Battery pack

A battery pack includes a plurality of secondary batteries and a plurality of bus bars. The secondary batteries are connected to each other in series and in parallel. Each of the secondary batteries includes first and second electrode terminals. Each of the bus bars electrically connects one of the secondary batteries to a neighboring one of the secondary batteries. The bus bars include a first bus bar having a first sectional area and a second bus bar having a second sectional area different from the first sectional area.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2015-0116023, filed on Aug. 18, 2015, and entitled, “Battery Pack,” is incorporated by reference herein in its entirety.

BACKGROUND

One or more embodiments described herein relate to a battery pack.

2. Description of the Related Art

A secondary battery is a rechargeable energy source that may be used to power a variety of systems and devices. Examples include mobile terminals and electric and hybrid vehicles. Cellular phones and other small mobile devices may operate for a predetermined time based on the power output and capacity of a single secondary battery. When long-time and high-power driving is required (e.g., such as in the case of electric or hybrid vehicles), a large-capacity battery pack may be used. The battery pack may be equipped with multiple secondary batteries electrically connected together. The output voltage and current of the battery pack may be proportional to the number of batteries in the pack.

SUMMARY

In accordance with one or more embodiments, a battery pack includes a plurality of secondary batteries connected to each other in series and in parallel, each of the secondary batteries including a first electrode terminal and a second electrode terminal; and a plurality of bus bars, each of the bus bars electrically connecting one of the secondary batteries to a neighboring one of the secondary batteries, wherein the bus bars include a first bus bar having a first sectional area and a second bus bar having a second sectional area larger than the first sectional area.

The secondary batteries may be included in at least two parallel groups connected to each other in parallel, and the at least two parallel groups may be connected to each other in series. The first bus bar may connect, in parallel, the secondary batteries to each other in the parallel groups, and the second bus bar may electrically connect the at least two parallel groups to each other. Each of the bus bars may include a pair of blade portions extending from a bent portion, and the blade portions may be connected to a first or a second electrode terminal of each of the secondary batteries.

A thickness of the bent portion of the second bus bar may be greater than that of the bent portion of the first bus bar. A width of the bent portion of the second bus bar may be greater than that of the bent portion of the first bus bar. The second bus bar include an extending portion extending from the bent portion in a second direction crossing extending directions of the blade portions. A blade portion of one of the bus bars and a blade portion of a neighboring one of the bus bars may be spaced apart from each other.

Each of a first electrode terminal and a second electrode terminal of the secondary battery may include an upwardly extending fastening terminal, and each of the blade portions of the bus bars may include a penetration hole through which the fastening terminal passes.

A blade portion of one of the bus bars and a blade portion of a neighboring one of the bus bars may be superimposed, and one fastening terminal may pass through the blade portions of both of the bus bar and the neighboring one of the bus bars. The blade portion of the bus bar may include at least one groove and at least one protrusion, and the protrusion of the blade portion of the bus bar may be inserted into the groove of the blade portion of the neighboring one of the bus bars. The protrusion of the blade portion of the bus bar and the protrusion of the blade portion of the neighboring one of the bus bar may be connected to the first electrode terminal or the second electrode terminal of the secondary battery by a single welding line.

In accordance with one or more other embodiments, an apparatus includes a first bus bar; and a second bus bar, wherein the first bus bar is electrically connected to an electrode terminal of a first battery and an electrode terminal of a second battery, and the second bus bar is electrically connected to the electrode terminal of the second battery and an electrode terminal of a third battery, and wherein the first bus bar has a first section having a first thickness overlapping a space between the electrode telininals of the first and second batteries and the second bus bar has a second section having a second thickness overlapping a space between the electrode terminals of the second and third batteries.

Each of the first and second bus bars may include third and fourth sections contacting respective ones of the electrode terminals, and wherein the first and second sections are above the third and fourth sections. The second bus bar may connect the electrodes of the second and third batteries in series. The second thickness may be greater than the first thickness. The first bus bar may not overlap the second bus bar. The first bus bar may overlap the second bus bar.

