Patent Application
20110064993
1. Field of the Invention
The present invention relates to a battery array having a plurality of battery cells connected by metal plates, and in particular to a battery array optimally suited for use as a power source for a motor that drives an electric-powered vehicle such as a hybrid car, fuel-cell vehicle, electric automobile (electric vehicle EV), or electric motor-bike.
2. Description of the Related Art
A battery array can connect many battery cells in series to increase output voltage, and in parallel to increase charging current. Accordingly, a high power, high output battery array used as a power source for a motor that drives a vehicle has a plurality of battery cells connected in series to increase output voltage. Since a battery array used in this type of application is charged and discharged with high currents, the plurality of battery cells are connected by low-resistance metal plates. (Refer to Japanese Laid-Open Patent Publication No. H05 343105 (1993).)
In the battery array of JP H05 343105A, both ends of the metal plates are attached to battery cell electrode terminals via nuts. Specifically, electrode terminals are passed through through-holes in the metal plates, and nuts are threaded onto the electrode terminal bolts to attach the metal plates to the electrode terminals. In a battery array with this structure and battery cells having positive and negative electrode terminals made of different type (dissimilar) metals, the contact surfaces of the metal plates and the positive and negative electrode terminals cannot be the same metal type. For example, for lithium ion batteries having dissimilar metal positive and negative electrode terminals that are aluminum and copper connected by copper metal plates, dissimilar metal contact surfaces are formed at the aluminum electrode terminals. A battery array having metal plate and electrode terminal dissimilar metal contact surfaces has the drawback that galvanic corrosion can occur at the dissimilar metal contact surfaces, and stable low contact resistance connections cannot be maintained over a long period. Galvanic corrosion results from current flow between the dissimilar metals, and that current causes metal to electrically dissociate and corrode.
The present invention was developed with the object of correcting the drawback described above. Thus, it is a primary object of the present invention to provide a battery array that can connect battery cell electrode terminals with metal plates in a manner that maintains stable low resistance connections over a long period while connecting different type metals at the positive and negative electrode terminals of the battery cells.
The battery array of the present invention is provided with a plurality of battery cells 1, 31 having positive and negative electrode terminals 2, 32 that are different metals, and the positive and negative electrode terminals 2, 32 of each battery cell 1, 31 are connected by metal plates 3, 23, 33, 43, 53. Each metal plate 3, 23, 33, 43, 53 is clad material having a first metal plate 3A, 23A, 33A, 43A, 53A that connects to one electrode terminal 2, 32 of a battery cell 1, 31 and a second metal plate 3B, 23B, 33B, 43B, 53B that connects to a different electrode terminal 2, 32. The clad material first metal plate 3A, 23A, 33A, 43A, 53A and second metal plate 3B, 23B, 33B, 43B, 53B are joined at a junction between positive and negative electrode terminal 2, 32 connecting regions.
The battery array described above has the characteristic that it can connect battery cell electrode terminals in series or parallel with metal plates in a manner that maintains stable low resistance connections over a long period while connecting different type metals at the positive and negative electrode terminals of the battery cells. This is because the first metal plate that connects to one of the electrode terminals of a battery cell and the second metal plate that connects to a different electrode terminal are clad material joined at a junction between the positive and negative electrode terminal connecting regions. Clad material is not simply a laminate of different type metals, but rather is strongly joined together at the junction interface where the different metals are in an alloyed state. Accordingly, in a metal plate made of clad material, there is no ingress of water or air to the junction between the different metals, and galvanic corrosion does not occur at the junction interface. Therefore, metal plates that are dissimilar metal clad material joined at a junction between positive and negative electrode terminals have the characteristic that each electrode terminal can be connected with the same metal type to prevent galvanic corrosion and enable stable electrical connection over a long period.
In the battery array of the present invention, the battery cells 1 can be rectangular battery cells, and metal plates 3, 23, 43 can connect the positive and negative electrode terminals 2 of adjacent battery cells 1 to connect the battery cells 1 in series. Each metal plate 3, 23, 43 has through-holes 4 to insert battery cell 1 positive and negative electrode terminals 2, electrode terminals 2 can be inserted in the through-holes 4, and the electrode terminals 2 and metal plate 3, 23, 43 can be welded for connection. Further, at least one of the through-holes 4 can be an elongated hole 4A to allow the inserted electrode terminals 2 to move in the direction of battery cell 1 stacking. Welding rings 5, can be provided on the surface of the metal plates 3, 23, 43 to close-off open regions of the elongated holes 4A, and the electrode terminals 2 can be welded to the metal plates 3, 23, 43 via the welding rings 5, 25.
