How to connect batteries in a combined battery pack

Abstract

This invention provides a battery connection method for a long-life composite battery pack that incorporates measures to prevent sparks when switching on and off, and allows for simple and quick interconnection of the composite battery pack. [Solution] After the preliminary preparations are completed, the control device 16 charges the composite battery pack 10 as a voltage boosting operation until the voltage value is the product of the number of series-connected cells constituting each EV battery 12 and 4.00 to 4.10V, and then the control device 16 discharges the composite battery pack 10 until the voltage value is the product of the number of series-connected cells constituting each EV battery 12 and 2.90 to 3.05V, and this process is repeated. Furthermore, during this voltage boosting operation, the voltage difference ΔV between the voltage Va of one of the EV batteries 12 and the voltage Vb of the lead-acid battery series group 14 is given by equation (1): 0 ≤ |ΔV|

Description

Technical Field

[0001] The present invention relates to a battery connection method for a composite battery pack composed of a plurality of lead-acid batteries and a plurality of lithium-ion batteries connected in parallel to each other.

Background Art

[0002] Conventionally, it is known that a composite battery in which a lead-acid battery and a lithium-ion battery are connected in parallel can increase the energy held per unit weight and can particularly improve the low-temperature power performance. And, various techniques have been disclosed to enhance the safety of the composite battery.

[0003] On the other hand, regarding the safety during deterioration of secondary batteries constituting a power storage device, Patent Document 1 discloses a charge / discharge control device that measures the current value of each single battery during charging and disconnects an abnormal single battery detected based on this measured value from the parallel connection by controlling a switching element. Further, Patent Document 2 describes a battery system for a railway vehicle that includes one or more battery boxes in which a plurality of battery packs connected in parallel are stored and minimizes the number of contactors necessary to suppress cross current between the battery packs or between the battery boxes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 had the problem of not considering measures to prevent sparks when opening and closing the switch. Furthermore, Patent Document 2 had the problem of being complicated in that, in order to determine whether or not the contactor can be closed, the closed-circuit voltage when a crosscurrent occurs must be determined using the open-circuit voltage of the cell, and the criteria for determining whether the contactor can be closed must be changed depending on whether the crosscurrent is a charging current or a discharging current. In addition, since it does not take into account that both charging and discharging may occur when charging is possible, there was a problem that even if it was desired to quickly equalize the voltage of a group of batteries or a battery box and connect them to each other while charging was possible, it was not possible.

[0006] This invention has been made in view of the aforementioned problems of the conventional invention, and the object of this invention is to provide a battery connection method for a long-life composite battery pack that takes into consideration measures to prevent sparking when the switch is opened and closed. Another object of the present invention, in addition to the above object, is to provide a battery connection method for a composite battery pack that is simple in its processing and can be interconnected in a short amount of time. [Means for solving the problem]

[0007] To achieve the above objective, the inventors conducted extensive research and first discovered that by preventing overcurrent from flowing when the switch is turned on, sparks can be prevented or, if they do occur, damage to the switch can be minimized.

[0008] Furthermore, the inventors of the present invention discovered that by charging and discharging the composite battery pack and bringing the voltage of the composite battery pack close to the voltage of an unconnected battery, it is possible to prevent overcurrent from flowing when the switch is turned on, leading to the present invention.

[0009] In other words, the present invention, as a preliminary step to construct the composite battery pack 10, involves arranging multiple EV batteries inside the housing, connecting each EV battery in parallel to form a parallel group, connecting a pre-calculated number of lead-acid batteries in series to each parallel group of EV batteries, connecting a data line to measure the voltage Va of each EV battery between the control device and each EV battery, connecting a data line to measure the voltage Vb of the lead-acid battery series group between the control device and the lead-acid battery series group, and the control device pre-acquires the internal impedance R and maximum allowable current Imax of each EV battery, and confirms that the contactor switch connected in series to each EV battery is open, and the preliminary steps After completion, as a voltage rise / fall operation, the control device charges the composite battery pack until the voltage value is the product of the number of series-connected cells constituting each EV battery and 4.00 to 4.10V. Then, the control device discharges the composite battery pack until the voltage value is the product of the number of series-connected cells constituting each EV battery and 2.90 to 3.05V. This process is repeated, and during the voltage rise / fall operation, when the voltage difference ΔV between the voltage Va of one of the EV batteries and the voltage Vb of the series-connected lead-acid battery group satisfies equation (1) below, the control device performs a battery connection operation by closing the contactor switch connected in series to one of the EV batteries, and repeats the battery connection operation for the other EV batteries of the EV pack. 0 ≤ |ΔV| <Imax×R···(1)

[0010] In the above, the series group of lead-acid batteries is a group of multiple lead-acid batteries connected in parallel to each other. If the voltage difference between the series groups of lead-acid batteries increases while the control device repeatedly charges and discharges the composite battery pack, it is preferable for the control device to fully charge the composite battery pack and then leave it for 10 to 30 hours to equalize the voltages between the series groups of lead-acid batteries. [Effects of the Invention]

[0011] According to the present invention, measures to prevent sparks when opening and closing the switch are taken into consideration, thus extending the lifespan. Furthermore, in addition to the above effects, the present invention allows for simple processing and quick interconnection. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing a composite battery pack suitable for implementing the battery connection method of the composite battery pack of the present invention. [Modes for carrying out the invention]

[0013] The battery connection method for the composite battery pack of the present invention will be described in detail below based on a preferred embodiment shown in the attached drawings. Figure 1 is a block diagram showing a composite battery pack suitable for implementing the battery connection method for the composite battery pack of the present invention.

