DETACHABLE BATTERY MODULE, AND METHOD AND APPARATUS FOR THE CHARGE EQUALIZATION OF A BATTERY STRING USING SAME

Provided are a detachable battery module and a charge equalization method and apparatus for a battery string. According to the exemplary embodiments of the present invention, the charge equalization apparatus are modularized by being divided into the master unit and the slave unit, such that the charge equalization apparatus may be expanded and contracted independent of the number of batteries, the circuits are separated for each module, such that the circuits may be easily implemented, and when the circuits are damaged, only the damaged module is replaced, such that the effective countermeasure may be performed.

DESCRIPTION OF REFERENCE NUMERALS

BEST MODE

FIG. 1is a conceptual diagram implementing a charge equalization apparatus according to an embodiment of the present invention. The charge equalization apparatus according to the exemplary embodiment of the present invention includes detachable battery modules140ato140m, a control unit100which controls the detachable battery modules, an equalization converter130which provides charge equalization of the battery modules140ato140mdepending on a command of the control unit, and the like. These components will be described below.

The battery modules140ato140mare configured in a detachable type and include battery cells, a battery monitoring IC which monitors a state of the battery cells, and switches which switch the modules. This is illustrated inFIG. 2. This will be described below with reference toFIG. 2.

The control unit100may be a microprocessor, a microcomputer, and the like and is programmed with an algorithm which performs a balancing (that is, charge equalization) operation of the battery cells according to the embodiment of the present invention. To this end, the control unit100may include a memory, and as the memory, an internal memory of the control unit100may also be used, or a separate memory may be used.

As the separate memory, non-volatile memories, such as an electrically erasable programmable read-only memory (EEPROM), a static RAM (SRAM), a ferro-electric RAM (FRAM), a phase-change RAM (PRAM), and a magnetic RAM (MRAM) may be used.

The equalization converter130serves to perform the charge equalization of the battery modules140ato140mto implement at least one cell balancing (charge equalization) of the battery modules140ato140mdepending on the command of the control unit100. Therefore, as the equalization converter130a DC-DC converter of a chargeable and dischargeable type may be used.

FIG. 2is a circuit block diagram implementing the concept ofFIG. 1. Referring toFIG. 2, the battery module140aamong the detachable battery modules140ato140mis configured to include a battery pack113awhich is configured of battery cells B1,1to B1,K, a monitoring unit120awhich monitors a state of the battery cells B1,1to B1,Kin the battery pack113a, a switch block112awhich switches the battery cells B1,1to B1,Kin the battery pack113a, a module switch unit111awhich switches to charge or discharge the corresponding battery cells by selecting the switch block112a, and the like. The detachable battery module140ais arranged in plural (140ato140m) within the equalization apparatus. These components will be described below.

The battery packs113ato113ninclude the plurality of battery cells B1,1to B1,Kwhich are connected to each other in series, in which the plurality of battery cells are modularized in any number of batteries (normally, the battery cells are configured in 8, but the embodiment of the present invention is not limited thereto). Further, the case in which the battery cells B1,1to B1,Kare configured in series within the battery pack113ais illustrated, but the battery cells B1,1to B1,Kmay be configured in parallel. The battery cell may be a hybrid battery, such as a nickel metal battery and a lithium ion battery.

The battery monitoring units120aand120bmay be configured using a battery dedicated IC which is commercially used. The battery monitoring units each transfer the state information of the battery cells (for example, B1,1to B1,K) to the control unit100and take part in the battery protection and the cell balancing (referred to as the charge equalization) control depending on the command of the control unit.

The switch block units112ato112nserve to connect a specific battery cell, which is undercharged during the charge equalization or overcharged, to the equalization converter130.

In addition to the cell switch block units113ato113mconnected to the cells, the module switch units111ato111nare present in each module in each of the battery modules140ato140nand thus share the equalization converters130for each module. Further, these module switch units serve to insulate between the battery modules140ato140mto separate these battery modules as the individual module.

DescribingFIG. 2, voltage information and information such as temperature of the battery cells B1,1to BM,Kare collected and controlled by the battery monitoring units120ato120mand the battery monitoring unit is partially responsible for the control of the equalization converter130through communication between the control unit100and the battery monitoring units120ato120m. The operation of the equalization converter130for the charge equalization is controlled depending on a defined algorithm through the battery cell sensing information of the control unit100. The algorithm is illustrated inFIG. 6. This will be described below.

FIG. 3is an overall configuration diagram of the charge equalization apparatus according to the embodiment of the present invention. That is,FIG. 3illustrates an example of the charge equalization apparatus which uses one equalization converter130, the battery monitoring units120ato120m, and the control switches112ato112mand200.

