Patent Description:
A battery pack that supplies power to an electronic device includes a protection circuit for protecting a battery cell of the battery pack from overcurrent. If an electric current flowing to the battery cell exceeds the maximum value, the protection circuit can cut the electric current flowing to the battery cell by turning a switching element OFF.

<CIT> describes changing a current value for determining whether or not to cut an electric current flowing from a positive terminal to a battery cell according to the temperature, voltage, or remaining capacity of the battery pack.

However, the battery pack described in <CIT> is not a battery pack that includes positive terminals and negative terminals. Therefore, in a case where the battery pack described in <CIT> is connected to an electronic device, the battery pack cannot change a current value for determining whether or not to cut an electric current flowing from the battery cell to the electronic device based on the number of positive terminals and negative terminals that are connected to the electronic device. <CIT> discloses a battery pack having two cell units each providing independently two positive and negative electrode terminals and a microcomputer, which adapts the current limit value in accordance with a type of a connected device. In order to determine the type of the connected device, the microcomputer compares the potential of the positive and negative terminal. <CIT> discloses a battery device having a switching element for interrupting the current flowing through a cell group, in case the current would exceed a predetermined threshold.

According to an aspect of the embodiments, a device, a method, or a program that is capable of changing a current value for determining whether or not to cut a current flowing from a battery cell to an electronic device based on the number of positive terminals and negative terminals that are connected to the electronic device, is provided.

The present invention provides a battery pack, a method, and a program as specified in the appended claims.

Further aspects of the embodiments will become apparent from the following embodiments.

Exemplary embodiments, features, and aspects of the disclosure will be described below with reference to the drawings. However, aspects of the disclosure are not limited to the following embodiments.

<FIG> and <FIG> are block diagrams showing components of a battery pack <NUM> and components of an electronic device <NUM> that is connectable to the battery pack <NUM>.

The battery pack <NUM> is a battery pack that is connectable to the electronic device <NUM>. The battery pack <NUM> is connected to the electronic device <NUM> as a result of being housed in a battery pack housing portion of the electronic device <NUM>. The battery pack <NUM> includes a battery cell <NUM>, a first positive terminal 102a, a first negative terminal 102b, a second positive terminal 103a, a second negative terminal 103b, a current detection circuit <NUM>, a control unit <NUM>, an FET unit <NUM>, a communication unit <NUM>, and a communication terminal <NUM>.

The battery cell <NUM> is a rechargeable battery cell such as a lithium ion battery cell. The battery cell <NUM> includes one or more battery cells.

The first positive terminal 102a and the first negative terminal 102b are terminals that can sufficiently withstand an electric current of <NUM> A, for example. The second positive terminal 103a and the second negative terminal 103b are also terminals that can sufficiently withstand an electric current of <NUM> A, for example. In a case where the first positive terminal 102a and the first negative terminal 102b are connected to the electronic device <NUM>, the battery cell <NUM> can supply an electric current of up to <NUM> A, for example, to the electronic device <NUM>. In a case where the second positive terminal 103a and the second negative terminal 103b are connected to the electronic device <NUM> as well, the battery cell <NUM> can supply an electric current of up to <NUM> A, for example, to the electronic device <NUM>. In a case where positive terminals and negative terminals that are connected to the electronic device <NUM> are the terminals 102a, 102b, 103a, and 103b, the battery cell <NUM> can supply an electric current of up to <NUM> A, for example, to the electronic device <NUM>. Note that out of the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b, terminals via which the battery pack <NUM> is connected to the electronic device <NUM> change according to the type of the electronic device <NUM>.

The current detection circuit <NUM> is provided between the battery cell <NUM> and each of the first negative terminal 102b and the second negative terminal 103b, and detects an electric current that flows from the battery cell <NUM> to the electronic device <NUM> or an electric current that flows from the electronic device <NUM> to the battery cell <NUM>. The current detection circuit <NUM> detects the electric current flowing from the battery cell <NUM> to the electronic device <NUM> or the electric current flowing from the electronic device <NUM> to the battery cell <NUM> based on the magnitude of a voltage drop, for example. The control unit <NUM> is informed of the electric current detected by the current detection circuit <NUM>. Thus, the control unit <NUM> can be aware of the electric current flowing from the battery cell <NUM> to the electronic device <NUM> or the electric current flowing from the electronic device <NUM> to the battery cell <NUM>.