The battery array described above has the characteristic that the clad material metal plates can be stably and reliably weld-attached to the electrode terminals while absorbing dimensional error in the battery cells and metal plates via the elongated holes. This is because error in the dimensions of the battery cells and the metal plates can be absorbed by electrode terminal insertion in the elongated holes. In addition, gaps formed by insertion of the electrode terminals in the elongated holes can be closed-off by welding rings, and electrical connection can be made without gaps by welding the welding rings.
In the battery array of the present invention, a welding ring 5, 25 can be either a crimping ring 2X formed by pressure-deformation to widen the upper end of an electrode terminal 2 inserted in an elongated hole 4A, or a metal ring 6 that is a sheet-metal piece separate from the electrode terminal 2 and provided with a center hole 6A for electrode terminal 2 insertion. In this battery array, welding rings formed as crimping rings by widening the ends of the electrode terminals can be weld-attached to the metal plates for reliable connection. Further, with welding rings that are metal rings separate from the electrode terminals, the metal rings can be weld-attached to the electrode terminals and metal plates for reliable electrical connection without putting a load on the electrode terminals.
In the battery array of the present invention, the positive and negative electrode terminals 2, 32 of the battery cells 1, 31 can be aluminum and copper, and the metal plates 3, 23, 33, 43, 53 can be clad material with a junction between first metal plates 3A, 23A, 33A, 43A, 53A and second metal plates 3B, 23B, 33B, 43B, 53B that are aluminum and copper. However, in this patent application, the term aluminum is used in the wider sense to include aluminum alloys, and the term copper is used in the wider sense to include copper alloys.
In the battery array described above, since the electrode terminals are aluminum and copper and the metal plates are also aluminum and copper, the metal plates can be electrically connected to electrode terminals that are the same metal type in a stable manner that does not generate galvanic corrosion.
In the battery array of the present invention, the metal plates 3, 23, 33, 43, 53 can be first metal plates 3A, 23A, 33A, 43A, 53A and second metal plates 3B, 23B, 33B, 43B, 53B joined at junctions with step-shaped interfaces. This battery array has the characteristic that since the junction interfaces are step-shaped, the first metal plates and second metal plates can be stably and reliably joined in a robust manner.
In the battery array of the present invention, the battery cells 1, 31 can be lithium ion batteries. This battery array has the characteristic that since the battery cells are lithium ion batteries, it can increase charging and discharging capacities while being light-weight.
The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings.
The following describes embodiments of the present invention based on the figures.
The battery array of the present invention is primarily installed on-board an electric-powered vehicle such as a hybrid car or electric automobile (electric vehicle EV), and is used as a power source to supply power to a driving motor to drive the vehicle.
The battery array shown in
The external case 11 is deep drawn formed metal such as aluminum, and has a conducting surface. The stacked battery cells 1 are formed in thin rectangular-shapes. The sealing plates 12 are fabricated from the same metal as the external case 11 such as aluminum sheet-metal. Each sealing plate 12 has positive and negative electrode terminals 2 mounted on its end regions via insulating material 13. The positive and negative electrode terminals 2 are connected to the internal positive and negative electrode plates. In a lithium ion rechargeable battery, the external case 11 is not connected to an electrode. Since the external case 11 is connected to the internal electrode plates via electrolyte, it attains an intermediate potential between that of the positive and negative electrode plates. However, one of the battery cell electrode terminals can be connected to the external case via a lead-wire as well. In this battery cell, the electrode terminal connected to the external case can be mounted on the sealing plate without insulation.
The battery array has a plurality of battery cells 1 stacked to form a rectangular solid block configuration. The battery cells 1 in the figures are stacked in a block configuration in a manner that aligns the electrode terminal 2 surfaces, which are the sealing plate 12 surfaces, in the same plane. The battery array of
As shown in
The positive and negative electrode terminals 2 are not the same type of metal, but rather are different (dissimilar) metals. A lithium ion battery has an aluminum positive electrode 2A and a copper negative electrode 2B. The metal plates 3 have metals connected at either end that are the same as the dissimilar metal electrode terminals 2. A metal plate 3 that connects battery cells 1 with aluminum and copper electrode terminals 2 is clad material with an aluminum first metal plate 3A and a copper second metal plate 3B. A metal plate 3 is clad material with a junction between the first metal plate 3A and the second metal plate 3B at the boundary between electrode terminal 2 connecting regions. This metal plate 3 is connected to battery cell 1 positive and negative electrode terminals 2 with the first metal plate 3A in contact with an aluminum positive electrode 2A and the second metal plate 3B in contact with a copper negative electrode 2B. The first metal plate 3A aluminum does not contact the copper negative electrode 2B, and the second metal plate 3B copper does not contact the aluminum positive electrode 2A.
