To detect the abnormality of a cell that constitutes a battery pack without using an isolator.

This is an abnormality detecting device of a battery pack that detects the abnormality of a battery pack which is constituted by connecting in series 'n' pieces ('n' is a natural number of 3 or more) of cells capable of charge and discharge. The device comprises an abnormality detecting means that is provided for every 'n' pieces of cells and detects the abnormality of the corresponding cells, a first logical sum computing means that computes the logical sum of the output from the first abnormality detecting means corresponding to the utmost top level cells and the output from the second abnormality detecting means corresponding to the cells one level lower than the utmost top level, and a kth ä'k' is all the natural numbers of 2 or more and (n-1) or less} logical sum computing means that computes the logical sum of the output from the (k-1)th logical sum computing means and the output from the (k+1)th abnormality detecting means corresponding to the cells 'k' level lower than the utmost top level.

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