The FET unit <NUM> includes a charge FET 106a and a discharge FET 106b. The charge FET 106a is a switch that is controlled by the control unit <NUM> to be turned ON or OFF. The discharge FET 106b is also a switch that is controlled by the control unit <NUM> to be turned ON or OFF. If the charge FET 106a is turned OFF and the discharge FET 106b is turned ON, an electric current flows from the battery cell <NUM> to the electronic device <NUM>. In this case, the electric current flowing from the battery cell <NUM> to the electronic device <NUM> is cut as a result of the control unit <NUM> turning the discharge FET 106b OFF. If the charge FET 106a is turned ON and the discharge FET 106b is turned OFF, an electric current flows from the electronic device <NUM> to the battery cell <NUM>. In this case, the electric current flowing from the electronic device <NUM> to the battery cell <NUM> is cut as a result of the control unit <NUM> turning the charge FET 106a OFF.

The communication unit <NUM> communicates with a communication unit <NUM> of the electronic device <NUM> via communication terminals <NUM> and <NUM>. When the battery pack <NUM> is connected to the electronic device <NUM>, the communication unit <NUM> is electrically connected to the communication unit <NUM> via the communication terminals <NUM> and <NUM>.

The control unit <NUM> controls discharging and charging of the battery cell <NUM> and detects information regarding the battery cell <NUM> (the remaining charge, degradation state, temperature, etc., of the battery cell <NUM>). The control unit <NUM> includes a memory and a processor, for example. The components of the battery pack <NUM> are controlled as a result of the processor of the control unit <NUM> executing a program that is stored in the memory of the control unit <NUM>. The control unit <NUM> can be constituted by an integrated circuit such as an ASIC (Application Specific Integrated Circuit), for example. Information regarding the battery cell <NUM> (the remaining charge, degradation state, temperature, etc., of the battery cell <NUM>) is detected by the processor of the control unit <NUM> and is stored in the memory of the control unit <NUM>, for example.

The control unit <NUM> can control operations of the communication unit <NUM>. The control unit <NUM> can communicate with a control unit <NUM> of the electronic device <NUM> by controlling operations of the communication unit <NUM>. The control unit <NUM> can detect the number of positive terminals and negative terminals that are connected to the electronic device <NUM> based on information that is received from the control unit <NUM> via the communication terminal <NUM> and the communication unit <NUM>.

The control unit <NUM> can control operations of the charge FET 106a and the discharge FET 106b. The control unit <NUM> can operate as a protection circuit that cuts an electric current flowing from the battery cell <NUM> to the electronic device <NUM> or an electric current flowing from the electronic device <NUM> to the battery cell <NUM> by controlling operations of the charge FET 106a and the discharge FET 106b. For example, the control unit <NUM> cuts an electric current flowing from the battery cell <NUM> to the electronic device <NUM> by turning the discharge FET 106b OFF upon determining that the electric current flowing from the battery cell <NUM> to the electronic device <NUM> has exceeded the maximum current value (a predetermined current value) of the battery pack <NUM>.

The control unit <NUM> can monitor the voltage of the communication terminal <NUM>. The control unit <NUM> determines whether or not a period during which the voltage of the communication terminal <NUM> does not exceed a first voltage value has exceeded a first predetermined period. Upon determining that the period during which the voltage of the communication terminal <NUM> does not exceed the first voltage value has exceeded the first predetermined period, the control unit <NUM> determines that the battery pack <NUM> has been detached from the electronic device <NUM>. The control unit <NUM> determines whether or not a period during which the voltage of the communication terminal <NUM> is larger than a second voltage value has exceeded a second predetermined period. Upon determining that the period during which the voltage of the communication terminal <NUM> is larger than the second voltage value has exceeded the second predetermined period, the control unit <NUM> determines that the battery pack <NUM> has been connected to the electronic device <NUM>. Here, the second voltage value is larger than or equal to the first voltage value. The second predetermined period is the same as or is different from the first predetermined period. The first voltage value, the second voltage value, the first predetermined period, and the second predetermined period are stored in the memory of the control unit <NUM>.

