This nonprovisional application is based on Japanese Patent Application No. 2019-088234 filed on May 8, 2019 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND

Field

The present disclosure relates to power storage devices.

Description of the Background Art

A power storage device includes a plurality of power storage cells. Generally, the internal resistance in the power storage cell increases as the temperature of the power storage cell decreases. In view of this, a power storage device disclosed in Japanese Patent Laying-Open No. 2018-32548 is provided with a heater that increases the temperature of a power storage cell when the power storage cell has a low temperature.

Specifically, the power storage device disclosed in Japanese Patent Laying-Open No. 2018-32548 includes a plurality of power storage cells, a heater disposed on the lower surface side of the power storage cells, and an elastic member that presses the heater against the power storage cells.

The heater includes a nonwoven fabric and a heater wire sewn on the nonwoven fabric, and when a current passes through the heater wire, the temperature of the heater wire increases.

SUMMARY

In the power storage device disclosed in Japanese Patent Laying-Open No. 2018-32548, the heater wire may break due to aged deterioration or the like.

It is thus conceivable that, for example, a sensor such as a thermistor will be attached to the heater wire. If the heater wire is broken during driving of the heater, no current passes through the heater wire, and accordingly, the temperature of the heater wire does not increase. Thus, a break of the heater wire can be detected based on a value output from the sensor. On the other hand, the heater is pressed against the power storage cells with an insulating member therebetween. Thus, when the sensor is attached to the heater wire, the sensor is disposed between the heater and the power storage cells.

Even when the heater wire is broken, for example, as the temperature of the power storage cells increases through charging of the power storage cells, the sensor is heated by the heat of the power storage cells. This may lead to a fear that the presence or absence of a break of the heater wire may be mistakenly determined when the presence or absence of a break of the heater wire is determined based on a signal from the sensor.

The present disclosure has been made in view of the above problem, and an object thereof is to provide a power storage device capable of successfully determining the presence or absence of a break of a heater wire.

A power storage device according to the present disclosure includes at least one power storage cell, a heater that increases a temperature of the at least one power storage cell, a pressing member that presses the heater against the at least one power storage cell, and a sensor provided in the heater. The heater includes a base material and a heater wire provided on the base material. The base material includes a lead portion drawn from between the pressing member and the at least one power storage cell. The heater wire includes a heater lead wire formed on the lead portion. The sensor is provided on the heater lead wire.

In the power storage device, the sensor is provided at a position apart from the pressing member and the power storage cell. In measurement of the temperature of heater lead wire, thus, the sensor can be restrained from being thermally affected by the power storage cell and can accurately measure the temperature of the heater wire. This facilitates the determination of the presence or absence of a break of the heater wire.

The lead portion is formed to surround the sensor. The power storage device can restrain the sensor from directly contacting an external member, thus reducing damage to the sensor.

The power storage device further includes a housing case that houses the at least one power storage cell, the pressing member, the heater, and the sensor, and a controller that controls driving of the heater and the sensor. The controller obtains a signal from the sensor as information indicating a temperature in the housing case when driving of the heater is stopped.

In the power storage device, the sensor measures the temperature in the housing case when the heater is not driven. At this time, the sensor is apart from the power storage cell and is less thermally affected by the power storage cell, and thus, can accurately measure the temperature in the housing case.

The foregoing and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings.