DETAILED DESCRIPTION

FIG. 1illustrates an embodiment of a battery pack.FIG. 2illustrates an embodiment of a secondary battery which, for example, may be included in the battery pack ofFIG. 1.FIG. 3illustrates an embodiment of a bus bar which, for example, may be included in the battery pack ofFIG. 1.FIG. 4illustrates a portion of the battery pack taken along section line A-A′ inFIG. 1.FIG. 5is a graph illustrating an example of a temperature distribution of one type of bus bar.FIG. 6is a graph illustrating an example of a temperature distribution of a bus bar in a battery pack according to one embodiment.

Referring toFIG. 1, the battery pack1000includes a plurality of secondary batteries110a,110b,110c,110d,120a,120b,120c,120d,130a,130b,130cand130dand bus bars200. The secondary batteries110a,110b,110c,110d,120a,120b,120c,120d,130a,130b,130cand130dare connected to each other in series and in parallel through the bus bars200.

In one embodiment, the secondary batteries110a,110b,110c,110d,120a,120b,120c,120d,130a,130b,130cand130dconstitute parallel groups110,120and130connected to each other in parallel, which are then connected to each other in series. Three groups, (e.g., parallel groups110,120and130) in the battery pack1000are illustrated inFIG. 1for illustrative purposes. The number of parallel groups may be different in another embodiment.

Referring toFIG. 2, one secondary battery110a(which may be representative of all the secondary batteries) includes an electrode assembly111having a first electrode plate and a second electrode plate stacked with a separator therebetween, a case112accommodating the electrode assembly111and an electrolyte and having a top opening, a cap plate113sealing the top opening of the case112, and a first electrode terminal114and a second electrode terminal115electrically connected to the first electrode plate and the second electrode plate and protruding outside of the cap plate113.

The cap plate113may include an electrolyte injection hole, a safety vent, and a membrane, and insulating and seal gaskets may be provided between the cap plate113and each of the first electrode terminal114and the second electrode terminal115.

Referring toFIGS. 3 and 4, the bus bar200may be made from a highly conductive metal material. The bus bar200may include a pair of blade portions200aconnected to the first electrode terminal114and the second electrode terminal115of each of the secondary batteries110ato130d, and a bent portion200bupwardly protruding/bent at the center of the pair of blade portions200a.

The pair of blade portions200amay be mounted and fixed on a top surface of the first electrode terminal114or the second electrode terminal115, for example, by a bonding method, e.g., welding. The blade portion200aof the bus bar200and the blade portion200aof a neighboring bus bar of the bus bar200may be spaced a predetermined D1apart from each other. The space may be sufficient to prevent the bus bar200from being deformed during the bonding process of the bus bar200and/or due to an externally applied pressure.

The bent portion200bis at a predetermined location (e.g., the center) between the pair of blade portions200ain a substantially “n” shape. The bent portion200bis capable of absorbing vibration applied to the bus bar200, thereby preventing damage and electrical contact failure.

The bus bar200may include first bus bars210and230and a second bus bar220. Each of the first bus bars210and230and the second bus bar220may have a pair of blade portions and a bent portion. The bus bars may have similar shapes.

The first bus bar210electrically connects the first electrode terminal114of the secondary battery110cand the first electrode terminal114of its neighboring secondary battery110dto each other in a first parallel group110. In other words, the first bus bar210connects the secondary battery110cand its neighboring secondary battery110dto each other in parallel.

The first bus bar230electrically connects the second electrode terminal115of the secondary battery120aand the second electrode terminal115of its neighboring secondary battery120bto each other in a second parallel group120. That is to say, the first bus bar230connects the secondary battery120aand its neighboring secondary battery120bto each other in parallel.

