Parallel connection charging method of batteries and charger of parallel connection batteries

Abstract

A plurality of batteries are connected in parallel and charged safely and quickly. In a method and a charger for charging batteries connected in parallel, charging of the batteries connected in parallel is started by setting an output current of the charger to a minimum charging current (Imin), after which a detected charging current for each battery is compared with a maximum required current (Imax) permitted for charging, and the maximum required current (Imax) permitted for charging is calculated. The detected charging current (Id) of all the batteries does not exceed the maximum required current (Imax). Each battery is charged at the same time by gradually increasing the output current of the charger such that the charging current closest to the battery, in which the current difference (I [delta]) between the detected charging current (Id) and the maximum required current (Imax) is minimum, becomes the maximum charging current (Ic) at which the battery can be safely charged.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and a charger for charging a plurality of batteries connected in parallel. BACKGROUND

[0002] If a plurality of batteries having the same rated voltage are connected in parallel for charging, the charging current of each battery can be uneven. This is because the open circuit voltage (OCV) and internal resistance of the battery vary depending on the charging and discharging environment, storage environment. If a battery having a higher open circuit voltage (OCV) and a battery having a lower open circuit voltage (OCV) are connected in parallel for charging, the charging current of the battery having the higher open circuit voltage (OCV) is smaller, and the charging current of the battery having the lower open circuit voltage (OCV) is larger. The internal resistance of the battery is a main cause of variation in the charging current of the battery, and therefore, if batteries having different internal resistances are connected in parallel for charging, the charging current is different, the charging current of the battery having a smaller internal resistance is larger, and the charging current of the battery having a larger internal resistance is smaller. For a battery, a maximum required current (Imax) is determined in advance, and if charging is performed at a current higher than the maximum required current (Imax), a protection circuit operates and the charging current is cut off. For a battery without a protection circuit, there is a problem that if charging is performed at a current larger than the maximum required current (Imax), safety cannot be ensured in addition to deterioration of electrical characteristics.

[0003] By sequentially switching a plurality of batteries for charging, charging can be performed under preferable conditions not exceeding the maximum required current (Imax) of the battery (Patent Documents 1 and 2).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2007-166723

[0007] Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 09-215218 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The method of charging a plurality of batteries in turn can charge each battery under preferred conditions, but has the disadvantage that if the number of batteries being charged increases, the charging time becomes quite long. In particular, for secondary batteries such as lithium ion batteries and the like that are charged first by constant current charging in a manner such that the output voltage does not exceed a threshold value and are switched to constant voltage charging when the output voltage rises to the maximum voltage, in the constant voltage charging, the charging current gradually decreases, so the charging capacity per unit time gradually decreases, and the time until full charge becomes long. Therefore, if the batteries are switched in turn to be charged, there is a problem that charging the entire batteries takes an extremely long time.

[0010] The present application was developed to further eliminate the above problems, and one of the objects of the present application is to provide a parallel connection charging method of batteries and a charger that can efficiently charge a plurality of batteries in a short time while charging each battery with a preferred charging current.

[0011] Means for solving the problem

[0012] The parallel connection charging method of batteries of one technical solution of the present application is a method of connecting a plurality of batteries in parallel and controlling the output current of a charger to charge the plurality of batteries, the output current of the charger causing the charging current of the batteries to be the minimum charging current (Imin) to start charging of all the batteries, thereafter, detecting the charging current of each battery, comparing the detected charging current (Id) with the maximum required current (Imax) of the battery for which the current is being detected, within the range where the detected charging current (Id) of all the batteries does not exceed the maximum required current (Imax), gradually increasing the output current of the charger until the charging current of the closest battery between the detected charging current (Id) and the maximum required current (Imax) becomes the maximum charging current (Ic) that is the current value including the maximum required current (Imax), to simultaneously charge the plurality of batteries.

[0013] The charger of the parallelly connected batteries according to the aspect of the present application is a charger of parallelly connected batteries in which a plurality of batteries are connected in parallel, and the charger includes: a current detection circuit that detects a charging current of each battery connected to the charger; a comparator that compares a detected charging current (Id) of each battery detected by the current detection circuit with a reference current that determines a maximum required current (Imax) of each battery, and outputs a current difference signal of each battery; a selection circuit that selects a minimum difference signal from the current difference signals of each battery output from each comparator, and selects a minimum minimum difference signal from the current difference signals between the detected charging current (Id) and the maximum required current (Imax); a feedback circuit that controls an output current of the charger using the minimum difference signal selected by the selection circuit; and an output current control circuit that controls the output current using a control signal input from the feedback circuit, and the charger charges the parallelly connected batteries in such a manner that the output current control circuit is controlled by the minimum difference signal input from the feedback circuit, and the output current control circuit is controlled so that the charging current of the battery closest to the maximum charging current (Ic) becomes the output current.

[0014] Effects of the Invention

[0015] The parallelly connected battery charging method and the charger described above have the following advantages: the plurality of batteries can be charged with the preferred charging current while charging efficiently in a short time. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a graph showing the characteristics in which the output current of the charger is increased in steps so that the charging current of each battery is increased.

[0017] Figure 2 is a graph showing the characteristics in which the output current of the charger is continuously increased so that the charging current of each battery is increased.

[0018] Figure 3 is a block diagram of the charger that charges the plurality of batteries in the embodiment of the present application.

[0019] Figure 4 is a graph showing the current characteristics in which the output current of the charger is increased so that the detected charging current of the battery is increased.

[0020] Figure 5 is a graph showing the current characteristics in which the output current of the charger is increased so that the detected charging current of the battery is increased.

[0021] Figure 6 is a graph showing the current characteristics in which the output current of the charger is increased so that the detected charging current of the battery is increased.

[0022] Figure 7 is a graph showing a current characteristic in which a charging current closest to a battery is increased or decreased to become a maximum required current (Imax).

[0023] Figure 8 is a block diagram of a charger of an embodiment of the present application. DETAILED DESCRIPTION

[0024] Hereinafter, the present application will be described in detail based on the drawings. Furthermore, in the following description, terms indicating specific directions, positions (for example, "upper", "lower", and other terms including these terms) are used as necessary, but the use of these terms is for the purpose of making the understanding of the application with reference to the drawings easy, and the technical scope of the present application is not limited by the meanings of these terms. In addition, portions of the same reference numerals appearing in multiple drawings represent the same or equivalent portions or members.

