Patent Description:
In recent years, secondary batteries have been used for various applications, and particularly, secondary batteries having a large capacity have been used for applications such as automobile power supplies and electric power storage.

When a secondary battery is used as a single battery, a voltage of the secondary battery may be lower than a voltage required for a device in some cases. In such a case, it is necessary to connect a plurality of secondary batteries in series and to increase a supply voltage to a desired voltage. Furthermore, in a single battery, there are cases in which it is not possible to supply a sufficient amount of electricity required for a device. In such a case, it is necessary to connect a plurality of secondary batteries in parallel and to increase an amount of supplied electricity to a desired amount.

For this reason, electric power may be supplied from a power storage device having a plurality of secondary batteries connected to each other in series or in parallel accommodated in a casing to a device. Furthermore, a power storage device having a battery monitoring unit (BMU) configured to monitor a plurality of secondary batteries built thereinto is known (for example, refer to Patent Document <NUM>). The BMU usually measures a voltage or the like of each secondary battery and detects overcharging and overdischarging at the time of charging and discharging. Furthermore, the BMU can also have a function of maintaining a voltage balance between the respective secondary batteries.

On the other hand, lead storage batteries are usually installed in automobiles, motorcycles, and the like. There is a disadvantage concerning a lead storage battery being relatively heavy. Thus, an in-vehicle power storage device including a relatively light lithium ion battery has been developed.

When a lithium ion battery is used for an in-vehicle power storage device, it is necessary to install an electronic device such as a BMU in a power storage device to prevent overcharging or the like. Therefore, when rain water, washing water, or the like enters a power storage device, a BMU or a wiring may corrode, which may cause the power storage device to fail and cause electrical leakage.

The present invention was made in view of such circumstances and provides a power storage device capable of preventing rain water, washing water, or the like from entering a casing.

The present invention provides a power storage device including: a secondary battery, a casing having a sealed structure, a safety valve, wherein the casing includes an external container having the secondary battery accommodated therein and an upper lid disposed above the external container, the upper lid has an upper surface having a concave portion formed therein, the safety valve is disposed in the concave portion, characterized in that a drainage through hole is provided to pass through a side wall of the concave portion, the safety valve has convex shape extending along the side wall of the concave portion and is provided so that an upper end does not protrude from a main upper surface of the upper lid, the safety valve has an exhaust cylinder and a cap configured to close an external outlet of the exhaust cylinder, and the cap is disposed above an inlet of the drainage through hole.

A power storage device of the present invention can be charged and discharged because the power storage device includes a secondary battery.

The power storage device of the present invention includes a casing having a sealed structure. Thus, it is possible to prevent water from entering the casing and it is possible to prevent a power storage device from failing due to rain water, washing water, and the like.

The casing includes an external container having a secondary battery accommodated therein and an upper lid disposed above the external container. Thus, it is possible to manufacture a power storage device having a secondary battery accommodated in a casing having a sealed structure by placing the secondary battery in an external container and closing the external container using an upper lid.

The power storage device of the present invention includes a safety valve. Thus, even when a gas generated in the secondary battery is discharged into the casing and an internal pressure in the casing increases, the gas can be discharged outside of the casing through the safety valve. For this reason, it is possible to prevent the casing from expanding or rupturing.

The safety valve is disposed in a concave portion of the upper lid. Thus, it is possible to provide a safety valve without it protruding from a main upper surface of the upper lid and it is possible to adapt a size of the power storage device to an installation space. Furthermore, it is possible to effectively use a space below the main upper surface of the upper lid.

The power storage device of the present invention includes a drainage through hole provided to pass through a side wall of the concave portion. Thus, even when rain water or washing water enters the concave portion, it is possible for water to drain through this through hole. Thus, it is possible to prevent water from remaining in the concave portion having the safety valve disposed therein and it is possible to prevent water from entering the casing via the safety valve. The safety valve has convex shape extending along the side wall of the concave portion and is provided so that an upper end does not protrude from a main upper surface of the upper lid. The safety valve has an exhaust cylinder and a cap configured to close an external outlet of the exhaust cylinder. The cap is disposed above an inlet of the drainage through hole.

