DESC:FIELD OF INVENTION
[0001] The present disclosure relates to the field of battery management and, more particularly relates to a Battery Management System (BMS) for a lithium iron phosphate battery where cell equalization is not required.

BACKGROUND OF THE INVENTION
[0002] Batteries are extensively being used in transportation, military, aerospace and portable applications. Also, battery driven Electric Vehicles (EVs) are replacing conventional vehicles to reduce pollution and dependence on conventional energy resources.
[0003] Generally, batteries operate in the form of battery packs consisting of string of cells in series and parallel manner providing high voltage, current and power as required for different applications. In an ideal situation, each individual battery in the pack equally contributes to the system, but when it comes to batteries, all batteries are not made the same. Even if the batteries exhibit the same chemistry with the same physical size, shape, and weight, they can have different total capacities, different self-discharge rates, different internal resistances, and different aging which all have an effect on the overall battery life equation. These differences make batteries to face a major challenge of battery life, which can be extended by cell balancing.
[0004] Cell balancing is a technique that improves battery life by maximizing the capacity of a battery pack with multiple cells in series, ensuring that all of its energy is available for use. The two methods of cell balancing are passive and active cell balancing which offers different features to the battery pack. In passive cell balancing, a threshold value is selected and if difference between any two cells exceeds that threshold, then excess energy is wasted through bypass resistors using bypass resistors. Generally passive balancing is implemented while charging only. Active cell balancing is a charge redistribution method in which excess energy is distributed from highly charged cell to low charge cell using inductors or capacitors until both are equalized.
[0005] Battery management systems (BMS) monitors the critical parameters like voltage, capacity and performs cell balancing in a battery pack whenever required. The health of each individual battery cell in the pack is determined based on its state of charge (SOC) measurement, which measures the ratio of its remaining charge to its cell capacity. The SOC uses battery measurements such as voltage, integrated charge, and discharge currents and temperature to determine the charge remaining in the battery.
[0006] Although the aforesaid battery management system provides cell balancing, the existing passive active battery management system are often subjected to heating as the cells are charged to the maximum voltages prescribed by the manufacturer that leads to battery overcharging and de-equalization of cells leading to high power consumption by the BMS and reduced battery life.
[0007] Further, in the case of lithium iron phosphate batteries, the battery has high single-cell voltage (the voltage in the concentrated area of stored power is 3.2V), high cycle charge and discharge times, low self-discharge rate, not afraid of over-charge, light weight, small size, large energy storage capacity, and high energy efficiency to weight ratio. However, lithium iron phosphate batteries have a major physical weakness as overcharging the lithium iron phosphate battery causes permanent damage to the battery.
OBJECTIVES OF THE INVENTION
[0008] The present disclosure relates to a Battery Management System (BMS) for a lithium iron phosphate battery where equalization is not required.
[0009] It is an object of the present disclosure to provide a Battery Management System (BMS) with active equalization to monitor voltage of each cell and to start equalization only when the cell voltage exceeds the threshold value.
[0010] It is an object of the present disclosure to provide system and method of battery cell equalization for a lithium iron phosphate battery where equalization is performed only when the battery is in charged state i.e., when the battery charging process is over.
[0011] It is an object of the present disclosure to provide a method of self-equalization in battery cells by avoiding high level charging and discharging of the battery cells.
[0012] It is an object of the present disclosure to provide a method of battery cell equalization for a lithium iron phosphate battery which provides self-equalization of battery cells by charging the cells below high level of voltage. The method of battery equalization reduces heating of the cells and increases the cell life.
[00013] These and other objectives and advantages of the present disclosure will become more apparent when reference is made to the following description.