[0025] Furthermore, the embodiments shown below represent specific examples of the technical idea of the present application, and the present application is not limited to the following content. In addition, the sizes, materials, shapes, relative arrangements, and the like of the constituent members described below are not intended to limit the scope of the present application to only this, but are intended to be illustrative. In addition, the contents described in one embodiment, example can also be applied to other embodiments, examples. In addition, the sizes, positional relationships, and the like of the members shown in the drawings are sometimes exaggerated in order to make the description clear.

[0026] The parallel connection charging method of a battery of an embodiment of the present application is a method of connecting a plurality of batteries in parallel and controlling the output current of a charger to charge the plurality of batteries, the output current of the charger causing the charging current of the battery to become a minimum charging current (Imin) to start charging of all the batteries, thereafter, detecting the charging current of each battery, comparing the detected charging current (Id) with the maximum required current (Imax) of the battery for which the current detection is being performed, within the range where the detected charging current (Id) of all the batteries does not exceed the maximum required current (Imax), gradually increasing the output current of the charger until the charging current closest to the battery becomes a maximum charging current (Ic) that minimizes the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax), to simultaneously charge the plurality of batteries, the maximum charging current (Ic) being a current value including the maximum required current (Imax).

[0027] The parallel connection battery charging method of the above has the following advantages: since the charging current of each battery is detected and the output current of the charger is controlled in such a manner that the detected charging current (Id) does not exceed the maximum required current (Imax) of each battery, the batteries can be safely charged, and since the detected charging current (Id) of the battery is compared with the maximum required current (Imax) of the battery for which the charging current is being detected, the output current of the charger is gradually increased until the charging current of the battery closest to the maximum charging current (Ic) becomes the maximum charging current (Ic) at which the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax) is minimized, and the maximum charging current (Ic) is a current value including the maximum required current (Imax), the multiple batteries can be safely and efficiently charged in a short time without reducing the electrical characteristics.

[0028] The parallel connection battery charging method of the other embodiment of the present application can set the output current of the charger to be below the minimum of the maximum required currents (Imax) of the multiple batteries, and start charging the batteries with the charging current of the batteries being the minimum charging current (Imin).

[0029] The battery charging method of the above has the following advantages: by setting the output current of the charger to be below the minimum of the maximum required currents (Imax) of the multiple batteries, the charging current of the battery at the start of charging, i.e., the minimum charging current (Imin), can be prevented from exceeding the minimum of the maximum required currents (Imax) of the multiple batteries, and the charging of the batteries can be safely started.

[0030] The parallel connection battery charging method of the other embodiment of the present application can control the output current of the charger using a charging start step, a current detection step, and an output control step, and repeatedly perform the current detection step and the output control step at predetermined intervals to increase the output current of the charger until the charging current of the battery closest to the maximum charging current (Ic) becomes the maximum charging current (Ic), and in the charging start step, the output current of the charger is set to be the minimum charging current (Imin) of the batteries to start charging each battery, and after the charging start step, in the current detection step, the charging current of each battery is detected, and in the output control step, the current difference (IA) between the detected charging current (Id) of the battery detected in the current detection step and the maximum required current (Imax) of the battery for which the charging current is being detected is detected, and the output current of the charger is increased or decreased using the current difference (IA).

[0031] The charging method for the batteries described above has the following advantages: since the output current of the charger is set to an optimum value by repeatedly performing the current detection step and the output control step at predetermined cycles, each battery can be charged efficiently and in a short time, and a plurality of batteries can be charged under safe and preferable conditions at all times.

[0032] The parallel connection charging method for the batteries of the other embodiment of the present application can increase the output current of the charger in steps by adding an addition current value (I+) to the output current of the charger in the output control step.

[0033] The parallel connection charging method for the batteries described above has the following advantages: the output current of the charger can be increased in steps to rapidly increase the charging current of the battery closest to the maximum charging current (Ic), and each battery can be charged efficiently in a short time.

[0034] In the parallel connection charging method for the batteries of the other embodiment of the present application, the addition current value (I+) of the output current of the charger can be determined in accordance with a current difference (IΔ) between the detected charging current (Id) of the battery closest to the maximum required current (Imax).

[0035] The parallel connection charging method for the batteries described above has the following advantages: the output current of the charger can be rapidly increased to the maximum charging current (Ic) while reducing the probability that the detected charging current (Id) of the battery closest to the maximum required current (Imax) is exceeded, and charging can be performed efficiently in a shorter time.

[0036] The parallel connection charging method for the batteries of the other embodiment of the present application can set the addition current value (I+) of the output current to a current value that gradually decreases from the charging start step.

[0037] The parallel connection charging method for the batteries described above has the following advantages: at a timing at which the current difference (IΔ) between the charging current and the maximum required current (Imax) is large, the addition current value (I+) is increased to rapidly increase the output current of the charger, the charging current of the battery is brought close to the maximum required current (Imax), and the charging time is shortened, and at a period in which the current difference (IΔ) between the charging current and the maximum required current (Imax) is small, the addition current value (I+) is decreased to reduce the degree to which the output current of the charger is increased, the probability that the charging current of the battery exceeds the maximum required current (Imax) is reduced, and the charging current of the charger is accurately brought close to the maximum required current (Imax) to safely charge the battery.

[0038] The battery parallel connection charging method of the other embodiment of the present application has the advantage that the battery can be charged with the output current close to the maximum required current (Imax) using simple control by setting the addition current value (I+) of the output current to a predetermined current value, a current value that changes at a certain rate, a certain ratio, a change amount, or the like, and reducing the current value.

[0039] The battery parallel connection charging method of the other embodiment of the present application can cycle from the output control step to the charging start step when the detection charging current (Id) exceeds the maximum required current (Imax), and reduce the output current of the charger so that the detection charging current (Id) is less than the maximum required current (Imax).

[0040] The battery parallel connection charging method described above has the advantage that the charging current closest to the battery can be made lower than the maximum required current (Imax) using extremely simple processing, and the disadvantages caused by overcharging of the battery can be prevented, and then the charging current of the battery can be increased again so that the charging current closest to the battery rises to the maximum charging current (Ic).