A power storage device in the present invention includes a secondary battery (a secondary battery cell), a casing having a sealed structure, a safety valve, wherein the casing includes an external container having the secondary battery accommodated therein and an upper lid disposed above the external container, the upper lid has an upper surface having a concave portion formed therein, the safety valve is disposed in the concave portion, characterized in that a drainage through hole is provided to pass through a side wall of the concave portion, the safety valve has convex shape extending along the side wall of the concave portion and is provided so that an upper end does not protrude from a main upper surface of the upper lid, the safety valve has an exhaust cylinder and a cap configured to close an external outlet of the exhaust cylinder, and the cap is disposed above an inlet of the drainage through hole.

The safety valve included in the power storage device of the present invention includes an exhaust cylinder and a cap configured to close an outlet on an outer side of the exhaust cylinder. According to such a safety valve, when an internal pressure of the casing increases, a cap elastically deforms due to this internal pressure, a gap can be formed between the cap and the exhaust cylinder, and a gas inside the casing can be discharged to the outside through this gap. When the pressure in the casing decreases to atmospheric pressure, the cap is restored to have its original shape and thus the inside of the casing can become a sealed space again.

The casing included in the power storage device of the present invention preferably includes an inner lid disposed between the secondary battery accommodated in the external container and the upper lid. The inner lid can function as a wiring board in which a wiring configured to connect the secondary battery to an external connection terminal or a wiring configured to connect the secondary battery to a battery monitoring unit is provided.

The power storage device in the present invention preferably includes a battery monitoring unit configured to monitor the secondary battery and the battery monitoring unit is preferably disposed between the inner lid and the upper lid. When the battery monitoring unit can monitor the secondary battery, it is thus possible to improve the safety of the power storage device.

Also, it is desirable that the battery monitoring unit be accommodated in the casing so as not to be located between the secondary battery and the safety valve. Thus, it is possible to dispose the battery monitoring unit at a position outside of a discharge path through which a gas generated in the secondary battery is discharged from the safety valve and to prevent adhering of a gas generated in the secondary battery or an electrolytic solution ejected from the secondary battery to the battery monitoring unit.

The power storage device in the present invention preferably further includes a protection case disposed between the inner lid and the upper lid, and it is preferable that the protection case accommodates the battery monitoring unit, and has its inside sealed. By providing the protection case, even if a solution in the secondary battery leaks, leaked electrolytic solution does not enter the protection case having the battery monitoring unit accommodated therein and it is possible to prevent damage to the battery monitoring unit.

The secondary battery included in the power storage device in the present invention preferably includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator sandwiched between the positive electrode and the negative electrode, a non-aqueous electrolyte, and a container having the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte accommodated therein.

A constitution shown in the drawings and the following description is merely an example and the scope of the present invention is not limited to that shown in the drawings and the following description.

<FIG> is a schematic perspective view of the power storage device in this embodiment and <FIG> is a schematic cross-sectional view of the power storage device taken along broken line A-A in <FIG>.

A power storage device <NUM> in this embodiment includes a secondary battery <NUM>, a casing <NUM> having a sealed structure, a safety valve <NUM>, and a drainage through hole <NUM>, the casing <NUM> includes an external container <NUM> having the secondary battery <NUM> accommodated therein and an upper lid <NUM> disposed above the external container <NUM>, the upper lid <NUM> has an upper surface having a concave portion <NUM> formed therein, the safety valve <NUM> is disposed in the concave portion <NUM>, and the drainage through hole <NUM> is provided to pass through a side wall of the concave portion <NUM>.

Also, the power storage device <NUM> in this embodiment may include a battery monitoring unit <NUM> or a protection case <NUM>.

The power storage device <NUM> in this embodiment will be described below.

The power storage device <NUM> in this embodiment is, for example, a power storage device used for a power supply of an automobile, a power supply of a motorcycle, a storage of photovoltaic power generation, a backup power supply, and the like. Furthermore, the power storage device <NUM> can be provided to be able to be charged and discharged. In addition, the power storage device <NUM> may be a sealed power storage device or an in-vehicle power storage device.

The power storage device <NUM> includes the secondary battery <NUM> accommodated in the casing <NUM>. The secondary battery <NUM> has a positive electrode battery terminal and a negative electrode battery terminal (the positive electrode battery terminal or the negative electrode battery terminal is referred to as a "battery terminal <NUM>" in this specification). Furthermore, the secondary battery <NUM> can be accommodated in the external container <NUM> in the casing <NUM> such that the positive electrode battery terminal and the negative electrode battery terminal are disposed on an upper side.

