Temperature-raising device and temperature-raising method for in-car battery

1. A temperature-raising device for an in-car battery, the temperature-raising device comprising:

a battery temperature acquisition unit configured to acquire a temperature of a battery mounted in a vehicle;

an environmental temperature acquisition unit configured to acquire an environmental temperature;

a heater configured to raise the temperature of the battery; and

a controller configured to

i) turn ON or OFF the heater based on a result of a comparison between the battery temperature acquired by the battery temperature acquisition unit and a predetermined threshold, and

ii) reduce the threshold in accordance with a reduction in the environmental temperature acquired by the environmental temperature acquisition unit,

wherein the battery temperature acquisition unit includes a temperature sensor installed around the in-car battery, and

wherein the environmental temperature acquisition unit is configured to estimate the environmental temperature based on a battery temperature detected by the temperature sensor, and

wherein the environmental temperature acquisition unit is configured to

i) estimate a battery temperature after a passage of a predetermined period of time based on an estimated environmental temperature at a current point in time and the battery temperature detected by the temperature sensor at the current point in time, and

ii) correct the estimated environmental temperature in accordance with an error between the battery temperature detected by the temperature sensor and the estimated battery temperature after the passage of the predetermined period of time.

2. The temperature-raising device according to claim 1 ,

wherein the controller is configured to

i) set the threshold to a standard value defined in advance in a case where the environmental temperature acquired by the environmental temperature acquisition unit is equal to or higher than a reference environmental temperature defined in advance, and

ii) set the threshold to a value lower than the standard value in a case where the environmental temperature acquired by the environmental temperature acquisition unit is lower than the reference environmental temperature.

3. The temperature-raising device according to claim 1 ,

wherein the controller is configured to execute a temperature-raising operation for the in-car battery in a plug-in state where the in-car battery is electrically connected to an external electric power supply.

4. A temperature-raising method for a battery mounted in a vehicle,

the vehicle including a temperature sensor configured to acquire a temperature of the battery and a controller, the temperature-raising method comprising:

acquiring the temperature of the battery mounted in the vehicle by the temperature sensor;

turning ON or OFF the heater raising the temperature of the battery by the controller based on a result of a comparison between the acquired battery temperature and a predetermined threshold;

acquiring an environmental temperature of the vehicle by the controller; and

reducing the threshold by the controller in accordance with a reduction in the acquired environmental temperature,

wherein the acquiring the environmental temperature includes estimating the environmental temperature based on a battery temperature detected by the temperature sensor, including:

i) estimating a battery temperature after a passage of a predetermined period of time based on an estimated environmental temperature at a current point in time and the battery temperature detected by the temperature sensor at the current point in time, and

ii) correcting the estimated environmental temperature in accordance with an error between the battery temperature detected by the temperature sensor and the estimated battery temperature after the passage of the predetermined period of time.