High output battery pack and method of controlling the high output battery pack

A battery pack and a method of controlling the battery pack. The battery pack includes a battery cell and a capacitor connected in parallel to the battery pack. Accordingly, the battery power and the distance travelled by an electric transport device that requires an instantaneous high power output, such as an E-bike, may be increased.

CLAIM OF PRIORITY

This application makes reference to, incorporates into this specification the entire contents of, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on Mar. 29, 2010, and there duly assigned Serial No. 10-2010-0028078.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One or more embodiments of the present invention relate to a battery pack, and more particularly, to a high output battery pack and a method of controlling the battery pack.

2. Description of the Related Art

In general, rechargeable batteries are actively researched due to the development of mobile electronic appliances such as cellular phones, laptop computers, camcorders, personal digital assistants (PDA), and the like. In particular, examples of rechargeable batteries are nickel-cadmium batteries, lead storage batteries, nickel metal hydride batteries, lithium ion batteries, lithium polymer batteries, metal lithium batteries, and air zinc storage batteries. A rechargeable battery is combined with a circuit to form a battery pack, and is charged or recharged via an external terminal of the battery pack.

SUMMARY OF THE INVENTION

It is therefore an aspect of the present invention to provide an improved battery pack and an improved method for controlling the battery pack.

It is another aspect of the present invention to provide a battery pack capable of supplying a high amount of current to an electric transport that requires an instantaneous high power output.

According to one or more embodiments of the present invention, a battery pack may be constructed with a battery cell, a first discharging device connected between the battery cell and a first node, a capacitor connected to the first node in parallel with the battery cell, a second discharging device connected between the first node and a load, and a microcomputer controlling the first discharging device and the second discharging device.

The capacitor may be a motor-driving capacitor of an electric transport device.

The load may be a motor of an electric transport device.

When initially driving the motor, an electric energy charged in the capacitor may be discharged to the load according to the controlling of the microcomputer.

The electric transport device may be an E-bike.

The battery pack may further include a capacitor charging and discharging control unit connected between the first node and the capacitor. The microcomputer may control the capacitor charging and discharging control unit.

The capacitor charging and discharging control unit may include a current restricting unit connected to the capacitor and restricting an electric current flowing to the capacitor, a capacitor charging device connected between the first node and the current restricting unit, and a capacitor discharging device connected between the capacitor and the first node.

The microcomputer may control the capacitor charging device and the capacitor discharging device.

At least one of the first discharging device, the second discharging device, the capacitor charging device, and the capacitor discharging device may include a field effect transistor (FET).

According to one or more embodiments of the present invention, a method of controlling a battery pack is provided. The battery pack includes a battery cell, a capacitor connected in parallel with the battery cell, a first discharging device, a second discharging device, and a microcomputer. The method includes charging the capacitor according to a voltage across the battery cell by turning on the first discharging device, and discharging an electric energy charged in the capacitor to a load by turning on the second discharging device.

The discharging may be performed when the load is a motor of an electric transport device.

The load may be a motor of an electric transport device.

In the discharging, the electric energy charged in the capacitor may be discharged to the load according to the controlling of the microcomputer.

According to one or more embodiments of the present invention, a method of controlling a battery pack is provided. The battery pack includes a battery cell, a capacitor connected in parallel with the battery cell, a capacitor charging device, a current restricting unit, and a capacitor discharging device connected between the battery cell and the capacitor, a first discharging device, a second discharging device, and a microcomputer. The method includes turning on the first discharging device and the capacitor charging device, restrictively charging the capacitor according to a voltage across the battery cell by using the current restricting unit, and discharging an electric energy charged in the capacitor by turning on the capacitor discharging device and the second discharging device.

The load may be a motor of an electric transport device.

In the discharging, when initially driving the motor, the electric energy charged in the capacitor may be discharged to the load by turning on the capacitor discharging device and the second discharging device according to the controlling of the microcomputer.

At least one of the first discharging device, the second discharging device, the capacitor charging device, and the capacitor discharging device may be a field effect transistor (FET).

DETAILED DESCRIPTION

A contemporary battery pack includes a battery cell and a peripheral circuit including a charge and discharge circuit. The peripheral circuit is formed of a printed circuit board and is combined with the battery cell. When an external power source is connected to the battery pack via an external terminal, the battery cell is charged by the external power source via the external terminal and the charge and discharge circuit. When a load is connected to the external terminal, the battery cell supplies power to the load via the charge and discharge circuit and the external terminal. The charge and discharge circuit is arranged between the external terminal and the battery cell and controls charging and discharging of the battery cell.

Embodiments of the present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the description of the present invention, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention. Also, the meaning of the terms used in the present specification and claims of the present invention should not be limited to be of ordinary or literary meaning but construed as meanings and concepts not departing from the spirit and scope of the invention based on the principle that the inventor is capable of defining concepts of terms in order to describe his or her invention in the most appropriate way.