SUMMARY
[0014] In a first aspect, the present disclosure provides a system for self-equalization of cells of a battery. The system comprises the battery having at least two cells, a Battery Management System (BMS) connected to the battery. The BMS monitors each cell voltage and performs active cell equalization. The system also includes a charge controller connected to the BMS
[0015] The charge controller automatically reduces a boost-cut off voltage. The system further includes a microcontroller of the charge controller. The micro-controller is connected to a relay to automatically stop charging when a pre-defined threshold value is reached, where the pre-defined threshold value is the difference of voltage between at least two cells. Where the self-equalization of at least two cells occurs only when the battery is fully charged and the cell voltage exceeds the pre-defined threshold value.
[0016] In a second aspect, the present disclosure provides a method of self-equalization of cells of the battery. The method comprises the step of monitoring each cell voltage and performing active cell equalization of the battery cells, automatically reducing the boost-cut off voltage, automatically stop charging when a pre-defined threshold value is reached, wherein the pre-defined threshold value is the difference of voltage between at least two cells. Where the self-equalization of at least two cells occurs only when the battery is fully charged and the cell voltage exceeds the threshold value.
BRIEF DESCRIPTION OF DRAWINGS
[0017] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
[0018] FIG. 1 illustrates a system for self-equalization of cells of a battery, in accordance with an embodiment of the present disclosure; and
[0019] FIG. 2 illustrates a flow chart representing steps of a method, in accordance with an embodiment of the present disclosure.
[0020] It should be noted that the accompanying figures are intended to present illustrations of exemplary embodiments of the present disclosure. These figures are not intended to limit the scope of the present disclosure. It should also be noted that accompanying figures are not necessarily drawn to scale.
DETAILED DESCRIPTION
[0021] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
[0022] Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present technology. The appearance of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but no other embodiments.
[0023] Moreover, although the following description contains many specifics for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present technology. Similarly, although many of the features of the present technology are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the present technology is set forth without any loss of generality to, and without imposing limitations upon, the present technology.
[0024] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures proceeded by "comprises.. a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or additional devices or additional sub-systems or additional elements or additional structures.
[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The method, system, and examples provided herein are illustrative only and not intended to be limiting.
[0026] The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the term sterile barrier and sterile adapter denotes the same meaning and may be used interchangeably throughout the description.
[0027] The present disclosure relates to a system 100 and a method 200 for self-equalization of cells of a lithium iron phosphate (LiFePO4) battery 102. Referring to Figure 1, the system 100 for self-equalization of cells of a lithium iron phosphate (LiFePO4) battery 102, is shown. The system comprises a Battery Management System (BMS) for the battery 102 where equalization is not required, when the battery 102 is fully charged. The BMS 104 is in-built battery management system.
[0028] The BMS is an electronic system that manages a rechargeable battery, such as by protecting the battery from operating outside its safe operating area, monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and/or balancing it. A BMS is essential for ensuring the safe and efficient operation of rechargeable batteries, and is found in a wide range of applications, from laptops and smartphones to electric vehicles and grid energy storage.
[0029] According to an embodiment of the present disclosure, the BMS 104 performs active equalization to monitor each cell voltage and starts the equalization only when the cell voltage exceeds a pre-defined threshold voltage value. Active cell balancing is a technology used in battery packs with multiple cells connected in series. Its purpose is to maintain equal levels of charge (State of Charge, SoC) across all the cells in the pack. This is crucial because unevenly charged cells can lead to overcharging of some cells and undercharging of others, both of which can damage the cells and shorten the lifespan of the entire pack. The performance and capacity of the entire pack is limited by the weakest cell. When one cell is depleted, the whole pack stops delivering even if other cells still have energy left.
[0030] Unlike passive balancing which dissipates excess energy from overcharged cells as heat, active balancing actively redistributes charge between cells via electronic circuits. This involves monitoring the voltage and SoC of each individual cell, controlling the monitored data, the BMS decides which cells need to be balanced and activates the balancing circuits, charge transfer from cells with higher SoC to those with lower SoC. This technique may involve capacitors, inductors, DC/DC converters, or switching circuits. The active balancing has many benefits like increased battery life, improved performance, faster charging, and enhanced safety.