[0041] The battery parallel connection charging method of the other embodiment of the present application can reduce the output current of the charger in the output control step by subtracting the subtraction current value (I-) from the output current of the charger.

[0042] The battery parallel connection charging method described above has the advantage that the output current of the charger can be reduced in steps and the charging current closest to the battery can be reduced quickly and safely, and each battery can be charged safely.

[0043] The battery parallel connection charging method of the other embodiment of the present application can determine the subtraction current value (I-) based on the excess current (Iover) by which the detection charging current (Id) of the battery exceeds the maximum required current (Imax).

[0044] The battery parallel connection charging method described above has the advantage that the subtraction current value (I-) can be determined based on the excess current (Iover) by which the detection charging current (Id) of the battery exceeds the maximum required current (Imax), the output current of the charger can be reduced quickly, and the battery can be charged more safely.

[0045] The battery parallel connection charging method of the other embodiment of the present application can increase the output current by adding the addition current value (I+) to the output current, reduce the output current by subtracting the subtraction current value (I-) from the output current, and set the subtraction current value (I-) and the addition current value (I+) to the same current value.

[0046] In the above parallel connection charging method of the battery, since the increase and decrease values of the output current of the charger are made equal, even if the state where the output current of the charger exceeds the maximum required current (Imax) occurs, it is possible to reliably return to below the maximum required current (Imax). Therefore, there is an advantage that the output current can be quickly returned to a safe region.

[0047] The parallel connection charging method of the battery of the other embodiment of the present application can compare the detected charging current (Id) of each battery with the maximum required current (Imax) of the battery where the detection of the charging current is performed in the output control step, and if the detected charging current (Id) of the closest battery is smaller than the maximum required current (Imax) and the current difference (IA) between the detected charging current (Id) of the closest battery and the maximum required current (Imax) is above a threshold value set in advance, the charger charges the plurality of batteries connected in parallel while increasing the output current.

[0048] The above parallel connection charging method of the battery has an advantage that, since the charging current of the closest battery is quickly increased to the maximum charging current (Ic) by increasing the output current of the charger with a simple process to charge the battery efficiently while confirming that the detected charging current (Id) of the closest battery is smaller than the maximum required current (Imax) and the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax) is above a threshold value set in advance, the output current is increased and controlled so that the charging current does not exceed the maximum required current (Imax), and it is also possible to ensure high safety while quickly increasing the charging current of the closest battery to the maximum charging current (Ic).

[0049] The parallel connection charging method of the battery of the other embodiment of the present application can compare the detected charging current (Id) of each battery with the maximum required current (Imax) of the battery where the detection of the charging current is performed in the output control step of the charger, and if the detected charging current (Id) of any battery is larger than the maximum required current (Imax), the plurality of batteries connected in parallel are charged while decreasing the output current of the charger.

[0050] The above parallel connection charging method of the battery has an advantage that, even if the charging current of the charger is increased and it is assumed that the charging current of any battery exceeds the maximum required current (Imax), it is possible to safely charge the battery by decreasing the charging current of the charger.

[0051] The battery parallel connection charging method of the other embodiment of the present application can, in the output control step of the charger, charge the plurality of batteries connected in parallel without increasing or decreasing the output current of the charger if the detected charging current (Id) of the closest battery is the maximum charging current (Ic).

[0052] The battery parallel connection charging method described above has the advantage that, if the detected charging current (Id) of the closest battery is the maximum charging current (Ic), the state in which the closest battery can be safely and efficiently charged is achieved, and thus the output current of the charger can be kept constant and each battery can be safely and efficiently charged.

[0053] The battery parallel connection charging method of the other embodiment of the present application has the advantage that, while charging a plurality of batteries having different charging capacities (Ah) connected in parallel, the output current of the charger can be controlled to a state in which the charging current of each battery does not exceed the maximum required current (Imax), and the plurality of batteries having different charging capacities (Ah) can be safely and efficiently charged in a short time.

[0054] The charger for the parallel connection battery of a plurality of batteries connected in parallel according to the other embodiment of the present application can be configured to include a current detection circuit that detects the charging current of each battery, a comparator that compares the detected charging current (Id) of each battery detected by the current detection circuit with a reference current that determines the maximum required current (Imax) of each battery and outputs a current difference signal of each battery, a selection circuit that selects the minimum difference signal from the current difference signals of each battery output from each comparator and selects the minimum minimum difference signal from the current difference signals between the detected charging current (Id) and the maximum required current (Imax), a feedback circuit that controls the output current using the minimum difference signal selected by the selection circuit, and an output current control circuit that controls the output current using the control signal input from the feedback circuit, the minimum difference signal input from the feedback circuit controls the output current control circuit, and the output current control circuit is controlled to an output current in which the charging current of the closest battery becomes the maximum charging current (Ic).

[0055] The charger described above detects the current difference signals of the respective batteries by comparing the detected charging currents (Id) with the reference current determined by comparing the maximum required current (Imax) of the battery for which the current is detected using a comparator, selects the minimum difference signal from the current difference signals of the respective batteries, and controls the output current of the charger using the selected minimum difference signal, so that the charging current closest to the battery can be controlled to the maximum charging current (Ic). The minimum difference signal is the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax) for which the detected charging current (Id) is closest to the battery, so that the output current of the charger can be controlled using the minimum difference signal to control the charging current closest to the battery to the maximum charging current (Ic). Therefore, the charger described above has the advantage that the multiple batteries can be safely and efficiently charged in a short time without reducing the electrical characteristics while the charging current of all the batteries is below the maximum required current (Imax).

[0056] (Embodiment 1)

[0057] If multiple batteries with the same rated voltage are connected in parallel for charging, the charging current of each battery will not be the same current. This is because, due to the difference in internal resistance and open circuit voltage (OCV) of each battery, a difference in charging current will occur. For a battery, the maximum value of the charging current, i.e., the maximum required current (Imax), is set in advance. If charging is performed at a current exceeding the maximum required current (Imax), safety cannot always be ensured, and this can cause a reduction in electrical characteristics.

