CLAIMS
1. A power storage device comprising:
a housing;
battery cells disposed apart from each other within the housing;
a partition member dividing a space within the housing into (i) a high temperature region containing, among the battery cells, the battery cells disposed centrally in an arrangement direction, and (ii) a low temperature region containing, among the battery cells, the battery cells disposed in end portions in the arrangement direction; and
a fan to supply a cooling air flow to the high temperature region,
wherein the cooling air flow supplied from the fan to the high temperature region passes between the battery cells contained in the high temperature region, passes through a ventilation hole disposed in the partition member, and enters the low temperature region, and
the cooling air flow passing through the ventilation hole and entering the low temperature region passes between the battery cells contained in the low temperature region, passes through a discharge hole disposed in the housing, and flows to an exterior of the housing.
2. The power storage device according to claim 1, further comprising:
an adjuster to adjust an amount of the cooling air flow by controlling the fan in response to a value indicating a degree of deviation of a temperature distribution of the battery cells.
3. The power storage device according to claim 2, wherein the adjuster:
(i) causes the fan to operate when the value indicating the degree of deviation of the temperature distribution of the battery cells is greater than or equal to a first threshold, or when a value corresponding to a maximum temperature of the battery cells is greater

than or equal to a second threshold, and
(ii) stops the fan after operation of the fan, when a value corresponding to a minimum temperature of the battery cells is greater than or equal to a third threshold, the value indicating the degree of deviation of the temperature distribution of the battery cells is less than the first threshold, and the value corresponding to the maximum temperature of the battery cells is less than the second threshold.
4. The power storage device according to claim 2, further comprising:
a central discharge hole disposed in the housing where the housing contacts the high temperature region, the central discharge hole to allow the cooling air flow supplied from the fan to the high temperature region and passing between the battery cells contained in the high temperature region to flow to the exterior of the housing; and
a valve to adjust the amount of the cooling air flow passing through each of the ventilation hole and the central discharge hole and flowing out from the high temperature region,
wherein the adjuster controls the valve in response to a value corresponding to a minimum temperature of the battery cells.
5. The power storage device according to claim 4, wherein the adjuster:
(i) causes the fan to operate when the value indicating the degree of deviation of the temperature distribution of the battery cells is greater than or equal to a first threshold, or when a value corresponding to a maximum temperature of the battery cells is greater than or equal to a second threshold,
(ii) after operation of the fan, controls the valve in response to the value corresponding to the minimum temperature of the battery cells, and
(iii) stops the fan when a value corresponding to the minimum temperature of the battery cells is greater than or equal to a third threshold, the value indicating the degree of

deviation of the temperature distribution of the battery cells is less than the first threshold, and the value corresponding to the maximum temperature of the battery cells is less than the second threshold.
6. The power storage device according to claim 2, further comprising:
a temperature determiner to measure temperatures of the battery cells,
wherein the adjuster controls the fan in response to the value indicating the degree
of deviation of the temperature distribution based on the temperatures of the battery cells measured by the temperature determiner.
7. The power storage device according to claim 2, further comprising:
an internal resistance calculator to calculate internal resistances of the battery cells based on voltages of the battery cells and current flowing through the battery cells; and
a temperature estimator to estimate the temperatures of the battery cells based on (i) a predetermined relationship between the internal resistances and the temperatures, and (ii) the internal resistances calculated by the internal resistance calculator,
wherein the adjuster controls the fan in response to the value indicating the degree of deviation of the temperature distribution based on the temperatures of the battery cells estimated by the temperature estimator.
8. The power storage device according to claim 2, wherein the value indicating
the degree of deviation of the temperature distribution is determined by temperatures of,
among the battery cells, a portion of the battery cells contained in the high temperature
region and a portion of the battery cells contained in the low temperature region, the
portion of the battery cells contained in the high temperature region and the portion of the
battery cells contained in the low temperature region being determined in accordance
with the temperature distribution of the battery cells when the fan is not operated.