FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
A SYSTEM AND METHOD FOR DETERMINING STATE OF CHARGE
OF A BATTERY
MAHINDRA TWO WHEELERS LTD.,
an Indian Company of D-l block, Plot no. 18/2, Chinchwad, Pune - 411 019, Maharashtra, India
Inventor:
GANESAN ANAND
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE DISCLOSURE
The present disclosure relates to a system and method for determining the State Of Charge (SOC) of a battery.
More particularly, the present disclosure relates to a system and method for determining the State Of Charge (SOC) of a rechargeable battery.
DEFINITION
The expression 'battery' used hereinafter in the specification refers to but is not limited to rechargeable batteries of all types and applications including those that are used in the automotive industry.
This definition is in addition to that expressed in the art.
BACKGROUND
Battery performance deteriorates over time regardless of use. End-of-life of a battery is typically a state when it can no longer hold a proper charge or when available battery capacity drops to 60% or less than what the battery was rated for. Since batteries depend on a chemical reaction to produce electricity, their available capacity depends in part on how quickly they are charged or discharged relative to their total capacity. The total capacity is a measure of how much energy the battery can store. Available capacity is always less than total capacity. Life of lead acid batteries is typically limited by factors including age, design, cycle life and sulphation. Sulphation is a constant threat to batteries that are not fully re-charged.
The State of Charge (SOC) of a storage battery is the available capacity remaining in the battery to meet load demand at any instant.

Towards end-of-life, the battery's actual capacity is almost only 60% of its rated capacity and even if the battery were fully charged, its SOC would only be 60% of its rated capacity. Temperature and discharge rate effects reduce the effective capacity even further. To get an accurate estimate of the charge remaining in the battery, it is necessary that ageing, usage pattern and environmental factors are also taken into account.
One of the conventional methods of determining SOC is based on temperature compensated value of the specific gravity of the electrolytes. Since measuring specific gravity is not possible in batteries, typically used in automobiles, Open Circuit Voltage (OCV) is used as a parameter to predict SOC. But OCV can indicate SOC accurately only after the battery has a sufficient period of rest without which the measured voltage would be a misleading indicator of charge. Also, the OCV Vs SOC relation varies between batteries, due to several factors like temperature, ageing, electrolyte volume, internal construction and the like.
Thus there is felt a need for a method and a system that provides a real time estimate of the SOC of a battery by taking into account the variables mentioned herein above that affect battery life.
OBJECTS
Some of the objects of the present disclosure aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative are described herein below:
An object of the disclosure is to provide a method and a system for accurately determining State Of Charge (SOC) of a battery.
Another object of the disclosure is to provide a method and a system for determining State Of Charge (SOC) of a battery by assessing variables

including temperature, ageing, electrolyte volume, internal construction that affect battery life.
Yet another object of the disclosure is to provide a method and a system for determining State Of Charge (SOC) of a battery by eliminating cumulative error that occurs in energy measurement.
Still another object of the disclosure is to provide a method and a system for
determining State Of Charge (SOC) of a battery, irrespective of the electrical
systems' quiescent current differences.
An additional object of the disclosure is to provide a method and a system for determining State Of Charge (SOC) of a battery that can be used in any battery circuit including that of an automobile.
Yet another object of the disclosure is to provide a system for determining and displaying State Of Charge (SOC) of a battery, such system being reliable, cost effective and efficient.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
In accordance with one aspect of the present disclosure, there is provided a
system for determining State Of Charge (SOC) of a battery, the system
comprising:
• a plurality of sensors configured to sense battery parameters selected from
the group consisting of battery current, battery voltage and battery temperature;