The electronic device <NUM> is an electronic device that is connectable to the battery pack <NUM>. The electronic device <NUM> includes a load circuit <NUM>, at least one of a first positive terminal 202a and a second positive terminal 203a, at least one of a first negative terminal 202b and a second negative terminal 203b, the control unit <NUM>, the communication unit <NUM>, and the communication terminal <NUM>. Which terminals of the first positive terminal 202a, the first negative terminal 202b, the second positive terminal 203a, and the second negative terminal 203b are included in the electronic device <NUM> changes according to the type of the electronic device <NUM>. For example, the electronic device <NUM> shown in <FIG> includes the first positive terminal 202a, the first negative terminal 202b, the second positive terminal 203a, and the second negative terminal 203b. The electronic device <NUM> shown in <FIG> can receive an electric current of up to a first current value (e.g., <NUM> A) from the battery pack <NUM> via the first positive terminal 202a, the first negative terminal 202b, the second positive terminal 203a, and the second negative terminal 203b. For example, the electronic device <NUM> shown in <FIG> does not include the first positive terminal 202a and the first negative terminal 202b but includes the second positive terminal 203a and the second negative terminal 203b. The electronic device <NUM> shown in <FIG> can receive an electric current of up to a second current value (e.g., <NUM> A) from the battery pack <NUM> via the second positive terminal 203a and the second negative terminal 203b.

The configuration of the load circuit <NUM> changes according to the type of the electronic device <NUM>. If the electronic device <NUM> is an electronic device that operates as a digital camera, for example, the load circuit <NUM> includes components (including an image capturing unit, an image processing unit, a recording unit, a reproduction unit, a display unit, etc.) that are necessary for the electronic device <NUM> to operate as the digital camera. If the electronic device <NUM> is an electronic device that operates as a charger, for example, the load circuit <NUM> includes components (including a voltage conversion unit, a charging unit, etc.) that are necessary for the electronic device <NUM> to operate as the charger.

The first positive terminal 202a is a terminal that is connected to the first positive terminal 102a of the battery pack <NUM>, and the first negative terminal 202b is a terminal that is connected to the first negative terminal 102b of the battery pack <NUM>. The second positive terminal 203a is a terminal that is connected to the second positive terminal 103a of the battery pack <NUM>, and the second negative terminal 203b is a terminal that is connected to the second negative terminal 103b of the battery pack <NUM>. The first positive terminal 202a and the first negative terminal 202b are terminals that can sufficiently withstand an electric current of <NUM> A, for example. The second positive terminal 203a and the second negative terminal 203b are also terminals that can sufficiently withstand an electric current of <NUM> A, for example. The communication terminal <NUM> is a terminal that is connected to the communication terminal <NUM> of the battery pack <NUM>.

The communication unit <NUM> communicates with the communication unit <NUM> of the battery pack <NUM> via the communication terminals <NUM> and <NUM>. When the battery pack <NUM> is connected to the electronic device <NUM>, the communication unit <NUM> is electrically connected to the communication unit <NUM> via the communication terminals <NUM> and <NUM>.

The control unit <NUM> controls the load circuit <NUM> and detects information regarding the load circuit <NUM>. The control unit <NUM> includes a memory and a processor, for example. The components of the electronic device <NUM> are controlled as a result of the processor of the control unit <NUM> executing a program that is stored in the memory of the control unit <NUM>. The control unit <NUM> can be constituted by an integrated circuit such as an ASIC (Application Specific Integrated Circuit), for example. Information (e.g., ID information of the electronic device <NUM>) that indicates the type of the electronic device <NUM> is stored in the memory of the control unit <NUM>.

The control unit <NUM> can control operations of the communication unit <NUM>. The control unit <NUM> can communicate with the control unit <NUM> of the battery pack <NUM> by controlling operations of the communication unit <NUM>. The control unit <NUM> transmits the information indicating the type of the electronic device <NUM> via the communication unit <NUM> and the communication terminal <NUM> to the control unit <NUM>.