That is, the control unit100responsible for the system control based on the information of all the battery cells B1,1to BM,Kis present and the one equalization converter130generating cell charge equalization energy is controlled by the control unit100and is connected to the module switch unit200. Further, according to the embodiment of the present invention, as the equalization converter130, the chargeable/dischargeable bidirectional DC-DC converter may be used.

However, the embodiment of the present invention is not limited thereto. The module switch units200each present in each battery module are shared by the bidirectional cell selective switches112ato112mconnected to each of the battery cells B1,1to BM,Kand the cell switch blocks112ato112mselecting the cells are controlled by control signals of the battery monitoring units120ato120m. The battery monitoring units120ato120mwhich are present in each battery module are directly connected to each of the battery cells B1,1to BM,Kto acquire the state information (for example, SOC, SOH, current, voltage, and the like) of the battery cells.

The battery monitoring units120ato120mcollects the state information of each of the battery cells B1,1to BM,Kand transfers the collected state information to the control unit100, which is a central processing unit, depending on a data communication protocol. That is, as described above, the battery monitoring unit120acollects the state information (for example, SOC, SOH, voltage, current, and the like) of each of the battery cells B1,1to B1,Kand the battery monitoring unit120mcollects the state information of each of the battery cells BM,1to BM,K.

The control unit100determines whether the charge of the specific battery cell is equalized by the defined algorithm to transmit the control signals to the battery monitoring units120ato120mof each of the battery modules140ato140m(FIG. 2). As such, the control unit100and the battery monitoring units120ato120mare connected to each other to transmit and receive the information to and from each other. That is, as illustrated inFIG. 3, the communication lines shown by a dotted line is connected to each other. Therefore, even though one of the battery modules140ato140m(FIG. 2) is removed due to an abnormal operation, the remaining battery modules may still communicate with the control unit100.

Referring back toFIG. 3, the battery monitoring units120ato120mare directly connected to each of the battery cells to obtain the battery information in real time and receive the command of the control unit100to generate the specific control signal. The control switches112ato112mand200connected to the battery monitoring units120ato120mreceive the control signals in the battery monitoring units120ato120mto turn on/off the switch block units112ato112mwhich select the corresponding battery cells BM,1to BM,K, such that a cell charge equalization current path for the specific cell may be generated.

Further, the battery monitoring units120ato120mcontrol turn on/off operations of the module switching units111ato111m(FIG. 2) of the corresponding battery modules140ato140m(FIG. 2). The control of the control unit100may be changed depending on the number of output pins of the battery monitoring units120ato120mand the control unit100may be configured to directly control the module switch units111ato111m(FIG. 2).

FIG. 4is a diagram illustrating a circuit operation of the charge equalization apparatus for a second cell of a second module inFIG. 2. For example, a battery stack monitor (Product Name: “LTC6802”, Linear Technology Co.) may be applied to the battery monitoring units120ato120mand the application example is illustrated inFIG. 4. The “LTC6802” is directly connected to each of the battery cells to measure a potential of the battery cell and measure a temperature of the battery cell and includes a switch controlling the corresponding battery cell disposed therein.

Further,FIG. 4illustrates only the case in which in order to understand the embodiment of the present invention, the “LTC6802” is applied, and therefore any electronic component having the above-mentioned function may also be applied.

Referring back toFIG. 4, the DC-DC converter130commonly used is operated by an overall voltage or an external voltage of battery cells B2,1to B2,Kand is controlled bidirectionally or unidirectionally. Therefore, the DC-DC converter130serves to charge or discharge the specific battery cells B2,1to B2,K. Further, the DC-DC converter130receives a pulse width modulation (PWM) signal of the control unit100or a PWM signal of a controller (a portion controlling the operation of the DC-DC converter130) which is controlled by the control unit100.

Low-voltage bidirectional control switches111band112bwhich control the charging and discharging current of the battery cells B2,1to B2,Kwithin the battery pack113bare operated by receiving turn on and off signals of the battery monitoring unit120b. In this case, the inputs of each of the bidirectional control switches111band112bare connected to simple circuits O2,2, S2,2, and the like, which receive the turn on/off signals of the battery monitoring unit120bto perform the turn on and off operations of the switch.

As illustrated inFIG. 4, the circuit uses the voltage of the battery cells B2,1to B2,Kas a power supply apparatus and needs to perform the high-reliability turn on/off switch operations.

It is already described that the embodiment of the present invention may be configured of two units in structure. The control unit100which is a central processing unit and the DC-DC converter130are a single master module and the control switches111band112band the battery monitoring unit120bis a slave module.

The master module controls the slave module based on the information on the overall battery situation and the system situation and generates charging/discharging energy for the cell charge equalization. The slave module serves to read the battery cell information which is connected to the module and control the switch for the charge equalization of the specific battery cell.

