Description:TECHNICAL FIELD
[001] Embodiments disclosed herein relate to cell balancing in battery packs of electric vehicles, and more particularly to correcting voltage of multiple cells of the battery pack simultaneously, by a multi-cell charging equipment.

BACKGROUND
[002] Lithium-ion (Li-ion) batteries are widely used in Electric Vehicles (EVs) as Li-ion batteries have a higher energy density than other rechargeable batteries, such as lead-acid, or nickel-cadmium batteries. A Li-ion battery pack comprises a plurality of Li-ion cells or modules. The cells or modules can be either connected in series, or in parallel combination, or both. The process of equalizing the voltages and the State of Charge (SoC) among the cells when they are connected and at full charge is called cell balancing. Cell balancing ensures that the State of Charge (SoC) is the same for every cell at the same time.
[003] The difference in the cell voltages is corrected instantaneously as much as possible or gradually by using by-passing cells. In EVs where the batteries are charged using current techniques, a decrease in mileage, or stoppage of the EV is observed at a higher State of Charge, thereby requiring voltage correction to be done in one or more of the Li-ion cells or modules present in the Li-ion battery pack.
[004] Currently, it is observed that one or more of the cells or modules reach the maximum cut-off voltage, i.e., ~3.65V, earlier than the other cells. Further, it is observed that, during the drive of the EV, one or more cells or modules reach the minimum cut-off voltage. i.e., ~2.5V, while the other cells or modules may not be fully depleted. Due to the non-uniformity of individual cell voltages observed during charging and discharging of the Li-ion batteries, a Battery management system (BMS), or an intelligent Energy Management System (iEMS) may result in shutting of the vehicle drive to protect the battery pack from over-charging, or deep discharging. If the deviation in the individual cell voltages within the battery pack is not corrected, the life of the battery pack can be affected.
[005] For identifying, charging, and correcting voltage in individual cells or modules in the Li-ion battery pack of the EV, a floor charger or discharger is used. The floor charger boosts a weak cell with a small amount of current, whereas the floor discharger discharges using small amount of resistance to meet the voltage of other cells in the Li-ion battery pack. For voltage correction, the time taken to floor charge the required set of cells or modules is higher when performed using conventional single cell or module charging equipment. Therefore, time taken for correcting voltage in each cell or module is high, thereby impacting the vehicle delivery time to a customer.

OBJECTS
[006] The principal object of embodiments herein is to disclose a multi-cell charging equipment comprising a plurality of modular channels for charging a plurality of Li-ion cells/modules of a Li-ion battery pack, that can floor-charge or discharge the cells or modules simultaneously, thereby reducing the time taken to charge and aiding to voltage correction and improved voltage of the Li-ion battery pack.
[007] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating at least one embodiment and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[008] Embodiments herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[009] FIG. 1a illustrates a block diagram of the multi-cell charging equipment, according to embodiments as disclosed herein;
[0010] FIG. 1b illustrates an isometric view of the multi-cell charging equipment, according to embodiments as disclosed herein;
[0011] FIG. 2a depicts a single cell or a module of the battery pack in an electric vehicle, according to embodiments as disclosed herein;
[0012] FIG. 2b depicts a parallel combination of individual cells of the battery pack, according to embodiments as disclosed herein;
[0013] FIG. 3a depicts an isometric view of the charging channel of the multi-cell charging equipment, according to embodiments as disclosed herein;
[0014] FIG. 3b depicts an isometric view of the discharging channel of the multi-cell charging equipment, according to embodiments as disclosed herein;
[0015] FIG. 4 illustrates a circuit diagram of the multi-cell charging equipment, according to embodiments as disclosed herein; and
[0016] FIG. 5 illustrates a flow chart of the method for correcting voltage using the multi-charging equipment, according to embodiments as disclosed herein.
DETAILED DESCRIPTION
[0017] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted 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.
[0018] Embodiments herein disclose a multi-cell charging equipment for simultaneously correcting voltage in a plurality of modules or cells in a modular battery pack in an Electric Vehicle (EV). The multi-cell charging equipment comprises a plurality of channels that are isolated and are capable of charging or discharging each cell or module without the interference of the other channels. The multi-cell charging equipment performs early detection of weak cells or modules to prevent any future breakdown. The multi-cell charging equipment optimizes the voltage of the battery pack by correcting the voltage in the individual cells or modules. Referring now to the drawings, and more particularly to FIGS. 1a through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0019] The terms “battery pack” and “battery” have been used interchangeably hereinafter. The terms “cells” and “modules” have been used interchangeably hereinafter. Further, embodiments herein have been explained by considering Lithium-ion batteries as an example of a battery being used in an electric vehicle. However, it may be obvious to a person of ordinary skill in the art that the embodiments herein can also be implemented in Lithium Ferro-Phosphate (LFP) batteries.
