Patent ID: 8829857

Claim:
A battery pack input/output control system comprising: a battery pack that is formed by combining a plurality of unit cells; an ambient temperature obtaining section that obtains an ambient temperature of the battery pack; a plurality of battery temperature sensors that detect a surface temperature of the battery pack at a plurality of locations on a surface of the battery pack; a plurality of voltage detecting sections that detect voltages of some of the unit cells at a plurality of any predetermined locations of the battery pack; a current value obtaining section that obtains a current value inputted to/outputted from the battery pack; a maximum temperature estimating section that estimates a maximum internal temperature of the battery pack; and an input/output limiting section that limits the input/output of the battery pack based on the estimated maximum internal temperature, wherein the maximum temperature estimating section includes: inside-outside temperature difference estimating portion that estimates a battery inside-outside temperature difference or a difference between the internal temperature and the surface temperature of the battery pack based on the ambient temperature; and internal resistance-dependent temperature difference estimating portion that estimates an internal resistance of each of the unit cells based on the current value and the voltages that are detected at the plurality of any predetermined locations, and thus for estimating an internal resistance-dependent temperature difference or a temperature difference within the battery pack, which is dependent on differences in internal resistance between the unit cells, based on the estimated internal resistance of the each unit cell, and wherein the maximum internal temperature of the battery pack is estimated by adding the sum of the battery inside-outside temperature difference and the internal resistance-dependent temperature difference to a maximum value of the detected surface temperature of the battery pack, the battery inside-outside temperature difference being estimated by the inside-outside temperature difference estimating portion, the internal resistance-dependent temperature difference being estimated by the internal resistance-dependent temperature difference estimating portion.