[0014] The battery connection method for the composite battery pack of the present invention involves, as a preliminary step to constructing the composite battery pack 10, first arranging a plurality of EV batteries 12 inside a housing (not shown) and connecting each EV battery 12 in parallel to each other to form a parallel group. Next, a series group of lead-acid batteries 14, which is constructed by connecting a pre-calculated number of lead-acid batteries in series with each other, is connected in parallel to each parallel group of EV batteries 12. At the same time, a data line 18a for measuring the voltage Va of each EV battery 12 is connected between the control device 16 and each EV battery 12, and a data line 18b for measuring the voltage Vb of the series group of lead-acid batteries 14 is connected between the control device 16 and the series group of lead-acid batteries 14. Next, the control device 16 obtains the internal impedance R and maximum allowable current Imax of each EV battery 12 in advance, and confirms that the contactor switch 20 connected in series with each EV battery 12 is open.

[0015] After the preliminary preparations are complete, the control device 16 charges the composite battery pack 10 as a voltage boost / decrease operation until the voltage value is the product of the number of series-connected cells constituting each EV battery 12 and 4.00 to 4.10V, and then the control device 16 discharges the composite battery pack 10 until the voltage value is the product of the number of series-connected cells constituting each EV battery 12 and 2.90 to 3.05V, and this process is repeated. Furthermore, during this voltage boost / decrease operation, when the voltage difference ΔV between the voltage Va of one of the EV batteries 12 and the voltage Vb of the lead-acid battery series group 14 satisfies equation (1) below, the control device 16 performs a battery connection operation by closing the contactor switch 20 connected in series to that EV battery. Then, the battery connection operation is repeated for the other EV battery among the EV batteries 12. 0 ≤ |ΔV| <Imax×R···(1)

[0016] If the lead-acid battery series group 14 consists of multiple lead-acid battery series groups connected in parallel to each other, and the voltage difference between the lead-acid battery series groups widens while the control device 16 repeatedly charges and discharges the composite battery pack 10, it is preferable for the control device 16 to fully charge the composite battery pack 10 and then leave it for 10 to 30 hours to equalize the voltages between the lead-acid battery series groups.

[0017] Here, EV batteries refer to secondary batteries installed in electric vehicles and hybrid vehicles, with lithium-ion batteries being a typical example. Spark refers to the phenomenon of sparks occurring between the positive and negative contacts of the contactor switch 20 due to discharge. When sparks occur, the contacts and surrounding resin components may deteriorate or be damaged. In the above explanation, A to BV refers to a voltage range of A volts or more and less than B volts.

[0018] Each EV battery 12 may be housed in an individual container as a battery pack 22. The means for measuring the voltage Va of each EV battery 12 are not limited, but it may be measured by a battery management system 24 provided in the individual container housing each EV battery 12. The means for measuring the voltage Vb of the series-connected lead-acid battery group 14 are not limited, but it may be measured by a control device 16.

[0019] By adopting such a configuration, the battery connection method of the composite battery pack of the present invention takes countermeasures against sparks when the switch is opened and closed, so it can have a long service life. Furthermore, in addition to the above effects, the battery connection method of the composite battery pack of the present invention has a simple processing content and can be interconnected in a short time. The battery connection method of the composite battery pack of the present invention is basically configured as described above.

[0020] As described above, the battery connection method of the composite battery pack of the present invention has been described in detail. However, the present invention is not limited to the above description, and various improvements and modifications can of course be made without departing from the gist of the present invention.

Industrial Applicability

[0021] The battery connection method of the composite battery pack of the present invention takes countermeasures against sparks when the switch is opened and closed, so in addition to the effect of being able to have a long service life, it also has the effect that the processing content is simple and can be interconnected in a short time, so it is industrially useful.

Explanation of Reference Numerals

[0022] 10 Composite battery pack 12 EV battery 14 Lead-acid battery series group 16 Control device 18a, 18b Data line 20 Contact switch 22 Battery pack 24 Battery management system

Claims

1. As a preliminary step to construct the composite battery pack 10, multiple EV batteries are placed inside the housing, and each EV battery is connected in parallel to form a parallel group. A series group of lead-acid batteries, each consisting of a predetermined number of lead-acid batteries connected in series, is connected in parallel to the parallel group of EV batteries. A data line for measuring the voltage Va of each EV battery is connected between the control device and each EV battery, and a data line for measuring the voltage Vb of the series group of lead-acid batteries is connected between the control device and the series group of lead-acid batteries. The control device obtains the internal impedance R and maximum allowable current Imax of each EV battery in advance, and confirms that the contactor switch connected in series with each EV battery is open. After the preliminary preparations are completed, the control device charges the composite battery pack as a voltage boosting operation until the voltage value is the product of the number of series-connected cells constituting each EV battery and 4.00 to 4.10V, and then the control device repeatedly discharges the composite battery pack until the voltage value is the product of the number of series-connected cells constituting each EV battery and 2.90 to 3.05V. During the voltage rise / fall operation, when the voltage difference ΔV between the voltage Va of one of the EV batteries and the voltage Vb of the series-connected lead-acid battery group satisfies the following equation (1), the control device performs a battery connection operation by closing the contactor switch connected in series to the one EV battery. A battery connection method for a composite battery pack, comprising repeating the battery connection operation for one of the other EV batteries in each of the composite battery packs. 0≦|ΔV|<Imax×R...(1)

2. The aforementioned series of lead-acid batteries is a series of multiple lead-acid batteries connected in parallel to each other. The battery connection method for a composite battery pack according to claim 1, wherein if the voltage difference between the series-connected lead-acid batteries increases while the control device repeatedly charges and discharges the composite battery pack, the control device fully charges the composite battery pack and then leaves it for 10 to 30 hours to equalize the voltages between the series-connected lead-acid batteries.

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