Also, the power storage device <NUM> can include a plurality of secondary batteries <NUM> accommodated in the casing <NUM>. The plurality of secondary batteries <NUM> may be connected to each other in parallel or in series. Furthermore, the plurality of secondary batteries <NUM> may be electrically connected to each other through a wiring and the battery terminals <NUM> of two neighboring batteries <NUM> may be electrically connected to each other by bringing the battery terminals <NUM> into contact with each other or joining the battery terminals <NUM>.

Each of the secondary batteries <NUM> is, for example, a lithium ion battery, a sodium ion battery, a nickel/hydrogen battery, a nickel/cadmium battery, and the like. The secondary battery <NUM> may be a sealed battery. Furthermore, the secondary battery <NUM> may be of an angular shape, a cylindrical type, or a pouch type. The secondary battery <NUM> can include a positive electrode <NUM> including a positive electrode active material, a negative electrode <NUM> including a negative electrode active material, a separator <NUM> sandwiched between the positive electrode <NUM> and the negative electrode <NUM>, a non-aqueous electrolyte <NUM>, and a container <NUM> having the positive electrode <NUM>, the negative electrode <NUM>, the separator <NUM>, and the non-aqueous electrolyte <NUM> accommodated therein.

The power storage device <NUM> includes the casing <NUM> configured to accommodate the secondary battery <NUM> and having a sealed structure. The casing <NUM> includes the external container <NUM> having the secondary battery <NUM> accommodated therein and the upper lid <NUM> disposed above the external container <NUM>. Furthermore, the casing <NUM> can include an inner lid <NUM> disposed between the external container <NUM> and the upper lid <NUM>. The secondary battery <NUM> can be accommodated in the casing <NUM> having the sealed structure by inserting the secondary battery <NUM> into the external container <NUM> before these members constituting the casing <NUM> are bonded together.

The inner lid <NUM> can function as a wiring board in which a wiring <NUM> configured to connect the secondary battery <NUM> to an external connection terminal <NUM> or the wiring <NUM> configured to connect the secondary battery <NUM> to the battery monitoring unit <NUM> is provided. Furthermore, the inner lid <NUM> can have a slit through which the battery terminal <NUM> of the secondary battery <NUM> passes and the battery terminal <NUM> can be joined to a connection portion <NUM> provided on an upper surface of the inner lid <NUM>. Thus, the wiring <NUM> on the upper surface of the inner lid <NUM> and the secondary battery <NUM> can be electrically connected to each other.

The inner lid <NUM> can have a through hole <NUM> immediately below the safety valve <NUM>. Thus, when a gas is generated from the secondary battery <NUM>, the gas can be discharged outside of the power storage device <NUM> using the through hole <NUM> and the safety valve <NUM> as a discharge path. Thus, it is possible to prevent the casing <NUM> from being filled with a gas generated from the secondary battery <NUM> and to prevent the battery monitoring unit <NUM> from being corroded due to the gas generated from the secondary battery <NUM>.

The members constituting the casing <NUM> can be adhered so that the inside of the casing <NUM> is a sealed space. Thus, it is possible to prevent water or the like from entering the casing <NUM> and to improve the safety and the lifespan characteristics of the power storage device <NUM>. The members constituting the casing <NUM> can be adhered using, for example, an adhesive. It should be noted that a material of the casing <NUM> may be a plastic.

The upper lid <NUM> has an upper surface having the concave portion <NUM> formed therein. Furthermore, the safety valve <NUM> (relief valve) is provided in the concave portion <NUM> of the upper lid <NUM>. The safety valve <NUM> has a structure in which, when an internal pressure of the casing <NUM> increases abnormally, the valve automatically opens, a gas inside the casing <NUM> is discharged to the outside, the internal pressure decreases, and when the internal pressure decreases, the valve automatically closes. By providing the safety valve <NUM> in the upper lid <NUM>, even when a gas generated in the secondary battery <NUM> is discharged into the casing <NUM> and an internal pressure of the casing <NUM> increases, it is possible to discharge the gas outside of the casing <NUM> through the safety valve <NUM>. For this reason, it is possible to prevent the casing <NUM> from expanding, rupturing, or being damaged.

