A lithium ion secondary battery having a positive electrode 3 which contains, as a positive electrode active material, a composite metal oxide containing at least one of Li, Co, Mn, and Ni as a metal component thereof; a negative electrode 2 which contains a negative electrode active material; and a nonaqueous electrolyte solution containing a lithium salt. The target has an active section and an inactive section. When the maintenance execution time reaches a preset time, an asterisk * is displayed on a display portion 18 of the operating panel 16. Note that the encoding function depends on a preceding codeword in the stream of codewords, so that when the preceding codeword changes to the current codeword, rising transitions are substantially matched with falling transitions within the bundle. The main supporting beams are preferably arranged at least partially between the flue gas channels extending over the roof of the furnace.