[0058] The parallel connection charging method and charger of the battery of the following embodiment can safely and quickly charge all the batteries in a short time and efficiently. The batteries set for the charger are the same rated voltage, but they are not necessarily the same charging capacity (Ah), and batteries with different charging capacities (Ah) can be connected in parallel for charging. If multiple batteries with different charging capacities (Ah) are connected in parallel for charging, the difference in charging current of each battery becomes large, but the charging and discharging of the following embodiment is performed while detecting the charging current of each battery in such a manner that the charging current does not exceed the maximum required current (Imax), so that charging can be safely performed for batteries with different charging capacities (Ah).

[0059] Figure 1 The charging current of each battery Bl, B2, B3 connected in parallel to the charger and charged is indicated. Figure 1a charging current of a specific example in which the charging current of the battery is increased in steps and the charging current of the battery closest to the battery (B2) is increased to the maximum charging current (Ic), Figure 2 a charging current of a specific example in which the charging current of the batteries B1, B2, B3 is continuously increased and the charging current of the battery closest to the battery (B2) is increased to the maximum charging current (Ic).

[0060] Here, in the present specification, the "battery closest to the battery" means a battery in which the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax) is the smallest. The "maximum charging current (Ic)" is a current value that is equal to or less than the maximum required current (Imax), for example, a current value in a specific range including the maximum required current (Imax), and the battery closest to the battery can be charged with the maximum charging current (Ic) so that the charging is performed safely and efficiently.

[0061] The "maximum charging current (Ic)" can be preferably set to a current value that is equal to the maximum required current (Imax), and can be set to a current value in a range of the maximum required current (Imax) - 15%, and can be set to a current value within the maximum required current (Imax) - 10%.

[0062] The charging current is a current that charges each battery connected in parallel, and the detected charging current (Id) is a current value obtained by detecting the charging current of each battery. The maximum required current (Imax) is a current value at which the protection circuit operates and the charging current is cut off if the charging is performed with a current higher than the maximum required current, and if the battery without the protection circuit is charged with a current greater than the maximum required current, deterioration of the electrical characteristics and safety problems can occur.

[0063] with the current characteristics of Figure 1 The charging method in which the plurality of batteries B1, B2, B3 are charged with the current characteristics of

[0064] In the charging method in which the plurality of batteries B1, B2, B3 are charged with the current characteristics of Figure 1In the charging method in which the current characteristics of the batteries B1, B2, B3 are charged, a charging current equivalent to the minimum of the maximum required currents (Imax) of the respective batteries B1, B2, B3 connected in parallel to the charger is required. The minimum of the maximum required currents (Imax) of the respective batteries B1, B2, B3 is set as the output current of the charger, and the charging current is made the minimum charging current (Imin) to start charging of all the batteries (charging start step), after which the charging current of each battery is detected (current detection step), the detected charging current (Id) is compared with the maximum required current (Imax) of the battery for which the current detection is being performed, and within the range in which the detected charging current (Id) of all the batteries does not exceed the maximum required current (Imax), the output current of the charger is controlled (output control step) so that the charging current of the closest battery becomes the maximum charging current (Ic) at which the current difference (IA) between the detected charging current (Id) and the maximum required current (Imax) is minimized.

[0065] In Figure 3A block diagram of a charger that charges the parallelly connected batteries using the above method is shown in FIG. 1. The charger of this diagram is provided with a power supply circuit 1, an output current control circuit 2 that controls the output current of the power supply circuit 1, and a current detection circuit 4 that is set for each battery Bl, B2, B3, detects the charging current of each battery Bl, B2, B3, and inputs the charging current to the output current control circuit 2. The output current control circuit 2 is provided with a microprocessor (not shown) and a semiconductor element (not shown) that controls the output current of the charger using the output signal of the microprocessor. If each battery Bl, B2, B3 is connected to the charger and charging is requested, a charging current equivalent to the smallest of the maximum required currents of each battery Bl, B2, B3 is requested. Thus, the charger sets the output current to be below the smallest of the maximum required currents of each battery Bl, B2, B3, and starts charging. The output current of the charger is controlled in such a way that the charging current becomes the maximum charging current (Ic) based on the detected charging current (Id) input from each current detection circuit 4 and each maximum required current (Imax) that is detected or input in advance, and all of the batteries Bl, B2, B3 are simultaneously charged. Furthermore, from the viewpoint of shortening the charging time, it is preferable that at the start of charging, the output current of the charger is set to be below the smallest of the maximum required currents of each battery Bl, B2, B3 so as not to exceed the maximum required current of each battery Bl, B2, B3, and the output current of the charger is set to be below the smallest of the maximum required currents of each battery Bl, B2, B3 that becomes the maximum current.

[0066] In the charging method in which the parallelly connected batteries Bl, B2, B3 are charged by the charger using Figure 3 , the output current control circuit 2 repeatedly performs the voltage detection step and the output control step at a predetermined cycle, and the battery whose charging current is closest to the maximum required current (Imax) (the closest battery) is charged. The output current of the charger is controlled in such a way that the charging current becomes the maximum charging current (Ic) based on the detected charging current (Id) input from each current detection circuit 4 and each maximum required current (Imax) that is detected or input in advance, and all of the batteries Bl, B2, B3 are simultaneously charged. Furthermore, from the viewpoint of shortening the charging time, it is preferable that at the start of charging, the output current of the charger is set to be below the smallest of the maximum required currents of each battery Bl, B2, B3 so as not to exceed the maximum required current of each battery Bl, B2, B3, and the output current of the charger is set to be below the smallest of the maximum required currents of each battery Bl, B2, B3 that becomes the maximum current. Figure 1 and Figure 2The charging current of each battery Bl, B2, B3 is set to the maximum charging current (Ic) and charging is performed simultaneously. The period in which the voltage detection step and the output control step are repeated to bring the output current close to the maximum charging current (Ic) is, for example, 0.2 seconds or more and 5 minutes or less, preferably 10 seconds or more and 3 minutes or less, and further preferably 30 seconds or more and 3 minutes or less. If the period is too long, it takes time to control the charging current of the batteries Bl, B2, B3 to the maximum charging current (Ic), and if the period is too short, it is difficult to stably detect and control the charging current, and therefore, the period is set to the above range in consideration of the fact that the charging current of the batteries Bl, B2, B3 can be quickly controlled to the maximum charging current (Ic) while the charging current is accurately detected and controlled.

[0067] (Charging start step)

[0068] The charging start step starts charging of each battery using the output current from the charger.