• a processing unit comprising an Analog to Digital Converter (ADC) module configured to generate digital values corresponding to the sensed battery parameters;
• a self-learning module configured to define a plurality of calibrating reference values including zero current value, discharge limit value, charge limit value and rate of battery discharge and rate of battery charging, based on a sensed initial battery current;
• a first SOC estimation module configured to determine initial SOC of the battery based on the sensed battery voltage, the sensed battery temperature and the rate of battery discharge;
• a current activity checking module configured to determine a deviation in the value of the sensed battery current with respect to the zero current value;
• a coulomb counting module configured to determine the battery current polarity based on the determined deviation; and
% a second SOC estimation module configured to calculate a dynamic SOC of the battery based on the determined battery current polarity.
In accordance with one embodiment, the system described herein above further comprises at least one of an initialization module configured to initialize the processing unit and a timer module configured to generate predetermined time delays.
In accordance with another embodiment, the system described herein above further comprises a sleep mode activation module configured to disable at least one of the self-learning module, the first SOC estimation module, the coulomb counting module and the second SOC estimation module for a pre-determined time duration.

In accordance with yet another embodiment, the system described herein above further comprises a plurality of registers configured to store at least one of the digital values corresponding to the sensed battery parameters and the plurality of calibrating reference values.
In accordance with still another embodiment, the system described herein above further comprises a display means configured to display the calculated dynamic SOC, the display means being selected from the group consisting of Liquid Crystal Display (LCD), Light Emitting Diode (LED) and Segment display.
In accordance with another aspect of the present disclosure, there is provided a method for determining the State Of Charge (SOC) of a battery, the method comprising the steps of:
• initializing a processing unit;
• sensing battery current including initial battery current and dynamic battery current;
• defining a plurality of calibrating reference values including zero current value, discharge limit value, charge limit value, rate of battery charging and rate of battery discharge, based on the sensed initial battery current;
• sensing battery voltage and battery temperature;
• calculating initial SOC of the battery based on the sensed battery voltage, the sensed battery temperature and the rate of battery discharge;
• determining current activity of the battery;
• determining battery current polarity based on the determined current activity with respect to the calibrating reference values;
• calculating a dynamic SOC of the battery based on the determined battery current polarity; and
• displaying the calculated SOC.

Typically, the step of initializing, described herein above includes the steps of initializing input ports, output ports, ADC module and a timer module of the processing unit.
Typically, the step of calculating initial SOC of the battery, described herein above includes the steps of:
• selecting appropriate battery characteristics based on the sensed battery temperature; and
• co-relating the sensed battery voltage and the rate of battery discharge with a selected battery characteristic using a 3D curve fitting mechanism by referencing a look up table comprising the sensed battery voltage, the sensed battery temperature and associated SOC.
Typically, the step of checking current activity, described herein above includes the steps of:
• sensing the dynamic battery current;
• cumulating the current values corresponding to the sensed dynamic battery current in a first register for a first pre-determined time duration; and
• cumulating the cumulated current va\ue in the first register into a second register for a second pre-determined time duration; and
• checking a deviation in the cumulated current value in the second register with respect to the calibrating reference value after a third pre-determined time duration.
Typically, the step of calculating a dynamic SOC of the battery, described herein above further comprises the steps of:
• cumulating the current value corresponding to the sensed battery current in
at least one of:

o a charge register and recording the associated rate of charge and the battery temperature for positive battery current polarity; and o a discharge register and recording the associated rate of discharge and the battery temperature for negative battery current polarity;
• calculating net charge by at least one of:
o co-relating the recorded rate of battery charging and the recorded battery temperature with appropriate battery charging compensation characteristics using a 3D curve fitting mechanism by referencing a look up table comprising the rate of battery charging, the sensed battery temperature and associated charge compensation factor; and
o co-relating the recorded rate of battery discharge and the recorded battery temperature with appropriate battery discharging compensation characteristics by 3D curve fitting mechanism by referencing a look up table comprising the rate of battery discharge, the sensed battery temperature and associated charge compensation factor;
• adding the calculated initial SOC and the calculated net charge for positive battery current polarity; and
• subtracting the calculated net charge from the calculated initial SOC for negative battery current polarity.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The method and system for determining State Of Charge (SOC) of a battery of the present disclosure will now be described with the help of accompanying drawings, in which:
Figure 1 illustrates a block diagram of the architecture of a system for determining State Of Charge (SOC) of a battery in accordance with one aspect of the present disclosure;

