METHOD THEREOF

Field of the invention:

The present invention generally relates to a system and method for fast charging of battery, and more particularly it relates to a low cost high efficiency, portable battery charging system and thermal management method that provides high battery life.

Background of the invention:

Battery charging and discharging time is bottle neck for all the battery operated or related products. The exact electrical characteristic of battery is not always known to the user, and the battery charging time may vary depending upon the battery capacity and charging point. In such cases, faster charging of batteries may cause some problems like thermal runaway, battery life reduction, low capacity, high size, high cost, low efficiency, and like. The battery may catch fire as the temperature of battery rises rapidly and the energy stored in the battery is suddenly released due to unstoppable chain reaction. This can even cause the batteries to explode. Uneven distribution of temperature throughout the battery pack may also lead to reduced performance and reduced battery life. As such, it is necessary to reduce the uneven distribution of temperature throughout the battery pack. Generally, batteries degrade gradually due to the chemical and mechanical changes to the electrodes, leading to reduced capacity. Thus, for battery packs, thermal management is very important for optimum performance and battery life. Battery charging time is largely depended on charging current which is directly depended on external environment temperature. At lower temperature, battery characteristics limit high and in some cases nominal charging current. US patent application 2012139482A1 discloses a battery charging management apparatus including an information obtaining unit and a controlling unit coupled to the information obtaining unit. The information obtaining unit obtains parameter information for temperature of a battery during a charging process performed by a charger for the battery. The controlling unit controls the charger to charge the battery based on the parameter information of the battery, so that operation of the charger conforms to a charging rule corresponding to the charging process. The controlling unit decreases a charging signal of the charger by a predetermined decrement if the temperature of the battery increases by a predefined increment. An Indian patent application IN-DEL-2012-00485A claiming the priority of Chinese application CN201110051408 proposes battery charging management apparatus controlling charging signal in accordance with the obtained battery temperature information.

Current technologies like VOOC and super VOOC use higher current than normal USB charging. VOOC operates on 5 volts and 4 to 6 amps while super VOOC operates on 10 volts and 5 amp to match the internal battery voltage but produces unwanted temperature rise. High wattage power delivery chargers like PD 1.0 Micro-USB, PD 1.0 Type-A/B and PD 2.0/3.0 Type-C charger are also used for charging a single cell battery. In these chargers, the high wattage is achieved through high voltage. Maximum combination wattage is not more than 15W and Achieving higher wattage requires more cell stacks since voltage is increased.

Above mentioned prior art emphasizes on thermal management of the battery system but fails to reduce the time required for charging the battery. Also, temperature sensing and communication between the battery and the charger is done digitally using communication bus, which increases the power consumption and also makes the system complicated and expensive.

Accordingly, there exists a need to provide a battery charging system that is appropriately built together with correct battery chemistry for fast charging of the battery with consideration of battery temperature, voltage and current to address the aforementioned problems.

Objects of the invention:

A primary object of the present invention is to provide a portable battery charging system that will reduce the battery charging time.

Another object of the present invention is to increase the battery life by using appropriate battery chemistry and adaptive battery charging curve which considers battery internal resistance, charged voltage and internal and external thermal condition to control charging current and cut-in and cut-off voltage.

Yet another object of the present invention is to provide a battery charging system that will sense and adapt the charging rate to reduce probability of thermal runaway.

Yet another object of the present invention is to provide mechanical design and thermal mechanism to reduce changes of thermal runaway and increase external battery temperature in low temperature to increase battery current.

Still another object of the present invention is to provide a battery system that will indicate status of the battery to understand the expected capacity, battery life and probability of thermal runaway.

Summary of the invention

Accordingly, the present invention provides a portable system for fast charging of a battery. The system comprises a charging unit and a battery capsule. The charging unit receives power from an AC power supply. The charging unit includes a power control module, a power supply modulator, a control circuit, a current sensing module, a voltage sensing module and a temperature converter module, a first user interface and a connector socket. The power control module is enclosed in the charging unit for receiving an input voltage from an AC supply means through the power supply modulator. The control circuit is connected to the power control module and receives signal from the current sensing module, the voltage sensing module and a temperature converter module. The first user interface is configured on a side of the charging unit for indicating load status. Specifically, the first user interface is a light emitting diode indicator that indicates a load status of the charging unit. The connector socket is configured in a cavity provided on a top portion of the charging unit.