The safety valve <NUM> includes an exhaust cylinder <NUM> and a cap <NUM> configured to close an outlet on an outer side of the exhaust cylinder <NUM>. As in the power storage device <NUM> shown in <FIG>, the exhaust cylinder <NUM> and the cap <NUM> is provided. The exhaust cylinder <NUM> can be provided in the upper lid <NUM>. Furthermore, an opening in the exhaust cylinder <NUM> can be provided to pass through the upper lid <NUM>. A material of the cap <NUM> can be rubber and the cap <NUM> can be formed in a shape in which the cap <NUM> covers an outer end of the exhaust cylinder <NUM>. The inside of the casing <NUM> can be made a sealed space by the rubber elasticity of the cap <NUM>. Furthermore, when an internal pressure of the casing <NUM> increases, the cap <NUM> elastically deforms due to this internal pressure, a gap can be formed between the cap <NUM> and the exhaust cylinder <NUM>, and a gas inside the casing <NUM> can be discharged to the outside through this gap. When the pressure in the casing <NUM> decreases to atmospheric pressure, the cap <NUM> is restored to have its original shape and thus the inside of the casing <NUM> can become a sealed space.

The safety valve <NUM> can include a valve pressing plate above the cap <NUM>. Thus, when a gas inside the casing <NUM> is discharged through the safety valve <NUM>, it is possible to prevent the cap <NUM> from being removed from the exhaust cylinder <NUM>.

The safety valve <NUM> is disposed in the concave portion <NUM> of the upper lid <NUM>. For this reason, the safety valve <NUM> can be provided without it protruding from a main upper surface of the upper lid <NUM> and a size of the power storage device <NUM> can be adapted for an installation space. Furthermore, it is possible to effectively use a space below the main upper surface of the upper lid <NUM>. When the power storage device <NUM> is, for example, a battery for a motorcycle, it is necessary to form the power storage device <NUM> so that the power storage device <NUM> can be installed in various motorcycles of various vehicle types and it is necessary to match the power storage device <NUM> to a predetermined size. For this reason, when the safety valve <NUM> is provided to protrude from the main upper surface of the upper lid <NUM>, an unavailable dead space is generated above the main upper surface. By disposing the safety valve <NUM> in the concave portion <NUM>, it is possible to prevent the generation of such a dead space. Furthermore, for example, it is possible to accommodate a battery monitoring unit (BMU) below the main upper surface of the upper lid <NUM> and it is possible to increase the size of the secondary battery <NUM>. Thus, it is possible to increase a battery capacity of the power storage device <NUM>.

The power storage device <NUM> has the drainage through hole <NUM> provided to pass through the side wall of the concave portion <NUM>. Furthermore, the drainage through hole <NUM> can have an inlet located in an inner wall surface of the concave portion <NUM> and an outlet located in a side surface of the upper lid <NUM>. Thus, even if rain water or washing water enters the concave portion <NUM>, it is possible for water to drain through the through hole <NUM>. Thus, it is possible to prevent water from remaining in the concave portion <NUM> having the safety valve <NUM> disposed therein and to prevent water from entering the casing <NUM> via the safety valve <NUM>.

The inlet of the through hole <NUM> can be provided close to the bottom of the concave portion <NUM>. Furthermore, the through hole <NUM> can be provided to be inclined downward from the inlet toward the outlet.

The drainage through hole <NUM> may be a through hole configured to pass through a part of the upper lid <NUM>. Furthermore, the drainage through hole <NUM> may be formed by forming a tubular portion in the upper lid <NUM>. The drainage through hole <NUM> may be formed by combining a tubular member with the upper lid <NUM>.

The battery monitoring unit <NUM> is a part configured to monitor the secondary battery <NUM>. The battery monitoring unit <NUM> can be disposed between the inner lid <NUM> and the upper lid <NUM>. Furthermore, the battery monitoring unit <NUM> can be provided not to overlap the concave portion <NUM>. The battery monitoring unit <NUM> can be disposed not to be located on the discharge path through which a gas generated from the secondary battery <NUM> is discharged from the safety valve <NUM>.

The battery monitoring unit <NUM> may be, for example, an electronic circuit board obtained by mounting electronic components thereon. The battery monitoring unit <NUM> may be a part of an electronic circuit board. The battery monitoring unit <NUM> may include a plurality of electronic circuit boards. Furthermore, the battery monitoring unit <NUM> can be accommodated in the protection case <NUM>. The battery monitoring unit <NUM> can be electrically connected to the secondary battery <NUM>, a fuse, a relay, or the external connection terminal <NUM>. Thus, the battery monitoring unit <NUM> can monitor the battery.