FIGURE 2 illustrates a flow diagram indicating the steps performed by an initialization module and a self-learning module in a method for determining State Of Charge (SOC) of a battery in accordance with another aspect of the present disclosure;
FIGURE 3 illustrates a flow diagram indicating steps performed by a first SOC estimation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure;
FIGURE 4 illustrates a flow diagram indicating steps performed by a current activity checking module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure;
FIGURE 5 illustrates a flow diagram indicating steps performed by a coulomb counting module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure;
FIGURE 6 illustrates a flow diagram indicating steps performed by a second SOC estimation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure; and
FIGURE 7 illustrates a flow diagram indicating steps performed by a sleep mode activation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure.
DETAILED DESCRIPTION
A system and a method of the present disclosure will now be described with reference to the embodiments which do not limit the scope and ambit of the disclosure.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Conventional methods for determining the SOC of a battery are not accurate since they do not take into account factors like temperature, ageing, electrolyte volume, internal construction and the like that contribute considerably to the life of a battery and accordingly to the estimation of available capacity of the battery.

The present disclosure envisages a method and a system to overcome the drawbacks of the prior art. The initial state of a battery is estimated by temperature compensated OCV (Open Circuit Voltage) versus SOC (State Of Charge) characteristics, followed by dynamic prediction of SOC using temperature compensated columbic / energy measurement. The method in accordance with the present disclosure includes a 'self learning feature' to predict OCV based initial SOC of a battery more accurately irrespective of the quiescent current differences of the electrical systems.
The method in accordance with the present disclosure is applicable to secondary (rechargeable) batteries including lead acid batteries, particularly used in two / three wheelers and in general to any automobile. For ease of explanation, the method is described with reference to estimating SOC of secondary batteries used in an automobile. However, the method in accordance with the present disclosure is also applicable to secondary batteries, in general and traction batteries used in electric vehicles, hybrid vehicles and the like.
The system and method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure is described herein below with respect to Figure 1 through Figure 7 wherein key components of the system are generally referenced by numerals as indicated.
Figure 1 illustrates a block diagram of the architecture of a system 100 for determining State Of Charge (SOC) of a battery in accordance with one aspect of the present disclosure. As illustrated, the system 100 comprises:
a processing unit 102;
an ADC(Analog to Digital Converter) module 104;
at least one sensor 106;
a timer module 112;
an initialization module 110;

a self-learning module 114;
a first SOC estimation module 116;
a current activity checking module 124;
a coulomb counting module 118;
a second SOC estimation module 120;
a sleep mode activation module 126 ;
a displaying means 122; and
a plurality of registers 134.
The system 100 is utilized to measure State Of Charge (SOC) of a battery 108 in accordance with an embodiment of the present disclosure. The ADC module 104 receives sensed data corresponding to battery parameters including current, voltage and temperature of the battery 108. The sensors 106 sense battery parameters and generate sensed data which is further provided to pre-defined channels of the ADC module 104. The ADC module 104 receives the sensed data and correspondingly generates digital data comprising sensed current value, sensed voltage value and sensed temperature value. The battery voltage sensed for the initial state of the battery 108 is typically an open circuit voltage OCV. The ADC module 104 is typically inbuilt within the processing unit 102. In accordance with another embodiment, the ADC module 104 is a separate unit associated with the processing unit 102. The processing unit 102 is typically a microcontroller that serves as a centralized processing unit of the system 100 and is associated with various modules of the system 100 for estimating the State Of Charge (SOC) of the battery. The processing unit 102 further comprises the timer module 112 for providing pre-determined time delays for executing pre-determined steps. An IDLE counter (not shown) is typically utilized here to set the processing unit 102 in idle mode for pre-defined time duration. The ADC module 104, the timer module 112 and input and output ports (not shown) of the processing unit 102 are initialized by the initialization