The battery capsule is removably connected to the charger unit with a connector plug provided on a side thereof, for charging the battery enclosed therein. The connector plug gets connected to the connector socket of the charging unit when the battery capsule is positioned in the cavity of the charging unit. The battery capsule includes an input-output circuit, a battery management module, a temperature sensing module, a multiple number of input- output sockets and a second user interface. The input-output circuit is enclosed in the battery capsule for receiving power from the charging unit through the connecting means for charging the battery. The battery management module is operably connected to the input-output circuit, the battery and the temperature sensing module. The battery management module receives battery voltage and battery temperature data to determine charging stage of and output power to the battery. The battery management module includes a temperature control circuit, a short circuit protection circuit, an input overvoltage protection circuit and an overcharge and over-discharge protection circuit. The temperature control circuit is used for ensuring operation of the battery within safe temperature zone through a heat- sensitive temperature control mechanism. The short circuit protection circuit is used for providing an automatic protection to a motherboard when a short circuit occurs. The input overvoltage protection circuit prevents voltage surges. The overcharge and over-discharge protection circuit prevents overcharging and over- discharging of the battery. The temperature sensing module includes a temperature sensors embedded therein for continuously sensing the temperature of the battery. Specifically, the temperature sensor is selected from any one of a negative temperature coefficient (NTC) type temperature sensor and an analog output chip type LM35 temperature sensor. The multiple number of input- output sockets are provided on the battery capsule adjacent to the connector plug. The second user interface is provided on a top portion of the battery capsule for enabling a user to know the battery charging status and battery capsule load status. In accordance with the present invention, the system advantageously allows the battery capsule to receive wattage up to SOW with current ranging up to 10 A and voltage ranging up to 5 V to charge the battery up to 80% of the battery capacity in minimum time period ranging from 20 to 30 min with maximum current supported by the battery.

In another aspect, the present invention provides a method for fast charging of a battery.

Brief description of the drawings:

The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein Figure 1 shows block diagram of a battery charging system, in accordance with the present invention;

Figure 2 shows the detailed view of a battery capsule and a charging unit of the battery charging system, in accordance with the present invention;

Figure 3 shows charge curve at various C rates in fast charging mode, in accordance with the present invention; Figure 4 shows a graphical representation of charge rate performance of the battery charging system, in accordance with the present invention;

Figure 5 shows a graphical representation of change in battery voltage with time while charging the battery, in accordance with the present invention;

Figure 6 shows graphical representation of change in battery temperature with charging current, in accordance with the present invention; Figure 7 shows graphical representation of change in battery temperature with charging voltage, in accordance with the present invention;

Detailed description of the invention: The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments. The present invention provides a portable system for fast charging of a batteryin the least possible amount of time by keeping a control on battery voltage and battery current curve for given temperature range. The system for fast charging mainly comprises a charging unit and a battery capsule. The portable system of the present invention solves issues of an optimized heat and a battery management system, which is the need of the hour in the fast charging domain.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and in the table given below.

Table 1 Ref. no. Component Ref. no. Component

A Charging unit 55 Battery management module

B Battery capsule 60 Temperature sensing module

10 AC source 65 Second user interface

15 Power supply module 70 Battery

20 Power control module 75 Input/output ports

25 Current sensing module 80 Switch

30 First user interface 85A Connector socket

35 Control circuit 85B Connector plug

40 Temp, converter module 100 System for fast charging of battery

45 Voltage sensing module 200 Standard connector

50 Input-Output circuit

Referring to figures 1-2, a system (100) for fast charging of a battery (70)in accordance with the present invention is shown. The system (100) comprises a charging unit (A) and a battery capsule (B).

The charging unit (A) receives power from an AC source. The charging unit (A) includes a power supply modulator (15), a power control module (20), a current sensing module (25), a first user interface (30), a control circuit (35), a temperature converter module (40), a voltage sensing module (45) and a connector socket (85 A).

The power control module (20) is enclosed in the charging unit (A) and receives an input voltage of 85~ 264V AC with frequency of 47 ~ 63Hzfroman AC supply means (10) through the power supply modulator (15). The power supply modulator (15) sources SOW, 5V DC source to the power control module (20) which further stabilizes the power needs as per the need of battery charging stages and controls circuits power regulation. However, it is understood here that the specifications of current and voltage frequency may vary in other alternative embodiments of the present invention as per the intended application.