The control unit <NUM> can monitor the voltage of the first positive terminal 202a and the voltage of the second positive terminal 203a. The control unit <NUM> can detect the number of positive terminals and negative terminals that are connected to the battery pack <NUM> based on the voltage of the first positive terminal 202a and the voltage of the second positive terminal 203a. Upon detecting the number of positive terminals and negative terminals connected to the battery pack <NUM>, the control unit <NUM> transmits information indicating the number of positive terminals and negative terminals connected to the battery pack <NUM>, to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>.

The electronic device <NUM> further includes a battery pack housing portion for housing the battery pack <NUM>, a lid that is provided in the vicinity of an opening portion of the battery pack housing portion, and a lock mechanism that maintains connection between the battery pack <NUM> and the electronic device <NUM> even when the lid is open. The control unit <NUM> is configured to detect whether the lid of the battery pack housing portion is open or closed. Upon detecting that the lid of the battery pack housing portion is open, the control unit <NUM> transmits information indicating that the lid of the battery pack housing portion is open, to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>.

Next, first change processing for changing the maximum current value of the battery pack <NUM> will be described with reference to the flowchart shown in <FIG>. Note that the first change processing is started in a case where the control unit <NUM> has detected that the battery pack <NUM> is connected to the electronic device <NUM>.

In step S201, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to an initial value. The initial value is a current value that is the safest, and is the same as the second current value (e.g., <NUM> A) or is smaller than the second current value. Accordingly, upon determining that an electric current flowing from the battery cell <NUM> to the electronic device <NUM> has exceeded the initial value, the control unit <NUM> can cut the electric current flowing from the battery cell <NUM> to the electronic device <NUM> by turning the discharge FET 106b OFF. As described above, the maximum current value of the battery pack <NUM> is changed to the initial value to prevent an electric current flowing from the battery cell <NUM> to the electronic device <NUM> from exceeding the initial value. As a result, the control unit <NUM> can protect the battery cell <NUM>, the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b from overcurrent.

In step S202, the control unit <NUM> receives information for detecting the number of positive terminals and negative terminals that are connected to the electronic device <NUM> from the control unit <NUM> via the communication terminal <NUM> and the communication unit <NUM>. The information for detecting the number of positive terminals and negative terminals connected to the electronic device <NUM> may be information indicating the type of the electronic device <NUM> or information indicating the number of positive terminals and negative terminals that are connected to the battery pack <NUM>. A case will be described as an example in which the information for detecting the number of positive terminals and negative terminals connected to the electronic device <NUM> is information indicating the type of the electronic device <NUM>. In this case, the control unit <NUM> transmits the information indicating the type of the electronic device <NUM>, which is stored in the memory of the control unit <NUM>, to the control unit <NUM>. A case will be described as an example in which the information for detecting the number of positive terminals and negative terminals connected to the electronic device <NUM> is information indicating the number of positive terminals and negative terminals that are connected to the battery pack <NUM>. In this case, the control unit <NUM> detects the number of positive terminals and negative terminals connected to the battery pack <NUM> based on a predetermined method, and transmits information indicating the detected number to the control unit <NUM>.

In step S203, the control unit <NUM> detects the number of positive terminals and negative terminals that are connected to the electronic device <NUM> based on the information received in step S202. A case will be described as an example in which the information received in step S202 is the information indicating the type of the electronic device <NUM>. In this case, the control unit <NUM> detects the number of terminals that corresponds to the type of the electronic device <NUM> as the number of positive terminals and negative terminals connected to the electronic device <NUM>, based on a correspondence between the type of the electronic device <NUM> and the number of terminals. Note that the correspondence between the type of the electronic device <NUM> and the number of terminals is stored in the memory of the control unit <NUM> in advance. A case will be described as an example in which the information received in step S202 is the information indicating the number of positive terminals and negative terminals connected to the battery pack <NUM>. In this case, the control unit <NUM> detects the number of positive terminals and negative terminals connected to the battery pack <NUM> as the number of positive terminals and negative terminals connected to the electronic device <NUM>.