[0031] The active cell balancing technique increases the total useable charge in the battery stack and decreases heat generated while balancing. In addition, in active cell balancing charge is redistributed from stronger cell to weaker cell, result in fully battery stack profile.
[0032] According to an embodiment of the present disclosure, the in-built battery management system 104 ensures protection from any abusive conditions such as overload and/or short circuit. The lithium phosphate battery 102 uses active cell balancing technique. The active cell balancing redistributes charge between battery cells post charge cycle, thereby increasing system run time. The in-built battery management system 104 individually monitors the charging of the individual respective battery cell. The in-built battery management system 104 establishes a shunt across the individual battery cell for allowing a continued charging of the remaining battery cells at the time of reaching a maximum charging state. The in-built battery management system 104 serves during discharging of the battery to monitor the state of the individual respective battery cell and to inform a microcontroller 108 of a charge controller 106 in case a minimum charging state has been reached. The micro-controller 108 disconnects the battery from the load in order to prevent excessive discharging of the individual battery cells.
[0033] The charge controller 106, also known as a charge regulator or battery regulator, is an essential component in any system that uses rechargeable batteries, especially in off-grid and renewable energy applications. It plays a crucial role in ensuring the safety, longevity, and efficient operation of your batteries.
[0034] In an embodiment, the charge controller 106 is designed for the lithium iron phosphate battery 102 charging, where the charge controller 106 automatically reduces the boost cut-off voltage of the battery 102 and a relay 112 stops the charging once it reaches the desired voltage. Once the charge controller 106 reduces the boost cut-off voltage of the battery 102, the charging is stopped thus avoiding high level charging and discharging of the battery cells and increasing the number of charge and discharge cycles of the lithium phosphate battery 102 before losing performance.
[0035] According to an embodiment of the present disclosure, the BMS performs active cell equalization when a pre-defined threshold voltage value is exceeded. The pre-defined threshold voltage value is set by a user.
[0036] According to an embodiment of the present disclosure, the pre-defined threshold voltage value for the lithium iron phosphate battery 102 is the voltage where 100% back up time, as per specifications of the battery cells, is achieved.
[0037] The pre-defined threshold voltage value is the difference of voltage between at least two cells of the LiFePO4 battery 102. The BMS 104 starts cell equalization when the voltage difference between any two cells exceeds the threshold value. Thus, the BMS 104 only takes power when the cell equalization takes place resulting in power saving. In an embodiment, the pre-defined threshold voltage value described by the user can be changed through the computer or an external device like phones etc.
[0038] According to an embodiment of the present disclosure, the microcontroller 108 is programmed to track the voltages of each cell and compare it with the pre-defined threshold voltage value. If the cell value exceeds the pre-defined threshold voltage value, the microcontroller 108 initiates a cell equalization process automatically and continues until cell are balanced. In an embodiment, the cell equalization occurs only when the battery 102 is in charged state i.e., when the battery charging process is over.
[0039] According to an embodiment of the present disclosure, the BMS is provided with an inherent IoT connectivity 110 to report battery 102 related data to a central server 114 for further analysis. The IoT connectivity can be achieved via a universal asynchronous receiver/transmitter (UART) or the like. The BMS 104 has the provision for IoT monitoring through the GSM, wifi and Bluetooth and also the BMS has built GPS to check the location. The BMS 104 can be stopped at any given position in case of all type of warnings like overload short circuit over temperature or any other alerts the user wants to programme in future as well.
[0040] Referring to Figure 2, a flow chart of the method 200 for battery cell equalization for a lithium iron phosphate battery 102, is shown. The method provides battery charging up to particular level below the maximum limit.
[0041] At first step of the method 200, the BMS 104 monitors each cell voltage of the battery 102. At the second step of the method 200, the BMS checks whether the pre-defined threshold voltage value has been reached, and accordingly, takes decision, either perform an active equalization of the battery cells, or to communicate with the charge controller 106 to automatically reduce boost cut-off voltage, at the third step.