[0069] In the charging start step, the output current of the charger sets the charging current of each battery to the minimum charging current (Imin) of each battery and starts charging. The minimum charging current (Imin) is a current value that starts charging of the parallelly connected batteries Bl, B2, B3, and sets the charging current of all the batteries Bl, B2, B3 to a current value that is equal to or less than the maximum required current (Imax). The minimum charging current (Imin) is set to a current value that is equal to or less than the maximum required current (Imax) of the battery with the minimum maximum required current (Imax).

[0070] In the charging start step, the maximum required current (Imax) of each battery Bl, B2, B3 is detected, and the minimum charging current (Imin) is set to the maximum required current of the battery with the minimum maximum required current (Imax) among the maximum required currents (Imax) of all the batteries Bl, B2, B3, and the charging current is set to the minimum charging current (Imin) to start charging of each battery. For the parallelly connected batteries Bl, B2, B3, the charging current of all the batteries Bl, B2, B3 is set to a current value that is equal to or less than the maximum required current (Imax) and charging is performed.

[0071] The charging current corresponding to the minimum of the maximum required currents of the respective batteries Bl, B2, B3 connected in parallel to the charger is required. In the charging start step, the charging of each battery is started with the output current from the charger so that the charging current becomes the minimum charging current (Imin). The minimum charging current (Imin) is set to be lower than the maximum required current (Imax) of the battery with the lowest maximum required current (Imax). Also, the output current of the charger at the time of the start of charging is set to be lower than the maximum required current (Imax) of the battery with the minimum of the maximum required currents (Imax) of the respective batteries. By setting the output current of the charger at the time of the start of charging to be lower than the maximum required current (Imax) of the battery with the lowest maximum required current (Imax) among the maximum required currents (Imax) of the respective batteries, the minimum charging current (Imin) at which the charging of each battery is started does not exceed the maximum required current (Imax) of the battery with the lowest maximum required current (Imax), and the charging of each battery can be started safely. The output current of the charger is usually divided and flows as the charging current of each battery, and thus the charging current of each battery is smaller than the maximum required current (Imax). Even in the case where the output current of the charger is not divided and flows to the battery with the lowest maximum required current (Imax), for example, the output current remains as it is, and the maximum value of the charging current flowing to the battery is the maximum required current (Imax) of the battery with the lowest maximum required current (Imax), and the minimum charging current (Imin) does not exceed the maximum required current (Imax) of the battery, and the safety can be ensured reliably.

[0072] The output current of the charger at the time of the start of charging is preferably set to be the minimum of the maximum required currents (Imax) of the respective batteries. This is because the charging of each battery can be started safely without exceeding the maximum required current (Imax) of each battery, and by making the minimum charging current (Imin) at which the charging is started as large as possible and starting the charging from a current value close to the maximum required current (Imax), the charging current of the battery closest to the maximum required current (Imax) can be increased rapidly to the maximum charging current (Ic), and each battery can be charged efficiently in a short time, and the charging time can be shortened.

[0073] In the above charging method, the output current of the charger is increased, the charging current is gradually increased from the minimum charging current (Imin), and the batteries Bl, B2, B3 are charged with the detection charging current (Id) increased to the maximum charging current (Ic). The charging method is repeatedly performed in a predetermined cycle after the charging start step, that is, the current detection step and the output control step, the output current is controlled to be increased, and the charging current is increased to the maximum charging current (Ic) to charge the batteries connected in parallel.

[0074] (current detection step)

[0075] In this step, the charging current of each battery after the start of charging is detected. The charging current of each battery can be detected independently by the respective independent current detection circuit 4. However, although not shown, one current detection circuit can be switched in time series to sequentially detect the charging current of a plurality of batteries. The current detection of the battery can be performed, for example, by connecting a current detection resistor in series with the battery and detecting the voltage induced across the current detection resistor. However, for the current detection, other all current detection circuits, current sensors can be used for detection. The current sensor can also use a sensor that detects based on the magnetic flux radiated from the lead of the battery, etc.

[0076] (output control step)

[0077] In this step, the current difference (IA) between the detected charging current (Id) of each battery detected in the current detection step and the maximum required current (Imax) of the battery for which the current detection is performed is detected, and the output current of the charger is controlled using the detected current difference (IA) so that the charging current closest to the battery becomes the maximum charging current (Ic). At the initial timing of the start of charging, the output current of the charger is set to be low, and therefore the current difference (IA) between the detected charging current (Id) of each battery and the maximum required current (Imax) is sufficiently large. Therefore, at the beginning of the start of charging, in this output control step, even if the charger increases the output current, the probability that each charging current exceeds the maximum required current (Imax) is low. However, if the output current of the charger gradually increases and the detected charging current (Id) of each battery increases so that the charging current closest to the battery increases to a current value close to the maximum charging current (Ic), the current difference (IA) becomes small, and if the output current of the charger is increased by a certain amount or more, the detected charging current (Id) closest to the battery can sometimes exceed the maximum charging current (Ic). If the detected charging current (Id) closest to the battery exceeds the maximum charging current (Ic), the output current of the charger is reduced so that the detected charging current (Id) is lower than the maximum required current (Imax).

[0078] In the output control step, the output current of the charger is increased or decreased so that the detected charging current (Id) of the battery closest to the battery is charged as the maximum charging current (Ic) for all the batteries, but the increase or decrease of the output current of the charger is determined using the current difference (IA) between the detected charging current (Id) of the battery closest to the battery and the maximum required current (Imax). The output current of the charger can be increased when the detected charging current (Id) of the battery closest to the battery is less than the maximum required current (Imax), but it is preferable that the output current of the charger be increased when the detected charging current (Id) of the battery closest to the battery is less than the maximum charging current (Ic) and the current difference (IA) is greater than a threshold value set in advance.

[0079] The output current of the charger can also be set to a current value obtained by adding the current difference (IA) between the detected charging current (Id) of the battery closest to the battery and the maximum required current (Imax) to the current output of the charger as it is, and can be repeatedly set to a current value obtained by adding the current difference (IA) to the current output of the charger as it is so that the current difference (IA) becomes within a threshold range, thereby controlling so that the detected charging current (Id) does not exceed the maximum required current (Imax).

