According to some embodiments, a battery control device has a current detector, a storage, and a state determiner. The current detector detects a current value of a current which flows into a second battery which is connected in parallel to a first battery. The first battery and the second battery are charged with a fixed current. The storage stores an initial value of the current which flows into the second battery if the second battery is charged with the fixed current in an initial use stage of the second battery. The state determiner determines a state of the first battery based on the current value detected by the current detector and the initial value stored in the storage.