estimates the SOC and the SOH of the battery 102 using both current value and the voltage value. The calculation unit 106 uses both current value and the voltage value to improve the accuracy in estimation of SOC and the SOH. The system 100 also includes a managing unit 108 which receives the value of SOC and SOH at each of the predefined interval from the calculation unit 106 through a Control Area Network (CAN). The managing unit 108 includes a display (not shown in Figure 1) which displays the status of the battery i.e. the display displays the value of SOC and SOH the battery 102 to the driver/user. In this preferred embodiment, the battery 102 is a vehicle battery used to power the electrical/electronic components in the vehicle. The system 100 estimates the SOC and SOH of the battery 102 (vehicle battery) in real time a predefined interval.

[0019] Figure 2 illustrates a method for estimating the SOC and the SOH of the battery in real time in accordance to the preferred embodiment herein. In step 202, initializing the value of a maximum SOC, a maximum ideal SOC and a SOH to 100. In step 204, the voltage value (V) and the current value (I) is received in the calculation unit 106 from the sensor unit 104 at a predefined interval. In step 206, the current discharge time (Tj) is calculated for the current value based on a battery capacity (C). In the preferred embodiment, the current discharge time (Tj) is calculated by divining the battery capacity (C) by the current value (I).

[0020] In step 208, a voltage fall rate is computed using the voltage value and the current discharge time. In the preferred embodiment, the voltage fall rate is computed in accordance with the below equation Vf=(V-Vth)/Ti, wherein Vth is a maximum threshold value of the battery and the Vth is defined by the battery manufacturer.

[0021] In step 210, the voltage discharge time (Tv) is calculated using the voltage value and the voltage fall rate. In the preferred embodiment, the voltage discharge time is computed in accordance with the below equation Tv=(V-VPREv)/Vf wherein VPREV is voltage value obtained from the sensor unit in the previous interval of the predefined interval. Initially the VPREV is equal to Vth. The calculation unit 106 stores the voltage value received from the sensor unit 104 in each of the predefined interval until the next interval.

[0022] In step 212, the SOC is calculated based on the maximum SOC, the current value and the voltage discharge time. In the preferred embodiment, the SOC is computed in accordance with the below equation SOC = SOC -(I*T * 100) -KC* 3600) maxwherein SOC max is the maximum SOC.

[0023] In step 214, an ideal SOC is calculated based on the maximum ideal SOC, and the current value. In the preferred embodiment, the ideal SOC is computed in accordance with the below equation SOC = SOC - (/ * 100) + (C * 3600) ideal max- ideal wherein SOC max-ideal is the maximum ideal SOC and initially the value SOC max-ideal is assigned to 100.

[0024] In step 216, the SOH is calculated based on the ideal SOC and the SOC. In the preferred embodiment, the SOH is computed in accordance with the below equation SOH = 100 -100 * (SOC - SOC) -r SOC ideal ideal

[0025] In step 218, the value of SOC is assigned to the maximum SOC (SOC max) and the value of ideal SOC (SOC ideal) is assigned to the maximum ideal SOC (SOC max. ideal.) SOCmax=SOC; bOC max-ideal = OC ideal;

[0026] The value of SOC and the SOH is transmitted to the managing unit 108 through a Control Area Network (CAN).

[0027] The steps 204-218 is repeated for the each of the predefined intervals for continuously monitoring the status of the battery in real time by calculating the SOC and the SOH in each of the predefined interval.

[0028] The present embodiment facilitates to provide the system and method for estimating the SOH and SOC of the battery with a reduced complexity and accurate estimation. The method uses both the current value and voltage value for estimating the SOC and the SOH of the battery. Further, the method does not use a surface charge, a temperature and hysteresis values of the battery for reducing the complexity.

[0029] Several exemplary embodiments have thus been described. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

We claim:

1. A method for estimating a State-Of-Charge and a State-Of-Health of a battery (102), said method comprising the steps of receiving (204), at a calculation unit (106), a voltage value and a current value sensed in a sensor unit (104) at a predefined intervals;

estimating (206 and 210) (i) a current discharge time (Tj) for said current value and (ii) a voltage discharge time (Tv) for said voltage value;

estimating (212) said SOC based on a maximum SOC, said current (I), and said voltage discharge time; and estimating (216) said SOH based on said SOC.

2. The method as claimed in claim 1, comprising:

estimating (214) an ideal SOC based on a maximum ideal SOC, and said current; estimating (216) said SOH based on said ideal SOC and said SOC; and assigning (218) (i) a value of said SOC to a value of said maximum SOC and (ii)

a value of said ideal SOC to a value of said maximum ideal SOC in each of said predefined intervals.

3. The method as claimed in claim 1, wherein said voltage discharge time is computed based on a voltage fall rate, and said voltage fall rate is computed (208) based on said current discharge time.

4. The method as claimed in claim 1, wherein said battery is a vehicle battery and said SOH and said SOC is estimated for said vehicle battery in real time.

5. A system (100) for estimating a State-Of-Charge and a State-Of-Health of a battery (102), said system comprising:

a sensor unit (104) for sensing a voltage value and a current value of said battery in a predefined interval; and

a calculation unit (106) that receives said voltage value and said current value sensed in said sensor unit and estimates said SOC and said SOH based on said method claimed in any of the preceding claims.