POWER SUPPLY APPARATUS, PROTECTION APPARATUS, AND PROTECTION METHOD

When it has been determined according to a voltage detected by a voltage detecting unit that a voltage detection line between a focused-on battery and the voltage detecting unit has been broken, operations of each of switches are controlled to separate a battery module that includes the voltage detection line from a power supply apparatus . When it has been determined according to the voltage detected by the voltage detecting unit that the focused-on battery has been overcharged or overdischarged, power input to, or output from, every battery module is limited.