The power control module (20) is connected to the current sensing module (25), the first user interface (30) and the control circuit (35). The current sensing module (25) detects current provided to the battery capsule (B). Specifically, the current sensing module (25) is a low resistance high current handling circuit that helps to convert current to voltage. This feedback of current is given to the control circuit (35) for current and voltage regulations. The control circuit (35) is connected to the power control module (20) and receives signal from the current sensing module (25), the voltage sensing module (45) and the temperature converter module (40),

The first user interface (30) is configured on a side of the charging unit (A). In an embodiment, the first user interface (30) is a light emitting diode (LED) indicator for indicating load status of the charging unit (A). However, it is understood here that any other type of interface may be used to indicate the load status of the charging unit (A) in other embodiment of the present invention. The connector socket (85A) is configured in a cavity provided on a top portion of the charging unit (A) and facilitates connection of the battery capsule (B) thereto.

The battery capsule (B) is removably connected to the charger unit (A) for fast charging thereof. The battery capsule (B) includes an input-output circuit (50), a battery management module (55), a temperature sensing module (60), a second user interface (65), a battery (70), a multiple number of input- output sockets (75), a connector plug (85B)and a switch (80).

The input-output circuit (50) is enclosed in the battery capsule (B) and receives power from the charging unit (A) through the connector socket (85 A). The battery management module (55) is operably connected to the input-output circuit (50), the temperature sensing module (60), the second user interface (65)and the battery (70). The battery management module (55) receives battery voltage and battery temperature data to determine charging stage of and output power tothe battery (70). The battery management module (55) includes a temperature resistance circuit, a short circuit protection circuit, an input overvoltage protection circuit and an overcharge and over-discharge protection circuit. The temperature control circuit ensures operation of the battery (70) within safe temperature zone through a heat-sensitive temperature control mechanism. The short circuit protection circuit provides automatic protection to the motherboard when a short circuit occurs. The input overvoltage protection circuit prevents voltage surges from damaging the device. The overcharge and over-discharge protection circuit prevents overcharging and over-discharging of the battery (70) thereby preventing any damage thereto.

The battery (70) is fitted in the battery capsule (B).The battery (70) is operably connected to the input-output circuit (50), the battery management module (55) and temperature sensing module (60).

The battery (70) is selected by taking into account the maximum charging current rate supported by the battery. The parameters like battery capacity, battery operating temperature, thermal management requirements for the battery and safety and efficiency of the battery are considered. The cut-off voltage for charging-discharging curve is optimized and the protection circuit requirements are analyzed for the selected battery. In case there is an adverse impact on the temperature and life cycle of the selected battery, then the charging current is adjusted accordingly that may increase the charging time but maintain the optimum level of other parameters. The battery (70) is preferably a single cell Lithium-ion, rechargeable battery having specifications as below:

Capacity: greater than 20 mah

Nominal voltage: 3.65V

Charging current supported by the battery: greater than 1.88 C Discharge current supported by the battery: greater than 0.5 C, depending on application

Cut off voltage: greater than 0.5 V, depending on application Maximum voltage: Less than 5V The battery (70) is preferably a single cell Lithium-ion, rechargeable 3.7V, 5300mah, IS IP battery.

However, it is understood here that the battery (70) having other specifications may be used in other alternative embodiments of the system (100).The battery is charged in a fast mode using the charging unit (A). Alternatively, the battery (70) is charged in a normal mode using a micro USB charger or USB-C charger. The system has novel arrangement of a single cell configuration of battery used along with a high current charger and the battery management module (55). The battery management module (55) automatically detects the type of charger and enables an appropriate mode of charging. In the fast charging mode, time taken to charge the battery (70) is reduced via consideration of current battery charge state, internal thermal condition and external thermal condition to control charge rate at a particular instance by the charging unit and the battery management module (55).

The temperature sensing module (60) includes temperature sensors embedded therein for continuously sensing the temperature of the battery (70). In an embodiment, the temperature sensor is any one selected from a negative temperature coefficient (NTC) type temperature sensor and an analog output chip type LM35 temperature sensor. In a preferred embodiment, the cost effective NTC type 10K temperature sensor is used. LM35 temperature sensor is used in case of high precision temperature control type applications. There is no digitalization of the temperature signals sent to the charger unit (A).

The connector plug (85B) is provided on a side of the battery capsule (B). The connector plug (85B) gets connected to the connector socket (85A) of the charging unit (A) when the battery capsule (B) is positioned in the cavity of the charging unit (A).

The battery charging period depends upon the maximum charging current rate (C) supported by the battery. Time (T) required for charging the battery (70) up to 80 to 90% battery capacity is :

T = — C— -ί 0—.12 c 60 min.