FIG. 1is a circuit diagram illustrating a battery pack100according to the related art.

Referring toFIG. 1, battery pack100includes a rechargeable battery cell120and a protection circuit, and is installed in an external system such as a portable laptop computer and charges or discharges battery cell120.

In detail, battery pack100includes battery cell120, an external terminal (not shown) that is connected in parallel to battery cell120, and a charging device130and a discharging device140that are serially connected to a high current path (HCP) between battery cell120and the external terminal, and the protection circuit, which includes a microcomputer110that is connected in parallel to battery cell120, charging device130, and discharging device140.

Although not shown inFIG. 1, the protection circuit of battery pack100may further include a current sensing unit that is serially connected to the HCP between battery cell120and the external terminal and that is also connected to microcomputer110, and a self-protecting control unit that is used to break a fuse positioned on the HCP according to the controlling of microcomputer110or the external system. If battery cell120is determined to be over-charged or over-discharged, microcomputer110turns off charging device130and discharging device120or breaks the fuse to block overcharging or over-discharging of battery cell120. That is, when battery cell120is determined to be over-charged or over-discharged, microcomputer110outputs a corresponding control signal to turn off charging device130and discharging device140, or to blow the fuse using the self-protecting control unit.

Battery pack100is connected to the external system via the external terminal to be charged or discharged. The HCP between the external terminal and battery cell120is used as a charge and discharge path, and a relatively large electric current flows through the HCP. Battery pack100may further include a system management BUS (SMBUS) between microcomputer110of the protection circuit and the external terminal for the purpose of communicating with the external system.

When driving an electrically driven transport device such as an E-bike, an E-scooter, etc., by using battery pack100according to the related art, a large number of battery cells needs to be connected in parallel in order to supply a current that is needed when starting the transport device or driving the transport device uphill, due to the characteristics of the transport device. When a lot of battery cells are connected in parallel, however, the volume of battery pack100increases, and the lifespan of and the distance traveled by the transport device that may be covered by battery pack100are reduced due to a high current flowing in battery pack100.

FIG. 2is a circuit diagram illustrating a battery pack200constructed as an embodiment according to the principles of the present invention.

Referring toFIG. 2, battery pack200includes a microcomputer210, a battery cell220, a first discharging device240, a second discharging device250, and a capacitor260. Although not shown inFIG. 2, battery pack200may further include a charging device to prevent overcharging of battery cell220. When an external power source is connected to charging and discharging terminals P+ and P− to charge battery cell220, microcomputer210checks a voltage across battery cell220, and if microcomputer210determines that the voltage across battery cell220is over a predetermined voltage, the charging device is turned off to prevent charging.

First discharging device240is connected between battery cell220and a first node N1. First discharging device240functions as a switch for discharging battery cell220and prevents over-discharging of battery cell220by being turned according to the controlling of microcomputer210. First discharging device240may be formed of a field electric transistor and a parasitic diode, or may be an electric device that performs the function described above as well as other types of switching functions.

A capacitor260is connected to first node N1in parallel to battery cell220. When first discharging device240is turned on, an electric current flows from battery cell220to capacitor260, and electric energy is stored in capacitor260while first discharging device240is turned on. The electric energy stored in capacitor260is proportional to a capacity of capacitor260, that is, a capacitance C, and thus capacitor260may be used as a capacitor for driving a motor of an electric transport device. For example, capacitor260may be a super-capacitor of several farads or greater.

Second discharging device250is connected between first node N1and a load201. When second discharging device250is turned on, an electric current flows from battery cell220to load201. Also, an electric current corresponding to the electric energy stored in capacitor260is also transmitted to load201. Accordingly, the current from battery cell220and the current from capacitor260are supplied together to load201. Here, the load requires a sudden high power output. For example, load201may be a motor that is used in electric transport devices such as E-bikes, E-scooters, electric wheel chairs, and electromotive carts, and the motor may be used when a high current is required as the motor is initially driven or when climbing an uphill road. Second discharging device250is a switch for driving a load connected to discharging terminal (P−), and may include a field effect transistor and a parasitic diode, but is not limited thereto, and instead may be an electric device that performs the function described above as well as other types of switching functions.

Microcomputer210controls switching operations of first discharging device240and second discharging device250. When capacitor260needs to be charged, first discharging device240and second discharging device250are turned on to charge capacitor260. When there is no need to supply a current to load201, for example, when an E-bike is stopped, first discharging device240is turned on and second discharging device250is turned off, so that a current is supplied only to capacitor260.

FIG. 4is a flowchart illustrating a method of controlling battery pack200ofFIG. 2, as an embodiment according to the principles of the present invention.

