A battery system comprising a battery group including first to n th battery modules (30_1 to 30_n) connected in series, wherein n is a natural number of 2 or greater, and a battery temperature control apparatus, the battery temperature control apparatus comprising: first to n th cooling fans (210_1 to 210_n) provided to the first to n th battery modules (30_1 to 30_n) in a one-to-one relationship; first to n th slave management units (220_1 to 220_n) provided to the first to n th battery modules (30_1 to 30_n) in a one-to-one relationship; and a master management unit operably coupled to the first to n th cooling fans (210_1 to 210_n) and the first to n th slave management units (220_1 to 220_n), wherein the master management unit is configured to: determine battery temperature information including first to n th temperature values and a first reference value based on a notification signal from each of the first to n th slave management units (220_1 to 220_n), wherein the first to n th temperature values indicate temperatures of the first to n th battery modules (30_1 to 30_n), and the first reference value is an average or a median of the first to n th temperature values, and control a rotation speed of each of the first to n th cooling fans (210_1 to 210_n) based on the battery temperature information, characterized in that the master management unit is configured to: determine battery life information including first to n th states of health (SOHs) and a second reference value based on the notification signal, wherein the first to n th SOHs indicate a remaining life span of the first to n th battery modules, and the second reference value is an average or a median of the first to n th SOHs, and determine the rotation speed of each of the first to n th cooling fans (210_1 to 210_n) further based on the battery life information. first to n th cooling fans (210_1 to 210_n) provided to the first to n th battery modules (30_1 to 30_n) in a one-to-one relationship; first to n th slave management units (220_1 to 220_n) provided to the first to n th battery modules (30_1 to 30_n) in a one-to-one relationship; and a master management unit operably coupled to the first to n th cooling fans (210_1 to 210_n) and the first to n th slave management units (220_1 to 220_n), wherein the master management unit is configured to: determine battery temperature information including first to n th temperature values and a first reference value based on a notification signal from each of the first to n th slave management units (220_1 to 220_n), wherein the first to n th temperature values indicate temperatures of the first to n th battery modules (30_1 to 30_n), and the first reference value is an average or a median of the first to n th temperature values, and control a rotation speed of each of the first to n th cooling fans (210_1 to 210_n) based on the battery temperature information, characterized in that the master management unit is configured to: determine battery life information including first to n th states of health (SOHs) and a second reference value based on the notification signal, wherein the first to n th SOHs indicate a remaining life span of the first to n th battery modules, and the second reference value is an average or a median of the first to n th SOHs, and determine the rotation speed of each of the first to n th cooling fans (210_1 to 210_n) further based on the battery life information. determine battery temperature information including first to n th temperature values and a first reference value based on a notification signal from each of the first to n th slave management units (220_1 to 220_n), wherein the first to n th temperature values indicate temperatures of the first to n th battery modules (30_1 to 30_n), and the first reference value is an average or a median of the first to n th temperature values, and control a rotation speed of each of the first to n th cooling fans (210_1 to 210_n) based on the battery temperature information, characterized in that the master management unit is configured to: determine battery life information including first to n th states of health (SOHs) and a second reference value based on the notification signal, wherein the first to n th SOHs indicate a remaining life span of the first to n th battery modules, and the second reference value is an average or a median of the first to n th SOHs, and determine the rotation speed of each of the first to n th cooling fans (210_1 to 210_n) further based on the battery life information. determine battery life information including first to n th states of health (SOHs) and a second reference value based on the notification signal, wherein the first to n th SOHs indicate a remaining life span of the first to n th battery modules, and the second reference value is an average or a median of the first to n th SOHs, and determine the rotation speed of each of the first to n th cooling fans (210_1 to 210_n) further based on the battery life information.