Hence, for a battery supporting maximum charging current of 2C, the charging time will be nearly 30 min

The multiple numbers of input- output sockets (75) are provided on side of the battery capsule (B) adjacent to the connector plug (85B). The input-output sockets (75) are selected from:

• USB 2.0 (Type A socket) having output capacity of 5V/2A

• USB 3.0 (Type A socket) having output capacity of 5V/3A, 9V/2Aused for fast charging

• USB type C socket for charging from a universal charger and also for discharging (For charging applications like mobile phone)

• Micro USB socket: provided as an alternate path for charging the battery (70). The switch (80) is provided on the side of the battery capsule (B) adjacent to the multiple numbers of input- output sockets (75). The switch (80) is provided for knowing battery charging status and battery load status on the second user interface (65). The second user interface (65) is provided on a top portion of the battery capsule (B) and includes multiple numbers of color LED indicators for indicating battery load status and battery charging status, specifically % of charging. However, it is understood here that any other type of interface may be used to indicate the battery load status and battery charging status in other embodiment of the present invention. The second user interface (65) indicates different battery charging modes and stages as below with multiple number of color LEDs, when the switch (80) is pressed.

> Charging of battery (70) through charging unit (A),

> Charging of battery (70) through a charger other than the charging unit (A),

> Fully charged state of battery (70),

> Fully discharged state of battery (70),

> During battery capsule charging, the battery capacity i.e. % charge on battery (70) is indicated by multiple LEDs e.g. one LED glows when the battery (70) is 25% charged, two LEDs glow when the battery (70) is 50% charged, three LEDs glow when the battery (70) is 75% charged, four LEDs glow when the battery (70) is 100% charged

> Low battery charge

> During battery capsule discharging, the LED shows battery capacity for a predefined period of 5 to 10 sec and turns off.

The battery discharging process is stopped or halted by pressing the switch (80) for predefined period of 2 to 6 sec.

In another aspect, the present invention provides a method for fast charging of the battery (70). The method is specifically described in conjunction with the system (100) of figures 1-2. In accordance with the present invention, the method comprises the following steps: a. connecting a charging unit (A) to an AC power source; b. connecting a battery capsule (B) to the charging unit (A) using connector plug and socket arrangement (85A, 85B); c. sensing the output voltage, battery voltage and battery temperature to determine charging stage and output power to the battery capsule (B); d. setting a minimum charging time interval for a constant current charging stage, constant voltage charging stage and float voltage charging stage; e. charging the battery (70) with a constant current of maximum supported battery current to reach the maximum supported battery voltage; f. charging the battery with a constant voltage of maximum supported battery voltage till the battery current drops below C/50; g. maintaining the full charged condition of battery (70) at maximum supported battery voltage; and h. receiving continuous temperature feedback from a temperature sensing module (60) and maintaining the battery temperature in a safe temperature zone by adjusting the charging current by a battery management module (55) throughout the battery charging process.

The steps of the method are now described in detail herein below: The battery (70) is charged in fast charging mode by first connecting the charging unit (A) to the power source and then connecting the charging unit (A) to the battery capsule (B) using connector plug and socket arrangement (85A, 85B).In an embodiment, the connector plug and socket arrangement (85A, 85B) provides a four pin connector having two power lines between charger and 2 digital signals for measuring temperature of battery on charger side. Alternatively, the battery (70) is charged in normal charging mode using a micro USB charger and a USB-C charger through the corresponding input ports on the battery capsule (B). The battery management module (55) through plug and play mechanism detects the type of charger connected to the battery capsule (B) and enables an appropriate method for charging the battery.

The charging unit (A) through the battery management module (55) senses output voltage, battery voltage and battery temperature to determine charging stage and output power to the battery capsule (B). A minimum charging time interval is set for a constant current charging stage, constant voltage charging stage and float voltage charging stage. In accordance with the present invention, AC power supplied to the charging unit (A) charges the battery (70) in three modes as explained with the graphs shown in figures 3 to 7. The battery (70) is charged in constant current mode, constant voltage mode and float charge mode. The different charging modes are described below: i) Constant Current mode: Charging unit (A) charges the battery (70) with maximum supported charging current with controlling temperature in a closed loop system. In case the battery voltage is below 4.2 V, the battery (70) is charged with constant current of 1.88C rate (10 Amp) till it reaches 4.2V. If the battery temperature goes beyond the threshold (20°C above the ambient temperature) while the constant current charging stage, the current is controlled by controlling the output voltage of the charging unit (A). Reduction of the voltage is the differential of the temperature from the threshold value.