The second bus bar220electrically connects the first electrode terminal114of the secondary battery110din the first parallel group110to the second electrode terminal115of the secondary battery120ain the second parallel group120. That is to say, the second bus bar220connects the first parallel group110and the second parallel group120adjacent to the first parallel group110to each other in series.

In the battery pack1000having series and parallel configurations, the flow of current may concentrate on a series-connected portion of the battery pack1000and a high current flows in the series-connected portion.

Accordingly, in one embodiment, the bent portion of the first bus bars210and230connecting neighboring secondary batteries in parallel may have a first thickness T1, and the bent portion of the second bus bar220connecting neighboring parallel groups in series may have a second thickness T2which is greater than the first thickness T1. As a result, according to one embodiment, resistance of the second bus bar220in the series-connected portion on which the flow of current concentrates may be selectively reduced. This may prevent a voltage drop and heat generation from occurring. In addition, since the first bus bars210and230in the parallel-connected portion, on which the flow of current does not concentrate, are formed to have a relatively smaller thickness, material costs may be reduced.

FIG. 5is a graph illustrating an example of a change in temperature of the first bus bar210having a same sectional area as a parallel-connected portion, after the first bus bar210is positioned on a series-connected portion. As shown inFIG. 5, the temperature of the first bus bar210positioned on the series-connected portion series-connected portion rises up to approximately 100° C.

FIG. 6is a graph illustrating an example of a change in temperature of a second bus bar220having a relatively large thickness, after the second bus bar220is selectively positioned on a series-connected portion in a battery pack according to one embodiment. As shown inFIG. 6, the temperature of the second bus bar220positioned on the series-connected portion rises up to approximately 45° C. Thus, a considerable amount of heat is generated due to the current concentrating on the series-connected portion, and the second bus bar220having a relatively large sectional area is positioned on the series-connected portion, thereby reducing the resistance of the series-connected portion.

FIG. 7illustrates another embodiment of a battery pack2000.FIG. 8illustrates another embodiment of a bus bar which, for example, may be used in the battery pack2000.FIG. 9illustrates a portion of the battery pack along section line B-B′ inFIG. 7.

Referring toFIGS. 1 and 7, the battery pack2000is different from the battery pack1000in view of configurations of fastening terminals114aand115aand a bus bar300. Therefore, the following description of the battery pack2000will focus on the fastening terminals114aand115aand the bus bar300.

Referring toFIGS. 8 and 9, the battery pack2000includes a plurality of secondary batteries110a,110b,110c,110d,120a,120b,120c,120d,130a,130b,130cand130dand a bus bar300. The secondary batteries110a,110b,110c,110d,120a,120b,120c,120d,130a,130b,130cand130dare connected to another in series and in parallel through the bus bar300.

Each of the secondary batteries110ato130dincludes a first fastening terminal114aupwardly extending from a first electrode terminal114and a second fastening terminal115aupwardly extending from a second electrode terminal115. The fastening terminals114aand115aare electrically and physically coupled to the first and second electrode terminals114and115, and threads are formed on outer peripheral surfaces of the fastening terminals114aand115a.

The bus bar300is made of a highly conductive metal material. The bus bar300includes a pair of blade portions300aconnected to the first electrode terminal114and the second electrode terminal115of each of the secondary batteries110ato130d, a bent portion300bupwardly protruding/bent at a predetermined location (e.g., center) of the pair of blade portions300a, and a penetration hole300cin each of the pair of blade portions300a.

The fastening terminals114aand115apass through the penetration hole300cin each of the pair of blade portions300aand are then coupled to each other. Nuts or other fasteners are coupled to each other to the fastening terminals114aand115apassing through the penetration hole300c.

A blade portion of the bus bar300and a blade portion of its neighboring bus bar300are superimposed, and one fastening terminal fastening terminals114a,115apasses through the blade portions of the neighboring bus bars300.

The bus bar300includes first bus bars310and330and a second bus bar320. Each of the first bus bars310and330and the second bus bar320has a pair of blade portions and a bent portion, which have similar shapes.