module 110. The sensed voltage value and sensed temperature value generated by the ADC module 104 is utilized by the first SOC estimation module 116 to calculate an initial State Of Charge (SOC). The initial state of the battery 108 represents the condition when there is no load connected to the battery 108 and hence the first SOC estimation module 116 utilizes the sensed voltage value which is the open circuit voltage (OCV) of the battery 108 to estimate temperature compensated initial State Of Charge (SOC) of the battery 108. After calculating the initial State Of Charge (SOC), the current activity checking module 124 checks for any current activity by determining dynamic current of the battery 108. If any current activity is detected, the coulomb counting module 118 determines the polarity of the battery 108 current. Based on the polarity of the battery 108 current, the second SOC estimation module 120 calculates the net charge flowing in and out of the battery and estimates the dynamic SOC which is displayed by the displaying means 122. The displaying means 122 is typically an SOC indicator being at least one of an LED display, an LCD display, a segment display and the like. The plurality of registers 134 is interfaced with the processing unit 102 for storing data processed by the processing unit 102. The plurality of registers typically includes a charge register, a discharge register, first register and a second register..
FIGURE 2 illustrates a flow diagram indicating the steps performed by an initialization module and a self-learning module in a method for determining State Of Charge (SOC) of a battery in accordance with another aspect of the present disclosure. The initialization module 110 typically performs the following steps;
initialization of data ports of the processing unit 102; initialization of the ADC module 104; and initialization of the timer module 112.

The self-learning module 114 typically performs the steps including:
reading sensed current value (A) from the pre-defined current channel of
the ADC module 104; and
defining auto calibrating reference values including zero current value,
discharge limit value (B), charge limit value (C) and rate of discharge
(D).
The reference values including zero current value, discharge limit value (B) and charge limit value (C) are constants for a particular system but vary for each system.
FIGURE 3 illustrates a flow diagram indicating steps performed by a first SOC estimation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure. The first SOC estimation module 116 typically performs the steps including:
reading sensed voltage value (X) and sensed temperature value (Y) from
the pre-defined channels of the ADC module 104;
selecting appropriate battery characteristics based on the sensed
temperature value (Y) corresponding to the sensed temperature of the
battery 108;
co-relating the sensed battery voltage (X) and at least one reference value,
typically the rate of discharge (D) with the selected battery characteristic
using a 3D curve fitting mechanism by referencing a look up table
comprising the sensed battery voltage, the sensed battery temperature and
associated SOC.
The look up tables are stepwise approximations of the performance response curves which represent the battery performance as a function of temperature,

rate of discharge or other parameters. The first SOC estimation module 116 estimates the temperature compensated State Of Charge (SOC) of the battery 108 when there is no load connected to the battery.
FIGURE 4 illustrates a flow diagram indicating steps performed by a current activity checking module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure. The current activity checking module 124 typically performs the steps including:
reading the sensed current value (A) from the pre-defined current channel of the ADC module 104;
repeatedly cumulating the sensed current value (A) in a first register after a pre-determined first time duration; and
checking whether the time elapsed is less than or equal to a predetermined second time duration,
If the time elapsed is less than or equal to the pre-determined second time duration, control is transferred back to the current activity checking module 124, as illustrated in FIGURE 4.
If the time elapsed is greater than the pre-determined second time duration, the value stored in the first register is cumulated in a second register. Again a check is performed to ascertain whether the time elapsed is less than or equal to a predetermined third time duration.
If the time elapsed is less than or equal to the third pre-determined time duration, control is transferred back to the current activity checking module 124, as illustrated in FIGURE 4.