[0080] As for the method of increasing the output current of the charger when the detected current difference (IA) exceeds the threshold value, the threshold value can be increased to reduce the probability that the charging current of the battery closest to the battery exceeds the maximum required current (Imax) while increasing the output current of the charger. In particular, by making the threshold value greater than the current value at which the output current of the charger is increased to increase the charging current of the battery closest to the battery, the probability that the detected charging current (Id) of the battery closest to the battery exceeds the maximum required current (Imax) when the output current of the charger is increased can be reduced. This method, for example, can set the threshold value to be equal to or greater than the added current value (I+) at which the output current is increased in steps, and reduce the probability that the detected charging current (Id) of the battery closest to the battery exceeds the maximum charging current (Ic) after the output current of the charger is increased. Making the threshold value greater than the added current value (I+) so that the detected charging current (Id) of the battery closest to the battery does not exceed the maximum charging current (Ic) is because the output current of the charger is divided and flows to the plurality of batteries.

[0081] For example, in the case of a charger that connects three batteries in parallel to charge, the output current is divided into three currents to flow to charge each battery, and therefore, if it is assumed that the charging current of each battery flows approximately, the detected charging current (Id) of the battery becomes approximately 1 / 3 of the output current. That is, the sum current value (I+) is divided to increase the charging current of the closest battery, and therefore, even if the sum current value (I+) is set as the threshold value, the increase in the charging current of the closest battery becomes approximately 1 / 3 of the sum current value (I+), and does not exceed the maximum required current (Imax). However, the output current of the charger does not necessarily flow to each battery in equal division, and even if the sum current value (I+) is set as the threshold value, the increase in the charging current of the closest battery does not always become 1 / 3 of the sum current value (I+). Even if it is assumed that the output current of the charger flows only to the closest battery, the increase in the output current of the charger is the same as the increase current of the charging current of the closest battery, and therefore, the threshold value is set to be equal to the sum current value (I+), and the increase in the output current of the closest battery becomes the sum current value (I+). In the case where a plurality of batteries are connected in parallel to the charger to charge, the probability that the output current of the charger flows only to a specific battery is extremely low, and generally, the increase in the output current of the charger to flow to each battery is the increase current below the output current.

[0082] Figures 4-6 The output current of the charger and the detected charging current (Id) of the closest battery that increases in correspondence with the output current are indicated. The detected charging current (Id) becomes large in proportion to the output current, and therefore, the current characteristic curve in which the output current and the detected charging current (Id) change is approximately linear. Therefore, Figures 4-6 The Y axis on the left side is set as the output current of the charger, and the Y axis on the right side is set as the detected charging current (Id) of the closest battery.

[0083] The charger can increase the output current in steps by adding the sum current value (I+) to the output current at the timing at which the charging current is detected. As Figure 4As shown, the added current value (I+) can be increased in steps (I+1, 2, 3) that are large at the start of charging and gradually smaller over time. This method can increase the added current value (I+) at the initial stage of starting charging, during which the charging current of the battery is smaller than the maximum required current (Imax), to rapidly increase the charging current closest to the battery to the maximum charging current (Ic). At the initial stage of charging, the detected charging current (Id) is small, and the current difference (IA1) between it and the maximum required current (Imax) is large. This method can increase the added current value (I+1) to rapidly bring the charging current closest to the maximum required current (Imax) at the initial stage of charging during which the detected charging current (Id) is small and sufficiently below the maximum required current (Imax), and thus reduce the charging time of the battery. As the charging time passes, the detected charging current (Id) closest to the battery gradually increases, and the current difference (IA2, 3) between it and the maximum required current (Imax) decreases. Therefore, by decreasing the added current value (I+2, 3) as the charging time passes, the increase in the charging current closest to the battery is reduced to control the detected charging current (Id) so as not to exceed the maximum required current (Imax), and thus the charging current can be accurately brought closer to the maximum required current (Imax) to more safely charge all batteries.

[0084] The added current value (I+) of the output current of the charger can also be set to the current difference (IA) between the detected charging current (Id) closest to the battery and the maximum required current (Imax), in which case the added current value (I+) can be appropriately set within the range in which the detected charging current (Id) does not exceed the maximum required current (Imax).

[0085] For the charger, as Figure 5As shown, the summed current value (I+) can be determined based on the current difference (IΔ) between the detection charging current (Id) closest to the battery and the maximum required current (Imax). For example, the summed current value (I+) can be determined by using the current difference (IΔ) as a function, and this function can also increase the summed current value (I+) proportionally to the current difference (IΔ). This method can determine the summed current value (I+1, 2, 3) based on the closest current difference (IΔ1, 2, 3) closest to the battery via a function f. This method has the following advantages: it can determine the summed current value (I+) based on the current difference (IΔ) of the closest battery, and can increase the summed current value (I+1) when the current difference (e.g., IΔ1) of the closest battery is large, and decrease the summed current value (I+2, I+3) as the current difference (e.g., IΔ2, IΔ3) decreases, so that the output current of the charger can increase rapidly, and the charging current of the closest battery can be increased to the maximum charging current (Ic), so that charging can be carried out efficiently in a shorter time.

[0086] Moreover, such as Figure 6 As shown, the charger's output current can also be increased in a stepwise manner by setting the added current value (I+) to a preset current value. This method detects the charging current closest to the battery at predetermined intervals. Whenever it is determined that the output current can be increased based on the detected charging current (Id), a preset added current value (I+) is added to the charger's output current, increasing the output current in a stepwise manner. Therefore, without calculating the added current value (I+), the battery can be charged using simple control to make the charging current closest to the battery the maximum charging current (Ic). Although not shown, the charger's output current can also be increased in a stepwise manner by setting the added current value (I+) to a current value that decreases by a preset percentage, rate of change, or amplitude.

[0087] The method of increasing the charging current in a stepwise manner by adding an additional current value (I+) to the charger's output current may sometimes increase the charger's output current to the point that the detected charging current (Id) closest to the battery, or the detected charging current (Id) of any battery, exceeds the maximum required current (Imax). If the detected charging current (Id) is detected to exceed the maximum required current (Imax), the charger's output current is reduced in a way that the detected charging current (Id) of the battery whose detected charging current (Id) exceeds the maximum required current (Imax) is reduced to below the maximum required current (Imax).

