Battery pack

A battery pack comprises battery blocks 210 each of which includes base batteries 211 having a cylindrical exterior container, and a battery spacer 212 for holding said base batteries in parallel; pairs of lead plates 220 each of which connect the end surfaces of said base batteries 211 held by said battery spacer 212 so that the base batteries are connected to each other in parallel, and one of one pair of the lead plates 220 in one battery block is serially connected to one of one pair of the lead plates 220 in another battery block; a circuit board 240 that is electrically connected to said pairs of lead plates 220; and an exterior case 230 that accommodates said battery blocks 210 and the circuit board, wherein said battery blocks 210 are classified into battery block rows 202 in that the classified battery blocks are arranged side by side in parallel to each other so that the end surfaces of the base batteries 211 included in the battery blocks are arranged coplanar with each other, wherein said battery block rows 202 are arranged side by side so that the end surfaces of said base batteries 211 of said battery block rows are opposed to each other and so that said base batteries 211 of said battery block rows 202 are aligned in substantially straight lines and extend in the center axes of cylindrical shapes whereby composing a battery assembly 201, wherein battery block rows 202 that are arranged side by side include lead plate 220 extension parts extending along side surfaces of said battery assembly 201, and the battery pack comprises lead connection portions 225 that electrically connect the lead plate 220 extension parts to each other, wherein the lead connection portions 225 are alternately arranged on parts of the side surfaces of said battery assembly 201 between adjacent battery block rows 202 to connect said lead plates to each other.