STORAGE BATTERY CONTROL DEVICE, ELECTRICITY STORAGE SYSTEM, AND STORAGE BATTERY CONTROL METHOD

An electricity storage system controller executes a charge and discharge mode in which a part of the plurality of electricity storage strings is in a discharge state and the electricity storage strings other than the part are in a charge standby state, or a part of the plurality of electricity storage strings is in a charge state and the electricity storage strings other than the part are in a discharge standby state, and determines a ratio of the electricity storage strings in the discharge state to the electricity storage strings in the charge standby state or a ratio of the electricity storage strings in the charge state to the electricity storage strings in the discharge standby state, based on transition prediction information in which transitions of generated power of a solar power generation device and consumption power of a load connected to a power reception point are predicted.