[0088] For example, for the output current of the charger, the output control step can be looped to the charging start step to reduce the output current of the charger to the minimum charging current (Imin), and then the detected charging current (Id) is stepped up to control it to the maximum charging current (Ic). This method can quickly reduce the detected charging current (Id) of the battery that exceeds the maximum charging current (Ic) or the maximum required current (Imax) to the minimum charging current (Imin).

[0089] For the reduction of the output current of the charger, the subtraction current value (I-) can also be subtracted from the output current of the charger without looping from the output control step to the charging start step. This method, for example, can use the increase current (Iup) of the detected charging current (Id) that is increased by adding the addition current value (I+) to the output current and the exceeding current (Iover) that detects the detected charging current (Id) exceeding the maximum required current (Imax) by adding the addition current value (I+) to the output current of the charger to calculate the subtraction current value (I-). Figure 7 Figure 7 The characteristic indicates that the detected charging current (Id) is increased by adding the addition current value (I+) to the output current, and the detected charging current (Id) is reduced by subtracting the subtraction current value (I-) from the output current. This method can calculate the subtraction current value (I-) of the output current that reduces the exceeding current (Iover) according to the ratio of the increase current (Iup) of the detected charging current (Id) to the exceeding current (Iover). For example, if the increase current (Iup) is 1 A and the exceeding current (Iover) is 0.5 A when the addition current value (I+) is added to the output current, the exceeding current (Iover) can be reduced by 0.5 A by subtracting a current value that is half of the addition current value (I+), and therefore the subtraction current value (I-) can be set to 0.5 A.

[0090] In addition, the output current of the charger is also suitable for setting to a current value obtained by adding the current difference (IΔ) between the detected charging current (Id) of the battery closest to the maximum required current (Imax) to the output current of the charger at the present time, and the output current of the charger at the present time is set to the output current of the charger by repeatedly adding the current difference (IΔ) to the output current of the charger at the present time to make the current difference (IΔ) within the threshold range, thereby controlling the detected charging current (Id) not to exceed the maximum required current (Imax), and the exceeding current (Iover) can be avoided.

[0091] (Constant current charging and constant voltage charging)

[0092] ​The above charging method sets the charging current of each battery to below the maximum required current (Imax) for constant current charging. However, for batteries like lithium-ion rechargeable batteries, which are fully charged by constant voltage charging after constant current charging, after using the above method to charge each battery with constant current until the battery voltage rises to the preset maximum voltage (e.g., 4.2V in lithium-ion rechargeable batteries), it can switch to constant voltage charging for full charging. While the above batteries cannot be fully charged by constant current charging alone, constant current charging can efficiently charge the batteries to a considerable remaining capacity. Therefore, it is also possible to charge and use the batteries using only constant current charging.

[0093] (Implementation Method 2)

[0094] Figure 8 The block diagram illustrates a charger that controls the output current in a manner that ensures the charging current closest to the battery is close to the maximum charging current (Ic) in real time. This charger uses a current detection circuit 4 to detect the charging current of each battery B1, B2, and B3, and feeds the detection signal back to the input of a current control circuit 6, which incorporates semiconductor elements such as FETs and bipolar transistors to control the output current, via a feedback circuit 5. The charger shown in this block diagram can be configured as follows: Figure 2 As shown, the output current is continuously varied to control the charging current closest to the battery to the maximum charging current (Ic).

[0095] Figure 8 The charger includes: a current detection circuit 4 that detects the charging current of each battery; a comparator 7 that compares the detected charging current (Id) of each battery B1, B2, B3 detected by the current detection circuit 4 with a reference voltage 11 that determines the maximum required current (Imax) of each battery, and outputs a current difference signal between the detected charging current (Id) and the maximum required current (Imax) of each battery; a selection circuit 10 that selects the minimum difference signal from the current difference signals of each battery output from each comparator 7 and outputs the minimum difference signal; and a feedback circuit 5 that uses the minimum difference signal selected by the selection circuit 10 to control the output current.

[0096] The current detection circuit 4 includes a current sensing resistor 8 connected in series with each of the batteries B1, B2, and B3, and a differential amplifier 9 that senses the voltage across the current sensing resistor 8. The differential amplifier 9 outputs a voltage proportional to the current of each of the batteries B1, B2, and B3. The differential amplifier 9 amplifies the voltage sensed by the current sensing resistor 8, converting the current into a voltage signal and outputting it. By amplifying the voltage across the current sensing resistor 8 using the differential amplifier 9, the current detection circuit 4 can reduce the resistance of the current sensing resistor 8 and increase the output voltage relative to the battery current. The current detection circuit 4 outputs an analog voltage signal proportional to the current of each of the batteries B1, B2, and B3.

[0097] Comparator 7 is also a differential amplifier. It receives an analog signal from the current detection circuit 4, which determines the battery current value, at one input terminal, and a reference voltage 11, which determines the maximum required current (Imax), at the other input terminal. Its output is a current difference signal proportional to the voltage difference between the analog signal determining the battery current value and the reference signal. The reference voltage 11 is set to be equal to the voltage output by the current detection circuit 4 when the battery current reaches the maximum required current (Imax). The output signal of comparator 7 is 0V when the battery charging current reaches the maximum required current (Imax). As the battery charging current deviates from the maximum required current (Imax), the comparator's output signal becomes a current difference signal that increases towards the positive or negative side. The current difference signal of the comparator is proportional to the voltage difference between the output signal from the current detection circuit 4 and the reference voltage 11. That is, the sign changes depending on whether the current difference (IΔ) between the detected charging current (Id) and the maximum required current (Imax) is larger, or whether the detected charging current (Id) is below or above the maximum required current (Imax). Therefore, the magnitude of the current difference between the detected charging current (Id) and the maximum required current (Imax) can be detected based on the current difference signal from the comparator 7, and the sign of the current difference signal can be used to determine whether the detected charging current (Id) exceeds the maximum required current (Imax).

[0098] The selection circuit 10 selects the minimum voltage difference signal from the current difference signal input from the comparator 7 and feeds it back to the current control circuit 6 via the feedback circuit 5. The current difference signal output from the comparator 7 determines the current difference (IΔ) between the detected charging current (Id) and the maximum required current (Imax) of each battery B1, B2, and B3. Therefore, the selected minimum difference signal becomes the signal that determines the current difference (IΔ) between the detected charging current (Id) and the maximum required current (Imax) of the closest battery.