The first bus bar310electrically connects the first electrode terminal114of the secondary battery110cand the first electrode terminal114of its neighboring secondary battery110dto each other in a first parallel group110. That is to say, the first bus bar310connects the secondary battery110cand its neighboring secondary battery110dto each other in parallel.

The first bus bar330electrically connects the second electrode terminal115of the secondary battery120aand the second electrode terminal115of its neighboring secondary battery120bto each other in a second parallel group120. That is to say, the first bus bar330connects the secondary battery120aand its neighboring secondary battery110dto each other in parallel.

The second bus bar320electrically connects the first electrode terminal114of the secondary battery110din the first parallel group110and the second electrode terminal115of the secondary battery120ato each other in the second parallel group120adjacent to the first parallel group110. That is to say, the second bus bar320connects the first parallel group110and the second parallel group120adjacent to the first parallel group110to each other in series.

In the battery pack2000having series and parallel configurations, the flow of current concentrates on a series-connected portion of the battery pack2000and a high current flows in the series-connected portion.

Accordingly, in another embodiment, the bent portion of the first bus bars310and330connecting neighboring secondary batteries in parallel has a first thickness T1, and the bent portion of the second bus bar320connecting neighboring parallel groups in series has a second thickness T2greater than the first thickness T1.

Therefore, according to the present embodiment, resistance of the second bus bar320in the series-connected portion, on which the flow of current concentrates, may be selectively reduced, thereby preventing a voltage drop and heat generation. In addition, since the first bus bars310and330in the parallel-connected portion, on which the flow of current does not concentrate, are not formed to have relative large thicknesses, material costs may be reduced.

FIG. 10illustrates another embodiment of portion of a battery pack, andFIG. 11illustrates another embodiment of a bus bar which, for example, may be used in the battery pack ofFIG. 10.

Referring toFIGS. 10 and 11, the battery pack is different from the battery pack1000in view of a configuration of a bus bar400. Therefore, the following description will focus on the bus bar400.

The bus bar400is made of a highly conductive metal material and includes first bus bars410and430and a second bus bar420. The first bus bar410electrically connects a first electrode terminal114of a secondary battery110cand a first electrode terminal114of its neighboring secondary battery110dto each other in a first parallel group110. That is to say, the first bus bar410connects the secondary battery110cand its neighboring secondary battery110dto each other in parallel.

The first bus bar430electrically connects a second electrode terminal115of a secondary battery120aand a second electrode terminal115of its neighboring secondary battery120bto each other in a second parallel group120. That is to say, the first bus bar430connects the secondary battery120aand its neighboring secondary battery120bto each other in parallel.

The second bus bar420electrically connects the first electrode terminal114of the secondary battery110din the first parallel group110to the second electrode terminal115of the secondary battery120ain the second parallel group120. That is to say, the second bus bar420connects the first parallel group110and the second parallel group120adjacent to the first parallel group110to each other in series.

The first bus bars410and430may have the same shape as the first bus bars210and230of the battery pack1000. For example, the first bus bars410and430include a pair of blade portions connected to the first electrode terminal114and the second electrode terminal115of each of the secondary batteries110ato130d, and a bent portion upwardly protruding/bent at the center of the pair of blade portions and having a first thickness T1.

The second bus bar420includes a pair of blade portions420aconnected to the first electrode terminal114in the first parallel group110and the second electrode terminal115in the second parallel group120, a bent portion420bupwardly protruding/bent at the center of the pair of blade portions420a, and an extending portion420cextending from the bent portion420b. The pair of blade portions420amay be mounted and fixed on a top surface of the first electrode terminal114or the second electrode terminal115, for example, by a bonding method, e.g., welding.

The bent portion420bis formed at a predetermined location (e.g., center) between the pair of blade portions420ain a substantially “n” shape. The bent portion420bis able to absorb vibration applied to the bus bar420, thereby preventing damages and electrical contact failures. The bent portion420bmay have a first thickness T1.