If the time elapsed is greater than the pre-determined third time duration, a check for current activity is initiated. When there is any deviation in the sensed current value (A) with respect to the calibrated reference values as mentioned herein above with reference to FIGURE 2, current activity is said to exist.
If there is no current activity observed, the steps performed include the
following:
incrementing an IDLE counter; and
checking whether the time elapsed is greater than or equal to a predetermined fourth time duration, typically 2 hours.
If the time elapsed is greater than or equal to the pre-determined fourth time duration, then control is transferred to the sleep mode activation module 126 as illustrated in FIGURE 7.
If the time elapsed is less than the pre-determined fourth time duration, then control is transferred to the coulomb counting module as illustrated in FIGURE
5.
If there is current activity observed, control is transferred to the coulomb counting module as illustrated in FIGURE 5.
FIGURE 5 illustrates a flow diagram indicating steps performed by a coulomb counting module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure. The coulomb counting module 118 typically includes a step of:
determining battery current polarity, wherein the polarity is determined with respect to at least one calibrated reference value.

Positive or negative polarity depends on how much deviation and on which side of the predetermined limits of the calibrated values (as mentioned herein above with reference to FIGURE 3) is seen.
The steps after checking for battery current polarity include the following:
if the polarity is positive, the sensed current value (A) is cumulated in the charge register and the sensed temperature value (Y) and rate of charge (E) are recorded for reference;
if the polarity is negative, the sensed current value is cumulated in the discharge register and the temperature (Y) and rate of discharge (D) are recorded for reference; resetting the IDLE counter; and
checking whether the time elapsed is less than or equal to a fifth predetermined time duration, typically of 16 seconds.
If the time elapsed is less than or equal to the pre-determined fifth time duration then the control is shifted to the current activity checking module 124, as illustrated in FIGURE 4.
If the time elapsed is greater than the pre-determined fifth time duration, then control is transferred to the second SOC estimation module 120, as illustrated in FIGURE 6.
FIGURE 6 illustrates a flow diagram indicating steps performed by a second SOC estimation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure. As illustrated, the second SOC estimation module 120 typically performs the steps including:
compensating the charging Ampere hour (Ah) by 3D curve fitting mechanism using values of the recorded rate of charge (E) and temperature (Y). The 3D curve fitting mechanism merges the recorded

rate of charge (E) and recorded sensed temperature value (Y) in the charging compensation characteristics, wherein charging compensation characteristics are referenced from a look up table comprising rate of charge (E), temperature (Y) and a charge compensation factor; compensating the discharging Ah by 3D curve fitting technique using recorded rate of discharge (D) and recorded sensed temperature value (Y). The 3D curve fitting mechanism merges the recorded rate of discharge (E) and recorded sensed temperature value (Y) in the discharging compensation characteristics, wherein the discharging compensation characteristics are referenced from a look up table comprising rate of discharge (D), temperature (Y) and a discharge compensation factor; calculating net charge with polarity; and checking for polarity with respect to the calibrated reference values.
The steps performed by the second SOC estimation module after checking for
polarity include the following:
if the polarity is positive, the calculated net charge is combined with the
initial State Of Charge (SOC) calculated by the first SOC estimation
module 116, thus determining the dynamic State Of Charge (SOC) as
indicated by the FIGURE 6;
if the polarity is negative, the calculated net charge is subtracted from the
initial State Of Charge (SOC) calculated by the first SOC estimation
module 116, thus determining the dynamic State Of Charge (SOC) as
indicated by the FIGURE 6;
displaying the State Of Charge (SOC) in the displaying means 122; and
transferring control to the current activity checking module 124, as
illustrated in FIGURE 4.