[0020] FIG. 1a illustrates a block diagram of a multi-cell charging equipment 100 for charging and correcting voltage of a plurality of cells or modules of a battery pack simultaneously, according to the embodiments herein. The multi-cell charging equipment 100, according to the embodiments herein, is, but not limited to, an off-board charger that can be present outside the EV and provide DC power to the battery pack present in the EV. For example, the multi-cell charging equipment 100 can be present in a workstation, a residence, an office, a commercial premise, a shopping center, a public space, or a charging station. The battery pack includes a plurality of cells or modules. The multi-cell charging equipment 100 comprises a plurality of modular charging and discharging channels (channels 1-8). FIG. 1b illustrates an isometric view of the multi-cell charging equipment 100 that is capable of correcting voltage of eight cells of the battery pack, according to the embodiments herein. The embodiments herein are not limited to correcting voltage of eight cells and are scalable to correcting voltages of plurality of cells or modules of a battery pack.
[0021] FIG. 1c illustrates a modular charging/discharging channel of the charging equipment 100, in accordance with the embodiments herein. Each of the modular channel comprises, but not limited to, an electronic power supply, such as, but not limited to, a switch-mode power supply (SMPS) charger 102, a current selector 104, a protection circuit 106, a charge control and display board control unit 108, a display board 110, an auxiliary power supply 112, and an alternating current electrical power system 115.
[0022] The SMPS charger 102 converts an electrical power source, such as an Alternating current (AC) source, into a regulated direct current (DC) voltage. The SMPS charger 102 is connected to the protection circuit 106. The protection circuit 106 may be, but not limited to, an overvolt, undervolt, reverse protection control. The protection circuit 106 protects the battery and the charger from overcharging, over discharging, and other abnormal conditions. The protection circuit may include components, such as, a fuse, a thermal switch, and the like for ensuring safe charging. The terminals of the battery cells or modules are connected to the protection circuit 106. The protection circuit 106 is connected to the charge control and display board control unit 108. The charge control and display board control unit 108 controls the charging process. The charge control and display board control unit 108 can include, but not limited to, a microcontroller or a specialized charging integrated circuit that helps in the regulation of charging voltage and current, and for monitoring the battery’s voltage and temperature. The charge control and display board control unit 108 is connected to the display board 110 which indicates the charging status and the battery’s charging levels.
[0023] The SMPS charger 102 is connected to the current selector 104. The current selector 104 is a type of electrical switch that controls the amount of current flowing through a circuit. The current selector 104 allows a user to select between various levels of current. The switching of current can be manually driven, or automatic. The current selector 104 can be used to switch between different current ranges, or to switch between various sources of current. The current selector switch can be used to protect an electrical equipment from overcurrent, and it is done by switching off the current supply when the current level exceeds a certain threshold. The protection circuit 106, the charge control and display board control unit 108, and the SMPS charger 102 are connected to an auxiliary power supply 112. The auxiliary power supply 112 serves as a backup to the main power source, in the event of a power outage or failure. The auxiliary power supply 112 can be, for example, but not limited to batteries, generators, uninterruptible power supplies (UPS), and the like. The auxiliary power supply 112 can be connected to an alternating current power system 115. The AC power system 115 can supply a voltage of 230 V, for example. The AC power system 115 comprises Power (P), Neutral (N), and Earth (E) components. The P component is a live wire that carries an electrical current from a source, the N component is the return path for the current and is connected to a power source, and the E component is a safety feature that provides a low-resistance path to ground in the event of damage or any faults in the charging equipment 100.
[0024] FIG. 2a illustrates a single cell 202 of the Li-ion battery pack, according to the embodiments herein. Fig. 2b illustrates a parallel combination 204 of individual cells connected by a bus bar. The parallel combination of the individual cells can be, for example, but not limited to, 2P, 3P, 4P, and so on. In an example implementation, nominal voltage of each cell is 3.2V and nominal capacity is 72AH. In an example, the module voltage of a single cell in a parallel combination is 3.2V and module capacity of a 3-cell module is 216AH and that of a 4-cell module is 288AH.
[0025] The multi-cell charging equipment 100, according to embodiments herein, floor-charges a plurality of cells simultaneously. Each of the plurality of channels are isolated to facilitate simultaneous charging of multiple cells at a time. As an example, the embodiments herein are explained by considering charging of eight cells or modules simultaneously.
[0026] As shown in FIG. 1b, the charging equipment 100 comprises eight channels, Channels 1-8. The channels 1-6 are charging channels and the channels 7 and 8 are discharging channels. The embodiments herein are not limited to charging of eight cells or modules only. Charging of eight cells or modules using the eight channels has been used as an example to explain the various aspects of the embodiments.