[0099] The feedback circuit 5 feeds back the minimum difference signal, i.e., the current difference (IΔ) closest to the battery, input from the selection circuit 10 to the current control circuit 6, to control the output current of the current control circuit 6, i.e., the output current of the charger, in such a manner that the charging current closest to the battery becomes the maximum charging current (Ic).

[0100] Figure 8 The charger of the present application controls the output current in such a manner that the detected charging current (Id) becomes the maximum charging current (Ic), and therefore has the advantage that the battery can be charged efficiently and quickly in such a manner that the charging current closest to the battery becomes the maximum charging current (Ic) at all times.

[0101] Industrial Applicability

[0102] The battery parallel connection charging method and the charger of the present application can be effectively used for a method and a charger in which a plurality of batteries are connected in parallel and charged at the same time.

[0103] Explanation of Reference Numerals

[0104] 1... power supply circuit

[0105] 2... output current control circuit

[0106] 4... current detection circuit

[0107] 5... feedback circuit

[0108] 6... current control circuit

[0109] 7... comparator

[0110] 8... current detection resistor

[0111] 9... differential amplifier

[0112] 10... selection circuit

[0113] 11... reference voltage

[0114] B1, B2, B3... battery

Claims

1. A parallel connection charging method of a battery, which is a method of charging a plurality of batteries connected in parallel by controlling an output current of a charger, the output current of the charger makes a charging current of the battery a minimum charging current (Imin) to start charging of all the batteries, after that, a charging current of each of the batteries is detected, a detected charging current (Id) is compared with a maximum required current (Imax) of the battery for which the detection of the charging current is being performed, in a range where the detected charging current (Id) of all the batteries does not exceed the maximum required current (Imax), the output current of the charger is gradually increased until a charging current of the closest battery between the detected charging current (Id) and the maximum required current (Imax) becomes a maximum charging current (Ic) which is a current value including the maximum required current (Imax) to simultaneously charge the plurality of batteries.

2. The parallel connection charging method of a battery according to claim 1, a minimum of the maximum required currents (Imax) of the plurality of batteries is set to the output current of the charger below the minimum to make the charging current of the battery the minimum charging current (Imin) to start charging of the battery.

3. The parallel connection charging method of a battery according to claim 1 or 2, the charger controls the output current of the charger using a charging start step in which the charging current of the battery is made the minimum charging current (Imin) to start charging of each of the batteries, a current detection step in which the charging current of each of the batteries is detected after the charging start step, and an output control step in which a current difference (IA) between the detected charging current (Id) of the battery detected in the current detection step and the maximum required current (Imax) of the battery for which the detection of the charging current is being performed is detected to increase or decrease the output current of the charger using the current difference (IA), and the charger repeatedly performs the current detection step and the output control step at a predetermined cycle to increase the output current of the charger until the charging current of the closest battery becomes the maximum charging current (Ic) to charge the plurality of batteries connected in parallel.

4. The parallel connection charging method of a battery according to claim 3, in the output control step, the output current of the charger is added by an addition current value (I+) to increase the output current of the charger in steps.

5. The parallel connection charging method of a battery according to claim 4, the addition current value (I+) of the output current of the charger is a current value determined in accordance with the current difference (IA) between the detected charging current (Id) of the closest battery and the maximum required current (Imax).

6. The parallel connection charging method of a battery according to claim 4, The added current value (I+) of the output current of the charger is a current value that gradually decreases from the charging start step.

7. The parallel connection charging method of a battery according to claim 4, The added current value (I+) of the output current of the charger is set in advance.

8. The parallel connection charging method of a battery according to claim 3, In the output control step, the output current of the charger is decreased by subtracting a subtracted current value (I-) from the output current of the charger.

9. The parallel connection charging method of a battery according to claim 3, In the output control step, the output current of the charger is decreased by subtracting a subtracted current value (I-) from the output current of the charger.

10. The parallel connection charging method of a battery according to claim 9, The subtracted current value (I-) is determined from an excess current (Iover) that exceeds the maximum required current (Imax).

11. The parallel connection charging method of a battery according to claim 3, In the output control step, the detected charging current (Id) of each of the batteries is compared with the maximum required current (Imax) of the battery for which the charging current is detected, if the detected charging current (Id) of the closest battery is smaller than the maximum required current (Imax), and the current difference (IA) between the detected charging current (Id) of the closest battery and the maximum required current (Imax) is above a threshold value set in advance, the charger charges the plurality of batteries connected in parallel with an increased output current.

12. The parallel connection charging method of a battery according to claim 3, In the output control step, the detected charging current (Id) of each of the batteries is compared with the maximum required current (Imax) of the battery for which the charging current is detected, if the detected charging current (Id) of any of the batteries is larger than the maximum required current (Imax), the plurality of batteries connected in parallel is charged with a decreased output current of the charger.

13. The parallel connection charging method of a battery according to claim 3, In the output control step, if the detected charging current (Id) of the closest battery is the maximum charging current (Ic), the plurality of batteries connected in parallel is charged without increasing or decreasing the output current of the charger.

14. The parallel connection charging method of a battery according to claim 1, a plurality of batteries having different charging capacities (Ah) are connected in parallel to be charged.

15. A charger for parallel connection batteries that is a charger for parallel connection batteries in which a plurality of batteries are connected in parallel, the charger comprising: a current detection circuit that detects a charging current of each of the batteries connected to the charger; a comparator that compares a detected charging current (Id) of each of the batteries detected by the current detection circuit with a reference current that determines a maximum required current (Imax) of each of the batteries, and outputs a current difference signal of each of the batteries; a selection circuit that selects a minimum difference signal from among the current difference signals of the respective batteries output from the respective comparators, and selects a minimum minimum difference signal from among the current difference signals detected between the charging current (Id) and the maximum required current (Imax); a feedback circuit that controls the output current of the charger using the minimum difference signal selected by the selection circuit; and an output current control circuit that controls the output current using a control signal input from the feedback circuit, the charger charges the parallelly connected batteries in the following manner: the output current control circuit is controlled using the minimum difference signal input from the feedback circuit, the output current control circuit is controlled so that the charging current of the closest battery becomes the output current of the maximum charging current (Ic).

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