Reduced current ( Applicable above the temperature threshold ) = [ K ( constant ) * ( Battery temperature - Temperature Threshold ) ]

The constant (K) is decided as per the battery characteristics, e.g. For the given combination of the battery charger the constant K is kept 2. K value is controlled by selecting appropriate electronic components in the charger unit. The current going to the battery is the difference between the maximum current and the reduced current. ii) Constant voltage mode: The charger unit (A) charges the battery (70) with constant voltage of 4.2V till the battery current drops below C/50. iii) Float voltage charging Mode: The float mode is where the voltage on the battery is maintained at approximately 4.2 volts for a 4.2V battery. This voltage will maintain the full charge condition in the battery without boiling the electrolyte or overcharging the battery. Once the battery is charged and the current is reduced to C/50, the charging unit (A) operates at float voltage charging mode and maintains the battery voltage at 4.2V

The continuous temperature feedback is sent to the battery management module (55). During constant current charging phase if the temperature goes above 50°C

(or 20°C above the ambient temperature), the current is reduced to 1 Amp / min till the battery temperature is below 48°C.Further 1.88 C charge cycle is repeated till the battery reaches 4.20V. The battery management module (55) receives data from the temperature sensing module (60) and also receives output voltage and battery voltage data to determine charging stage and output power to the battery (70). Continuous temperature feedback is sent to the battery management module (55). In case the temperature goes above the predefined temperature limit, the charging current is reduced differentially in minimum step control of battery charger till the battery temperature reaches safe temperature zone, to achieve closed loop feedback. For example, if the battery temperature goes above 50 °C (i.e. 20 °C above room temperature), the current is reduced differentially in minimum step control of battery charger till the time the battery temperature goes below 40 °C to achieve closed loop feedback. Then the 1.88C charge cycle is repeated till the battery reaches 4.2 V.

The first user interface (30) on charging unit (A) and the second user interface (65) on the battery capsule (B) have multiple number of color LEDs for indicating different charging conditions of the battery capsule (B) and the charging unit (A). When the charging unit (A) is supplied with power, the first user interface (30) indicates no output load condition if the battery capsule is not connected thereto. When charging of battery is ongoing, it is indicated by different color LED. LED again indicates no output load condition when charging is complete. Thermal runaway is a critical condition arising during constant voltage charging in which the current and the temperature of the battery produces a cumulative, mutually reinforcing effect which further increases them, and may lead to the destruction of the battery. The system (100) is designed to conduct temperature generated by battery during fast charging such that the thermal runaway condition is reduced. The compensation feedback PID loop is applied as per difference between battery temperature and external temperature to reduce the thermal runaway condition by controlling charge current and voltage, due to which fast charging rate at lower milli-ampere hour capacity of the battery (70) is possible. Also, during low temperature same mechanical design helps to increase the battery temperature to reduce charging current time. Further, the system (100) has protection circuit which helps to control boundary condition scenario while battery charging and discharging. Referring to figure 9, the technical manifestation is in terms of charging up to SOW for single cell battery configuration with high current and low voltage ranging up to 10 A and 5V respectively. Ultra-fast charging innovative technology is 5 times faster vis-i-vis the industry parity in the conventional mobile chargers operating at 18 W. With this, the recharging time is reduced by 70-75%. Ultra-fast charging tech solution provides an industry parity efficiency of 85-90% from the 500 life cycles completed in the Battery life cycle test. The charging curve under the use of technology of present invention denotes that the time to reach a case in point max 4.2V is achieved in 45 to 50 minutes. This corresponds to a 100% completion of the battery with trickle charge.lt is noted from graphical representation In figure 9 that 80% of the battery capacity (until the trickle charge) is reached only in 15 to 20 minutes under the fast charge high current purview.

Advantages of the invention:

1. The system (100) generates high wattage with non-conventional combination of voltage and current. The unique combination of wattage parameters reduces dependencies on cells stack combinations to achieve higher wattage.

2. With the system (100), reduced charging time remains unaffected even when the mah increases by battery stacking.

3. The system (100)is portable and ensures faster charging than the existing conventional technology setup.

4. The system (100) solves issues of an optimized heat and battery management system, which is the need of the hour in the fast charging domain.

5. The system (100) achieves small form factor on design engineering.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention 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 invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention 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 circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.