A battery system, comprising: a battery; and a battery management system, BMS, configured to control charging of the battery depending on a normal mode where the battery is charged with a first battery capacity between a first lower limit state of charge, SOC, and a first upper limit SOC or an eco-friendly mode, ECO MODE, where the battery is charged with a second battery capacity between a second lower limit SOC and a second upper limit SOC, wherein the first lower limit SOC is smaller than the second lower limit SOC, and the first upper limit SOC is greater than the second upper limit SOC, wherein the BMS is configured to, in an on state of the normal mode, calculate a current SOC by estimating a SOC of the battery every predetermined period, and start charging of the battery when the current SOC reaches the first lower limit SOC and end the charging of the battery when the current SOC reaches the first upper limit SOC, wherein the BMS is configured to, in an on state of the normal mode, control charging of the battery by using a rapid charging method of charging the battery for completing the charging of the battery from when the current SOC reaches the first lower limit SOC until when the current SOC reaches the first upper limit SOC within a predetermined reference time or performing a slow charging method of charging the battery for completing the charging of the battery from when the current SOC reaches the first lower limit SOC until when the current SOC reaches the first upper limit SOC after exceeding the predetermined reference time, wherein the BMS is configured to, in an on state of the normal mode, control the charging of the battery by the rapid charging method or the slow charging method depending on user selection. a battery; and a battery management system, BMS, configured to control charging of the battery depending on a normal mode where the battery is charged with a first battery capacity between a first lower limit state of charge, SOC, and a first upper limit SOC or an eco-friendly mode, ECO MODE, where the battery is charged with a second battery capacity between a second lower limit SOC and a second upper limit SOC, wherein the first lower limit SOC is smaller than the second lower limit SOC, and the first upper limit SOC is greater than the second upper limit SOC, wherein the BMS is configured to, in an on state of the normal mode, calculate a current SOC by estimating a SOC of the battery every predetermined period, and start charging of the battery when the current SOC reaches the first lower limit SOC and end the charging of the battery when the current SOC reaches the first upper limit SOC, wherein the BMS is configured to, in an on state of the normal mode, control charging of the battery by using a rapid charging method of charging the battery for completing the charging of the battery from when the current SOC reaches the first lower limit SOC until when the current SOC reaches the first upper limit SOC within a predetermined reference time or performing a slow charging method of charging the battery for completing the charging of the battery from when the current SOC reaches the first lower limit SOC until when the current SOC reaches the first upper limit SOC after exceeding the predetermined reference time, wherein the BMS is configured to, in an on state of the normal mode, control the charging of the battery by the rapid charging method or the slow charging method depending on user selection. <EOS>