<FIG> shows an example of the correspondence between the type of the electronic device <NUM> and the number of terminals. If the control unit <NUM> has determined that the type of the electronic device <NUM> is a camera A or a charger, for example, the control unit <NUM> detects <NUM> as the number of positive terminals and negative terminals connected to the electronic device <NUM>. If the control unit <NUM> has determined that the type of the electronic device <NUM> is a camera B or a stroboscope device, for example, the control unit <NUM> detects <NUM> as the number of positive terminals and negative terminals connected to the electronic device <NUM>.

In step S204, the control unit <NUM> determines whether or not the number detected in step S203 is correct. If the number detected in step S203 matches either a first number (e.g., <NUM>) or a second number (e.g., <NUM>), the control unit <NUM> determines that the number detected in step S203 is correct. Here, the first number and the second number are stored in the memory of the control unit <NUM> in advance. If the number detected in step S203 does not match the first number (e.g., <NUM>) and the second number (e.g., <NUM>), the control unit <NUM> determines that the number detected in step S203 is not correct. In a case where the number of positive terminals and negative terminals connected to the electronic device <NUM> could not be detected in step S203 as well, the control unit <NUM> determines that the number detected in step S203 is not correct. If the control unit <NUM> has determined that the number detected in step S203 is correct, the control unit <NUM> proceeds to step S205. If the control unit <NUM> has determined that the number detected in step S203 is not correct, the flowchart shown in <FIG> ends in the state where the maximum current value of the battery pack <NUM> is the initial value. Note that, if the control unit <NUM> has determined that the number detected in step S203 is not correct, the control unit <NUM> may also transmit error information indicating that the number of positive terminals and negative terminals connected to the electronic device <NUM> could not be correctly detected, to the control unit <NUM>.

In step S205, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to a current value (a first current value or a second current value) that corresponds to the number detected in step S203, based on a correspondence between the number detected in step S203 and the maximum current value. Note that the correspondence between the number detected in step S203 and the maximum current value is stored in the memory of the control unit <NUM> in advance. <FIG> shows an example of the correspondence between the number (detected number) detected in step S203 and the maximum current value. As shown in <FIG>, the maximum current value becomes larger as the number (detected number) detected in step S203 becomes larger. If the number detected in step S203 is the second number (e.g., <NUM>), for example, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the second current value (e.g., <NUM> A). If the number detected in step S203 is the first number (e.g., <NUM>), for example, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the first current value (e.g., <NUM> A).

Thus, the control unit <NUM> can change the maximum current value of the battery pack <NUM> to the current value (the first current value or the second current value) corresponding to the number of positive terminals and negative terminals connected to the electronic device <NUM>. As a result, the battery pack <NUM> can protect the battery cell <NUM>, the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b from overcurrent.

In step S206, the control unit <NUM> transmits information indicating the number detected in step S203 (which is equivalent to the number of positive terminals and negative terminals connected to the electronic device <NUM>) to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>. The control unit <NUM> further transmits information indicating the maximum current value changed in step S205 (which is equivalent to the current value corresponding to the number detected in step S203) to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>. Thus, the control unit <NUM> can be aware of the number of positive terminals and negative terminals connected to the electronic device <NUM> and the maximum current value of the battery pack <NUM>.

Next, second change processing for changing the maximum current value of the battery pack <NUM> will be described with reference to the flowchart shown in <FIG>. Note that the second change processing is started in a case where the battery pack <NUM> is connected to the electronic device <NUM>.

In step S301, the control unit <NUM> determines whether or not the voltage of the communication terminal <NUM> exceeds the first voltage value. If the control unit <NUM> has determined that the voltage of the communication terminal <NUM> does not exceed the first voltage value, the control unit <NUM> proceeds to step S302. If the control unit <NUM> has determined that the voltage of the communication terminal <NUM> exceeds the first voltage value, the control unit <NUM> repeats step S301.