[0027] FIG. 3a illustrates a charging channel 301 in the multi-cell charging equipment 100, according to the embodiments herein. In the example multi-cell charging equipment 100 for charging eight cells or modules, the channels 1-6 constitute the charging channels. Each of the charging channels 1-6 is capable of charging cells, including deep discharged cells. In an example, an output voltage range for charging the eight cells or modules of the Lithium-ion battery pack is to be 0V to 4.2V (DC output). According to embodiments herein, the maximum voltage to be attained by a cell or module of the battery pack prior to cut-off is pre-determined. In an example, while charging, the maximum voltage to be attained by the cell or module prior to cut-off should not be more than 3.7V. The design of the multi-cell charging equipment allows for charging the cells or modules based on the current value. In an example, after the charging equipment 100 reaches a value of 3.65V at 40A, the charging equipment 100 switches to 10A for charging up to 3.7V and then cuts-off. Charging at low current once the cell reaches a certain voltage, reduces the risk of overcharging, thereby eliminating permanent damage to the cells. Each of the charging channel 1-6 comprises a display unit 302 which includes one or more sub-units. One of the sub-units includes a LED arrangement which is configured to indicate one of statuses, namely, “charging ON” 303, “charging cut-off” 304, and “fault LED” 305. Each of the charging channel 1-6 comprises a positive terminal 306 and a negative terminal 307 for establishing an electrical connection with the cells of the Li-ion battery pack in the vehicle.
[0028] FIG. 3b illustrates a discharging channel 308 in the charging equipment 100, according to the embodiments herein. According to the embodiments herein, channels 7 and 8 are discharging channels. Each of the discharging channel 7 and 8 comprises a charge selector 309 for selecting a suitable current value. Each of the discharging channel 7 and 8 are provided for discharging so that higher energy cell voltage can be brought down to verify the charge holding capability of them, if required. In an example, the minimum DC current value selectable by the charge selector 309 is 10A and the maximum DC current value is 40A. The discharging channel comprises a discharge switch 310. Each of the discharging channel facilitates discharging of the cells through internal resistance. Each of the discharging channel comprises an LED arrangement which indicates statuses corresponding to one of “charging ON” 312, “charge cut-off” 314, and “fault LED” 316. Each of the discharging channel 7 and 8 comprises a positive terminal 318 and a negative terminal 319 for establishing an electrical connection with the cells of the Li-ion battery pack in the vehicle. In an example implementation, while discharging, the cell voltage is to be brought down from 3.7V to any of the following ranges: 3.55V, 3.45V, 3.35V and 3.25V. The cut-off voltage value to be input is done manually by an operator. In an example implementation, the final cut-off limit for discharge option is 3.25V.
[0029] In an example implementation, the output voltage range of the equipment for charging is to be 0V to 4.2V (DC output). In case the cell cannot start from 0V, the charging equipment 100 provides cell wake up or capacity/voltage built up till the lowest minimum specifications before charging through individual channel. The charging equipment 100 is configured to operate in such a way that, while charging, once the maximum voltage is attained, the charging equipment 100 switches to another operating voltage and cuts-off. In an example implementation, while charging, the maximum voltage to be attained by the cell prior cut-off should not be more than 3.7V. The design of the charging equipment 100 can be made in such a way that after reaching 3.65V at 40A, the charging equipment 100 switches to 10A for charging up to 3.7V and then cuts-off. In other words, if the cells are connected with low voltage and if a current value of 40A is selected, and once the value of cells’ voltage is 3.65V, the charging current is changed to 10A and taper charging is performed. Taper charging refers to the gradual decrease in the rate of charging for electric vehicles as the battery approaches full charge. This is done to extend the life of the battery and to increase its overall efficiency.
[0030] The charging equipment 100 comprises protection, such as voltage protection, temperature protection, reverse polarity error protection by operator, and current protection. The protections safeguard the Li-ion cells from damage. In an example implementation, the cells are not allowed to get discharged below 2.7V.
[0031] The charging equipment 100 is configured with a warning light, or an alarm, such as but not limited to an LED, or a buzzer, to indicate the completion of charging, discharging, faults, reverse polarity faults, and the like. The charging equipment 100 is configured with a display in each of the plurality of channels. The display provides information, such as, but not limited to, current from charger, voltage of the cell/module, amount of current charged, and time taken to charge. The charging equipment 100 is configured to provide an option for selecting a type of battery to be charged. The charging equipment 100 charges the cells using a detachable cable wire for ease of maintenance and movement of the charging equipment 100. In an example implementation, the length of the cable wire is about 2 metres and the end of the cable wire has a crocodile clip arrangement.
