A management device that manages a plurality of power storage modules each connected in parallel to a load via a corresponding switch and includes a first state in which a switch corresponding to each of one or more power storage modules of the plurality of power storage modules is turned on and a switch corresponding to each of one or more remaining power storage modules of the plurality of power storage modules is turned off, the management device comprising:
- an acquisition unit configured to acquire at least a state of charge for each of the plurality of power storage modules;
- a calculator configured to estimate an upper limit value of current or power allowed to be discharged from all of the plurality of power storage modules, based on SOC-discharge upper limit characteristics that define a relationship between the state of charge of each of the plurality of power storage modules and an upper limit value of current or power allowed to be discharged from a corresponding one of the plurality of power storage modules,
- wherein the SOC-discharge upper limit characteristics show that the upper limit value of current or power allowed to be discharged from each of the plurality of power storage modules decreases as the state of charge of the corresponding one of the plurality of power storage modules decreases;
- and
- a determination unit configured to not permit turning on the switch corresponding to at least one of the one or more remaining power storage modules and turned off in the first state when;
- the switch corresponding to each of the one or more power storage modules of the plurality of power storage modules is turned on, and
- the upper limit value of current or power that is allowed to be discharged to the load from all of the plurality of power storage modules in a state where the switch corresponding to the at least one of the one or more remaining power storage module is turned on is lower than a first threshold based on a maximum value of current or power required by the load,
- wherein
- the acquisition unit acquires an open circuit voltage of a power storage module of a connection candidate among the one or more remaining power storage modules,
- the calculator derives a first upper limit value of current or power allowed to be discharged from each of the plurality of power storage modules connected to the load based on the SOC-discharge upper limit characteristics and the state of charge of each of the plurality of power storage modules connected to the load, and estimates a closed circuit voltage of each of the plurality of power storage modules connected to the load when discharging is performed from the plurality of power storage modules connected to the load at the first upper limit value,
- the determination unit permits turning on the switch connected to the power storage module of the connection candidate among the one or more remaining power storage modules, when the open circuit voltage of the power storage module of the connection candidate among the one or more remaining power storage modules is larger than or equal to the closed circuit voltage of each of the plurality of power storage modules connected to the load,
- the calculator estimates, when the open circuit voltage of the power storage module of the connection candidate among the one or more remaining power storage modules is lower than or equal to the closed circuit voltage of each of the plurality of power storage modules connected to the load, a current value flowing through the power storage module of the connection candidate among the one or more remaining power storage modules when the closed circuit voltage of the power storage module of the connection candidate corresponds to the closed circuit voltage of each of the plurality of power storage modules connected to the load when discharging is performed at the first upper limit value, and
- the determination unit permits turning on the switch connected to the power storage module of the connection candidate among the one or more remaining power storage modules when a second upper limit value of current or power allowed to be discharged from all of the plurality of power storage modules is larger than or equal to the first threshold, the second upper limit value being acquired by subtracting the current value from the first upper limit value.