The extending portion420cextends from bent portion420bby a first width W1in a direction perpendicular to extending directions of the pair of blade portions420a. The extending portion420cmay have the first thickness T1.

Thus, since the second bus bar420of the battery pack has the width W1, which is greater than widths of the first bus bars410and430, resistance of the second bus bar420in a series-connected portion on which the flow of current concentrates may be selectively reduced, thereby preventing a voltage drop and heat generation. In addition, since the first bus bars410and430in a parallel-connected portion on which the flow of current does not concentrate are not formed to have relatively large thicknesses, material costs may be reduced.

FIG. 12illustrates another embodiment of a battery pack,FIG. 13illustrates another embodiment of a bus bar which, for example, may be used in the battery pack inFIG. 12, andFIG. 14illustrates an example of a welding line of the bus bar ofFIG. 12.

Referring toFIGS. 12 and 13, the battery pack is different from the battery pack1000in view of a configuration of a bus bar500. Therefore, the following description will focus on the bus bar500.

The bus bar500is made of a highly conductive metal material and includes a first blade portion500a, a second blade portion500cand a bent portion500b. The first blade portion500aand the second blade portion500cmay be mounted and fixed on a top surface of a first electrode terminal114or a second electrode terminal115, for example, by a bonding method, e.g., welding. The first blade portion500aincludes at least one protrusion500aand at least one groove500a″. The second blade portion500bincludes at least one protrusion500c′ corresponding to the groove500a″ of the first blade portion500aand at least one groove500c″ corresponding to the groove500a″ of the first blade portion500a.

The protrusion500a′ of the first blade portion500aof the bus bar500is inserted into the groove500c″ of the second blade portion500cof a neighboring bus bar500. The protrusion500c′ of the second blade portion500cof the bus bar500is inserted into the groove500a″ of the first blade portion500aof the neighboring bus bar500. That is to say, the first blade portion500aof the bus bar500and the second blade portion500cof the neighboring bus bar500engage each other in a serrated shape. Accordingly, as shown inFIG. 14, the bus bar500and its adjacent bus bar500may be simultaneously welded through a single welding line WL.

The bus bar500includes first bus bars510and530and a second bus bar520. Each of the first bus bars510and530and the second bus bar520includes a first blade portion, a second blade portion and a bent portion, which have similar shapes.

The first bus bar510electrically connects a first electrode terminal114of a secondary battery110cand a first electrode terminal114of its neighboring secondary battery110dto each other in a first parallel group110. That is to say, the first bus bar510connects the secondary battery110cand its neighboring secondary battery110dto each other in parallel.

The first bus bar530electrically connects a second electrode terminal115of a secondary battery120aand a second electrode terminal115of its neighboring secondary battery120bto each other in a second parallel group120. That is to say, the first bus bar530connects the secondary battery120aand its neighboring secondary battery120bto each other in parallel.

The second bus bar520electrically connects the first electrode terminal114of the secondary battery110din the first parallel group110and the second electrode terminal115of the secondary battery120ato each other in the second parallel group120adjacent to the first parallel group110. That is to say, the second bus bar520connects the first parallel group110and the second parallel group120adjacent to the first parallel group110to each other in series.

In the aforementioned battery pack having series and parallel configurations, the flow of current concentrates on a series-connected portion of the battery pack2000and a high current flows in the series-connected portion.

In another embodiment, the bent portion of the first bus bars510and530connecting neighboring secondary batteries in parallel has a first thickness T1, and the bent portion of the second bus bar520connecting neighboring parallel groups in series has a second thickness T2greater than the first thickness T1. Thus, resistance of the second bus bar520in a series-connected portion on which the flow of current concentrates may be selectively reduced, thereby preventing a voltage drop and heat generation. In addition, since the first bus bars510and530in a parallel-connected portion on which the flow of current does not concentrate are not formed to have relatively large thicknesses, material costs may be reduced.