PURPOSE: To have automatic replacement of batteries for trolleys in an unmanned plant, etc. by furnishing a storage device equipped with a plurality of battery storing parts and a battery transfer device for replacing any discharged battery on the trolley with a charged battery stored in the storing parts.

CONSTITUTION: This battery storage device 2 is made in such a construction that rotary shelves are installed one over another, where each shelf 8 has four battery storing parts 1 equipped each with a charger 9 and a charging terminal 6 with automatic separability. On the other hand, the battery transfer device 5 comprises a battery detaining finger 10 equipped with hooking latch 19 with easy separability from the battery 4, a battery table 11, a hanging rotary frame 12, an elevating frame 13 and an elevating guide 14, being in charge of taking out a discharged battery 4 from the trolley 3, transferring it to one of the storing parts 1, taking out a charged battery 4 from storing part 1, and transferring it to the trolley 3. The trolley 3 is equipped with a receptacle terminal, which is automatically separable from the battery 4.