FIG. 4illustrates a circuit which connects the low-voltage bidirectional control switches to each of the battery modules140ato140m(FIG. 2) and performs the individual charge equalization operation using the one common DC-DC converter130.

Further,FIG. 4illustrates an example in which the sensing circuit part which is intricately configured to sense the cell voltage information of each of the plurality of cells B2,1to B2,Kis simply configured by using an integrated monitoring IC element. Further,FIG. 4illustrates an example in which the battery stack monitor (Product Name “LTC6802”, Linear Technology Co.) is applied, but the embodiment of the present invention is not limited thereto.

Next, the operation process of the charge equalization apparatus illustrated inFIG. 4will be described. The battery cell to be charged (referring toFIG. 4, assumed to correspond to one of the battery cells B2,1to B2,Kwithin the battery module140b) is determined, and thus it is assumed that the bidirectional control switch112bcorresponding thereto is turned on and a relay switch116bwhich is the module switch unit of the battery module140bbelonging to the battery cell to be charged is turned on. In this case, the bidirectional DC-DC converter130commonly used is operated by the control of the control unit100.

In the case of the bidirectional DC-DC converter130, the DC-DC converter may be operated to meet the charging or the discharging situation and in the case of the unidirectional DC-DC converter130, the DC-DC converter130may be operated by a predefined direction. In this case, the operation of the used DC-DC converter may be changed depending on the used converter type. Further, in the case of a switched-mode power supply (SMPS) which receives the PWM control signal and in the case of performing an operation of a bipolar junction transistor (BJT) or other switches, the control method may be changed.

The amount of the charge equalization charging and discharging current may be simply and efficiently generated depending on the capacity of the battery cell by the one common DC-DC converter130illustrated inFIG. 4and the use of the battery monitoring unit120bmay lead to the reduction in the cost and volume of the charge equalization apparatus.

The above-mentioned DC-DC converter130may be configured of a combination of the existing various types of DC-DC converters or linear regulators. In this case, each of the converters or regulators includes a switch unit and thus may be output bidirectionally or unidirectionally. The switch unit may be configured of a combination of switches electrically insulated from each other, such as an electrical switch and a mechanical switch. This is illustrated inFIG. 5.

FIG. 5is a circuit diagram illustrating a configuration example of an element of the charge equalization apparatus according to the embodiment of the present invention. Referring toFIG. 5, as the DC-DC converter, a flyback type bidirectional DC-DC converter130may be used and as the switch unit, a metal oxide semiconductor field effect transistor (MOSFET) may be used. Further,FIG. 5illustrates an example in which the charge equalization apparatus illustrated inFIG. 1is implemented using other circuit elements, and therefore it may be understood that the DC-DC converter and the switch may be configured of a combination of other apparatuses.

The charge equalization apparatus according to the embodiment of the present invention is performed when potentials of each of the serially connected batteries are different from each other under the situation in which the serially connected batteries are not connected to an electrical charging apparatus or electrical loads. However, when a current capacity of the charge equalization apparatus is large or a magnitude in the charged current or the discharged current is small, the charge equalization apparatus may be performed even though the serially connected batteries are connected to the electrical charging apparatus or the electrical loads.

The charge equalization apparatus according to the embodiment of the present invention starts to operate when the potentials of each of the battery cells are different from each other and the starting of the charge equalization apparatus is determined according to the algorithm previously programmed in the control unit100(FIG. 1) based on a battery cell voltage measurement value input to the control unit100, a state of charge (SOC) value by the battery cell voltage, or a stage of health (SOH).

Next, a process of performing the charge equalization operation will be described with reference to the configuration and the operation of the charge equalization apparatus illustrated inFIGS. 1 to 5.FIG. 6is a flow chart illustrating a sequence of the charge equalization operation according to the embodiment of the present invention.

Referring to the flow chart ofFIG. 6, when the charge equalization algorithm stored in the control unit100is operated, the battery monitoring units120ato120m(FIG. 2) sense the potentials of the battery cells B1,1to BM,Kdisposed in each of the battery modules140ato140min real time (steps S600and S610).

The sensed cell potential values (that is, voltage values) of the battery cells B1,1to BM,Kare transmitted to the control unit100from the battery monitoring units120ato120mthrough the communication lines between the battery monitoring units120ato120mand the control unit100. Further, the transmission may be performed in real time or at each predetermined time period. Therefore, the control unit100determined whether the transmission is completed (step S620).

As the determination result, when the transmission from the battery monitoring units120ato120mto the control unit100is completed, the control unit100generates a list of the battery cells exceeding a reference value and the battery cells less than the reference value based on a cell balancing targeted voltage of all of the batteries (step S630).

Unlike this, as the determination result of the step S620, when the transmission of the potential values of the battery cells is not completed, the steps S600to S620are executed again.

