a monitoring IC including a plurality of channels for simultaneously measuring a plurality of voltages of respective battery cells;

a busbar connected to one or more battery cell of the battery cells; and

an auxiliary channel of the monitoring IC configured to measure a reverse voltage of the busbar, the auxiliary channel being different than the plurality of channels,

wherein the monitoring IC is configured to determine a voltage of a battery cell of the battery cells using a channel voltage measured through at least one channel of the plurality of channels and the reverse voltage measured by the auxiliary channel, and

wherein the monitoring IC comprises a plurality of switch elements connected to the auxiliary channel.