FIGURE 7 illustrates a flow diagram indicating steps performed by a sleep mode activation module in a method for determining State Of Charge (SOC) of a battery in accordance with the present disclosure. The sleep mode activation module 126 typically performs steps including:
reading the sensed current value (A) from the pre-defined current channel
of the ADC module 104;
auto calibrating reference values including zero current value, discharge
limit value (B) charge limit value (C) and Rate of Discharge (D);
reading the sensed voltage value (X) and the sensed temperature value
(Y) from the pre-defined channels of the ADC module 104;
selecting appropriate battery characteristics based on temperature (Y)
from a look up table;
calculating SOC by 3D curve fitting mechanism using sensed voltage
value (X) and the sensed temperature value (Y) as inputs and selected
battery characteristics in the look up table comprising open circuit voltage
value (X), the sensed temperature value (Y), and State Of Charge (Z);
resetting the IDLE counter; and
activating sleep mode.
The sleep mode activation module 126 disables all current draining / consuming signal lines which are directly connected to the battery 108 except the supply to the system 100 by activating a signal disabling circuitry. The sleep mode activation module 126 also activates hibernate or a sleep mode of the processing unit 102 of the system 100 to put the system in sleep mode.
The system 100 wakes up from sleep mode by a predetermined wakeup signal, generated either internally and / or external to the system 100 to perform functions as specified in a set of predetermined steps of the method in accordance with the present disclosure. Also, the apparatus wakes up from the

sleep mode whenever an activity is observed in the channel of the ADC module 104 predetermined for current measurement, i.e. if any deviation / change in sensed current value is observed with respect to the calibrated zero current value.
The method in accordance with the present disclosure includes utilization of a hybrid method combining both SOC prediction based on OCV and SOC prediction based on energy measurement. The drawback of cumulative error in energy measurement is overcome by compensating the SOC value based on temperature compensated OCV after sufficient rest, after the electrical systems' has been switched off. For improving the accuracy of dynamic prediction, the method in accordance with the present disclosure also compensates the predicted SOC value with respect to factors such as rate of discharge, rate of charging, ageing, self discharge and temperature. The method in accordance with the present disclosure has a 'self learning feature' to predict OCV based on the initial SOC of the battery more accurately, irrespective of the quiescent current differences of the electrical systems. For instance, after the SOC estimation unit is connected to battery, the system as envisaged by the present disclosure automatically calibrates itself with respect to the electrical systems' drain current.
In accordance with another embodiment of the present disclosure, the sleep mode activation module reduces current consumption when the system is in a rest or unused condition. It wakes up from sleep mode to measure self discharge current of battery.
The method in accordance with the present disclosure as illustrated in the flow charts of FIGURES 2 to 6 is based on parameters mentioned herein above. However, in accordance with various aspects of the present disclosure, there can be additional parameters / modules added to the method for estimation of SOC,

like self discharge compensation module, compensation module for ageing of the battery and the like to arrive at more accurate SOC estimation. For instance, an estimation module for SOH (State Of Health) of a battery can be additionally added to this SOC estimation system.
The system for determining State Of Charge (SOC) of a battery, as described herein above, finds application in batteries that are employed for illumination, ignition, traction and such other purposes in automotive vehicles.
TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The technical advancements offered by the present disclosure include the realization of:
a method and a system for accurately determining State Of Charge (SOC) of a battery;
a method and a system for determining State Of Charge (SOC) of a battery by including variables like temperature, ageing, electrolyte volume, internal construction that affect battery life;
a method and a system for determining State Of Charge (SOC) of a battery by eliminating cumulative error that occurs in energy measurement;
a method and a system for determining State Of Charge (SOC) of a battery, irrespective of electrical systems' quiescent current differences;
a method and a system for determining State Of Charge (SOC) of a battery that can be used in any automobile; and

a system for determining and displaying State Of Charge (SOC) of a battery, such system being reliable, cost effective and efficient.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.
Wherever a range of values is specified, a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is

to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:
1. A system for determining State Of Charge (SOC) of a battery, said system comprising:
• a plurality of sensors configured to sense battery parameters selected from the group consisting of battery current, battery voltage and battery temperature;
• a processing unit comprising an Analog to Digital Converter (ADC) module configured to generate digital values corresponding to the sensed battery parameters;
• a self-learning module configured to define a plurality of calibrating reference values including zero current value, discharge limit value, charge limit value and rate of battery discharge and rate of battery charging, based on a sensed initial battery current;
• a first SOC estimation module configured to determine initial SOC of the battery based on the sensed battery voltage, the sensed battery temperature and said rate of battery discharge;
• a current activity checking module configured to determine a deviation in the value of the sensed battery current with respect to said zero current value;
• a coulomb counting module configured to determine the battery current polarity based on the determined deviation; and
• a second SOC estimation module configured to calculate a dynamic SOC of the battery based on the determined battery current polarity.