[0042] At the fourth step, the micro-controller stops further charging of the battery 102. Thereafter, the battery cells are charged up to a particular level below the maximum limit prescribed by the manufacturer for reducing the heat in to the cell. The charged cells are then left idle for some time for self-equalization. The method provides cell equalization with increased battery cell life as the battery cells are not subjected to high level charging and discharging.
[0043] The battery cell after being charged are left idle without charging for a pre-defined time period for self-equalization. The method of self-equalization of cells avoids cell imbalance due to battery charging beyond a certain voltage.
[0044] Thus, the aspects of the present disclosure ensure that Battery Management System 104 provides cell equalization only when the cell voltage exceeds the pre-defined threshold voltage value. Also, the cells are charged below the maximum voltage for self-equalization in the case of lithium iron phosphate battery 102.
Advantages:
[0045] The of the present disclosure has various advantages including but not limited to –
1. Overcharging and Heating of Lithium Phosphate battery is avoided.
2. The charge cycle and system run time are increased.
3. Self-equalization increases the cell life.
Industrial Applicability:
[0046] The system and method of self-equalization of cells of a battery according to claims 1-12 of the instant application, can be implemented for Lithium ion phosphate batteries used in power back-up systems of household or commercial work space, electric vehicles etc.
[0047] The foregoing descriptions of specific embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present technology and its practical application, to thereby enable others skilled in the art to best utilize the present technology and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present technology.
List of reference numerals:
S. No. Items Reference Numeral
1 System 100
2 Battery 102
3 BMS 104
4 Charge Controller 106
5 Micro-controller 108
6 IoT connectivity 110
7 Relay 112
8 Central server 114 ,CLAIMS: WE CLAIM:

1. A system (100) for self-equalization of cells of a battery (102), comprising:
- the battery (102) having at least two cells;
- a Battery Management System (BMS) connected to the battery (102), monitors each cell voltage and performs active cell equalization when a pre-defined threshold voltage value is exceeded;
- a charge controller (106) connected to the BMS (104), automatically reduces a boost-cut off voltage;
- a microcontroller (108) of the charge controller (106) connected to a relay (112) to automatically stop charging when said pre-defined threshold value is reached,
wherein the self-equalization of at least two cells occurs only when the battery (102) is fully charged.
2. The system (100) as claimed in claim 1, wherein the pre-defined threshold voltage value is the difference of voltage between at least two cells of the battery (102).
3. The system (100) as claimed in claim 1, wherein the at least two charged cells are left idle without charging for a pre-defined time period for self-equalization.
4. The system (100) as claimed in claim 1, wherein each cell of the battery (102) is charged to a pre-defined level of charging below a maximum limit prescribed by a manufacturer.
5. The system (100) as claimed in claim 1-3, wherein the self-equalization of cells prevents high level charging and discharging.
6. The system (100) as claimed in claim 1, wherein the BMS (104) is enabled with IoT connectivity (110) and Global Positioning System (GPS).
7. The system (100) as claimed in claim 6, wherein the BMS (104) remotely shares self-equalization data with a central server (114).
8. The system (100) for battery equalization of the battery (102) as claimed in claim 1, wherein the battery (102) is Lithium Iron Phosphate (LiFePO4).
9. The system (100) as claimed in claim 8, wherein the battery (102) is used in electric vehicle.
10. A method (200) of self-equalization of cells of the battery (102) as claimed in claim 1-9, comprising:
- monitoring each cell voltage by the BMS (104) and performing active cell equalization of the battery cells only when the pre-defined threshold voltage value is exceeded, wherein the pre-defined threshold value is the difference of voltage between at least two cells;
- automatically reducing the boost-cut off voltage by the charge controller (106) when the pre-defined threshold voltage value is exceeded;
- automatically stop charging when the pre-defined threshold value is reached by the micro-controller (108) of the charge controller (106),
wherein the self-equalization of at least two cells occurs only when the battery (102) is fully charged.