In step S302, the control unit <NUM> determines whether or not a period during which the voltage of the communication terminal <NUM> does not exceed the first voltage value has reached the first predetermined period. If the control unit <NUM> has determined that the period during which the voltage of the communication terminal <NUM> does not exceed the first voltage value has reached the first predetermined period, the control unit <NUM> proceeds to step S303. If the control unit <NUM> has determined that the period during which the voltage of the communication terminal <NUM> does not exceed the first voltage value has not reached the first predetermined period, the control unit <NUM> returns to step S301.

In step S303, the control unit <NUM> determines that the battery pack <NUM> has been detached from the electronic device <NUM>.

In step S304, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the initial value described above. Accordingly, upon determining that an electric current flowing from the battery cell <NUM> to the electronic device <NUM> has exceeded the initial value, the control unit <NUM> can cut the electric current flowing from the battery cell <NUM> to the electronic device <NUM> by turning the discharge FET 106b OFF. As described above, the maximum current value of the battery pack <NUM> is changed to the initial value to prevent an electric current flowing from the battery cell <NUM> to the electronic device <NUM> from exceeding the initial value. As a result, the control unit <NUM> can protect the battery cell <NUM>, the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b from overcurrent.

Next, third change processing for changing the maximum current value of the battery pack <NUM> will be described with reference to the flowchart shown in <FIG>. Note that the third change processing is started in a case where the battery pack <NUM> is connected to the electronic device <NUM>.

In step S401, the control unit <NUM> detects whether the lid of the battery pack housing portion is open or closed. If the control unit <NUM> has detected that the lid of the battery pack housing portion is open, the control unit <NUM> determines that it is highly likely that the battery pack <NUM> will be detached from the electronic device <NUM>, and proceeds to step S402. If the control unit <NUM> has detected that the lid of the battery pack housing portion is closed, the control unit <NUM> determines that it is not highly likely that the battery pack <NUM> will be detached from the electronic device <NUM>, and repeats step S401. As described above, the control unit <NUM> determines whether or not it is highly likely that the battery pack <NUM> will be detached from the electronic device <NUM>, by detecting whether the lid of the battery pack housing portion is open or closed. Note that another method may also be used to determine whether or not it is highly likely that the battery pack <NUM> will be detached from the electronic device <NUM>. For example, the control unit <NUM> may also detect whether or not a predetermined operation that is performed before the battery pack <NUM> is detached has been performed, to determine whether or not it is highly likely that the battery pack <NUM> will be detached from the electronic device <NUM>. In this case, the control unit <NUM> is configured to detect whether or not the predetermined operation that is performed before the battery pack <NUM> is detached has been performed.

In step S402, the control unit <NUM> transmits information indicating that the lid of the battery pack housing portion is open, to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>. Furthermore, the control unit <NUM> may also suspend or end a portion of processing that is performed by the load circuit <NUM>. For example, the control unit <NUM> may also suspend or end processing that consumes a large amount of power. For example, the control unit <NUM> may also end processing (processing for storing image data, settings of the electronic device <NUM>, etc.) that is to be ended before the battery pack <NUM> is detached from the electronic device <NUM>.

In step S403, the control unit <NUM> receives the information indicating that the lid of the battery pack housing portion is open, from the control unit <NUM> via the communication terminal <NUM> and the communication unit <NUM>.

In step S404, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the initial value described above. Accordingly, upon determining that an electric current flowing from the battery cell <NUM> to the electronic device <NUM> has exceeded the initial value, the control unit <NUM> can cut the electric current flowing from the battery cell <NUM> to the electronic device <NUM> by turning the discharge FET 106b OFF. As described above, the maximum current value of the battery pack <NUM> is changed to the initial value to prevent an electric current flowing from the battery cell <NUM> to the electronic device <NUM> from exceeding the initial value. As a result, the control unit <NUM> can protect the battery cell <NUM>, the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b from overcurrent.

Note that, if the lid of the battery pack housing portion has been opened but is closed without the battery pack <NUM> being detached from the electronic device <NUM>, the control unit <NUM> may also transmit information indicating that the lid of the battery pack housing portion is closed, to the control unit <NUM> via the communication unit <NUM> and the communication terminal <NUM>. In this case, the control unit <NUM> performs the processing in step S202 and the following steps shown in <FIG> after receiving the information indicating that the lid of the battery pack housing portion is closed, from the control unit <NUM>. As a result of the processing in step S202 and the following steps shown in <FIG> being performed, the maximum current value of the battery pack <NUM> can be changed to a current value that corresponds to the number of positive terminals and negative terminals connected to the electronic device <NUM>.