2. The system as claimed in claim 1 further comprising at least one of an initialization module configured to initialize said processing unit and comprises a timer module configured to generate predetermined time delays.
3. The system as claimed in claim 1 further comprising a sleep mode activation module configured to disable at least one of said self-learning module, said first SOC estimation module, said coulomb counting module and said second SOC estimation module for a pre-determined time duration.
4. The system as claimed in claim 1 further comprising a plurality of registers configured to store at least one of said digital values corresponding to the sensed battery parameters and said plurality of calibrating reference values.
5. The system as claimed in claim 1 further comprising a display means configured to display the calculated dynamic SOC, said display means being selected from the group consisting of Liquid Crystal Display (LCD), Light Emitting Diode (LED) and Segment display.
6. The system as claimed in claim 1 further comprising at least one of a self-discharge compensation module, compensation module for ageing and estimation module for SOH (State Of Health) of a battery.
7. A method for determining the State Of Charge (SOC) of a battery, said method comprising the steps of:
• initializing a processing unit;

• sensing battery current including initial battery current and dynamic battery current;
• defining a plurality of calibrating reference values including zero current value, discharge limit value, charge limit value, rate of battery charging and rate of battery discharge, based on the sensed initial battery current;
• sensing battery voltage and battery temperature;
• calculating initial SOC of the battery based on the sensed battery voltage, the sensed battery temperature and said rate of battery discharge;
• determining current activity of the battery;
• determining battery current polarity based on the determined current activity with respect to said calibrating reference values;
• calculating a dynamic SOC of the battery based on the determined battery current polarity; and
• displaying the calculated SOC.

8. The method as claimed in claim 7, wherein the step of initializing includes the steps of initializing input ports, output ports, ADC module and a timer module of said processing unit.
9. The method as claimed in claim 7, wherein the step of calculating initial SOC of the battery includes the steps of:

• selecting appropriate battery characteristics based on the sensed battery temperature; and
• co-relating the sensed battery voltage and said rate of battery charging with a selected battery characteristic using a 3D curve fitting mechanism by referencing a look up table comprising said sensed battery voltage, said sensed battery temperature and associated SOC.

10. The method as claimed in claim 7, wherein the step of checking current
activity includes the steps of:
• sensing the dynamic battery current;
• cumulating the current values corresponding to the sensed dynamic battery current in a first register for a first pre-determined time duration; and
• cumulating the cumulated current value in said first register into a second register for a second pre-determined time duration; and
• checking a deviation in the cumulated current value in said second register with respect to said calibrating reference value after a third predetermined time duration.
11. The method for as claimed in claim 7, wherein the step of calculating a
dynamic SOC of the battery further comprises the steps of:
• cumulating the current value corresponding to the sensed battery
current in at least one of:
o a charge register and recording the associated rate of charge and the battery temperature for positive battery current polarity; and o a discharge register and recording the associated rate of discharge and the battery temperature for negative battery current polarity;
• calculating net charge by at least one of:
o co-relating the recorded rate of battery charging o and the recorded battery temperature with appropriate battery charging compensation characteristics using a 3D curve fitting mechanism by referencing a look up table comprising said rate of battery charging, said sensed battery temperature and associated charge compensation factor; and

o co-relating the recorded rate of battery discharge and the recorded battery temperature with appropriate battery discharging compensation characteristics by 3D curve fitting mechanism by referencing a look up table comprising said rate of battery discharge, said sensed battery temperature and associated charge compensation factor;
• adding the calculated initial SOC and the calculated net charge for positive battery current polarity; and
• subtracting the calculated net charge from the calculated initial SOC for negative battery current polarity.