[0032] FIG. 4 illustrates an electronic schematic 400 of the multi-cell charging equipment 100, according to the embodiments herein. The electronic schematic 400 illustrates each of the charging/discharging channels being modular and isolated from each other, as shown in FIGs. 1a, 1b, and 1c. The individual charging/discharging channel is represented in the form of a block diagram in FIG. 1c. The EV can be connected to a power grid by means of an Electric Vehicle Supply Equipment (EVSE), an inline control box being extended to the employed EVSE. On the other hand, the EV can be connected to the power grid by means of an off-board battery charger through a DC connection. The charging equipment 100 performs conductive charging in which the charging equipment 100 uses a physical contact between the connector and a charge inlet, such as a cable wire. The electronic schematic 400 shows a power source 402 that provides sinusoidal current (AC). The power source 402 is connected to an Electromagnetic Interference (EMI) board 404 and a Power Factor Correction (PFC) board 406. The PFC board ensures a unity power factor correction when converting AC to DC by taking in the sinusoidal current from the power source. The PFC board 406 is connected to bias boards 408-1 to 408-8 and the control boards 409-1 to 409-8 corresponding to the eight channels. Each of the control board 409-1 to 409-8 is connected to each of a DC-DC board 410-1 to 410-8. Each of the DC-DC board 410-1 to 410-8 is connected to each of an output filter board 412-1 to 412-8.
[0033] Each of the output filter board 412-1 to 412-8 is connected to each of a correction unit 414-1 to 414-8 comprising control circuit arrangement. The control circuit arrangement comprises diodes and a control circuit for controlling and correcting the voltage flow. The discharging channel comprises a filter and a switch to control the discharging. Each of the correction unit 414-1 to 414-8 is isolated from each other by means of an isolation means made up of an insulting material.
[0034] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Fig. 4 include blocks which can be at least one of a hardware device, or a combination of hardware device and software module. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in at least one embodiment through or together with a software program written in e.g. Very high speed integrated circuit Hardware Description Language (VHDL) another programming language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g., hardware means like e.g. an ASIC, or a combination of hardware and software means, e.g. an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively, the invention may be implemented on different hardware devices, e.g., using a plurality of CPUs
[0035] FIG. 5 illustrates a method 500 for correcting voltage in eight cells of the Li-ion battery pack using the charging equipment, according to the embodiments herein. At step 502, each of the modular, isolated channels 1-8 is connected to each of a cell of a plurality of cells or modules of the battery pack. At step 504, the each of the correction unit 414-1 to 414-8 performs cell balancing depending on factors, but not limited to, cell chemistry, depth of discharge, and State of Charge (SoC) of each of the cells connected to the charging equipment.
[0036] The various actions in method 500 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 5 may be omitted.
[0037] The embodiment disclosed herein describes a multi-cell charging equipment with discharger of Li-ion cells/modules of a Li-ion battery pack, that can charge the cells or modules in the least possible time aiding to voltage correction and improved voltage of the Battery Pack, for utility in Automotive Service Workshops (Dealership) for Electric Vehicles.
[0038] 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 embodiments and examples, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

, Claims:1. A multi-cell charging equipment (100) for correcting voltage in a plurality of battery cells in a battery pack, said multi-cell charging equipment (100) comprising:
a plurality of charging channels (channels 1-8) and a plurality of discharging channels (channels 1-8), wherein the plurality of charging channels and the plurality of discharging channels are modular and isolated from each other, and wherein the multi-cell charging equipment (100) is to charge the plurality of battery cells simultaneously, and wherein a correction unit (414-1 to 414-8) performs a cell balancing based on a plurality of factors related to each of the plurality of cells.
2. The multi-cell charging equipment (100) as claimed in claim 1, comprising a user selectable switch (309) for selecting one of a maximum voltage and a minimum voltage.
3. The multi-cell charging equipment (100) as claimed in claim 1, wherein each of the plurality of discharging channels comprises a discharging switch (310).
4. The multi-cell charging equipment (100) as claimed in claim 1, wherein each of the plurality of charging channels and the plurality of discharging channels comprises a display unit (302) including one or more sub-units, wherein the one or more sub-units includes a LED arrangement configured to indicate one of charging ON (303, 312), charging cut-off (304, 314), and fault LED (305, 316).
5. The multi-cell charging equipment (100) as claimed in claim 1, wherein the multi-cell charging equipment (100) is to charge a plurality of cells of the battery pack of the electric vehicle using a detachable cable wire.
6. The multi-cell charging equipment (100) as claimed in claim 5, wherein an end of the detachable cable wire includes a crocodile clip arrangement.
7. A method for correcting voltage in a plurality of battery cells in a battery pack, the method performed by a multi-cell charging equipment (100), the method comprising:
connecting (502) each of a plurality of charging channels (channels 1-8) and a plurality of discharging channels (channels 1-8) to each cell of a plurality of cells of the battery pack; and
performing (504), by a correction unit (414-1 to 414-8), cell balancing based on a plurality of factors related to each of the plurality of cells connected to the multi-cell charging equipment (100).