ESTIMATION SYSTEM

An estimation system includes a battery (5), an inverter (20), a motor (25), a current sensor (30u), and an ECU (100). The inverter (20) includes an upper arm circuit (22u) and a lower arm circuit (23u), an upper arm circuit (22v) and a lower arm circuit (23v), and an upper arm circuit (22w) and a lower arm circuit (23w). A mode of the inverter (20) includes a first mode in which the upper arm circuit (22u), the lower arm circuit (23v), and the lower arm circuit (23w) are on and a second mode in which the lower arm circuit (23u), the upper arm circuit (22v), and the upper arm circuit (22w) are on. The ECU (100) performs estimation processing for estimating a current value of the battery (5). The estimation processing includes first processing for estimating the current value in accordance with a detection value from the current sensor (30u) when the mode of the inverter (20) is set to the first mode or the second mode.