Referring toFIG. 4, in operation400, first discharging device240is turned on. When both first and second discharging devices240and250are turned on, part of an electrical current from battery cell220flows to capacitor260and electrically energy is stored in the capacitor260, and the remaining-part of the current from battery cell220flows through load201at the same time. When first discharging device240is turned on and second discharging device250is turned off, electric energy is only stored in capacitor260, and no electrically current flows through load201. In operation402, battery cell220charges capacitor260to the voltage of battery cell220. Capacitor260is a motor driving capacitor of an electric transport device, and may be an F-unit super capacitor, that is, a super capacitor having a capacitance of several farads. In operations404and406, second discharging device250is turned on to discharge the voltage stored in capacitor260to load201. When first discharging device240and second discharging device250are turned on, a current from battery cell220and a current from capacitor260are transmitted to load201together, thereby transmitting a high current to load201.

FIG. 3is a circuit diagram illustrating a battery pack300constructed as another embodiment according to the principles of the present invention.

Referring toFIG. 3, battery pack300includes a microcomputer310, a battery cell320, a first discharging device340, a second discharging device350, a capacitor360, and a capacitor charge and discharge control unit370. Capacitor charge and discharge control unit370includes a capacitor charging device371, a current restricting unit372, and a capacitor discharging device373. Battery pack300ofFIG. 3is different from battery pack200ofFIG. 2in that capacitor charge and discharge control unit370is further included. Thus, battery pack300will be described by focusing on differences between battery packs200and300ofFIGS. 2 and 3.

Due to the characteristics of capacitors, a current is continuously input to a capacitor while no electric energy has been accumulated in the capacitor. If an initial discharging switch, that is, a first discharging device, is turned off and the capacitor is empty, that is, when there is no accumulated electric energy in the capacitor, then when the initial discharging switch is turned on, the capacitor behaves the same as a load. That is, since the capacitor tends to receive a current as high as possible from a battery cell and thus there is a possibility of danger due to an over-current, capacitor charge and discharge control unit370for controlling charging and discharging of the capacitor is required.

Capacitor charge and discharge control unit370is connected between a first node N1and capacitor360. Capacitor charge and discharge control unit370controls charging or discharging of capacitor360according to the controlling of microcomputer310. Capacitor charge and discharge control unit370includes capacitor charging device371, current restricting unit372, and capacitor discharging device373. Capacitor charging device371and capacitor discharging device373may also be formed of a field effect transistor (FET) and a parasitic diode like first discharging device340and second discharging device350, but are not limited thereto, and may instead be electric devices that perform the functions described above as well as other types of switching functions.

Capacitor charging device371is connected between first node N1and current restricting unit372. Capacitor charging device371is turned on according to the controlling of microcomputer310when electric energy needs to be stored in capacitor360so that a current from battery cell320flows to capacitor360.

Current restricting unit372is connected between capacitor charging device371and capacitor360. Current restricting unit372prevents an excessive current from flowing to capacitor360when capacitor360is empty, that is, when there is no accumulated electric energy in capacitor360. Current restricting unit372may be formed of, for example, a diode or a static current circuit, and controls a current amount according to the controlling of microcomputer310.

Capacitor discharging device373is connected between first node N1and capacitor360. Capacitor discharging device373is turned on by microcomputer310to supply a current to a load301and to discharge the electric energy charged in capacitor360.

Microcomputer310controls switching operations of first discharging device340, capacitor charging device371, capacitor discharging device373, and second discharging device350.

When capacitor360is to be charged, first discharging device340and capacitor charging device371are turned on to charge capacitor360. Also, when energy accumulated in capacitor360is to be used, microcomputer310turns on capacitor discharging device373to supply a current from capacitor360to load301.

FIG. 5is a flowchart illustrating a method of controlling battery pack300ofFIG. 3, as an embodiment according to the principles of the present invention.

Referring toFIG. 5, in operation500, first discharging device340is turned on. Second discharging device350may be turned on or turned off when first discharging device340is turned on. Second discharging device350is turned on when a great current is not required for load301, and thus a remaining part of the current that flows from battery cell320flows to capacitor360and is stored in capacitor360.

In operation502, capacitor charging device371is turned on. In operation504, battery cell320charges capacitor360restrictively accordingly to a voltage of battery cell320. A current is restrictively transmitted from battery cell320through current restricting unit372to thereby restrictively charge capacitor360. By using current restricting unit372, an excessive current flow may be prevented if capacitor360is empty, thereby achieving stability.

In operations506through510, capacitor discharging device373is turned on. When all of the electric energy stored in capacitor360is to be used, for example, when load301is a motor of an electric transport device which is initially driven or is driven uphill, capacitor discharging device373is turned on to supply a current to load301from capacitor360.

According to the embodiment of the present invention, the battery pack includes a battery cell and a capacitor that is arranged in parallel to the battery cell. By using the battery cell, the battery power and the distance covered by an electric transport that requires an instantaneous high power output may be increased, such as an E-bike, are increased.

Also, by controlling charging and discharging of the capacitor to stably operate the capacitor, a current may be stably used in the battery pack and the lifespan of the battery pack may be increased.

While the exemplary the embodiments of the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the embodiments of invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the embodiments of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the embodiments of the present invention.