As described above, according to Embodiment <NUM>, the battery pack <NUM> can change the maximum current value of the battery pack <NUM> to the current value (the first current value or the second current value) corresponding to the number of positive terminals and negative terminals connected to the electronic device <NUM>. As a result, the battery pack <NUM> can protect the battery cell <NUM>, the first positive terminal 102a, the first negative terminal 102b, the second positive terminal 103a, and the second negative terminal 103b from overcurrent.

Next, a variation of Embodiment <NUM> will be described. <FIG> is a block diagram showing another example of components of the battery pack <NUM> and components of the electronic device <NUM>. Note that among the components shown in <FIG>, components that are similar to those shown in <FIG> are denoted with the same reference signs as those used in <FIG>, and detailed descriptions of which are omitted. However, unlike the first positive terminal 102a and the first negative terminal 102b shown in <FIG>, the first positive terminal 102a and the first negative terminal 102b shown in <FIG> are terminals that can sufficiently withstand an electric current of <NUM> A, for example. Unlike the control unit <NUM> shown in <FIG>, the control unit <NUM> shown in <FIG> can also detect the type of positive terminals and negative terminals that are connected to the electronic device <NUM>. The control unit <NUM> can detect the type of positive terminals and negative terminals connected to the electronic device <NUM> based on information for detecting the type of positive terminals and negative terminals connected to the electronic device <NUM>, for example. The information for detecting the type of positive terminals and negative terminals connected to the electronic device <NUM> is information that is transmitted from the control unit <NUM> to the control unit <NUM>, for example. The information for detecting the type of positive terminals and negative terminals connected to the electronic device <NUM> may be information indicating the type of the electronic device <NUM> or information indicating the type of positive terminals and negative terminals that are connected to the battery pack <NUM>. A case will be described as an example in which the information for detecting the type of positive terminals and negative terminals connected to the electronic device <NUM> is information indicating the type of the electronic device <NUM>. In this case, the control unit <NUM> detects, as the type of positive terminals and negative terminals connected to the electronic device <NUM>, a type of positive terminals and negative terminals that corresponds to the type of the electronic device <NUM> based on a correspondence between the type of the electronic device <NUM> and the type of positive terminals and negative terminals. Note that the correspondence between the type of the electronic device <NUM> and the type of positive terminals and negative terminals is stored in the memory of the control unit <NUM> in advance. A case will be described as an example in which the information for detecting the type of positive terminals and negative terminals connected to the electronic device <NUM> is information indicating the type of positive terminals and negative terminals that are connected to the battery pack <NUM>. In this case, the control unit <NUM> detects the type of positive terminals and negative terminals connected to the battery pack <NUM> based on a predetermined method, and transmits information indicating the detected type to the control unit <NUM> together with information indicating the number of positive terminals and negative terminals connected to the battery pack <NUM>. The control unit <NUM> detects the type of positive terminals and negative terminals connected to the battery pack <NUM> as the type of positive terminals and negative terminals connected to the electronic device <NUM>.

Unlike the battery pack <NUM> shown in <FIG>, the battery pack <NUM> shown in <FIG> includes a fuse <NUM>. The fuse <NUM> is provided between the second positive terminal 103a and the FET unit <NUM>. The fuse <NUM> is configured to melt if an electric current that flows from the battery cell <NUM> to the second positive terminal 103a exceeds a current value (e.g., <NUM> A). Note that the current value at which the fuse <NUM> melts is set according to the performance of the second positive terminal 103a and the second negative terminal 103b. As a result of the fuse <NUM> being provided between the second positive terminal 103a and the FET unit <NUM>, the second positive terminal 103a, the second negative terminal 103b, the battery pack <NUM>, and the electronic device <NUM> can be protected even if an electric current of <NUM> A flows to the second positive terminal 103a and the second negative terminal 103b for some reason.