The battery monitoring unit <NUM> can be provided to measure a voltage of each secondary battery <NUM>. Furthermore, the battery monitoring unit <NUM> can be provided to detect overcharging on the basis of the results of voltage measurement of the secondary battery <NUM>. The battery monitoring unit <NUM> can be provided to output a signal for disconnecting the connection between the secondary battery <NUM> and the external connection terminal <NUM> through the fuse or the relay when detecting overcharging in at least one of the secondary batteries <NUM>. Thus, it is possible to forcibly cut off a current and to improve the safety of the power storage device <NUM> when overcharging is generated in at least one of the secondary batteries <NUM>.

The battery monitoring unit <NUM> may be provided to detect overdischarging of the secondary battery <NUM>, to measure a temperature inside the casing <NUM>, or to detect an overcurrent. Furthermore, the battery monitoring unit <NUM> can be provided to maintain a balance between voltages of a plurality of secondary batteries <NUM> accommodated in the external container <NUM>. Thus, it is possible to reduce damage to the plurality of secondary batteries <NUM> generated due to imbalance in the voltages of the secondary batteries <NUM> and to improve lifespan characteristics of the power storage device <NUM>. It should be noted that the battery monitoring unit <NUM> can include a balancer corresponding to each of the secondary batteries <NUM>.

The protection case <NUM> is a case having the battery monitoring unit <NUM> accommodated therein, is accommodated in the casing <NUM>, and is sealed so that the inside thereof is a sealed space. For this reason, it is possible to separate a space having the secondary battery <NUM> in the casing <NUM> accommodated therein from a space having the battery monitoring unit <NUM> accommodated therein. With this constitution, even if a solution in the secondary battery <NUM> leaks, leaked electrolytic solution does not enter the protection case <NUM> having the battery monitoring unit <NUM> accommodated therein and it is possible to prevent damage to the battery monitoring unit <NUM>. For this reason, it is possible to improve the safety of the power storage device <NUM>. The protection case <NUM> can be disposed between the inner lid <NUM> and the upper lid <NUM>. The protection case <NUM> is, for example, a plastic case.

As in the power storage device <NUM> shown in <FIG>, a sealed space having the battery monitoring unit <NUM> disposed therein may be formed by the protection case <NUM> and a seal member <NUM>. Furthermore, this sealed space may be formed by the protection case <NUM>, the seal member <NUM>, and the casing <NUM>, may be formed by the protection case <NUM> and the casing <NUM>, and may be formed by only the protection case <NUM>. The seal member <NUM> is, for example, a rubber sheet. As in the power storage device <NUM> shown in <FIG>, the seal member <NUM> may be provided to cover an opening of the protection case <NUM>. Furthermore, the seal member <NUM> may be provided between the casing <NUM> and an upper surface of a side wall of the protection case <NUM>. The seal member <NUM> may be sandwiched between the protection case <NUM> and the casing <NUM>. Thus, the seal member <NUM>, the protection case <NUM>, and the casing <NUM> can be brought into contact with each other and the inside of the protection case <NUM> can become a sealed space. Furthermore, for example, the inside of the protection case <NUM> may be made a sealed space by adhering the protection case <NUM> to the casing <NUM> using an adhesive.

Claim 1:
A power storage device comprising:
a secondary battery (<NUM>, 5a, 5b), a casing (<NUM>) having a sealed structure, a safety valve (<NUM>),
wherein the casing (<NUM>) includes an external container (<NUM>) having the secondary battery (<NUM>, 5a, 5b) accommodated therein and an upper lid (<NUM>) disposed above the external container (<NUM>),
the upper lid (<NUM>) has an upper surface having a concave portion (<NUM>) formed therein,
the safety valve (<NUM>) is disposed in the concave portion (<NUM>),
characterized in that
a drainage through hole (<NUM>) is provided to pass through a side wall of the concave portion (<NUM>),
the safety valve (<NUM>) has convex shape extending along the side wall of the concave portion (<NUM>) and is provided so that an upper end does not protrude from a main upper surface of the upper lid,
the safety valve (<NUM>) has an exhaust cylinder (<NUM>) and a cap (<NUM>) configured to close an external outlet of the exhaust cylinder, and
the cap (<NUM>) is disposed above an inlet of the drainage through hole (<NUM>).