As shown in
The metal plates 3 of the figures are provided with through-holes 4 at either end for electrode terminal 2 insertion. Electrode terminals 2 of adjacently disposed battery cells 1 are connected by inserting the electrode terminals 2 through the two through-holes 4 established at the ends of a metal plate 3. Here, an electrode terminal 2 is inserted in a through-hole 4. With the electrode terminal 2 inserted in the through-hole 4, a laser is shined on the boundary between the outside surface of the electrode terminal 2 and the inside surface of the through-hole 4 to laser-weld and attach the electrode terminal 2 and the metal plate 3. To stably and reliably laser-weld a metal plate 3 to an electrode terminal 2, it is important to contact the outside surface of the electrode terminal 2 to the inside surface of the through-hole 4 without gaps. This is because gaps between a through-hole 4 and electrode terminal 2 impede stable connection via laser-welding. Accordingly, the through-holes 4 have an inside diameter that allows tight contact of the inside surface with inserted electrode terminals 2, and specifically, the inside diameter of the through-holes 4 is essentially the same size as the outside diameter of the electrode terminals 2. Therefore, it is necessary to make the inside diameter of the through-holes 4 a size that allows no play between the inserted electrode terminals 2.
To insert two electrode terminals without play in the two through-holes, it is necessary to make the distance between the two electrode terminals precisely equal to the distance between the two through-holes. However, there is error in the dimensions of a battery cell 1, and in a configuration that sandwiches insulating spacers 15 between battery cells 1, there is also error in the dimensions of the insulating spacers 15. Consequently, it is difficult to establish a uniform distance between two adjacent electrode terminals 2. To enable reliable laser-welding of the electrode terminals 2 even when the distance between electrode terminals 2 varies due to dimensional errors, the metal plates 3 of the figures have one of the through-holes 4 made as an elongated hole 4A. An elongated hole 4A has a long narrow shape that extends in a direction allowing the distance between through-holes 4 to vary, which is in the lengthwise direction of the metal plate 3. This allows two electrode terminals 2 with variable distance between the electrode terminals 2 to be inserted in the metal plate 3.
As shown in
In the battery array of the figures, the through-hole 4 for negative electrode terminal 2B insertion is formed as an elongated hole 4A. Specifically, a circular through-hole 4 is established in the aluminum first metal plate 3A, and an elongated hole 4A is established in the copper second metal plate 3B. In the battery array of
The electrode terminals 2 and metal plates 3 of the battery array described above are connected by the following steps.
(1) As shown in
(2) As shown in
(3) As shown in
Although the metal plates 3 described above have one of the through-holes 4 formed as an elongated hole 4A, the battery array of the present invention can also have both through-holes formed as elongated holes. In this battery array, crimping rings are formed by widening the ends of both electrode terminals and perimeter edges of the crimping rings are laser-welded to the metal plates for connection.
Further, the battery array of
The electrode terminals 2 and metal plates 3 of the battery array described above are connected by the following steps.
(1) As shown in
(2) As shown in
(3) As shown in
Although the metal plates 3 described above have one of the through-holes 4 formed as an elongated hole 4A, the battery array of the present invention can also have both through-holes formed as elongated holes. In this battery array, both electrode terminals can be inserted through the center holes of metal rings, and the inside and outside perimeter edges of the metal rings can be laser-welded to connect the metal rings to both the electrode terminals and the metal plate.
Further, the battery array of
Further, the metal plate 43 of
Further, the battery array of
The metal plate 53 shown in
As shown in
The battery cells 1 stacked with intervening insulating spacers 15 are held in fixed positions by fastening components 17 (see
It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the spirit and scope of the invention as defined in the appended claims. The present application is based on Application No. 2009-210045 filed in Japan on Sep. 11, 2009, the content of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-210045 | Sep 2009 | JP | national |