After detecting that the number of positive terminals and negative terminals connected to the electronic device <NUM> is the second number (e.g., <NUM>), the control unit <NUM> detects the type of positive terminals and negative terminals connected to the electronic device <NUM> based on the information received from the control unit <NUM>. Then, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the first current value or the second current value based on a correspondence between the type of positive terminals and negative terminals connected to the electronic device <NUM> and the maximum current value. Note that the correspondence between the type of positive terminals and negative terminals connected to the electronic device <NUM> and the maximum current value is stored in the memory of the control unit <NUM> in advance. If the first positive terminal 102a and the first negative terminal 102b are connected to the electronic device <NUM>, for example, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the first current value (e.g., <NUM> A). If the second positive terminal 103a and the second negative terminal 103b are connected to the electronic device <NUM>, for example, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the second current value (e.g., <NUM> A). Accordingly, if the first positive terminal 102a and the first negative terminal 102b are connected to the electronic device <NUM>, the battery cell <NUM> can supply an electric current of up to the first current value (e.g., <NUM> A) to the electronic device <NUM>. On the other hand, if the second positive terminal 103a and the second negative terminal 103b are connected to the electronic device <NUM>, the battery cell <NUM> can supply an electric current of up to the second current value (e.g., <NUM> A) to the electronic device <NUM>. Note that if positive terminals and negative terminals that are connected to the electronic device <NUM> are the terminals 102a, 102b, 103a, and 103b, the battery cell <NUM> can supply an electric current of up to the first current value (e.g., <NUM> A) to the electronic device <NUM>.

Unlike the electronic device <NUM> shown in <FIG>, the electronic device <NUM> shown in <FIG> does not include the second positive terminal 203a and the second negative terminal 203b, but includes the first positive terminal 202a and the first negative terminal 202b. As described above, if the first positive terminal 102a and the first negative terminal 102b are connected to the electronic device <NUM>, the control unit <NUM> changes the maximum current value of the battery pack <NUM> to the first current value (e.g., <NUM> A). Accordingly, the battery cell <NUM> can supply an electric current of up to the first current value (e.g., <NUM> A) to the electronic device <NUM>. The electronic device <NUM> shown in <FIG> can receive an electric current of up to the first current value (e.g., <NUM> A) from the battery pack <NUM> via the first positive terminal 202a and the first negative terminal 202b.

The various functions, processes, or methods described in Embodiment <NUM> can also be implemented as a result of a personal computer, a microcomputer, a CPU (Central Processing Unit), or a processor executing a program. In Embodiment <NUM>, the personal computer, the microcomputer, the CPU, or the processor will be referred to as a "computer X". Also, in Embodiment <NUM>, the program for controlling the computer X and implementing the various functions, processes, or methods described in Embodiment <NUM> will be referred to as a "program Y".

The various functions, processes, or methods described in Embodiment <NUM> are implemented as a result of the computer X executing the program Y. In this case, the program Y is supplied to the computer X via a computer-readable storage medium. The computer-readable storage medium in Embodiment <NUM> includes at least one of a hard disk device, a magnetic storage device, an optical storage device, a magneto-optical storage device, a memory card, a volatile memory, a non-volatile memory, or the like. The computer-readable storage medium in Embodiment <NUM> is a non-transitory storage medium.

Claim 1:
A battery pack (<NUM>) that is connectable to an electronic device (<NUM>), comprising:
positive terminals (102a, 103a);
negative terminals (102b, 103b);
a cutting means (106b) for cutting a current that flows from a battery cell (<NUM>) to the electronic device (<NUM>) in a case where the current flowing from the battery cell (<NUM>) to the electronic device (<NUM>) exceeds a maximum current value; and
a control means (<NUM>) for changing the maximum current value to an initial value upon detecting that the battery pack (<NUM>) is connected to the electronic device (<NUM>),
wherein the initial value is equal to or smaller than a current value in a case in which one positive terminal (102a, 103a) and one negative terminal (102b, 103b) is connected to the electronic device (<NUM>),
wherein the control means (<NUM>) further changes the maximum current value, after changing the maximum current value to the initial value, based on the number of positive terminals and negative terminals that are connected to the electronic device (<NUM>).