When the battery cell to be charged or discharged by the cell list is defined, the control unit100first connects the corresponding battery modules140ato140mof at least one of the module switch units110ato110m(FIG. 2) to the equalization converter130. Further, the battery monitoring units120ato120mconnect the corresponding battery modules to the equalization converters. When the corresponding battery module (this may be in singular or plural) is connected to the equalization converter130, the battery monitoring units120ato120mallow the switch block unit112ato select the corresponding battery cells B1,1to BM,K(step S640).

Further, the control unit100performs the following operation to perform the charge equalization process.

Step a): When the potential of any battery cell configuring the serially connected battery is higher or lower than a preset value, the control command is transferred to the battery monitoring units120ato120mof the corresponding battery modules140ato140m.

Step b): The battery monitoring units120ato120mof the corresponding battery modules140ato140mare operated. The battery monitoring units120ato120mpreferentially operate the bidirectional control switches111ato111mby the internal switch. Next, the control signal to operate the module switch units112ato112massociated with the battery modules in which the corresponding battery cells are included is transmitted.

Step c): The control unit100performs the charge equalization operation by operating the common equalization converter130(in particular, DC-DC converter) in the charging direction or the discharging direction.

Referring back toFIG. 6, when the corresponding battery cell is selected, the equalization converter130charges a charge in the corresponding battery cell or discharges a charge from the corresponding battery cell to perform the charge equalization (steps S650and S660). Further, the equalization converter130sequentially performs the charge equalization operation from the most preferential battery cell depending on the command of the control unit100.

The method of executing the charge equalization may be divided into largely four, which is as follows.

{circle around (1)} When it is determined that the specific battery cell is undercharged over other cells:

The potential of the corresponding undercharged battery cell is effectively increased by moving the total energy of the battery to an undercharged battery cell.

{circle around (2)} When it is determined that only the specific cell is undercharged:

The potential of the corresponding undercharged battery cell is effectively increased by moving the energy of the external power supply to the undercharged battery cell.

{circle around (3)} When it is determined that the specific battery cell is overcharged over other cells:

The potential of the overcharged battery cell is effectively reduced by moving the overcharged battery energy to all the battery calls.

{circle around (4)} When it is determined that only the specific battery cell is overcharged:

The potential of the corresponding overcharged battery cell may be reduced by moving the overcharged battery energy to the external power supply.

The overall charge equalization effect is implemented by repeating the above {circle around (1)} to {circle around (4)} processes.

Further, for the charge equalization, a predetermined operation time (hereinafter, referred to as the charge equalization time) is present and in defining the predetermined operation time, various methods may be present. These methods are as follows.

i) A method of defining the charge equalization time by mathematical modeling depending on the charging or discharging current quantity of the equalization converter130and an energy storage capacity of the battery cell. The charge equalization operation time is defined by the so obtained charge equalization time and the equalization converter may be turned on/off depending on the operation time.

ii) A method of using the value previously stored in the control unit100. Therefore, when the specific battery cell reaches the preset cell voltage value by the equalization converter130based on a relationship table between the stage of charge (SOC) value and the voltage of the corresponding battery cell, the method is a method of turning off the equalization converter.

Herein, the value of the corresponding battery cell which is previously stored may be changed by the user. As an example, the value of the specific cell may be an average value of all the batteries, an SOC average of all the batteries, and a specific value which is increased or reduced to a preset fixed value in the average or SOC of all the batteries.

iii) A method of periodically performing the charge equalization operation in the specific battery cell for a predetermined time, not driving the apparatus for the predetermined charge equalization time and then comparing the cell voltage or the user's desired value through the SOC and SOH measurement with the reference value which is programmed or previously stored. The reference value may be any one of the user's designated voltage, the battery pack or average voltage, and the user's designated voltage and the state of health (SOH) increased and decreased in the battery pack or average voltage.

By the comparison and the continuous driving of the cell, the charge equalization is performed after the predetermined time. In this case, the reference value of the specific cell may be defined by the above-mentioned method.

Referring back toFIG. 6, the control unit100(FIG. 2) determines whether the charge equalization is completed by the process (step S670).

As the determination result, when the charge equalization for the corresponding battery cells B1,1to BM,Kis completed, the battery monitoring units120ato120mre-measures the potentials of the battery cells to determine whether the potentials of the battery cells reach the reference value (step S680).

Unlike this, in the step S670, when the charge equalization for the corresponding battery cells B1,1to BM,Kis not completed, the steps S630to S670are performed.

In the step S680, when the re-measured potential of the battery cell reaches the reference value, the charge equalization process ends.

Although the exemplary embodiment of the present invention has been described above with reference to the accompanying drawings, it may be appreciated by those skilled in the art that the scope of the present invention is not limited to the above-mentioned exemplary embodiment, but may be variously modified